Simplify log messages to avoid redundant information

Co-authored-by: moooyo <42196638+moooyo@users.noreply.github.com>

.github/actions/spell-check/expect.txt

@@ -11,6 +11,7 @@ ACCESSDENIED
 ACCESSTOKEN
 acfs
 ACIE
+ACR
 AClient
 AColumn
 acrt
@@ -92,6 +93,7 @@ asf
 Ashcraft
 AShortcut
 ASingle
+ASUS
 ASSOCCHANGED
 ASSOCF
 ASSOCSTR
@@ -102,6 +104,7 @@ ATRIOX
 ATX
 aumid
 authenticode
+AUO
 AUTOBUDDY
 AUTOCHECKBOX
 AUTOHIDE
@@ -119,6 +122,10 @@ azureaiinference
 azureinference
 azureopenai
 backticks
+Backlight
+Badflags
+Badmode
+Badparam
 bbwe
 BCIE
 bck
@@ -190,7 +197,10 @@ CARETBLINKING
 Carlseibert
 CAtl
 caub
+CAuthn
+CAuthz
 CBN
+Cds
 cch
 CCHDEVICENAME
 CCHFORMNAME
@@ -209,9 +219,11 @@ changecursor
 CHILDACTIVATE
 CHILDWINDOW
 CHOOSEFONT
+Chunghwa
 cidl
 CIELCh
 cim
+CImp
 CImage
 cla
 CLASSDC
@@ -219,7 +231,7 @@ CLASSNOTAVAILABLE
 CLEARTYPE
 clickable
 clickonce
-CLIENTEDGE
+clientedge
 clientid
 clientside
 CLIPBOARDUPDATE
@@ -231,6 +243,7 @@ CLSCTX
 clsids
 Clusion
 cmder
+CMN
 CMDNOTFOUNDMODULEINTERFACE
 cmdpal
 CMIC
@@ -246,7 +259,7 @@ codereview
 Codespaces
 Coen
 cognitiveservices
-COINIT
+coinit
 colid
 colorconv
 colorformat
@@ -285,6 +298,7 @@ Corpor
 cotaskmem
 COULDNOT
 countof
+Cowait
 covrun
 cpcontrols
 cph
@@ -304,11 +318,13 @@ CRECT
 CRH
 critsec
 cropandlock
+crt
 Crossdevice
 csdevkit
 CSearch
 CSettings
 cso
+CSOT
 CSRW
 CStyle
 cswin
@@ -349,11 +365,17 @@ DBPROP
 DBPROPIDSET
 DBPROPSET
 DCBA
+DCapabilities
 DCOM
 DComposition
 DCR
+ddc
+Ddc
+Ddcci
+ddcutil
 DDEIf
 Deact
+debouncer
 debugbreak
 decryptor
 Dedup
@@ -370,6 +392,7 @@ DEFAULTTOPRIMARY
 DEFERERASE
 DEFPUSHBUTTON
 deinitialization
+DELA
 DELETEDKEYIMAGE
 DELETESCANS
 DEMOTYPE
@@ -399,18 +422,21 @@ DISABLEASACTIONKEY
 DISABLENOSCROLL
 diskmgmt
 DISPLAYCHANGE
-DISPLAYCONFIG
+displayconfig
 DISPLAYFLAGS
 DISPLAYFREQUENCY
 displayname
 DISPLAYORIENTATION
+Displayport
+diu
 divyan
 Dlg
 DLGFRAME
-DLGMODALFRAME
+dlgmodalframe
 dlib
 dllhost
 dllmain
+Dmdo
 DNLEN
 DONOTROUND
 DONTVALIDATEPATH
@@ -427,6 +453,7 @@ DRAWCLIPBOARD
 DRAWFRAME
 drawingcolor
 dreamsofameaningfullife
+DREGION
 drivedetectionwarning
 DROPFILES
 DSTINVERT
@@ -438,6 +465,7 @@ dutil
 DVASPECT
 DVASPECTINFO
 DVD
+dvi
 dvr
 DVTARGETDEVICE
 dwflags
@@ -457,15 +485,19 @@ DWMWINDOWMAXIMIZEDCHANGE
 DWORDLONG
 dworigin
 dwrite
+Dxva
 dxgi
 eab
+EAccess
 easeofaccess
 ecount
-Edid
+edid
 EDITKEYBOARD
 EDITSHORTCUTS
 EDITTEXT
 EFile
+EInvalid
+eep
 eku
 emojis
 ENABLEDELAYEDEXPANSION
@@ -475,14 +507,16 @@ ENABLETEMPLATE
 encodedlaunch
 encryptor
 ENDSESSION
+ENot
 ENSUREVISIBLE
 ENTERSIZEMOVE
 ENTRYW
 ENU
 environmentvariables
-EOAC
+eoac
 EPO
 epu
+EProvider
 ERASEBKGND
 EREOF
 EResize
@@ -536,6 +570,7 @@ fdx
 FErase
 fesf
 FFFF
+FFh
 FInc
 Figma
 FILEEXPLORER
@@ -577,7 +612,9 @@ FORMATDLGORD
 formatetc
 FORPARSING
 foundrylocal
+FPrimary
 FRAMECHANGED
+Framechanged
 FRestore
 frm
 FROMTOUCH
@@ -637,6 +674,8 @@ gwl
 GWLP
 GWLSTYLE
 hangeul
+Hann
+Hantai
 Hanzi
 Hardlines
 hardlinks
@@ -658,6 +697,8 @@ HCRYPTPROV
 hcursor
 hcwhite
 hdc
+hdmi
+HDMI
 hdr
 hdrop
 hdwwiz
@@ -694,6 +735,7 @@ HKPD
 HKU
 HMD
 hmenu
+HMON
 hmodule
 hmonitor
 homies
@@ -711,6 +753,7 @@ hotkeys
 hotlight
 hotspot
 HPAINTBUFFER
+HPhysical
 HRAWINPUT
 hredraw
 hres
@@ -721,6 +764,7 @@ hsb
 HSCROLL
 hsi
 HSpeed
+HSync
 HTCLIENT
 hthumbnail
 HTOUCHINPUT
@@ -730,6 +774,7 @@ HVal
 HValue
 Hvci
 hwb
+HWP
 HWHEEL
 HWINEVENTHOOK
 hwnd
@@ -786,6 +831,7 @@ INITTOLOGFONTSTRUCT
 INLINEPREFIX
 inlines
 Inno
+Innolux
 INPC
 inproc
 INPUTHARDWARE
@@ -827,6 +873,7 @@ istep
 ith
 ITHUMBNAIL
 IUI
+IVO
 IUWP
 IWIC
 jfif
@@ -838,6 +885,7 @@ jpnime
 Jsons
 jsonval
 jxr
+Kantai
 keybd
 KEYBDDATA
 KEYBDINPUT
@@ -859,6 +907,7 @@ KILLFOCUS
 killrunner
 kmph
 kvp
+KVM
 Kybd
 LARGEICON
 lastcodeanalysissucceeded
@@ -878,6 +927,8 @@ LEFTTEXT
 LError
 LEVELID
 LExit
+Lenovo
+LGD
 lhwnd
 LIBFUZZER
 LIBID
@@ -982,6 +1033,7 @@ MAPTOSAMESHORTCUT
 MAPVK
 MARKDOWNPREVIEWHANDLERCPP
 MAXIMIZEBOX
+Maximizebox
 MAXSHORTCUTSIZE
 maxversiontested
 mber
@@ -992,6 +1044,8 @@ MDL
 mdtext
 mdtxt
 mdwn
+Mccs
+mccs
 meme
 mcp
 memicmp
@@ -1013,6 +1067,7 @@ mikeclayton
 mindaro
 Minimizable
 MINIMIZEBOX
+Minimizebox
 MINIMIZEEND
 MINIMIZESTART
 MINMAXINFO
@@ -1032,6 +1087,7 @@ MODALFRAME
 MODESPRUNED
 MONITORENUMPROC
 MONITORINFO
+Monitorinfo
 MONITORINFOEX
 MONITORINFOEXW
 monitorinfof
@@ -1072,9 +1128,10 @@ MSLLHOOKSTRUCT
 Mso
 msrc
 msstore
+mstsc
+mswhql
 msvcp
 MT
-mstsc
 MTND
 MULTIPLEUSE
 multizone
@@ -1090,6 +1147,7 @@ MVVMTK
 MWBEx
 MYICON
 NAMECHANGE
+Nanjing
 namespaceanddescendants
 nao
 NCACTIVATE
@@ -1158,6 +1216,7 @@ NOMCX
 NOMINMAX
 NOMIRRORBITMAP
 NOMOVE
+Nomove
 NONANTIALIASED
 nonclient
 NONCLIENTMETRICSW
@@ -1179,6 +1238,7 @@ NORMALUSER
 NOSEARCH
 NOSENDCHANGING
 NOSIZE
+Nosize
 NOTHOUSANDS
 NOTICKS
 NOTIFICATIONSDLL
@@ -1186,9 +1246,11 @@ NOTIFYICONDATA
 NOTIFYICONDATAW
 NOTIMPL
 NOTOPMOST
+Notopmost
 NOTRACK
 NOTSRCCOPY
 NOTSRCERASE
+Notupdated
 notwindows
 NOTXORPEN
 nowarn
@@ -1230,10 +1292,9 @@ OPENFILENAME
 openrdp
 opensource
 openxmlformats
-ollama
-onnx
 openurl
 OPTIMIZEFORINVOKE
+Optronics
 ORPHANEDDIALOGTITLE
 ORSCANS
 oss
@@ -1269,6 +1330,7 @@ PATINVERT
 PATPAINT
 pbc
 pbi
+PBP
 PBlob
 pbrush
 pcb
@@ -1283,6 +1345,7 @@ PDBs
 PDEVMODE
 pdisp
 PDLL
+pdmodels
 pdo
 pdto
 pdtobj
@@ -1305,6 +1368,7 @@ pguid
 phbm
 phbmp
 phicon
+PHL
 Photoshop
 phwnd
 pici
@@ -1336,6 +1400,8 @@ Pomodoro
 Popups
 POPUPWINDOW
 POSITIONITEM
+powerdisplay
+POWERDISPLAYMODULEINTERFACE
 POWERRENAMECONTEXTMENU
 powerrenameinput
 POWERRENAMETEST
@@ -1390,6 +1456,7 @@ projectname
 PROPERTYKEY
 Propset
 PROPVARIANT
+prot
 PRTL
 prvpane
 psapi
@@ -1417,12 +1484,15 @@ PTOKEN
 PToy
 ptstr
 pui
+pvct
 PWAs
 pwcs
 PWSTR
 pwsz
 pwtd
 QDC
+qdc
+QDS
 qit
 QITAB
 QITABENT
@@ -1447,7 +1517,6 @@ RAWPATH
 rbhid
 rclsid
 RCZOOMIT
-remotedesktop
 rdp
 RDW
 READMODE
@@ -1476,6 +1545,7 @@ remappings
 REMAPSUCCESSFUL
 REMAPUNSUCCESSFUL
 Remotable
+remotedesktop
 remoteip
 Removelnk
 renamable
@@ -1549,6 +1619,7 @@ scrollviewer
 SDDL
 SDKDDK
 sdns
+Sdr
 searchterm
 SEARCHUI
 secondaryclickaction
@@ -1703,6 +1774,7 @@ STARTUPINFOW
 startupscreen
 STATFLAG
 STATICEDGE
+Staticedge
 STATSTG
 stdafx
 STDAPI
@@ -1745,7 +1817,7 @@ SVGIO
 svgz
 SVSI
 SWFO
-SWP
+swp
 SWPNOSIZE
 SWPNOZORDER
 SWRESTORE
@@ -1765,6 +1837,7 @@ syskeydown
 SYSKEYUP
 SYSLIB
 SYSMENU
+Sysmenu
 systemai
 SYSTEMAPPS
 SYSTEMMODAL
@@ -1804,7 +1877,9 @@ THEMECHANGED
 themeresources
 THH
 THICKFRAME
+Thickframe
 THISCOMPONENT
+Tianma
 throughs
 TILEDWINDOW
 TILLSON
@@ -1891,7 +1966,7 @@ unzoom
 UOffset
 UOI
 UPDATENOW
-UPDATEREGISTRY
+updateregistry
 updown
 UPGRADINGPRODUCTCODE
 upscaling
@@ -1918,6 +1993,9 @@ vcamp
 vcenter
 vcgtq
 VCINSTALLDIR
+Vcp
+vcp
+vcpname
 Vcpkg
 VCRT
 vcruntime
@@ -1930,7 +2008,10 @@ VERIFYCONTEXT
 VERSIONINFO
 VERTRES
 VERTSIZE
+VESA
+vesa
 VFT
+Vga
 vget
 vgetq
 viewmodels
@@ -1960,6 +2041,7 @@ VSM
 vso
 vsonline
 VSpeed
+VSync
 vstemplate
 vstest
 VSTHRD
@@ -2001,7 +2083,7 @@ winapi
 winappsdk
 windir
 WINDOWCREATED
-WINDOWEDGE
+windowedge
 WINDOWINFO
 WINDOWNAME
 WINDOWPLACEMENT
@@ -2025,7 +2107,7 @@ WINL
 winlogon
 winmd
 winml
-WINNT
+winnt
 winres
 winrt
 winsdk
@@ -2042,6 +2124,7 @@ WKSG
 Wlkr
 wmain
 Wman
+wmi
 WMI
 WMICIM
 wmimgmt

.pipelines/ESRPSigning_core.json

@@ -203,6 +203,11 @@
             "PowerToys.PowerAccentModuleInterface.dll",
             "PowerToys.PowerAccentKeyboardService.dll",
 
+            "PowerToys.PowerDisplayModuleInterface.dll",
+            "WinUI3Apps\\PowerToys.PowerDisplay.dll",
+            "WinUI3Apps\\PowerToys.PowerDisplay.exe",
+            "PowerDisplay.Lib.dll",
+
             "WinUI3Apps\\PowerToys.PowerRenameExt.dll",
             "WinUI3Apps\\PowerToys.PowerRename.exe",
             "WinUI3Apps\\PowerToys.PowerRenameContextMenu.dll",
@@ -371,6 +376,8 @@
                 "UnitsNet.dll",
                 "UtfUnknown.dll",
                 "Wpf.Ui.dll",
+                "WmiLight.dll",
+                "WmiLight.Native.dll",
                 "Shmuelie.WinRTServer.dll",
                 "ToolGood.Words.Pinyin.dll"
             ],

Directory.Packages.props

@@ -91,6 +91,7 @@
     <PackageVersion Include="NLog.Extensions.Logging" Version="5.3.8" />
     <PackageVersion Include="NLog.Schema" Version="5.2.8" />
     <PackageVersion Include="OpenAI" Version="2.5.0" />
+    <PackageVersion Include="Polly.Core" Version="8.6.5" />
     <PackageVersion Include="ReverseMarkdown" Version="4.1.0" />
     <PackageVersion Include="RtfPipe" Version="2.0.7677.4303" />
     <PackageVersion Include="ScipBe.Common.Office.OneNote" Version="3.0.1" />
@@ -102,6 +103,7 @@
     <PackageVersion Include="StyleCop.Analyzers" Version="1.2.0-beta.556" />
     <!-- Package System.CodeDom added as a hack for being able to exclude the runtime assets so they don't conflict with 8.0.1. This is a dependency of System.Management but the 8.0.1 version wasn't published to nuget. -->
     <PackageVersion Include="System.CodeDom" Version="9.0.10" />
+    <PackageVersion Include="System.Collections.Immutable" Version="9.0.0" />
     <PackageVersion Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
     <PackageVersion Include="System.ComponentModel.Composition" Version="9.0.10" />
     <PackageVersion Include="System.Configuration.ConfigurationManager" Version="9.0.10" />
@@ -131,6 +133,7 @@
     <PackageVersion Include="UnitsNet" Version="5.56.0" />
     <PackageVersion Include="UTF.Unknown" Version="2.6.0" />
     <PackageVersion Include="WinUIEx" Version="2.8.0" />
+    <PackageVersion Include="WmiLight" Version="6.14.0" />
     <PackageVersion Include="WPF-UI" Version="3.0.5" />
     <PackageVersion Include="WyHash" Version="1.0.5" />
     <PackageVersion Include="WixToolset.Heat" Version="5.0.2" />

NOTICE.md

@@ -10,6 +10,7 @@ This software incorporates material from third parties.
 - Installer/Runner
 - Measure tool
 - Peek
+- PowerDisplay
 - Registry Preview
 
 ## Utility: Color Picker
@@ -1519,6 +1520,35 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 ```
 
+## Utility: PowerDisplay
+
+### Twinkle Tray
+
+PowerDisplay's DDC/CI implementation references techniques from Twinkle Tray.
+
+**Source**: https://github.com/xanderfrangos/twinkle-tray
+
+MIT License
+
+Copyright © 2020 Xander Frangos
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
 
 ## NuGet Packages used by PowerToys
 
@@ -1557,6 +1587,7 @@ SOFTWARE.
 - NLog.Extensions.Logging
 - NLog.Schema
 - OpenAI
+- Polly.Core
 - ReverseMarkdown
 - ScipBe.Common.Office.OneNote
 - SharpCompress
@@ -1569,5 +1600,6 @@ SOFTWARE.
 - UnitsNet
 - UTF.Unknown
 - WinUIEx
+- WmiLight
 - WPF-UI
 - WyHash

PowerToys.slnx

@@ -667,6 +667,23 @@
       <Deploy />
     </Project>
   </Folder>
+  <Folder Name="/modules/PowerDisplay/">
+    <Project Path="src/modules/powerdisplay/PowerDisplay.Lib/PowerDisplay.Lib.csproj">
+      <Platform Solution="*|ARM64" Project="ARM64" />
+      <Platform Solution="*|x64" Project="x64" />
+    </Project>
+    <Project Path="src/modules/powerdisplay/PowerDisplay/PowerDisplay.csproj">
+      <Platform Solution="*|ARM64" Project="ARM64" />
+      <Platform Solution="*|x64" Project="x64" />
+    </Project>
+    <Project Path="src/modules/powerdisplay/PowerDisplayModuleInterface/PowerDisplayModuleInterface.vcxproj" Id="d1234567-8901-2345-6789-abcdef012345" />
+  </Folder>
+  <Folder Name="/modules/PowerDisplay/Tests/">
+    <Project Path="src/modules/powerdisplay/PowerDisplay.Lib.UnitTests/PowerDisplay.Lib.UnitTests.csproj">
+      <Platform Solution="*|ARM64" Project="ARM64" />
+      <Platform Solution="*|x64" Project="x64" />
+    </Project>
+  </Folder>
   <Folder Name="/modules/MeasureTool/">
     <Project Path="src/modules/MeasureTool/MeasureToolCore/PowerToys.MeasureToolCore.vcxproj" Id="54a93af7-60c7-4f6c-99d2-fbb1f75f853a">
       <BuildDependency Project="src/common/Display/Display.vcxproj" />

doc/devdocs/modules/powerdisplay/mccsParserDesign.md

@@ -0,0 +1,223 @@
+# MCCS Capabilities String Parser - Recursive Descent Design
+
+## Overview
+
+This document describes the recursive descent parser implementation for DDC/CI MCCS (Monitor Control Command Set) capabilities strings.
+
+### Attention!
+This document and the code implement are generated by Copilot.
+
+## Grammar Definition (BNF)
+
+```bnf
+capabilities      ::= ['('] segment* [')']
+segment           ::= identifier '(' segment_content ')'
+segment_content   ::= text | vcp_entries | hex_list
+vcp_entries       ::= vcp_entry*
+vcp_entry         ::= hex_byte [ '(' hex_list ')' ]
+hex_list          ::= hex_byte*
+hex_byte          ::= [0-9A-Fa-f]{2}
+identifier        ::= [a-z_A-Z]+
+text              ::= [^()]+
+```
+
+## Example Input
+
+```
+(prot(monitor)type(lcd)model(PD3220U)cmds(01 02 03 07)vcp(10 12 14(04 05 06) 16 60(11 12 0F) DC DF)mccs_ver(2.2)vcpname(F0(Custom Setting)))
+```
+
+## Parser Architecture
+
+### Component Hierarchy
+
+```
+MccsCapabilitiesParser (main parser)
+├── ParseCapabilities()      → MccsParseResult
+├── ParseSegment()           → ParsedSegment?
+├── ParseBalancedContent()   → string
+├── ParseIdentifier()        → ReadOnlySpan<char>
+├── ApplySegment()           → void
+│   ├── ParseHexList()       → List<byte>
+│   ├── ParseVcpEntries()    → Dictionary<byte, VcpCodeInfo>
+│   └── ParseVcpNames()      → void
+│
+├── VcpEntryParser (sub-parser for vcp() content)
+│   └── TryParseEntry()      → VcpEntry
+│
+├── VcpNameParser (sub-parser for vcpname() content)
+│   └── TryParseEntry()      → (byte code, string name)
+│
+└── WindowParser (sub-parser for windowN() content)
+    ├── Parse()              → WindowCapability
+    └── ParseSubSegment()    → (name, content)?
+```
+
+### Design Principles
+
+1. **ref struct for Zero Allocation**
+   - Main parser uses `ref struct` to avoid heap allocation
+   - Works with `ReadOnlySpan<char>` for efficient string slicing
+   - No intermediate string allocations during parsing
+
+2. **Recursive Descent Pattern**
+   - Each grammar rule has a corresponding parse method
+   - Methods call each other recursively for nested structures
+   - Single-character lookahead via `Peek()`
+
+3. **Error Recovery**
+   - Errors are accumulated, not thrown
+   - Parser attempts to continue after errors
+   - Returns partial results when possible
+
+4. **Sub-parsers for Specialized Content**
+   - `VcpEntryParser` for VCP code entries
+   - `VcpNameParser` for custom VCP names
+   - Each sub-parser handles its own grammar subset
+
+## Parse Methods Detail
+
+### ParseCapabilities()
+Entry point. Handles optional outer parentheses and iterates through segments.
+
+```csharp
+private MccsParseResult ParseCapabilities()
+{
+    // Handle optional outer parens
+    // while (!IsAtEnd()) { ParseSegment() }
+    // Return result with accumulated errors
+}
+```
+
+### ParseSegment()
+Parses a single `identifier(content)` segment.
+
+```csharp
+private ParsedSegment? ParseSegment()
+{
+    // 1. ParseIdentifier()
+    // 2. Expect '('
+    // 3. ParseBalancedContent()
+    // 4. Expect ')'
+}
+```
+
+### ParseBalancedContent()
+Extracts content between balanced parentheses, handling nested parens.
+
+```csharp
+private string ParseBalancedContent()
+{
+    int depth = 1;
+    while (depth > 0) {
+        if (char == '(') depth++;
+        if (char == ')') depth--;
+    }
+}
+```
+
+### ParseVcpEntries()
+Delegates to `VcpEntryParser` for the specialized VCP entry grammar.
+
+```csharp
+vcp_entry ::= hex_byte [ '(' hex_list ')' ]
+
+Examples:
+- "10"           → code=0x10, values=[]
+- "14(04 05 06)" → code=0x14, values=[4, 5, 6]
+- "60(11 12 0F)" → code=0x60, values=[0x11, 0x12, 0x0F]
+```
+
+## Comparison with Other Approaches
+
+| Approach | Pros | Cons |
+|----------|------|------|
+| **Recursive Descent** (this) | Clear structure, handles nesting, extensible | More code |
+| **Regex** (DDCSharp) | Concise | Hard to debug, limited nesting |
+| **Mixed** (original) | Pragmatic | Inconsistent, hard to maintain |
+
+## Performance Characteristics
+
+- **Time Complexity**: O(n) where n = input length
+- **Space Complexity**: O(1) for parsing + O(m) for output where m = number of VCP codes
+- **Allocations**: Minimal - only for output structures
+
+## Supported Segments
+
+| Segment | Description | Parser |
+|---------|-------------|--------|
+| `prot(...)` | Protocol type | Direct assignment |
+| `type(...)` | Display type (lcd/crt) | Direct assignment |
+| `model(...)` | Model name | Direct assignment |
+| `cmds(...)` | Supported commands | ParseHexList |
+| `vcp(...)` | VCP code entries | VcpEntryParser |
+| `mccs_ver(...)` | MCCS version | Direct assignment |
+| `vcpname(...)` | Custom VCP names | VcpNameParser |
+| `windowN(...)` | PIP/PBP window capabilities | WindowParser |
+
+### Window Segment Format
+
+The `windowN` segment (where N is 1, 2, 3, etc.) describes PIP/PBP window capabilities:
+
+```
+window1(type(PIP) area(25 25 1895 1175) max(640 480) min(10 10) window(10))
+```
+
+| Sub-field | Format | Description |
+|-----------|--------|-------------|
+| `type` | `type(PIP)` or `type(PBP)` | Window type (Picture-in-Picture or Picture-by-Picture) |
+| `area` | `area(x1 y1 x2 y2)` | Window area coordinates in pixels |
+| `max` | `max(width height)` | Maximum window dimensions |
+| `min` | `min(width height)` | Minimum window dimensions |
+| `window` | `window(id)` | Window identifier |
+
+All sub-fields are optional; missing fields default to zero values.
+
+## Error Handling
+
+```csharp
+public readonly struct ParseError
+{
+    public int Position { get; }    // Character position
+    public string Message { get; }  // Human-readable error
+}
+
+public sealed class MccsParseResult
+{
+    public VcpCapabilities Capabilities { get; }
+    public IReadOnlyList<ParseError> Errors { get; }
+    public bool HasErrors => Errors.Count > 0;
+    public bool IsValid => !HasErrors && Capabilities.SupportedVcpCodes.Count > 0;
+}
+```
+
+## Usage Example
+
+```csharp
+// Parse capabilities string
+var result = MccsCapabilitiesParser.Parse(capabilitiesString);
+
+if (result.IsValid)
+{
+    var caps = result.Capabilities;
+    Console.WriteLine($"Model: {caps.Model}");
+    Console.WriteLine($"MCCS Version: {caps.MccsVersion}");
+    Console.WriteLine($"VCP Codes: {caps.SupportedVcpCodes.Count}");
+}
+
+if (result.HasErrors)
+{
+    foreach (var error in result.Errors)
+    {
+        Console.WriteLine($"Parse error at {error.Position}: {error.Message}");
+    }
+}
+```
+
+## Edge Cases Handled
+
+1. **Missing outer parentheses** (Apple Cinema Display)
+2. **No spaces between hex bytes** (`010203` vs `01 02 03`)
+3. **Nested parentheses** in VCP values
+4. **Unknown segments** (logged but not fatal)
+5. **Malformed input** (partial results returned)

installer/PowerToysSetupCustomActionsVNext/CustomAction.cpp

@@ -1549,7 +1549,7 @@ UINT __stdcall TerminateProcessesCA(MSIHANDLE hInstall)
     }
     processes.resize(bytes / sizeof(processes[0]));
 
-    std::array<std::wstring_view, 42> processesToTerminate = {
+    std::array<std::wstring_view, 43> processesToTerminate = {
         L"PowerToys.PowerLauncher.exe",
         L"PowerToys.Settings.exe",
         L"PowerToys.AdvancedPaste.exe",
@@ -1565,6 +1565,7 @@ UINT __stdcall TerminateProcessesCA(MSIHANDLE hInstall)
         L"PowerToys.PowerRename.exe",
         L"PowerToys.ImageResizer.exe",
         L"PowerToys.LightSwitchService.exe",
+        L"PowerToys.PowerDisplay.exe",
         L"PowerToys.GcodeThumbnailProvider.exe",
         L"PowerToys.BgcodeThumbnailProvider.exe",
         L"PowerToys.PdfThumbnailProvider.exe",

installer/PowerToysSetupVNext/PowerDisplay.wxs

@@ -0,0 +1,29 @@
+<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs"
+     xmlns:util="http://wixtoolset.org/schemas/v4/wxs/util" >
+
+  <?include $(sys.CURRENTDIR)\Common.wxi?>
+
+  <?define PowerDisplayAssetsFiles=?>
+  <?define PowerDisplayAssetsFilesPath=$(var.BinDir)WinUI3Apps\Assets\PowerDisplay?>
+
+  <Fragment>
+    <!-- Power Display -->
+    <DirectoryRef Id="WinUI3AppsAssetsFolder">
+      <Directory Id="PowerDisplayAssetsInstallFolder" Name="PowerDisplay" />
+    </DirectoryRef>
+    <DirectoryRef Id="PowerDisplayAssetsInstallFolder" FileSource="$(var.PowerDisplayAssetsFilesPath)">
+    <!-- Generated by generateFileComponents.ps1 -->
+    <!--PowerDisplayAssetsFiles_Component_Def-->
+    </DirectoryRef>
+
+    <ComponentGroup Id="PowerDisplayComponentGroup">
+      <Component Id="RemovePowerDisplayFolder" Guid="B8F2E3A5-72C1-4A2D-9B3F-8E5D7C6A4F9B" Directory="PowerDisplayAssetsInstallFolder" >
+        <RegistryKey Root="$(var.RegistryScope)" Key="Software\Classes\powertoys\components">
+          <RegistryValue Type="string" Name="RemovePowerDisplayFolder" Value="" KeyPath="yes"/>
+        </RegistryKey>
+        <RemoveFolder Id="RemoveFolderPowerDisplayAssetsFolder" Directory="PowerDisplayAssetsInstallFolder" On="uninstall"/>
+      </Component>
+    </ComponentGroup>
+
+  </Fragment>
+</Wix>

installer/PowerToysSetupVNext/PowerToysInstallerVNext.wixproj

@@ -47,6 +47,7 @@ call powershell.exe -NonInteractive -executionpolicy Unrestricted -File $(MSBuil
       call move /Y ..\..\..\NewPlus.wxs.bk ..\..\..\NewPlus.wxs
       call move /Y ..\..\..\Peek.wxs.bk ..\..\..\Peek.wxs
       call move /Y ..\..\..\PowerRename.wxs.bk ..\..\..\PowerRename.wxs
+      call move /Y ..\..\..\PowerDisplay.wxs.bk ..\..\..\PowerDisplay.wxs
       call move /Y ..\..\..\Product.wxs.bk ..\..\..\Product.wxs
       call move /Y ..\..\..\RegistryPreview.wxs.bk ..\..\..\RegistryPreview.wxs
       call move /Y ..\..\..\Resources.wxs.bk ..\..\..\Resources.wxs
@@ -123,6 +124,7 @@ call powershell.exe -NonInteractive -executionpolicy Unrestricted -File $(MSBuil
     <Compile Include="KeyboardManager.wxs" />
     <Compile Include="Peek.wxs" />
     <Compile Include="PowerRename.wxs" />
+    <Compile Include="PowerDisplay.wxs" />
     <Compile Include="DscResources.wxs" />
     <Compile Include="RegistryPreview.wxs" />
     <Compile Include="Run.wxs" />

installer/PowerToysSetupVNext/Product.wxs

@@ -53,6 +53,7 @@
       <ComponentGroupRef Id="LightSwitchComponentGroup" />
       <ComponentGroupRef Id="PeekComponentGroup" />
       <ComponentGroupRef Id="PowerRenameComponentGroup" />
+      <ComponentGroupRef Id="PowerDisplayComponentGroup" />
       <ComponentGroupRef Id="RegistryPreviewComponentGroup" />
       <ComponentGroupRef Id="RunComponentGroup" />
       <ComponentGroupRef Id="SettingsComponentGroup" />

installer/PowerToysSetupVNext/generateAllFileComponents.ps1

@@ -176,6 +176,10 @@ Generate-FileComponents -fileListName "ImageResizerAssetsFiles" -wxsFilePath $PS
 Generate-FileList -fileDepsJson "" -fileListName LightSwitchFiles -wxsFilePath $PSScriptRoot\LightSwitch.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\LightSwitchService"
 Generate-FileComponents -fileListName "LightSwitchFiles" -wxsFilePath $PSScriptRoot\LightSwitch.wxs
 
+#PowerDisplay
+Generate-FileList -fileDepsJson "" -fileListName PowerDisplayAssetsFiles -wxsFilePath $PSScriptRoot\PowerDisplay.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps\Assets\PowerDisplay"
+Generate-FileComponents -fileListName "PowerDisplayAssetsFiles" -wxsFilePath $PSScriptRoot\PowerDisplay.wxs
+
 #New+
 Generate-FileList -fileDepsJson "" -fileListName NewPlusAssetsFiles -wxsFilePath $PSScriptRoot\NewPlus.wxs -depsPath "$PSScriptRoot..\..\..\$platform\Release\WinUI3Apps\Assets\NewPlus"
 Generate-FileComponents -fileListName "NewPlusAssetsFiles" -wxsFilePath $PSScriptRoot\NewPlus.wxs

src/common/Common.UI/SettingsDeepLink.cs

@@ -45,6 +45,7 @@ namespace Common.UI
             NewPlus,
             CmdPal,
             ZoomIt,
+            PowerDisplay,
         }
 
         private static string SettingsWindowNameToString(SettingsWindow value)
@@ -115,6 +116,8 @@ namespace Common.UI
                     return "CmdPal";
                 case SettingsWindow.ZoomIt:
                     return "ZoomIt";
+                case SettingsWindow.PowerDisplay:
+                    return "PowerDisplay";
                 default:
                     {
                         return string.Empty;

src/common/GPOWrapper/GPOWrapper.cpp

@@ -32,6 +32,10 @@ namespace winrt::PowerToys::GPOWrapper::implementation
     {
         return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredLightSwitchEnabledValue());
     }
+    GpoRuleConfigured GPOWrapper::GetConfiguredPowerDisplayEnabledValue()
+    {
+        return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredPowerDisplayEnabledValue());
+    }
     GpoRuleConfigured GPOWrapper::GetConfiguredFancyZonesEnabledValue()
     {
         return static_cast<GpoRuleConfigured>(powertoys_gpo::getConfiguredFancyZonesEnabledValue());

src/common/GPOWrapper/GPOWrapper.h

@@ -14,6 +14,7 @@ namespace winrt::PowerToys::GPOWrapper::implementation
         static GpoRuleConfigured GetConfiguredColorPickerEnabledValue();
         static GpoRuleConfigured GetConfiguredCropAndLockEnabledValue();
         static GpoRuleConfigured GetConfiguredLightSwitchEnabledValue();
+        static GpoRuleConfigured GetConfiguredPowerDisplayEnabledValue();
         static GpoRuleConfigured GetConfiguredFancyZonesEnabledValue();
         static GpoRuleConfigured GetConfiguredFileLocksmithEnabledValue();
         static GpoRuleConfigured GetConfiguredSvgPreviewEnabledValue();

src/common/GPOWrapper/GPOWrapper.idl

@@ -18,6 +18,7 @@ namespace PowerToys
             static GpoRuleConfigured GetConfiguredColorPickerEnabledValue();
             static GpoRuleConfigured GetConfiguredCropAndLockEnabledValue();
             static GpoRuleConfigured GetConfiguredLightSwitchEnabledValue();
+            static GpoRuleConfigured GetConfiguredPowerDisplayEnabledValue();
             static GpoRuleConfigured GetConfiguredFancyZonesEnabledValue();
             static GpoRuleConfigured GetConfiguredFileLocksmithEnabledValue();
             static GpoRuleConfigured GetConfiguredSvgPreviewEnabledValue();

src/common/ManagedCommon/ModuleType.cs

@@ -30,6 +30,7 @@ namespace ManagedCommon
         PowerRename,
         PowerLauncher,
         PowerAccent,
+        PowerDisplay,
         RegistryPreview,
         MeasureTool,
         ShortcutGuide,

src/common/interop/Constants.cpp

@@ -247,4 +247,36 @@ namespace winrt::PowerToys::Interop::implementation
     {
         return CommonSharedConstants::CMDPAL_SHOW_EVENT;
     }
+    hstring Constants::TogglePowerDisplayEvent()
+    {
+        return CommonSharedConstants::TOGGLE_POWER_DISPLAY_EVENT;
+    }
+    hstring Constants::TerminatePowerDisplayEvent()
+    {
+        return CommonSharedConstants::TERMINATE_POWER_DISPLAY_EVENT;
+    }
+    hstring Constants::RefreshPowerDisplayMonitorsEvent()
+    {
+        return CommonSharedConstants::REFRESH_POWER_DISPLAY_MONITORS_EVENT;
+    }
+    hstring Constants::SettingsUpdatedPowerDisplayEvent()
+    {
+        return CommonSharedConstants::SETTINGS_UPDATED_POWER_DISPLAY_EVENT;
+    }
+    hstring Constants::ApplyColorTemperaturePowerDisplayEvent()
+    {
+        return CommonSharedConstants::APPLY_COLOR_TEMPERATURE_POWER_DISPLAY_EVENT;
+    }
+    hstring Constants::ApplyProfilePowerDisplayEvent()
+    {
+        return CommonSharedConstants::APPLY_PROFILE_POWER_DISPLAY_EVENT;
+    }
+    hstring Constants::PowerDisplaySendSettingsTelemetryEvent()
+    {
+        return CommonSharedConstants::POWER_DISPLAY_SEND_SETTINGS_TELEMETRY_EVENT;
+    }
+    hstring Constants::HotkeyUpdatedPowerDisplayEvent()
+    {
+        return CommonSharedConstants::HOTKEY_UPDATED_POWER_DISPLAY_EVENT;
+    }
 }

src/common/interop/Constants.h

@@ -65,6 +65,14 @@ namespace winrt::PowerToys::Interop::implementation
         static hstring WorkspacesHotkeyEvent();
         static hstring PowerToysRunnerTerminateSettingsEvent();
         static hstring ShowCmdPalEvent();
+        static hstring TogglePowerDisplayEvent();
+        static hstring TerminatePowerDisplayEvent();
+        static hstring RefreshPowerDisplayMonitorsEvent();
+        static hstring SettingsUpdatedPowerDisplayEvent();
+        static hstring ApplyColorTemperaturePowerDisplayEvent();
+        static hstring ApplyProfilePowerDisplayEvent();
+        static hstring PowerDisplaySendSettingsTelemetryEvent();
+        static hstring HotkeyUpdatedPowerDisplayEvent();
     };
 }
 

src/common/interop/Constants.idl

@@ -62,6 +62,14 @@ namespace PowerToys
             static String WorkspacesHotkeyEvent();
             static String PowerToysRunnerTerminateSettingsEvent();
             static String ShowCmdPalEvent();
+            static String TogglePowerDisplayEvent();
+            static String TerminatePowerDisplayEvent();
+            static String RefreshPowerDisplayMonitorsEvent();
+            static String SettingsUpdatedPowerDisplayEvent();
+            static String ApplyColorTemperaturePowerDisplayEvent();
+            static String ApplyProfilePowerDisplayEvent();
+            static String PowerDisplaySendSettingsTelemetryEvent();
+            static String HotkeyUpdatedPowerDisplayEvent();
         }
     }
 }

src/common/interop/shared_constants.h

@@ -148,6 +148,20 @@ namespace CommonSharedConstants
     const wchar_t ZOOMIT_SNIP_EVENT[] = L"Local\\PowerToysZoomIt-SnipEvent-2fd9c211-436d-4f17-a902-2528aaae3e30";
     const wchar_t ZOOMIT_RECORD_EVENT[] = L"Local\\PowerToysZoomIt-RecordEvent-74539344-eaad-4711-8e83-23946e424512";
 
+    // Path to the events used by PowerDisplay
+    const wchar_t TOGGLE_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-ToggleEvent-5f1a9c3e-7d2b-4e8f-9a6c-3b5d7e9f1a2c";
+    const wchar_t TERMINATE_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-TerminateEvent-7b9c2e1f-8a5d-4c3e-9f6b-2a1d8c5e3b7a";
+    const wchar_t REFRESH_POWER_DISPLAY_MONITORS_EVENT[] = L"Local\\PowerToysPowerDisplay-RefreshMonitorsEvent-a3f5c8e7-9d1b-4e2f-8c6a-3b5d7e9f1a2c";
+    const wchar_t SETTINGS_UPDATED_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-SettingsUpdatedEvent-2e4d6f8a-1c3b-5e7f-9a1d-4c6e8f0b2d3e";
+    const wchar_t APPLY_COLOR_TEMPERATURE_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-ApplyColorTemperatureEvent-4b7e9f2a-3c6d-5a8e-7f1b-9d2e4c6a8b0d";
+    const wchar_t APPLY_PROFILE_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-ApplyProfileEvent-6e8a3c9d-4f7b-5d2e-8a1c-3e9f7b6d2a5c";
+    const wchar_t POWER_DISPLAY_SEND_SETTINGS_TELEMETRY_EVENT[] = L"Local\\PowerToysPowerDisplay-SettingsTelemetryEvent-8c4f2a1d-5e3b-7f9c-1a6d-3b8e5f2c9a7d";
+    const wchar_t HOTKEY_UPDATED_POWER_DISPLAY_EVENT[] = L"Local\\PowerToysPowerDisplay-HotkeyUpdatedEvent-9d5f3a2b-7e1c-4b8a-6f3d-2a9e5c7b1d4f";
+
+    // Path to the events used by LightSwitch to notify PowerDisplay of theme changes
+    const wchar_t LIGHT_SWITCH_LIGHT_THEME_EVENT[] = L"Local\\PowerToysLightSwitch-LightThemeEvent-50077121-2ffc-4841-9c86-ab1bd3f9baca";
+    const wchar_t LIGHT_SWITCH_DARK_THEME_EVENT[] = L"Local\\PowerToysLightSwitch-DarkThemeEvent-b3a835c0-eaa2-49b0-b8eb-f793e3df3368";
+
     // used from quick access window
     const wchar_t CMDPAL_SHOW_EVENT[] = L"Local\\PowerToysCmdPal-ShowEvent-62336fcd-8611-4023-9b30-091a6af4cc5a";
     const wchar_t CMDPAL_EXIT_EVENT[] = L"Local\\PowerToysCmdPal-ExitEvent-eb73f6be-3f22-4b36-aee3-62924ba40bfd";

src/common/logger/logger_settings.h

@@ -83,6 +83,7 @@ struct LogSettings
     inline const static std::wstring workspacesSnapshotToolLogPath = L"workspaces-snapshot-tool-log.log";
     inline const static std::string zoomItLoggerName = "zoom-it";
     inline const static std::string lightSwitchLoggerName = "light-switch";
+    inline const static std::string powerDisplayLoggerName = "powerdisplay";
     inline const static int retention = 30;
     std::wstring logLevel;
     LogSettings();

src/common/utils/gpo.h

@@ -32,6 +32,7 @@ namespace powertoys_gpo
     const std::wstring POLICY_CONFIGURE_ENABLED_COLOR_PICKER = L"ConfigureEnabledUtilityColorPicker";
     const std::wstring POLICY_CONFIGURE_ENABLED_CROP_AND_LOCK = L"ConfigureEnabledUtilityCropAndLock";
     const std::wstring POLICY_CONFIGURE_ENABLED_LIGHT_SWITCH = L"ConfigureEnabledUtilityLightSwitch";
+    const std::wstring POLICY_CONFIGURE_ENABLED_POWER_DISPLAY = L"ConfigureEnabledUtilityPowerDisplay";
     const std::wstring POLICY_CONFIGURE_ENABLED_FANCYZONES = L"ConfigureEnabledUtilityFancyZones";
     const std::wstring POLICY_CONFIGURE_ENABLED_FILE_LOCKSMITH = L"ConfigureEnabledUtilityFileLocksmith";
     const std::wstring POLICY_CONFIGURE_ENABLED_SVG_PREVIEW = L"ConfigureEnabledUtilityFileExplorerSVGPreview";
@@ -310,6 +311,11 @@ namespace powertoys_gpo
         return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_LIGHT_SWITCH);
     }
 
+    inline gpo_rule_configured_t getConfiguredPowerDisplayEnabledValue()
+    {
+        return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_POWER_DISPLAY);
+    }
+
     inline gpo_rule_configured_t getConfiguredFancyZonesEnabledValue()
     {
         return getUtilityEnabledValue(POLICY_CONFIGURE_ENABLED_FANCYZONES);

src/gpo/assets/PowerToys.admx

@@ -148,6 +148,16 @@
         <decimal value="0" />
       </disabledValue>
     </policy>
+    <policy name="ConfigureEnabledUtilityPowerDisplay" class="Both" displayName="$(string.ConfigureEnabledUtilityPowerDisplay)" explainText="$(string.ConfigureEnabledUtilityDescription)" key="Software\Policies\PowerToys" valueName="ConfigureEnabledUtilityPowerDisplay">
+      <parentCategory ref="PowerToys" />
+      <supportedOn ref="SUPPORTED_POWERTOYS_0_95_0" />
+      <enabledValue>
+        <decimal value="1" />
+      </enabledValue>
+      <disabledValue>
+        <decimal value="0" />
+      </disabledValue>
+    </policy>
     <policy name="ConfigureEnabledUtilityEnvironmentVariables" class="Both" displayName="$(string.ConfigureEnabledUtilityEnvironmentVariables)" explainText="$(string.ConfigureEnabledUtilityDescription)" key="Software\Policies\PowerToys" valueName="ConfigureEnabledUtilityEnvironmentVariables">
       <parentCategory ref="PowerToys" />
       <supportedOn ref="SUPPORTED_POWERTOYS_0_75_0" />

src/gpo/assets/en-US/PowerToys.adml

@@ -247,6 +247,7 @@ If you don't configure this policy, the user will be able to control the setting
       <string id="ConfigureEnabledUtilityCmdPal">CmdPal: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityCropAndLock">Crop And Lock: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityLightSwitch">Light Switch: Configure enabled state</string>
+      <string id="ConfigureEnabledUtilityPowerDisplay">PowerDisplay: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityEnvironmentVariables">Environment Variables: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityFancyZones">FancyZones: Configure enabled state</string>
       <string id="ConfigureEnabledUtilityFileLocksmith">File Locksmith: Configure enabled state</string>

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp

@@ -241,6 +241,46 @@ void LightSwitchSettings::LoadSettings()
                 NotifyObservers(SettingId::ChangeApps);
             }
         }
+
+        // EnableDarkModeProfile
+        if (const auto jsonVal = values.get_bool_value(L"enableDarkModeProfile"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.enableDarkModeProfile != val)
+            {
+                m_settings.enableDarkModeProfile = val;
+            }
+        }
+
+        // EnableLightModeProfile
+        if (const auto jsonVal = values.get_bool_value(L"enableLightModeProfile"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.enableLightModeProfile != val)
+            {
+                m_settings.enableLightModeProfile = val;
+            }
+        }
+
+        // DarkModeProfile
+        if (const auto jsonVal = values.get_string_value(L"darkModeProfile"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.darkModeProfile != val)
+            {
+                m_settings.darkModeProfile = val;
+            }
+        }
+
+        // LightModeProfile
+        if (const auto jsonVal = values.get_string_value(L"lightModeProfile"))
+        {
+            auto val = *jsonVal;
+            if (m_settings.lightModeProfile != val)
+            {
+                m_settings.lightModeProfile = val;
+            }
+        }
     }
     catch (...)
     {

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.h

@@ -67,6 +67,11 @@ struct LightSwitchConfig
 
     bool changeSystem = false;
     bool changeApps = false;
+
+    bool enableDarkModeProfile = false;
+    bool enableLightModeProfile = false;
+    std::wstring darkModeProfile = L"";
+    std::wstring lightModeProfile = L"";
 };
 
 class LightSwitchSettings

src/modules/LightSwitch/LightSwitchService/LightSwitchStateManager.cpp

@@ -4,6 +4,7 @@
 #include <LightSwitchUtils.h>
 #include "ThemeScheduler.h"
 #include <ThemeHelper.h>
+#include <common/interop/shared_constants.h>
 
 void ApplyTheme(bool shouldBeLight);
 
@@ -37,7 +38,7 @@ void LightSwitchStateManager::OnTick(int currentMinutes)
     }
 }
 
-// Called when manual override is triggered
+// Called when manual override is triggered (via hotkey)
 void LightSwitchStateManager::OnManualOverride()
 {
     std::lock_guard<std::mutex> lock(_stateMutex);
@@ -45,15 +46,19 @@ void LightSwitchStateManager::OnManualOverride()
     _state.isManualOverride = !_state.isManualOverride;
 
     // When entering manual override, sync internal theme state to match the current system
+    // The hotkey handler in ModuleInterface has already toggled the theme, so we read the new state
     if (_state.isManualOverride)
     {
         _state.isSystemLightActive = GetCurrentSystemTheme();
-
         _state.isAppsLightActive = GetCurrentAppsTheme();
 
         Logger::debug(L"[LightSwitchStateManager] Synced internal theme state to current system theme ({}) and apps theme ({}).",
                       (_state.isSystemLightActive ? L"light" : L"dark"),
                       (_state.isAppsLightActive ? L"light" : L"dark"));
+
+        // Notify PowerDisplay about the theme change triggered by hotkey
+        // The theme has already been applied by ModuleInterface, we just need to notify PowerDisplay
+        NotifyPowerDisplay(_state.isSystemLightActive);
     }
 
     EvaluateAndApplyIfNeeded();
@@ -264,7 +269,61 @@ void LightSwitchStateManager::EvaluateAndApplyIfNeeded()
 
         _state.isSystemLightActive = GetCurrentSystemTheme();
         _state.isAppsLightActive = GetCurrentAppsTheme();
+
+        // Notify PowerDisplay to apply display profile if configured
+        NotifyPowerDisplay(shouldBeLight);
     }
 
     _state.lastTickMinutes = now;
 }
+
+// Notify PowerDisplay module about theme change to apply display profiles
+void LightSwitchStateManager::NotifyPowerDisplay(bool isLight)
+{
+    const auto& settings = LightSwitchSettings::settings();
+
+    // Check if any profile is enabled and configured
+    bool shouldNotify = false;
+
+    if (isLight && settings.enableLightModeProfile && !settings.lightModeProfile.empty())
+    {
+        shouldNotify = true;
+    }
+    else if (!isLight && settings.enableDarkModeProfile && !settings.darkModeProfile.empty())
+    {
+        shouldNotify = true;
+    }
+
+    if (!shouldNotify)
+    {
+        return;
+    }
+
+    try
+    {
+        // Signal PowerDisplay with the specific theme event
+        // Using separate events for light/dark eliminates race conditions where PowerDisplay
+        // might read the registry before LightSwitch has finished updating it
+        const wchar_t* eventName = isLight
+            ? CommonSharedConstants::LIGHT_SWITCH_LIGHT_THEME_EVENT
+            : CommonSharedConstants::LIGHT_SWITCH_DARK_THEME_EVENT;
+
+        Logger::info(L"[LightSwitchStateManager] Notifying PowerDisplay about theme change (isLight: {})", isLight);
+
+        HANDLE hThemeEvent = CreateEventW(nullptr, FALSE, FALSE, eventName);
+        if (hThemeEvent)
+        {
+            SetEvent(hThemeEvent);
+            CloseHandle(hThemeEvent);
+            Logger::info(L"[LightSwitchStateManager] Theme event signaled to PowerDisplay: {}", eventName);
+        }
+        else
+        {
+            Logger::warn(L"[LightSwitchStateManager] Failed to create theme event (error: {})", GetLastError());
+        }
+    }
+    catch (...)
+    {
+        Logger::error(L"[LightSwitchStateManager] Failed to notify PowerDisplay");
+    }
+}

src/modules/LightSwitch/LightSwitchService/LightSwitchStateManager.h

@@ -48,4 +48,7 @@ private:
 
     void EvaluateAndApplyIfNeeded();
     bool CoordinatesAreValid(const std::wstring& lat, const std::wstring& lon);
+
+    // Notify PowerDisplay module about theme change to apply display profiles
+    void NotifyPowerDisplay(bool isLight);
 };

src/modules/powerdisplay/PowerDisplay.Lib.UnitTests/MccsCapabilitiesParserTests.cs

@@ -0,0 +1,741 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Linq;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using PowerDisplay.Common.Utils;
+
+namespace PowerDisplay.UnitTests;
+
+/// <summary>
+/// Unit tests for MccsCapabilitiesParser class.
+/// Tests parsing of DDC/CI MCCS capabilities strings using real-world examples.
+/// Reference: https://www.ddcutil.com/cap_u3011_verbose_output/
+/// </summary>
+[TestClass]
+public class MccsCapabilitiesParserTests
+{
+    // Real capabilities string from Dell U3011 monitor
+    // Source: https://www.ddcutil.com/cap_u3011_verbose_output/
+    private const string DellU3011Capabilities =
+        "(prot(monitor)type(lcd)model(U3011)cmds(01 02 03 07 0C E3 F3)vcp(02 04 05 06 08 10 12 14(01 05 08 0B 0C) 16 18 1A 52 60(01 03 04 0C 0F 11 12) AC AE B2 B6 C6 C8 C9 D6(01 04 05) DC(00 02 03 04 05) DF FD)mccs_ver(2.1)mswhql(1))";
+
+    // Real capabilities string from Dell P2416D monitor
+    private const string DellP2416DCapabilities =
+        "(prot(monitor)type(LCD)model(P2416D)cmds(01 02 03 07 0C E3 F3) vcp(02 04 05 08 10 12 14(05 08 0B 0C) 16 18 1A 52 60(01 11 0F) AA(01 02) AC AE B2 B6 C6 C8 C9 D6(01 04 05) DC(00 02 03 05) DF E0 E1 E2(00 01 02 04 0E 12 14 19) F0(00 08) F1(01 02) F2 FD) mswhql(1)asset_eep(40)mccs_ver(2.1))";
+
+    // Simple test string
+    private const string SimpleCapabilities =
+        "(prot(monitor)type(lcd)model(TestMonitor)vcp(10 12)mccs_ver(2.2))";
+
+    // Capabilities without outer parentheses (some monitors like Apple Cinema Display)
+    private const string NoOuterParensCapabilities =
+        "prot(monitor)type(lcd)model(TestMonitor)vcp(10 12)mccs_ver(2.0)";
+
+    // Concatenated hex format (no spaces between hex bytes)
+    private const string ConcatenatedHexCapabilities =
+        "(prot(monitor)cmds(01020307)vcp(101214)mccs_ver(2.1))";
+
+    [TestMethod]
+    public void Parse_NullInput_ReturnsEmptyCapabilities()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(null);
+
+        // Assert
+        Assert.IsNotNull(result);
+        Assert.IsNotNull(result.Capabilities);
+        Assert.AreEqual(0, result.Capabilities.SupportedVcpCodes.Count);
+        Assert.IsFalse(result.HasErrors);
+    }
+
+    [TestMethod]
+    public void Parse_EmptyString_ReturnsEmptyCapabilities()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(string.Empty);
+
+        // Assert
+        Assert.IsNotNull(result);
+        Assert.AreEqual(0, result.Capabilities.SupportedVcpCodes.Count);
+    }
+
+    [TestMethod]
+    public void Parse_WhitespaceOnly_ReturnsEmptyCapabilities()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse("   \t\n  ");
+
+        // Assert
+        Assert.IsNotNull(result);
+        Assert.AreEqual(0, result.Capabilities.SupportedVcpCodes.Count);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesProtocol()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        Assert.AreEqual("monitor", result.Capabilities.Protocol);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesType()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        Assert.AreEqual("lcd", result.Capabilities.Type);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesModel()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        Assert.AreEqual("U3011", result.Capabilities.Model);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesMccsVersion()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        Assert.AreEqual("2.1", result.Capabilities.MccsVersion);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesCommands()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        var cmds = result.Capabilities.SupportedCommands;
+        Assert.IsNotNull(cmds);
+        Assert.AreEqual(7, cmds.Count);
+        CollectionAssert.Contains(cmds, (byte)0x01);
+        CollectionAssert.Contains(cmds, (byte)0x02);
+        CollectionAssert.Contains(cmds, (byte)0x03);
+        CollectionAssert.Contains(cmds, (byte)0x07);
+        CollectionAssert.Contains(cmds, (byte)0x0C);
+        CollectionAssert.Contains(cmds, (byte)0xE3);
+        CollectionAssert.Contains(cmds, (byte)0xF3);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesBrightnessVcpCode()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP 0x10 is Brightness
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        var brightnessInfo = result.Capabilities.GetVcpCodeInfo(0x10);
+        Assert.IsNotNull(brightnessInfo);
+        Assert.AreEqual(0x10, brightnessInfo.Value.Code);
+        Assert.IsTrue(brightnessInfo.Value.IsContinuous);
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesContrastVcpCode()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP 0x12 is Contrast
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesInputSourceWithDiscreteValues()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP 0x60 is Input Source with discrete values
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x60));
+        var inputSourceInfo = result.Capabilities.GetVcpCodeInfo(0x60);
+        Assert.IsNotNull(inputSourceInfo);
+        Assert.IsTrue(inputSourceInfo.Value.HasDiscreteValues);
+
+        // Should have values: 01 03 04 0C 0F 11 12
+        var values = inputSourceInfo.Value.SupportedValues;
+        Assert.AreEqual(7, values.Count);
+        Assert.IsTrue(values.Contains(0x01));
+        Assert.IsTrue(values.Contains(0x03));
+        Assert.IsTrue(values.Contains(0x04));
+        Assert.IsTrue(values.Contains(0x0C));
+        Assert.IsTrue(values.Contains(0x0F));
+        Assert.IsTrue(values.Contains(0x11));
+        Assert.IsTrue(values.Contains(0x12));
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesColorPresetWithDiscreteValues()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP 0x14 is Color Preset
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x14));
+        var colorPresetInfo = result.Capabilities.GetVcpCodeInfo(0x14);
+        Assert.IsNotNull(colorPresetInfo);
+        Assert.IsTrue(colorPresetInfo.Value.HasDiscreteValues);
+
+        // Should have values: 01 05 08 0B 0C
+        var values = colorPresetInfo.Value.SupportedValues;
+        Assert.AreEqual(5, values.Count);
+        Assert.IsTrue(values.Contains(0x01));
+        Assert.IsTrue(values.Contains(0x05));
+        Assert.IsTrue(values.Contains(0x08));
+        Assert.IsTrue(values.Contains(0x0B));
+        Assert.IsTrue(values.Contains(0x0C));
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_ParsesPowerModeWithDiscreteValues()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP 0xD6 is Power Mode
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xD6));
+        var powerModeInfo = result.Capabilities.GetVcpCodeInfo(0xD6);
+        Assert.IsNotNull(powerModeInfo);
+        Assert.IsTrue(powerModeInfo.Value.HasDiscreteValues);
+
+        // Should have values: 01 04 05
+        var values = powerModeInfo.Value.SupportedValues;
+        Assert.AreEqual(3, values.Count);
+        Assert.IsTrue(values.Contains(0x01));
+        Assert.IsTrue(values.Contains(0x04));
+        Assert.IsTrue(values.Contains(0x05));
+    }
+
+    [TestMethod]
+    public void Parse_DellU3011_TotalVcpCodeCount()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert - VCP codes: 02 04 05 06 08 10 12 14 16 18 1A 52 60 AC AE B2 B6 C6 C8 C9 D6 DC DF FD
+        Assert.AreEqual(24, result.Capabilities.SupportedVcpCodes.Count);
+    }
+
+    [TestMethod]
+    public void Parse_DellP2416D_ParsesModel()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellP2416DCapabilities);
+
+        // Assert
+        Assert.AreEqual("P2416D", result.Capabilities.Model);
+    }
+
+    [TestMethod]
+    public void Parse_DellP2416D_ParsesTypeWithDifferentCase()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellP2416DCapabilities);
+
+        // Assert - Type is "LCD" (uppercase) in this monitor
+        Assert.AreEqual("LCD", result.Capabilities.Type);
+    }
+
+    [TestMethod]
+    public void Parse_DellP2416D_ParsesMccsVersion()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellP2416DCapabilities);
+
+        // Assert
+        Assert.AreEqual("2.1", result.Capabilities.MccsVersion);
+    }
+
+    [TestMethod]
+    public void Parse_DellP2416D_ParsesInputSourceWithThreeValues()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellP2416DCapabilities);
+
+        // Assert - VCP 0x60 Input Source has values: 01 11 0F
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x60));
+        var inputSourceInfo = result.Capabilities.GetVcpCodeInfo(0x60);
+        Assert.IsNotNull(inputSourceInfo);
+
+        var values = inputSourceInfo.Value.SupportedValues;
+        Assert.AreEqual(3, values.Count);
+        Assert.IsTrue(values.Contains(0x01));
+        Assert.IsTrue(values.Contains(0x11));
+        Assert.IsTrue(values.Contains(0x0F));
+    }
+
+    [TestMethod]
+    public void Parse_DellP2416D_ParsesE2WithManyValues()
+    {
+        // Act
+        var result = MccsCapabilitiesParser.Parse(DellP2416DCapabilities);
+
+        // Assert - VCP 0xE2 has values: 00 01 02 04 0E 12 14 19
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xE2));
+        var e2Info = result.Capabilities.GetVcpCodeInfo(0xE2);
+        Assert.IsNotNull(e2Info);
+
+        var values = e2Info.Value.SupportedValues;
+        Assert.AreEqual(8, values.Count);
+    }
+
+    [TestMethod]
+    public void Parse_NoOuterParentheses_StillParses()
+    {
+        // Act - Some monitors like Apple Cinema Display omit outer parens
+        var result = MccsCapabilitiesParser.Parse(NoOuterParensCapabilities);
+
+        // Assert
+        Assert.AreEqual("monitor", result.Capabilities.Protocol);
+        Assert.AreEqual("lcd", result.Capabilities.Type);
+        Assert.AreEqual("TestMonitor", result.Capabilities.Model);
+        Assert.AreEqual("2.0", result.Capabilities.MccsVersion);
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+    }
+
+    [TestMethod]
+    public void Parse_ConcatenatedHexFormat_ParsesCorrectly()
+    {
+        // Act - Some monitors output hex without spaces: cmds(01020307)
+        var result = MccsCapabilitiesParser.Parse(ConcatenatedHexCapabilities);
+
+        // Assert
+        var cmds = result.Capabilities.SupportedCommands;
+        Assert.AreEqual(4, cmds.Count);
+        CollectionAssert.Contains(cmds, (byte)0x01);
+        CollectionAssert.Contains(cmds, (byte)0x02);
+        CollectionAssert.Contains(cmds, (byte)0x03);
+        CollectionAssert.Contains(cmds, (byte)0x07);
+
+        // VCP codes without spaces
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x14));
+    }
+
+    [TestMethod]
+    public void Parse_NestedParenthesesInVcp_HandlesCorrectly()
+    {
+        // Arrange - VCP code 0x14 with nested discrete values
+        var input = "(vcp(14(01 05 08)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x14));
+        var vcpInfo = result.Capabilities.GetVcpCodeInfo(0x14);
+        Assert.IsNotNull(vcpInfo);
+        Assert.AreEqual(3, vcpInfo.Value.SupportedValues.Count);
+    }
+
+    [TestMethod]
+    public void Parse_MultipleVcpCodesWithMixedFormats_ParsesAll()
+    {
+        // Arrange - Mixed: some with values, some without
+        var input = "(vcp(10 12 14(01 05) 16 60(0F 11)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.AreEqual(5, result.Capabilities.SupportedVcpCodes.Count);
+
+        // Continuous codes (no discrete values)
+        var brightness = result.Capabilities.GetVcpCodeInfo(0x10);
+        Assert.IsTrue(brightness?.IsContinuous ?? false);
+
+        var contrast = result.Capabilities.GetVcpCodeInfo(0x12);
+        Assert.IsTrue(contrast?.IsContinuous ?? false);
+
+        // Discrete codes (with values)
+        var colorPreset = result.Capabilities.GetVcpCodeInfo(0x14);
+        Assert.IsTrue(colorPreset?.HasDiscreteValues ?? false);
+        Assert.AreEqual(2, colorPreset?.SupportedValues.Count);
+
+        var inputSource = result.Capabilities.GetVcpCodeInfo(0x60);
+        Assert.IsTrue(inputSource?.HasDiscreteValues ?? false);
+        Assert.AreEqual(2, inputSource?.SupportedValues.Count);
+    }
+
+    [TestMethod]
+    public void Parse_UnknownSegments_DoesNotFail()
+    {
+        // Arrange - Contains unknown segments like mswhql and asset_eep
+        var input = "(prot(monitor)mswhql(1)asset_eep(40)vcp(10))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsFalse(result.HasErrors);
+        Assert.AreEqual("monitor", result.Capabilities.Protocol);
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+    }
+
+    [TestMethod]
+    public void Parse_ExtraWhitespace_HandlesCorrectly()
+    {
+        // Arrange - Extra spaces everywhere
+        var input = "(  prot( monitor )  type( lcd )  vcp( 10   12   14( 01  05 ) )  )";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.AreEqual("monitor", result.Capabilities.Protocol);
+        Assert.AreEqual("lcd", result.Capabilities.Type);
+        Assert.AreEqual(3, result.Capabilities.SupportedVcpCodes.Count);
+    }
+
+    [TestMethod]
+    public void Parse_LowercaseHex_ParsesCorrectly()
+    {
+        // Arrange - All lowercase hex
+        var input = "(cmds(01 0c e3 f3)vcp(10 ac ae))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        CollectionAssert.Contains(result.Capabilities.SupportedCommands, (byte)0xE3);
+        CollectionAssert.Contains(result.Capabilities.SupportedCommands, (byte)0xF3);
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xAC));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xAE));
+    }
+
+    [TestMethod]
+    public void Parse_MixedCaseHex_ParsesCorrectly()
+    {
+        // Arrange - Mixed case hex
+        var input = "(vcp(Aa Bb cC Dd))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xAA));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xBB));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xCC));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0xDD));
+    }
+
+    [TestMethod]
+    public void Parse_MalformedInput_ReturnsPartialResults()
+    {
+        // Arrange - Missing closing paren for vcp section
+        var input = "(prot(monitor)vcp(10 12";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert - Should still parse what it can
+        Assert.AreEqual("monitor", result.Capabilities.Protocol);
+
+        // VCP codes should still be parsed
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+    }
+
+    [TestMethod]
+    public void Parse_InvalidHexInVcp_SkipsAndContinues()
+    {
+        // Arrange - Contains invalid hex "GG"
+        var input = "(vcp(10 GG 12 14))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert - Should skip invalid and parse valid codes
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x14));
+        Assert.AreEqual(3, result.Capabilities.SupportedVcpCodes.Count);
+    }
+
+    [TestMethod]
+    public void Parse_SingleCharacterHex_Skipped()
+    {
+        // Arrange - Single char "A" is not valid (need 2 chars)
+        var input = "(vcp(10 A 12))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert - Should only have 10 and 12
+        Assert.AreEqual(2, result.Capabilities.SupportedVcpCodes.Count);
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x10));
+        Assert.IsTrue(result.Capabilities.SupportsVcpCode(0x12));
+    }
+
+    [TestMethod]
+    public void GetVcpCodesAsHexStrings_ReturnsSortedList()
+    {
+        // Arrange
+        var result = MccsCapabilitiesParser.Parse("(vcp(60 10 14 12))");
+
+        // Act
+        var hexStrings = result.Capabilities.GetVcpCodesAsHexStrings();
+
+        // Assert - Should be sorted
+        Assert.AreEqual(4, hexStrings.Count);
+        Assert.AreEqual("0x10", hexStrings[0]);
+        Assert.AreEqual("0x12", hexStrings[1]);
+        Assert.AreEqual("0x14", hexStrings[2]);
+        Assert.AreEqual("0x60", hexStrings[3]);
+    }
+
+    [TestMethod]
+    public void GetSortedVcpCodes_ReturnsSortedEnumerable()
+    {
+        // Arrange
+        var result = MccsCapabilitiesParser.Parse("(vcp(60 10 14 12))");
+
+        // Act
+        var sortedCodes = result.Capabilities.GetSortedVcpCodes().ToList();
+
+        // Assert
+        Assert.AreEqual(0x10, sortedCodes[0].Code);
+        Assert.AreEqual(0x12, sortedCodes[1].Code);
+        Assert.AreEqual(0x14, sortedCodes[2].Code);
+        Assert.AreEqual(0x60, sortedCodes[3].Code);
+    }
+
+    [TestMethod]
+    public void HasDiscreteValues_ContinuousCode_ReturnsFalse()
+    {
+        // Arrange
+        var result = MccsCapabilitiesParser.Parse("(vcp(10))");
+
+        // Act & Assert
+        Assert.IsFalse(result.Capabilities.HasDiscreteValues(0x10));
+    }
+
+    [TestMethod]
+    public void HasDiscreteValues_DiscreteCode_ReturnsTrue()
+    {
+        // Arrange
+        var result = MccsCapabilitiesParser.Parse("(vcp(60(01 11)))");
+
+        // Act & Assert
+        Assert.IsTrue(result.Capabilities.HasDiscreteValues(0x60));
+    }
+
+    [TestMethod]
+    public void GetSupportedValues_DiscreteCode_ReturnsValues()
+    {
+        // Arrange
+        var result = MccsCapabilitiesParser.Parse("(vcp(60(01 11 0F)))");
+
+        // Act
+        var values = result.Capabilities.GetSupportedValues(0x60);
+
+        // Assert
+        Assert.IsNotNull(values);
+        Assert.AreEqual(3, values.Count);
+        Assert.IsTrue(values.Contains(0x01));
+        Assert.IsTrue(values.Contains(0x11));
+        Assert.IsTrue(values.Contains(0x0F));
+    }
+
+    [TestMethod]
+    public void IsValid_ValidCapabilities_ReturnsTrue()
+    {
+        // Arrange & Act
+        var result = MccsCapabilitiesParser.Parse(DellU3011Capabilities);
+
+        // Assert
+        Assert.IsTrue(result.IsValid);
+        Assert.IsFalse(result.HasErrors);
+    }
+
+    [TestMethod]
+    public void IsValid_EmptyVcpCodes_ReturnsFalse()
+    {
+        // Arrange & Act
+        var result = MccsCapabilitiesParser.Parse("(prot(monitor)type(lcd))");
+
+        // Assert - No VCP codes = not valid
+        Assert.IsFalse(result.IsValid);
+    }
+
+    [TestMethod]
+    public void Capabilities_RawProperty_ContainsOriginalString()
+    {
+        // Arrange & Act
+        var result = MccsCapabilitiesParser.Parse(SimpleCapabilities);
+
+        // Assert
+        Assert.AreEqual(SimpleCapabilities, result.Capabilities.Raw);
+    }
+
+    [TestMethod]
+    public void Parse_Window1Segment_ParsesCorrectly()
+    {
+        // Arrange - Full window segment with all fields
+        var input = "(vcp(10)window1(type(PIP) area(25 25 1895 1175) max(640 480) min(10 10) window(10)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual(1, result.Capabilities.Windows.Count);
+
+        var window = result.Capabilities.Windows[0];
+        Assert.AreEqual(1, window.WindowNumber);
+        Assert.AreEqual("PIP", window.Type);
+        Assert.AreEqual(25, window.Area.X1);
+        Assert.AreEqual(25, window.Area.Y1);
+        Assert.AreEqual(1895, window.Area.X2);
+        Assert.AreEqual(1175, window.Area.Y2);
+        Assert.AreEqual(640, window.MaxSize.Width);
+        Assert.AreEqual(480, window.MaxSize.Height);
+        Assert.AreEqual(10, window.MinSize.Width);
+        Assert.AreEqual(10, window.MinSize.Height);
+        Assert.AreEqual(10, window.WindowId);
+    }
+
+    [TestMethod]
+    public void Parse_MultipleWindows_ParsesAll()
+    {
+        // Arrange - Two windows (PIP and PBP)
+        var input = "(window1(type(PIP) area(0 0 640 480))window2(type(PBP) area(640 0 1280 480)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual(2, result.Capabilities.Windows.Count);
+
+        var window1 = result.Capabilities.Windows[0];
+        Assert.AreEqual(1, window1.WindowNumber);
+        Assert.AreEqual("PIP", window1.Type);
+        Assert.AreEqual(0, window1.Area.X1);
+        Assert.AreEqual(640, window1.Area.X2);
+
+        var window2 = result.Capabilities.Windows[1];
+        Assert.AreEqual(2, window2.WindowNumber);
+        Assert.AreEqual("PBP", window2.Type);
+        Assert.AreEqual(640, window2.Area.X1);
+        Assert.AreEqual(1280, window2.Area.X2);
+    }
+
+    [TestMethod]
+    public void Parse_WindowWithMissingFields_HandlesGracefully()
+    {
+        // Arrange - Window with only type and area (missing max, min, window)
+        var input = "(window1(type(PIP) area(0 0 640 480)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual(1, result.Capabilities.Windows.Count);
+
+        var window = result.Capabilities.Windows[0];
+        Assert.AreEqual(1, window.WindowNumber);
+        Assert.AreEqual("PIP", window.Type);
+        Assert.AreEqual(640, window.Area.X2);
+        Assert.AreEqual(480, window.Area.Y2);
+
+        // Default values for missing fields
+        Assert.AreEqual(0, window.MaxSize.Width);
+        Assert.AreEqual(0, window.MinSize.Width);
+        Assert.AreEqual(0, window.WindowId);
+    }
+
+    [TestMethod]
+    public void Parse_WindowWithOnlyType_ParsesType()
+    {
+        // Arrange
+        var input = "(window1(type(PBP)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual(1, result.Capabilities.Windows.Count);
+        Assert.AreEqual("PBP", result.Capabilities.Windows[0].Type);
+    }
+
+    [TestMethod]
+    public void Parse_NoWindowSegment_HasWindowSupportFalse()
+    {
+        // Arrange
+        var input = "(prot(monitor)vcp(10 12))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsFalse(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual(0, result.Capabilities.Windows.Count);
+    }
+
+    [TestMethod]
+    public void Parse_WindowAreaDimensions_CalculatesCorrectly()
+    {
+        // Arrange
+        var input = "(window1(area(100 200 500 600)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        var area = result.Capabilities.Windows[0].Area;
+        Assert.AreEqual(400, area.Width);  // 500 - 100
+        Assert.AreEqual(400, area.Height); // 600 - 200
+    }
+
+    [TestMethod]
+    public void Parse_RealWorldMccsWindowExample_ParsesCorrectly()
+    {
+        // Arrange - Example from MCCS 2.2a specification
+        var input = "(prot(display)type(lcd)model(PD3220U)cmds(01 02 03)vcp(10 12)mccs_ver(2.2)window1(type(PIP) area(25 25 1895 1175) max(640 480) min(10 10) window(10)))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.AreEqual("lcd", result.Capabilities.Type);
+        Assert.AreEqual("PD3220U", result.Capabilities.Model);
+        Assert.AreEqual("2.2", result.Capabilities.MccsVersion);
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual("PIP", result.Capabilities.Windows[0].Type);
+    }
+
+    [TestMethod]
+    public void Parse_WindowWithExtraSpaces_HandlesCorrectly()
+    {
+        // Arrange - Extra spaces in content
+        var input = "(window1(  type( PIP )  area( 0   0   640   480 )  ))";
+
+        // Act
+        var result = MccsCapabilitiesParser.Parse(input);
+
+        // Assert
+        Assert.IsTrue(result.Capabilities.HasWindowSupport);
+        Assert.AreEqual("PIP", result.Capabilities.Windows[0].Type);
+        Assert.AreEqual(640, result.Capabilities.Windows[0].Area.X2);
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib.UnitTests/MonitorMatchingHelperTests.cs

@@ -0,0 +1,94 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Utils;
+
+namespace PowerDisplay.UnitTests;
+
+/// <summary>
+/// Unit tests for MonitorMatchingHelper class.
+/// Tests monitor key generation and matching logic.
+/// </summary>
+[TestClass]
+public class MonitorMatchingHelperTests
+{
+    [TestMethod]
+    public void GetMonitorKey_WithMonitor_ReturnsId()
+    {
+        // Arrange
+        var monitor = new Monitor { Id = "DDC_GSM5C6D_1", Name = "LG Monitor" };
+
+        // Act
+        var result = MonitorMatchingHelper.GetMonitorKey(monitor);
+
+        // Assert
+        Assert.AreEqual("DDC_GSM5C6D_1", result);
+    }
+
+    [TestMethod]
+    public void GetMonitorKey_NullMonitor_ReturnsEmptyString()
+    {
+        // Act
+        var result = MonitorMatchingHelper.GetMonitorKey(null);
+
+        // Assert
+        Assert.AreEqual(string.Empty, result);
+    }
+
+    [TestMethod]
+    public void GetMonitorKey_EmptyId_ReturnsEmptyString()
+    {
+        // Arrange
+        var monitor = new Monitor { Id = string.Empty, Name = "Display Name" };
+
+        // Act
+        var result = MonitorMatchingHelper.GetMonitorKey(monitor);
+
+        // Assert
+        Assert.AreEqual(string.Empty, result);
+    }
+
+    [TestMethod]
+    public void AreMonitorsSame_SameId_ReturnsTrue()
+    {
+        // Arrange
+        var monitor1 = new Monitor { Id = "DDC_GSM5C6D_1", Name = "Monitor 1" };
+        var monitor2 = new Monitor { Id = "DDC_GSM5C6D_1", Name = "Monitor 2" };
+
+        // Act
+        var result = MonitorMatchingHelper.AreMonitorsSame(monitor1, monitor2);
+
+        // Assert
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public void AreMonitorsSame_DifferentId_ReturnsFalse()
+    {
+        // Arrange
+        var monitor1 = new Monitor { Id = "DDC_GSM5C6D_1", Name = "Monitor 1" };
+        var monitor2 = new Monitor { Id = "DDC_GSM5C6D_2", Name = "Monitor 2" };
+
+        // Act
+        var result = MonitorMatchingHelper.AreMonitorsSame(monitor1, monitor2);
+
+        // Assert
+        Assert.IsFalse(result);
+    }
+
+    [TestMethod]
+    public void AreMonitorsSame_NullMonitor_ReturnsFalse()
+    {
+        // Arrange
+        var monitor1 = new Monitor { Id = "DDC_GSM5C6D_1", Name = "Monitor 1" };
+
+        // Act
+        var result = MonitorMatchingHelper.AreMonitorsSame(monitor1, null!);
+
+        // Assert
+        Assert.IsFalse(result);
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib.UnitTests/PowerDisplay.Lib.UnitTests.csproj

@@ -0,0 +1,41 @@
+<!-- Copyright (c) Microsoft Corporation. All rights reserved. -->
+<!-- Licensed under the MIT License. See LICENSE file in the project root for license information. -->
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="..\..\..\Common.Dotnet.CsWinRT.props" />
+
+  <PropertyGroup>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+    <RootNamespace>PowerDisplay.UnitTests</RootNamespace>
+    <Platforms>x64;ARM64</Platforms>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
+    <OutputPath>$(SolutionDir)$(Platform)\$(Configuration)\tests\PowerDisplay.Lib.UnitTests\</OutputPath>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Hide build log files from Solution Explorer -->
+    <None Remove="*.log" />
+    <None Remove="*.binlog" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MSTest" />
+    <PackageReference Include="Moq" />
+    <PackageReference Include="System.CodeDom">
+      <!-- This package is a transitive dependency, but we need to set it here so we can exclude the assets,
+           so it doesn't conflict with the dll coming from .NET SDK. -->
+      <ExcludeAssets>runtime</ExcludeAssets>
+    </PackageReference>
+    <PackageReference Include="System.Diagnostics.EventLog">
+      <!-- This package is a transitive dependency, but we need to set it here so we can exclude the assets,
+           so it doesn't conflict with the dll coming from .NET SDK. -->
+      <ExcludeAssets>runtime</ExcludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\PowerDisplay.Lib\PowerDisplay.Lib.csproj" />
+  </ItemGroup>
+</Project>

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/DDC/DdcCiController.cs

@@ -0,0 +1,658 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Polly;
+using Polly.Retry;
+using PowerDisplay.Common.Interfaces;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Utils;
+using static PowerDisplay.Common.Drivers.NativeConstants;
+using static PowerDisplay.Common.Drivers.NativeDelegates;
+using static PowerDisplay.Common.Drivers.PInvoke;
+using Monitor = PowerDisplay.Common.Models.Monitor;
+
+// Type aliases matching Windows API naming conventions for better readability when working with native structures.
+// These uppercase aliases are used consistently throughout this file to match Win32 API documentation.
+using MONITORINFOEX = PowerDisplay.Common.Drivers.MonitorInfoEx;
+using PHYSICAL_MONITOR = PowerDisplay.Common.Drivers.PhysicalMonitor;
+using RECT = PowerDisplay.Common.Drivers.Rect;
+
+namespace PowerDisplay.Common.Drivers.DDC
+{
+    /// <summary>
+    /// DDC/CI monitor controller for controlling external monitors
+    /// </summary>
+    public partial class DdcCiController : IMonitorController, IDisposable
+    {
+        /// <summary>
+        /// Represents a candidate monitor discovered during Phase 1 of monitor enumeration.
+        /// </summary>
+        /// <param name="Handle">Physical monitor handle for DDC/CI communication</param>
+        /// <param name="PhysicalMonitor">Native physical monitor structure with description</param>
+        /// <param name="MonitorInfo">Display info from QueryDisplayConfig (HardwareId, FriendlyName, MonitorNumber)</param>
+        private readonly record struct CandidateMonitor(
+            IntPtr Handle,
+            PHYSICAL_MONITOR PhysicalMonitor,
+            MonitorDisplayInfo MonitorInfo);
+
+        /// <summary>
+        /// Delay between retry attempts for DDC/CI operations (in milliseconds)
+        /// </summary>
+        private const int RetryDelayMs = 100;
+
+        /// <summary>
+        /// Retry pipeline for getting capabilities string length (3 retries).
+        /// </summary>
+        private static readonly ResiliencePipeline<uint> CapabilitiesLengthRetryPipeline =
+            new ResiliencePipelineBuilder<uint>()
+                .AddRetry(new RetryStrategyOptions<uint>
+                {
+                    MaxRetryAttempts = 2, // 2 retries = 3 total attempts
+                    Delay = TimeSpan.FromMilliseconds(RetryDelayMs),
+                    ShouldHandle = new PredicateBuilder<uint>().HandleResult(len => len == 0),
+                    OnRetry = static args =>
+                    {
+                        Logger.LogWarning($"[Retry] GetCapabilitiesStringLength returned invalid result on attempt {args.AttemptNumber + 1}, retrying...");
+                        return default;
+                    },
+                })
+                .Build();
+
+        /// <summary>
+        /// Retry pipeline for getting capabilities string (5 retries).
+        /// </summary>
+        private static readonly ResiliencePipeline<string?> CapabilitiesStringRetryPipeline =
+            new ResiliencePipelineBuilder<string?>()
+                .AddRetry(new RetryStrategyOptions<string?>
+                {
+                    MaxRetryAttempts = 4, // 4 retries = 5 total attempts
+                    Delay = TimeSpan.FromMilliseconds(RetryDelayMs),
+                    ShouldHandle = new PredicateBuilder<string?>().HandleResult(static str => string.IsNullOrEmpty(str)),
+                    OnRetry = static args =>
+                    {
+                        Logger.LogWarning($"[Retry] GetCapabilitiesString returned invalid result on attempt {args.AttemptNumber + 1}, retrying...");
+                        return default;
+                    },
+                })
+                .Build();
+
+        private readonly PhysicalMonitorHandleManager _handleManager = new();
+        private readonly MonitorDiscoveryHelper _discoveryHelper;
+
+        private bool _disposed;
+
+        public DdcCiController()
+        {
+            _discoveryHelper = new MonitorDiscoveryHelper();
+        }
+
+        public string Name => "DDC/CI Monitor Controller";
+
+        /// <summary>
+        /// Get monitor brightness using VCP code 0x10
+        /// </summary>
+        public async Task<VcpFeatureValue> GetBrightnessAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+            return await GetVcpFeatureAsync(monitor, VcpCodeBrightness, "Brightness", cancellationToken);
+        }
+
+        /// <summary>
+        /// Set monitor brightness using VCP code 0x10
+        /// </summary>
+        public Task<MonitorOperationResult> SetBrightnessAsync(Monitor monitor, int brightness, CancellationToken cancellationToken = default)
+            => SetVcpFeatureAsync(monitor, NativeConstants.VcpCodeBrightness, brightness, cancellationToken);
+
+        /// <summary>
+        /// Set monitor contrast
+        /// </summary>
+        public Task<MonitorOperationResult> SetContrastAsync(Monitor monitor, int contrast, CancellationToken cancellationToken = default)
+            => SetVcpFeatureAsync(monitor, NativeConstants.VcpCodeContrast, contrast, cancellationToken);
+
+        /// <summary>
+        /// Set monitor volume
+        /// </summary>
+        public Task<MonitorOperationResult> SetVolumeAsync(Monitor monitor, int volume, CancellationToken cancellationToken = default)
+            => SetVcpFeatureAsync(monitor, NativeConstants.VcpCodeVolume, volume, cancellationToken);
+
+        /// <summary>
+        /// Get monitor color temperature using VCP code 0x14 (Select Color Preset)
+        /// Returns the raw VCP preset value (e.g., 0x05 for 6500K), not Kelvin temperature
+        /// </summary>
+        public async Task<VcpFeatureValue> GetColorTemperatureAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+            return await GetVcpFeatureAsync(monitor, VcpCodeSelectColorPreset, "Color temperature", cancellationToken);
+        }
+
+        /// <summary>
+        /// Set monitor color temperature using VCP code 0x14 (Select Color Preset)
+        /// </summary>
+        public Task<MonitorOperationResult> SetColorTemperatureAsync(Monitor monitor, int colorTemperature, CancellationToken cancellationToken = default)
+            => SetVcpFeatureAsync(monitor, VcpCodeSelectColorPreset, colorTemperature, cancellationToken);
+
+        /// <summary>
+        /// Get current input source using VCP code 0x60
+        /// Returns the raw VCP value (e.g., 0x11 for HDMI-1)
+        /// </summary>
+        public async Task<VcpFeatureValue> GetInputSourceAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+            return await GetVcpFeatureAsync(monitor, VcpCodeInputSource, "Input source", cancellationToken);
+        }
+
+        /// <summary>
+        /// Set input source using VCP code 0x60
+        /// </summary>
+        public Task<MonitorOperationResult> SetInputSourceAsync(Monitor monitor, int inputSource, CancellationToken cancellationToken = default)
+            => SetVcpFeatureAsync(monitor, VcpCodeInputSource, inputSource, cancellationToken);
+
+        /// <summary>
+        /// Get monitor capabilities string with retry logic.
+        /// Uses cached CapabilitiesRaw if available to avoid slow I2C operations.
+        /// </summary>
+        public async Task<string> GetCapabilitiesStringAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+
+            // Check if capabilities are already cached
+            if (!string.IsNullOrEmpty(monitor.CapabilitiesRaw))
+            {
+                return monitor.CapabilitiesRaw;
+            }
+
+            return await Task.Run(
+                () =>
+                {
+                    if (monitor.Handle == IntPtr.Zero)
+                    {
+                        return string.Empty;
+                    }
+
+                    try
+                    {
+                        // Step 1: Get capabilities string length with retry
+                        var length = CapabilitiesLengthRetryPipeline.Execute(() =>
+                        {
+                            if (GetCapabilitiesStringLength(monitor.Handle, out uint len) && len > 0)
+                            {
+                                return len;
+                            }
+
+                            return 0u;
+                        });
+
+                        if (length == 0)
+                        {
+                            Logger.LogWarning("[Retry] GetCapabilitiesStringLength failed after 3 attempts");
+                            return string.Empty;
+                        }
+
+                        // Step 2: Get actual capabilities string with retry
+                        var capsString = CapabilitiesStringRetryPipeline.Execute(
+                            () => TryGetCapabilitiesString(monitor.Handle, length));
+
+                        if (!string.IsNullOrEmpty(capsString))
+                        {
+                            return capsString;
+                        }
+
+                        Logger.LogWarning("[Retry] GetCapabilitiesString failed after 5 attempts");
+                    }
+                    catch (Exception ex)
+                    {
+                        Logger.LogError($"Exception getting capabilities string: {ex.Message}");
+                    }
+
+                    return string.Empty;
+                },
+                cancellationToken);
+        }
+
+        /// <summary>
+        /// Try to get capabilities string from monitor handle.
+        /// </summary>
+        private string? TryGetCapabilitiesString(IntPtr handle, uint length)
+        {
+            var buffer = System.Runtime.InteropServices.Marshal.AllocHGlobal((int)length);
+            try
+            {
+                if (CapabilitiesRequestAndCapabilitiesReply(handle, buffer, length))
+                {
+                    return System.Runtime.InteropServices.Marshal.PtrToStringAnsi(buffer);
+                }
+
+                return null;
+            }
+            finally
+            {
+                System.Runtime.InteropServices.Marshal.FreeHGlobal(buffer);
+            }
+        }
+
+        /// <summary>
+        /// Discover supported monitors using a three-phase approach:
+        /// Phase 1: Enumerate and collect candidate monitors with their handles
+        /// Phase 2: Fetch DDC/CI capabilities in parallel (slow I2C operations)
+        /// Phase 3: Create Monitor objects for valid DDC/CI monitors
+        /// </summary>
+        public async Task<IEnumerable<Monitor>> DiscoverMonitorsAsync(CancellationToken cancellationToken = default)
+        {
+            try
+            {
+                // Get monitor display info from QueryDisplayConfig, keyed by device path (unique per target)
+                var allMonitorDisplayInfo = DdcCiNative.GetAllMonitorDisplayInfo();
+
+                // Phase 1: Collect candidate monitors
+                var monitorHandles = EnumerateMonitorHandles();
+                if (monitorHandles.Count == 0)
+                {
+                    return Enumerable.Empty<Monitor>();
+                }
+
+                var candidateMonitors = await CollectCandidateMonitorsAsync(
+                    monitorHandles, allMonitorDisplayInfo, cancellationToken);
+
+                if (candidateMonitors.Count == 0)
+                {
+                    return Enumerable.Empty<Monitor>();
+                }
+
+                // Phase 2: Fetch capabilities in parallel
+                var fetchResults = await FetchCapabilitiesInParallelAsync(
+                    candidateMonitors, cancellationToken);
+
+                // Phase 3: Create monitor objects
+                return CreateValidMonitors(fetchResults);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"DDC: DiscoverMonitorsAsync exception: {ex.Message}\nStack: {ex.StackTrace}");
+                return Enumerable.Empty<Monitor>();
+            }
+        }
+
+        /// <summary>
+        /// Enumerate all logical monitor handles using Win32 API.
+        /// </summary>
+        private List<IntPtr> EnumerateMonitorHandles()
+        {
+            var handles = new List<IntPtr>();
+
+            bool EnumProc(IntPtr hMonitor, IntPtr hdcMonitor, IntPtr lprcMonitor, IntPtr dwData)
+            {
+                handles.Add(hMonitor);
+                return true;
+            }
+
+            if (!EnumDisplayMonitors(IntPtr.Zero, IntPtr.Zero, EnumProc, IntPtr.Zero))
+            {
+                Logger.LogWarning("DDC: EnumDisplayMonitors failed");
+            }
+
+            return handles;
+        }
+
+        /// <summary>
+        /// Get GDI device name for a monitor handle (e.g., "\\.\DISPLAY1").
+        /// </summary>
+        private unsafe string? GetGdiDeviceName(IntPtr hMonitor)
+        {
+            var monitorInfo = new MONITORINFOEX { CbSize = (uint)sizeof(MONITORINFOEX) };
+            if (GetMonitorInfo(hMonitor, ref monitorInfo))
+            {
+                return monitorInfo.GetDeviceName();
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Phase 1: Collect all candidate monitors with their physical handles.
+        /// Matches physical monitors with MonitorDisplayInfo using GDI device name and friendly name.
+        /// Supports mirror mode where multiple physical monitors share the same GDI name.
+        /// </summary>
+        private async Task<List<CandidateMonitor>> CollectCandidateMonitorsAsync(
+            List<IntPtr> monitorHandles,
+            Dictionary<string, MonitorDisplayInfo> allMonitorDisplayInfo,
+            CancellationToken cancellationToken)
+        {
+            var candidates = new List<CandidateMonitor>();
+
+            foreach (var hMonitor in monitorHandles)
+            {
+                // Get GDI device name for this monitor (e.g., "\\.\DISPLAY1")
+                var gdiDeviceName = GetGdiDeviceName(hMonitor);
+                if (string.IsNullOrEmpty(gdiDeviceName))
+                {
+                    Logger.LogWarning($"DDC: Failed to get GDI device name for hMonitor 0x{hMonitor:X}");
+                    continue;
+                }
+
+                var physicalMonitors = await GetPhysicalMonitorsWithRetryAsync(hMonitor, cancellationToken);
+                if (physicalMonitors == null || physicalMonitors.Length == 0)
+                {
+                    Logger.LogWarning($"DDC: Failed to get physical monitors for {gdiDeviceName} after retries");
+                    continue;
+                }
+
+                // Find all MonitorDisplayInfo entries that match this GDI device name
+                // In mirror mode, multiple targets share the same GDI name
+                var matchingInfos = allMonitorDisplayInfo.Values
+                    .Where(info => string.Equals(info.GdiDeviceName, gdiDeviceName, StringComparison.OrdinalIgnoreCase))
+                    .ToList();
+
+                if (matchingInfos.Count == 0)
+                {
+                    Logger.LogWarning($"DDC: No QueryDisplayConfig info for {gdiDeviceName}, skipping");
+                    continue;
+                }
+
+                for (int i = 0; i < physicalMonitors.Length; i++)
+                {
+                    var physicalMonitor = physicalMonitors[i];
+
+                    if (i >= matchingInfos.Count)
+                    {
+                        Logger.LogWarning($"DDC: Physical monitor index {i} exceeds available QueryDisplayConfig entries ({matchingInfos.Count}) for {gdiDeviceName}");
+                        break;
+                    }
+
+                    var monitorInfo = matchingInfos[i];
+
+                    candidates.Add(new CandidateMonitor(physicalMonitor.HPhysicalMonitor, physicalMonitor, monitorInfo));
+                }
+            }
+
+            return candidates;
+        }
+
+        /// <summary>
+        /// Phase 2: Fetch DDC/CI capabilities in parallel for all candidate monitors.
+        /// This is the slow I2C operation (~4s per monitor), but parallelization
+        /// significantly reduces total time when multiple monitors are connected.
+        /// </summary>
+        private async Task<(CandidateMonitor Candidate, DdcCiValidationResult Result)[]> FetchCapabilitiesInParallelAsync(
+            List<CandidateMonitor> candidates,
+            CancellationToken cancellationToken)
+        {
+            Logger.LogInfo($"DDC: Phase 2 - Fetching capabilities for {candidates.Count} monitors in parallel");
+
+            var tasks = candidates.Select(candidate =>
+                Task.Run(
+                    () => (Candidate: candidate, Result: DdcCiNative.FetchCapabilities(candidate.Handle)),
+                    cancellationToken));
+
+            var results = await Task.WhenAll(tasks);
+
+            Logger.LogInfo($"DDC: Phase 2 completed - Got results for {results.Length} monitors");
+            return results;
+        }
+
+        /// <summary>
+        /// Phase 3: Create Monitor objects for valid DDC/CI monitors.
+        /// A monitor is valid if it has capabilities with brightness support.
+        /// </summary>
+        private List<Monitor> CreateValidMonitors(
+            (CandidateMonitor Candidate, DdcCiValidationResult Result)[] fetchResults)
+        {
+            var monitors = new List<Monitor>();
+            var newHandleMap = new Dictionary<string, IntPtr>();
+
+            foreach (var (candidate, capResult) in fetchResults)
+            {
+                if (!capResult.IsValid)
+                {
+                    continue;
+                }
+
+                var monitor = _discoveryHelper.CreateMonitorFromPhysical(
+                    candidate.PhysicalMonitor,
+                    candidate.MonitorInfo);
+
+                if (monitor == null)
+                {
+                    continue;
+                }
+
+                // Set capabilities data
+                if (!string.IsNullOrEmpty(capResult.CapabilitiesString))
+                {
+                    monitor.CapabilitiesRaw = capResult.CapabilitiesString;
+                }
+
+                if (capResult.VcpCapabilitiesInfo != null)
+                {
+                    monitor.VcpCapabilitiesInfo = capResult.VcpCapabilitiesInfo;
+                    UpdateMonitorCapabilitiesFromVcp(monitor, capResult.VcpCapabilitiesInfo);
+
+                    // Initialize input source if supported
+                    if (monitor.SupportsInputSource)
+                    {
+                        InitializeInputSource(monitor, candidate.Handle);
+                    }
+
+                    // Initialize color temperature if supported
+                    if (monitor.SupportsColorTemperature)
+                    {
+                        InitializeColorTemperature(monitor, candidate.Handle);
+                    }
+                }
+
+                // Initialize brightness (always supported for DDC/CI monitors)
+                InitializeBrightness(monitor, candidate.Handle);
+
+                monitors.Add(monitor);
+                newHandleMap[monitor.Id] = candidate.Handle;
+
+                Logger.LogInfo($"DDC: Added monitor {monitor.Id} with {monitor.VcpCapabilitiesInfo?.SupportedVcpCodes.Count ?? 0} VCP codes");
+            }
+
+            _handleManager.UpdateHandleMap(newHandleMap);
+            return monitors;
+        }
+
+        /// <summary>
+        /// Initialize input source value for a monitor using VCP 0x60.
+        /// </summary>
+        private static void InitializeInputSource(Monitor monitor, IntPtr handle)
+        {
+            if (GetVCPFeatureAndVCPFeatureReply(handle, VcpCodeInputSource, IntPtr.Zero, out uint current, out uint _))
+            {
+                monitor.CurrentInputSource = (int)current;
+            }
+        }
+
+        /// <summary>
+        /// Initialize color temperature value for a monitor using VCP 0x14.
+        /// </summary>
+        private static void InitializeColorTemperature(Monitor monitor, IntPtr handle)
+        {
+            if (GetVCPFeatureAndVCPFeatureReply(handle, VcpCodeSelectColorPreset, IntPtr.Zero, out uint current, out uint _))
+            {
+                monitor.CurrentColorTemperature = (int)current;
+            }
+        }
+
+        /// <summary>
+        /// Initialize brightness value for a monitor using VCP 0x10.
+        /// </summary>
+        private static void InitializeBrightness(Monitor monitor, IntPtr handle)
+        {
+            if (GetVCPFeatureAndVCPFeatureReply(handle, VcpCodeBrightness, IntPtr.Zero, out uint current, out uint max))
+            {
+                var brightnessInfo = new VcpFeatureValue((int)current, 0, (int)max);
+                monitor.CurrentBrightness = brightnessInfo.ToPercentage();
+            }
+        }
+
+        /// <summary>
+        /// Update monitor capability flags based on parsed VCP capabilities.
+        /// </summary>
+        private static void UpdateMonitorCapabilitiesFromVcp(Monitor monitor, VcpCapabilities vcpCaps)
+        {
+            // Check for Contrast support (VCP 0x12)
+            if (vcpCaps.SupportsVcpCode(VcpCodeContrast))
+            {
+                monitor.Capabilities |= MonitorCapabilities.Contrast;
+            }
+
+            // Check for Volume support (VCP 0x62)
+            if (vcpCaps.SupportsVcpCode(VcpCodeVolume))
+            {
+                monitor.Capabilities |= MonitorCapabilities.Volume;
+            }
+
+            // Check for Color Temperature support (VCP 0x14)
+            if (vcpCaps.SupportsVcpCode(VcpCodeSelectColorPreset))
+            {
+                monitor.SupportsColorTemperature = true;
+            }
+        }
+
+        /// <summary>
+        /// Get physical monitors with retry logic to handle Windows API occasionally returning NULL handles.
+        /// NULL handles are automatically filtered out by GetPhysicalMonitors; retry if any were filtered.
+        /// </summary>
+        /// <param name="hMonitor">Handle to the monitor</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Array of valid physical monitors, or null if failed after retries</returns>
+        private async Task<PHYSICAL_MONITOR[]?> GetPhysicalMonitorsWithRetryAsync(
+            IntPtr hMonitor,
+            CancellationToken cancellationToken)
+        {
+            const int maxRetries = 3;
+            const int retryDelayMs = 200;
+
+            for (int attempt = 0; attempt < maxRetries; attempt++)
+            {
+                if (attempt > 0)
+                {
+                    await Task.Delay(retryDelayMs, cancellationToken);
+                }
+
+                var monitors = _discoveryHelper.GetPhysicalMonitors(hMonitor, out bool hasNullHandles);
+
+                // Success: got valid monitors with no NULL handles filtered out
+                if (monitors != null && !hasNullHandles)
+                {
+                    return monitors;
+                }
+
+                // Got monitors but some had NULL handles - retry to see if API stabilizes
+                if (monitors != null && hasNullHandles && attempt < maxRetries - 1)
+                {
+                    Logger.LogWarning($"DDC: Some monitors had NULL handles on attempt {attempt + 1}, will retry");
+                    continue;
+                }
+
+                // No monitors returned - retry
+                if (monitors == null && attempt < maxRetries - 1)
+                {
+                    Logger.LogWarning($"DDC: GetPhysicalMonitors returned null on attempt {attempt + 1}, will retry");
+                    continue;
+                }
+
+                // Last attempt - return whatever we have (may have NULL handles filtered)
+                if (monitors != null && hasNullHandles)
+                {
+                    Logger.LogWarning($"DDC: NULL handles still present after {maxRetries} attempts, using filtered result");
+                }
+
+                return monitors;
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Generic method to get VCP feature value with optional logging.
+        /// </summary>
+        /// <param name="monitor">Monitor to query</param>
+        /// <param name="vcpCode">VCP code to read</param>
+        /// <param name="featureName">Optional feature name for logging (e.g., "color temperature", "input source")</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        private async Task<VcpFeatureValue> GetVcpFeatureAsync(
+            Monitor monitor,
+            byte vcpCode,
+            string? featureName = null,
+            CancellationToken cancellationToken = default)
+        {
+            return await Task.Run(
+                () =>
+                {
+                    if (monitor.Handle == IntPtr.Zero)
+                    {
+                        return VcpFeatureValue.Invalid;
+                    }
+
+                    if (GetVCPFeatureAndVCPFeatureReply(monitor.Handle, vcpCode, IntPtr.Zero, out uint current, out uint max))
+                    {
+                        return new VcpFeatureValue((int)current, 0, (int)max);
+                    }
+
+                    return VcpFeatureValue.Invalid;
+                },
+                cancellationToken);
+        }
+
+        /// <summary>
+        /// Generic method to set VCP feature value directly.
+        /// </summary>
+        private Task<MonitorOperationResult> SetVcpFeatureAsync(
+            Monitor monitor,
+            byte vcpCode,
+            int value,
+            CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+
+            return Task.Run(
+                () =>
+                {
+                    if (monitor.Handle == IntPtr.Zero)
+                    {
+                        return MonitorOperationResult.Failure("Invalid monitor handle");
+                    }
+
+                    try
+                    {
+                        if (SetVCPFeature(monitor.Handle, vcpCode, (uint)value))
+                        {
+                            return MonitorOperationResult.Success();
+                        }
+
+                        var lastError = GetLastError();
+                        return MonitorOperationResult.Failure($"Failed to set VCP 0x{vcpCode:X2}", (int)lastError);
+                    }
+                    catch (Exception ex)
+                    {
+                        return MonitorOperationResult.Failure($"Exception setting VCP 0x{vcpCode:X2}: {ex.Message}");
+                    }
+                },
+                cancellationToken);
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed && disposing)
+            {
+                _handleManager?.Dispose();
+                _disposed = true;
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/DDC/DdcCiNative.cs

@@ -0,0 +1,374 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using ManagedCommon;
+using static PowerDisplay.Common.Drivers.NativeConstants;
+using static PowerDisplay.Common.Drivers.PInvoke;
+
+// Type aliases for Windows API naming conventions compatibility
+using LUID = PowerDisplay.Common.Drivers.Luid;
+
+#pragma warning disable SA1649 // File name should match first type name - Multiple related types for DDC/CI
+#pragma warning disable SA1402 // File may only contain a single type - Related DDC/CI types grouped together
+
+namespace PowerDisplay.Common.Drivers.DDC
+{
+    /// <summary>
+    /// DDC/CI validation result containing both validation status and cached capabilities data.
+    /// This allows reusing capabilities data retrieved during validation, avoiding duplicate I2C calls.
+    /// </summary>
+    public struct DdcCiValidationResult
+    {
+        /// <summary>
+        /// Gets a value indicating whether the monitor has a valid DDC/CI connection with brightness support.
+        /// </summary>
+        public bool IsValid { get; }
+
+        /// <summary>
+        /// Gets the raw capabilities string retrieved during validation.
+        /// Null if retrieval failed.
+        /// </summary>
+        public string? CapabilitiesString { get; }
+
+        /// <summary>
+        /// Gets the parsed VCP capabilities info retrieved during validation.
+        /// Null if parsing failed.
+        /// </summary>
+        public Models.VcpCapabilities? VcpCapabilitiesInfo { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether capabilities retrieval was attempted.
+        /// True means the result is from an actual attempt (success or failure).
+        /// </summary>
+        public bool WasAttempted { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DdcCiValidationResult"/> struct.
+        /// </summary>
+        public DdcCiValidationResult(bool isValid, string? capabilitiesString = null, Models.VcpCapabilities? vcpCapabilitiesInfo = null, bool wasAttempted = true)
+        {
+            IsValid = isValid;
+            CapabilitiesString = capabilitiesString;
+            VcpCapabilitiesInfo = vcpCapabilitiesInfo;
+            WasAttempted = wasAttempted;
+        }
+
+        /// <summary>
+        /// Gets an invalid validation result with no cached data.
+        /// </summary>
+        public static DdcCiValidationResult Invalid => new(false, null, null, true);
+
+        /// <summary>
+        /// Gets a result indicating validation was not attempted yet.
+        /// </summary>
+        public static DdcCiValidationResult NotAttempted => new(false, null, null, false);
+    }
+
+    /// <summary>
+    /// DDC/CI native API wrapper
+    /// </summary>
+    public static class DdcCiNative
+    {
+        /// <summary>
+        /// Fetches VCP capabilities string from a monitor and returns a validation result.
+        /// This is the slow I2C operation (~4 seconds per monitor) that should only be done once.
+        /// The result is cached regardless of success or failure.
+        /// </summary>
+        /// <param name="hPhysicalMonitor">Physical monitor handle</param>
+        /// <returns>Validation result with capabilities data (or failure status)</returns>
+        public static DdcCiValidationResult FetchCapabilities(IntPtr hPhysicalMonitor)
+        {
+            if (hPhysicalMonitor == IntPtr.Zero)
+            {
+                return DdcCiValidationResult.Invalid;
+            }
+
+            try
+            {
+                // Try to get capabilities string (slow I2C operation)
+                var capsString = TryGetCapabilitiesString(hPhysicalMonitor);
+                if (string.IsNullOrEmpty(capsString))
+                {
+                    return DdcCiValidationResult.Invalid;
+                }
+
+                // Parse the capabilities string
+                var parseResult = Utils.MccsCapabilitiesParser.Parse(capsString);
+                var capabilities = parseResult.Capabilities;
+                if (capabilities == null || capabilities.SupportedVcpCodes.Count == 0)
+                {
+                    return DdcCiValidationResult.Invalid;
+                }
+
+                // Check if brightness (VCP 0x10) is supported - determines DDC/CI validity
+                bool supportsBrightness = capabilities.SupportsVcpCode(NativeConstants.VcpCodeBrightness);
+                return new DdcCiValidationResult(supportsBrightness, capsString, capabilities);
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+                return DdcCiValidationResult.Invalid;
+            }
+        }
+
+        /// <summary>
+        /// Try to get capabilities string from a physical monitor handle.
+        /// </summary>
+        /// <param name="hPhysicalMonitor">Physical monitor handle</param>
+        /// <returns>Capabilities string, or null if failed</returns>
+        private static string? TryGetCapabilitiesString(IntPtr hPhysicalMonitor)
+        {
+            if (hPhysicalMonitor == IntPtr.Zero)
+            {
+                return null;
+            }
+
+            try
+            {
+                // Get capabilities string length
+                if (!GetCapabilitiesStringLength(hPhysicalMonitor, out uint length) || length == 0)
+                {
+                    return null;
+                }
+
+                // Allocate buffer and get capabilities string
+                var buffer = Marshal.AllocHGlobal((int)length);
+                try
+                {
+                    if (!CapabilitiesRequestAndCapabilitiesReply(hPhysicalMonitor, buffer, length))
+                    {
+                        return null;
+                    }
+
+                    return Marshal.PtrToStringAnsi(buffer);
+                }
+                finally
+                {
+                    Marshal.FreeHGlobal(buffer);
+                }
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Gets GDI device name for a source (e.g., "\\.\DISPLAY1").
+        /// </summary>
+        /// <param name="adapterId">Adapter ID</param>
+        /// <param name="sourceId">Source ID</param>
+        /// <returns>GDI device name, or null if retrieval fails</returns>
+        private static unsafe string? GetSourceGdiDeviceName(LUID adapterId, uint sourceId)
+        {
+            try
+            {
+                var sourceName = new DISPLAYCONFIG_SOURCE_DEVICE_NAME
+                {
+                    Header = new DISPLAYCONFIG_DEVICE_INFO_HEADER
+                    {
+                        Type = DisplayconfigDeviceInfoGetSourceName,
+                        Size = (uint)sizeof(DISPLAYCONFIG_SOURCE_DEVICE_NAME),
+                        AdapterId = adapterId,
+                        Id = sourceId,
+                    },
+                };
+
+                var result = DisplayConfigGetDeviceInfo(ref sourceName);
+                if (result == 0)
+                {
+                    return sourceName.GetViewGdiDeviceName();
+                }
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Gets friendly name, hardware ID, and device path for a monitor target.
+        /// </summary>
+        /// <param name="adapterId">Adapter ID</param>
+        /// <param name="targetId">Target ID</param>
+        /// <returns>Tuple of (friendlyName, hardwareId, devicePath), any may be null if retrieval fails</returns>
+        private static unsafe (string? FriendlyName, string? HardwareId, string? DevicePath) GetTargetDeviceInfo(LUID adapterId, uint targetId)
+        {
+            try
+            {
+                var deviceName = new DISPLAYCONFIG_TARGET_DEVICE_NAME
+                {
+                    Header = new DISPLAYCONFIG_DEVICE_INFO_HEADER
+                    {
+                        Type = DisplayconfigDeviceInfoGetTargetName,
+                        Size = (uint)sizeof(DISPLAYCONFIG_TARGET_DEVICE_NAME),
+                        AdapterId = adapterId,
+                        Id = targetId,
+                    },
+                };
+
+                var result = DisplayConfigGetDeviceInfo(ref deviceName);
+                if (result == 0)
+                {
+                    // Extract friendly name
+                    var friendlyName = deviceName.GetMonitorFriendlyDeviceName();
+
+                    // Extract device path (unique per target, used as key)
+                    var devicePath = deviceName.GetMonitorDevicePath();
+
+                    // Extract hardware ID from EDID data
+                    var manufacturerId = deviceName.EdidManufactureId;
+                    var manufactureCode = ConvertManufactureIdToString(manufacturerId);
+                    var productCode = deviceName.EdidProductCodeId.ToString("X4", System.Globalization.CultureInfo.InvariantCulture);
+                    var hardwareId = $"{manufactureCode}{productCode}";
+
+                    return (friendlyName, hardwareId, devicePath);
+                }
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+            }
+
+            return (null, null, null);
+        }
+
+        /// <summary>
+        /// Converts manufacturer ID to 3-character manufacturer code
+        /// </summary>
+        /// <param name="manufacturerId">Manufacturer ID</param>
+        /// <returns>3-character manufacturer code</returns>
+        private static string ConvertManufactureIdToString(ushort manufacturerId)
+        {
+            // EDID manufacturer ID requires byte order swap first
+            manufacturerId = (ushort)(((manufacturerId & 0xff00) >> 8) | ((manufacturerId & 0x00ff) << 8));
+
+            // Extract 3 5-bit characters (each character is A-Z, where A=1, B=2, ..., Z=26)
+            var char1 = (char)('A' - 1 + ((manufacturerId >> 0) & 0x1f));
+            var char2 = (char)('A' - 1 + ((manufacturerId >> 5) & 0x1f));
+            var char3 = (char)('A' - 1 + ((manufacturerId >> 10) & 0x1f));
+
+            // Combine characters in correct order
+            return $"{char3}{char2}{char1}";
+        }
+
+        /// <summary>
+        /// Gets complete information for all monitors, keyed by GDI device name (e.g., "\\.\DISPLAY1").
+        /// This allows reliable matching with GetMonitorInfo results.
+        /// </summary>
+        /// <returns>Dictionary keyed by GDI device name containing monitor information</returns>
+        public static unsafe Dictionary<string, MonitorDisplayInfo> GetAllMonitorDisplayInfo()
+        {
+            var monitorInfo = new Dictionary<string, MonitorDisplayInfo>(StringComparer.OrdinalIgnoreCase);
+
+            try
+            {
+                // Get buffer sizes
+                var result = GetDisplayConfigBufferSizes(QdcOnlyActivePaths, out uint pathCount, out uint modeCount);
+                if (result != 0)
+                {
+                    return monitorInfo;
+                }
+
+                // Allocate buffers
+                var paths = new DISPLAYCONFIG_PATH_INFO[pathCount];
+                var modes = new DISPLAYCONFIG_MODE_INFO[modeCount];
+
+                // Query display configuration using fixed pointer
+                fixed (DISPLAYCONFIG_PATH_INFO* pathsPtr = paths)
+                {
+                    fixed (DISPLAYCONFIG_MODE_INFO* modesPtr = modes)
+                    {
+                        result = QueryDisplayConfig(QdcOnlyActivePaths, ref pathCount, pathsPtr, ref modeCount, modesPtr, IntPtr.Zero);
+                        if (result != 0)
+                        {
+                            return monitorInfo;
+                        }
+                    }
+                }
+
+                // Get information for each path
+                // The path index corresponds to Windows Display Settings "Identify" number
+                for (int i = 0; i < pathCount; i++)
+                {
+                    var path = paths[i];
+
+                    // Get GDI device name from source info (e.g., "\\.\DISPLAY1")
+                    var gdiDeviceName = GetSourceGdiDeviceName(path.SourceInfo.AdapterId, path.SourceInfo.Id);
+                    if (string.IsNullOrEmpty(gdiDeviceName))
+                    {
+                        continue;
+                    }
+
+                    // Get target info (friendly name, hardware ID, device path)
+                    var (friendlyName, hardwareId, devicePath) = GetTargetDeviceInfo(path.TargetInfo.AdapterId, path.TargetInfo.Id);
+
+                    // Use device path as key - unique per target, supports mirror mode
+                    if (string.IsNullOrEmpty(devicePath))
+                    {
+                        continue;
+                    }
+
+                    monitorInfo[devicePath] = new MonitorDisplayInfo
+                    {
+                        DevicePath = devicePath,
+                        GdiDeviceName = gdiDeviceName,
+                        FriendlyName = friendlyName ?? string.Empty,
+                        HardwareId = hardwareId ?? string.Empty,
+                        AdapterId = path.TargetInfo.AdapterId,
+                        TargetId = path.TargetInfo.Id,
+                        MonitorNumber = i + 1, // 1-based, matches Windows Display Settings
+                    };
+                }
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+            }
+
+            return monitorInfo;
+        }
+    }
+
+    /// <summary>
+    /// Monitor display information structure
+    /// </summary>
+    public struct MonitorDisplayInfo
+    {
+        /// <summary>
+        /// Gets or sets the monitor device path (e.g., "\\?\DISPLAY#DELA1D8#...").
+        /// This is unique per target and used as the primary key.
+        /// </summary>
+        public string DevicePath { get; set; }
+
+        /// <summary>
+        /// Gets or sets the GDI device name (e.g., "\\.\DISPLAY1").
+        /// This is used to match with GetMonitorInfo results from HMONITOR.
+        /// In mirror mode, multiple targets may share the same GDI name.
+        /// </summary>
+        public string GdiDeviceName { get; set; }
+
+        /// <summary>
+        /// Gets or sets the friendly display name from EDID.
+        /// </summary>
+        public string FriendlyName { get; set; }
+
+        /// <summary>
+        /// Gets or sets the hardware ID derived from EDID manufacturer and product code.
+        /// </summary>
+        public string HardwareId { get; set; }
+
+        public LUID AdapterId { get; set; }
+
+        public uint TargetId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the monitor number based on QueryDisplayConfig path index.
+        /// This matches the number shown in Windows Display Settings "Identify" feature.
+        /// 1-based index (paths[0] = 1, paths[1] = 2, etc.)
+        /// </summary>
+        public int MonitorNumber { get; set; }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/DDC/MonitorDiscoveryHelper.cs

@@ -0,0 +1,154 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using ManagedCommon;
+using PowerDisplay.Common.Models;
+using static PowerDisplay.Common.Drivers.NativeConstants;
+using static PowerDisplay.Common.Drivers.PInvoke;
+using PHYSICAL_MONITOR = PowerDisplay.Common.Drivers.PhysicalMonitor;
+
+namespace PowerDisplay.Common.Drivers.DDC
+{
+    /// <summary>
+    /// Helper class for discovering and creating monitor objects
+    /// </summary>
+    public class MonitorDiscoveryHelper
+    {
+        public MonitorDiscoveryHelper()
+        {
+        }
+
+        /// <summary>
+        /// Get physical monitors for a logical monitor.
+        /// Filters out any monitors with NULL handles (Windows API bug workaround).
+        /// </summary>
+        /// <param name="hMonitor">Handle to the logical monitor</param>
+        /// <param name="hasNullHandles">Output: true if any NULL handles were filtered out</param>
+        /// <returns>Array of valid physical monitors, or null if API call failed</returns>
+        internal PHYSICAL_MONITOR[]? GetPhysicalMonitors(IntPtr hMonitor, out bool hasNullHandles)
+        {
+            hasNullHandles = false;
+
+            try
+            {
+                if (!GetNumberOfPhysicalMonitorsFromHMONITOR(hMonitor, out uint numMonitors))
+                {
+                    Logger.LogWarning($"GetPhysicalMonitors: GetNumberOfPhysicalMonitorsFromHMONITOR failed for 0x{hMonitor:X}");
+                    return null;
+                }
+
+                if (numMonitors == 0)
+                {
+                    Logger.LogWarning($"GetPhysicalMonitors: numMonitors is 0");
+                    return null;
+                }
+
+                var physicalMonitors = new PHYSICAL_MONITOR[numMonitors];
+                bool apiResult;
+                unsafe
+                {
+                    fixed (PHYSICAL_MONITOR* ptr = physicalMonitors)
+                    {
+                        apiResult = GetPhysicalMonitorsFromHMONITOR(hMonitor, numMonitors, ptr);
+                    }
+                }
+
+                if (!apiResult)
+                {
+                    Logger.LogWarning($"GetPhysicalMonitors: GetPhysicalMonitorsFromHMONITOR failed");
+                    return null;
+                }
+
+                // Filter out NULL handles and log each physical monitor
+                var validMonitors = new List<PHYSICAL_MONITOR>();
+                for (int i = 0; i < numMonitors; i++)
+                {
+                    IntPtr handle = physicalMonitors[i].HPhysicalMonitor;
+
+                    if (handle == IntPtr.Zero)
+                    {
+                        Logger.LogWarning($"GetPhysicalMonitors: Monitor [{i}] has NULL handle, filtering out");
+                        hasNullHandles = true;
+                        continue;
+                    }
+
+                    validMonitors.Add(physicalMonitors[i]);
+                }
+
+                return validMonitors.Count > 0 ? validMonitors.ToArray() : null;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"GetPhysicalMonitors: Exception: {ex.Message}");
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Create Monitor object from physical monitor and display info.
+        /// Uses MonitorDisplayInfo directly from QueryDisplayConfig for stable identification.
+        /// Note: Brightness is not initialized here - MonitorManager handles brightness initialization
+        /// after discovery to avoid slow I2C operations during the discovery phase.
+        /// </summary>
+        /// <param name="physicalMonitor">Physical monitor structure with handle and description</param>
+        /// <param name="monitorInfo">Display info from QueryDisplayConfig (HardwareId, FriendlyName, MonitorNumber)</param>
+        internal Monitor? CreateMonitorFromPhysical(
+            PHYSICAL_MONITOR physicalMonitor,
+            MonitorDisplayInfo monitorInfo)
+        {
+            try
+            {
+                // Get hardware ID and friendly name directly from MonitorDisplayInfo
+                string edidId = monitorInfo.HardwareId ?? string.Empty;
+                string name = physicalMonitor.GetDescription() ?? string.Empty;
+
+                // Use FriendlyName from QueryDisplayConfig if available and not generic
+                if (!string.IsNullOrEmpty(monitorInfo.FriendlyName) &&
+                    !monitorInfo.FriendlyName.Contains("Generic"))
+                {
+                    name = monitorInfo.FriendlyName;
+                }
+
+                // Generate unique monitor Id: "DDC_{EdidId}_{MonitorNumber}"
+                string monitorId = !string.IsNullOrEmpty(edidId)
+                    ? $"DDC_{edidId}_{monitorInfo.MonitorNumber}"
+                    : $"DDC_Unknown_{monitorInfo.MonitorNumber}";
+
+                // If still no good name, use default value
+                if (string.IsNullOrEmpty(name) || name.Contains("Generic") || name.Contains("PnP"))
+                {
+                    name = "External Display";
+                }
+
+                var monitor = new Monitor
+                {
+                    Id = monitorId,
+                    Name = name.Trim(),
+                    CurrentBrightness = 50, // Default value, will be updated by MonitorManager after discovery
+                    MinBrightness = 0,
+                    MaxBrightness = 100,
+                    IsAvailable = true,
+                    Handle = physicalMonitor.HPhysicalMonitor,
+                    Capabilities = MonitorCapabilities.DdcCi,
+                    CommunicationMethod = "DDC/CI",
+                    MonitorNumber = monitorInfo.MonitorNumber,
+                    GdiDeviceName = monitorInfo.GdiDeviceName ?? string.Empty,
+                    Orientation = DmdoDefault, // Orientation will be set separately if needed
+                };
+
+                // Note: Feature detection (brightness, contrast, color temp, volume) is now done
+                // in MonitorManager after capabilities string is retrieved and parsed.
+                // This ensures we rely on capabilities data rather than trial-and-error probing.
+                return monitor;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"DDC: CreateMonitorFromPhysical exception: {ex.Message}");
+                return null;
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/DDC/PhysicalMonitorHandleManager.cs

@@ -0,0 +1,106 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using ManagedCommon;
+using static PowerDisplay.Common.Drivers.PInvoke;
+
+namespace PowerDisplay.Common.Drivers.DDC
+{
+    /// <summary>
+    /// Manages physical monitor handles - reuse, cleanup, and validation
+    /// </summary>
+    public partial class PhysicalMonitorHandleManager : IDisposable
+    {
+        // Mapping: monitorId -> physical handle (thread-safe)
+        private readonly ConcurrentDictionary<string, IntPtr> _monitorIdToHandleMap = new();
+        private readonly object _handleLock = new();
+        private bool _disposed;
+
+        /// <summary>
+        /// Update the handle mapping with new handles
+        /// </summary>
+        public void UpdateHandleMap(Dictionary<string, IntPtr> newHandleMap)
+        {
+            // Lock to ensure atomic update (cleanup + replace)
+            lock (_handleLock)
+            {
+                // Clean up unused handles before updating
+                CleanupUnusedHandles(newHandleMap);
+
+                // Update the device key map
+                _monitorIdToHandleMap.Clear();
+                foreach (var kvp in newHandleMap)
+                {
+                    _monitorIdToHandleMap[kvp.Key] = kvp.Value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Clean up handles that are no longer in use.
+        /// Called within lock context. Optimized to O(n) using HashSet lookup.
+        /// </summary>
+        private void CleanupUnusedHandles(Dictionary<string, IntPtr> newHandles)
+        {
+            if (_monitorIdToHandleMap.IsEmpty)
+            {
+                return;
+            }
+
+            // Build HashSet of handles that will be reused (O(m))
+            var reusedHandles = new HashSet<IntPtr>(newHandles.Values);
+
+            // Find handles to destroy: in old map but not reused (O(n) with O(1) lookup)
+            var handlesToDestroy = _monitorIdToHandleMap.Values
+                .Where(h => h != IntPtr.Zero && !reusedHandles.Contains(h))
+                .ToList();
+
+            // Destroy unused handles
+            foreach (var handle in handlesToDestroy)
+            {
+                try
+                {
+                    DestroyPhysicalMonitor(handle);
+                }
+                catch
+                {
+                    // Silently ignore cleanup failures
+                }
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            // Release all physical monitor handles - get snapshot to avoid holding lock during cleanup
+            var handles = _monitorIdToHandleMap.Values.ToList();
+            foreach (var handle in handles)
+            {
+                if (handle != IntPtr.Zero)
+                {
+                    try
+                    {
+                        DestroyPhysicalMonitor(handle);
+                    }
+                    catch
+                    {
+                        // Silently ignore cleanup failures
+                    }
+                }
+            }
+
+            _monitorIdToHandleMap.Clear();
+            _disposed = true;
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/NativeConstants.cs

@@ -0,0 +1,425 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace PowerDisplay.Common.Drivers
+{
+    /// <summary>
+    /// Windows API constant definitions
+    /// </summary>
+    public static class NativeConstants
+    {
+        /// <summary>
+        /// VCP code: Brightness (0x10)
+        /// Standard VESA MCCS brightness control.
+        /// This is the ONLY brightness code used by PowerDisplay.
+        /// </summary>
+        public const byte VcpCodeBrightness = 0x10;
+
+        /// <summary>
+        /// VCP code: Contrast (0x12)
+        /// Standard VESA MCCS contrast control.
+        /// </summary>
+        public const byte VcpCodeContrast = 0x12;
+
+        /// <summary>
+        /// VCP code: Audio Speaker Volume (0x62)
+        /// Standard VESA MCCS volume control for monitors with built-in speakers.
+        /// </summary>
+        public const byte VcpCodeVolume = 0x62;
+
+        /// <summary>
+        /// VCP code: Audio mute (0x8D)
+        /// </summary>
+        public const byte VcpCodeMute = 0x8D;
+
+        /// <summary>
+        /// VCP code: Gamma correction (0x72)
+        /// </summary>
+        public const byte VcpCodeGamma = 0x72;
+
+        /// <summary>
+        /// VCP code: Select Color Preset (0x14)
+        /// Standard VESA MCCS color temperature preset selection.
+        /// Supports discrete values like: 0x01=sRGB, 0x04=5000K, 0x05=6500K, 0x08=9300K.
+        /// This is the standard method for color temperature control.
+        /// </summary>
+        public const byte VcpCodeSelectColorPreset = 0x14;
+
+        /// <summary>
+        /// VCP code: Input Source (0x60)
+        /// Standard VESA MCCS input source selection.
+        /// Supports values like: 0x0F=DisplayPort-1, 0x10=DisplayPort-2, 0x11=HDMI-1, 0x12=HDMI-2, 0x1B=USB-C.
+        /// Note: Actual supported values depend on monitor capabilities.
+        /// </summary>
+        public const byte VcpCodeInputSource = 0x60;
+
+        /// <summary>
+        /// VCP code: VCP version
+        /// </summary>
+        public const byte VcpCodeVcpVersion = 0xDF;
+
+        /// <summary>
+        /// VCP code: New control value
+        /// </summary>
+        public const byte VcpCodeNewControlValue = 0x02;
+
+        /// <summary>
+        /// Display device attached to desktop
+        /// </summary>
+        public const uint DisplayDeviceAttachedToDesktop = 0x00000001;
+
+        /// <summary>
+        /// Multi-monitor primary display
+        /// </summary>
+        public const uint DisplayDeviceMultiDriver = 0x00000002;
+
+        /// <summary>
+        /// Primary device
+        /// </summary>
+        public const uint DisplayDevicePrimaryDevice = 0x00000004;
+
+        /// <summary>
+        /// Mirroring driver
+        /// </summary>
+        public const uint DisplayDeviceMirroringDriver = 0x00000008;
+
+        /// <summary>
+        /// VGA compatible
+        /// </summary>
+        public const uint DisplayDeviceVgaCompatible = 0x00000010;
+
+        /// <summary>
+        /// Removable device
+        /// </summary>
+        public const uint DisplayDeviceRemovable = 0x00000020;
+
+        /// <summary>
+        /// Get device interface name
+        /// </summary>
+        public const uint EddGetDeviceInterfaceName = 0x00000001;
+
+        /// <summary>
+        /// Primary monitor
+        /// </summary>
+        public const uint MonitorinfoFPrimary = 0x00000001;
+
+        /// <summary>
+        /// Query display config: only active paths
+        /// </summary>
+        public const uint QdcOnlyActivePaths = 0x00000002;
+
+        /// <summary>
+        /// Query display config: all paths
+        /// </summary>
+        public const uint QdcAllPaths = 0x00000001;
+
+        /// <summary>
+        /// Set display config: apply
+        /// </summary>
+        public const uint SdcApply = 0x00000080;
+
+        /// <summary>
+        /// Set display config: use supplied display config
+        /// </summary>
+        public const uint SdcUseSuppliedDisplayConfig = 0x00000020;
+
+        /// <summary>
+        /// Set display config: save to database
+        /// </summary>
+        public const uint SdcSaveToDatabase = 0x00000200;
+
+        /// <summary>
+        /// Set display config: topology supplied
+        /// </summary>
+        public const uint SdcTopologySupplied = 0x00000010;
+
+        /// <summary>
+        /// Set display config: allow path order changes
+        /// </summary>
+        public const uint SdcAllowPathOrderChanges = 0x00002000;
+
+        /// <summary>
+        /// Get source name (GDI device name like "\\.\DISPLAY1")
+        /// </summary>
+        public const uint DisplayconfigDeviceInfoGetSourceName = 1;
+
+        /// <summary>
+        /// Get target name (monitor friendly name and hardware ID)
+        /// </summary>
+        public const uint DisplayconfigDeviceInfoGetTargetName = 2;
+
+        /// <summary>
+        /// Get SDR white level
+        /// </summary>
+        public const uint DisplayconfigDeviceInfoGetSdrWhiteLevel = 7;
+
+        /// <summary>
+        /// Get advanced color information
+        /// </summary>
+        public const uint DisplayconfigDeviceInfoGetAdvancedColorInfo = 9;
+
+        /// <summary>
+        /// Set SDR white level (custom)
+        /// </summary>
+        public const uint DisplayconfigDeviceInfoSetSdrWhiteLevel = 0xFFFFFFEE;
+
+        /// <summary>
+        /// Path active
+        /// </summary>
+        public const uint DisplayconfigPathActive = 0x00000001;
+
+        /// <summary>
+        /// Path mode index invalid
+        /// </summary>
+        public const uint DisplayconfigPathModeIdxInvalid = 0xFFFFFFFF;
+
+        /// <summary>
+        /// COM initialization: multithreaded
+        /// </summary>
+        public const uint CoinitMultithreaded = 0x0;
+
+        /// <summary>
+        /// RPC authentication level: connect
+        /// </summary>
+        public const uint RpcCAuthnLevelConnect = 2;
+
+        /// <summary>
+        /// RPC impersonation level: impersonate
+        /// </summary>
+        public const uint RpcCImpLevelImpersonate = 3;
+
+        /// <summary>
+        /// RPC authentication service: Win NT
+        /// </summary>
+        public const uint RpcCAuthnWinnt = 10;
+
+        /// <summary>
+        /// RPC authorization service: none
+        /// </summary>
+        public const uint RpcCAuthzNone = 0;
+
+        /// <summary>
+        /// RPC authentication level: call
+        /// </summary>
+        public const uint RpcCAuthnLevelCall = 3;
+
+        /// <summary>
+        /// EOAC: none
+        /// </summary>
+        public const uint EoacNone = 0;
+
+        /// <summary>
+        /// WMI flag: forward only
+        /// </summary>
+        public const long WbemFlagForwardOnly = 0x20;
+
+        /// <summary>
+        /// WMI flag: return immediately
+        /// </summary>
+        public const long WbemFlagReturnImmediately = 0x10;
+
+        /// <summary>
+        /// WMI flag: connect use max wait
+        /// </summary>
+        public const long WbemFlagConnectUseMaxWait = 0x80;
+
+        /// <summary>
+        /// Success
+        /// </summary>
+        public const int ErrorSuccess = 0;
+
+        /// <summary>
+        /// Insufficient buffer
+        /// </summary>
+        public const int ErrorInsufficientBuffer = 122;
+
+        /// <summary>
+        /// Invalid parameter
+        /// </summary>
+        public const int ErrorInvalidParameter = 87;
+
+        /// <summary>
+        /// Access denied
+        /// </summary>
+        public const int ErrorAccessDenied = 5;
+
+        /// <summary>
+        /// General failure
+        /// </summary>
+        public const int ErrorGenFailure = 31;
+
+        /// <summary>
+        /// Unsupported VCP code
+        /// </summary>
+        public const int ErrorGraphicsDdcciVcpNotSupported = -1071243251;
+
+        /// <summary>
+        /// Infinite wait
+        /// </summary>
+        public const uint Infinite = 0xFFFFFFFF;
+
+        /// <summary>
+        /// User message
+        /// </summary>
+        public const uint WmUser = 0x0400;
+
+        /// <summary>
+        /// Output technology: HDMI
+        /// </summary>
+        public const uint DisplayconfigOutputTechnologyHdmi = 5;
+
+        /// <summary>
+        /// Output technology: DVI
+        /// </summary>
+        public const uint DisplayconfigOutputTechnologyDvi = 4;
+
+        /// <summary>
+        /// Output technology: DisplayPort
+        /// </summary>
+        public const uint DisplayconfigOutputTechnologyDisplayportExternal = 6;
+
+        /// <summary>
+        /// Output technology: internal
+        /// </summary>
+        public const uint DisplayconfigOutputTechnologyInternal = 0x80000000;
+
+        /// <summary>
+        /// HDR minimum SDR white level (nits)
+        /// </summary>
+        public const int HdrMinSdrWhiteLevel = 80;
+
+        /// <summary>
+        /// HDR maximum SDR white level (nits)
+        /// </summary>
+        public const int HdrMaxSdrWhiteLevel = 480;
+
+        /// <summary>
+        /// SDR white level conversion factor
+        /// </summary>
+        public const int SdrWhiteLevelFactor = 80;
+
+        /// <summary>
+        /// Retrieve the current settings for the display device.
+        /// </summary>
+        public const int EnumCurrentSettings = -1;
+
+        /// <summary>
+        /// Retrieve the settings for the display device that are stored in the registry.
+        /// </summary>
+        public const int EnumRegistrySettings = -2;
+
+        /// <summary>
+        /// The display is in the natural orientation of the device.
+        /// </summary>
+        public const int DmdoDefault = 0;
+
+        /// <summary>
+        /// The display is rotated 90 degrees (measured clockwise) from its natural orientation.
+        /// </summary>
+        public const int Dmdo90 = 1;
+
+        /// <summary>
+        /// The display is rotated 180 degrees (measured clockwise) from its natural orientation.
+        /// </summary>
+        public const int Dmdo180 = 2;
+
+        /// <summary>
+        /// The display is rotated 270 degrees (measured clockwise) from its natural orientation.
+        /// </summary>
+        public const int Dmdo270 = 3;
+
+        // ==================== DEVMODE field flags ====================
+
+        /// <summary>
+        /// DmDisplayOrientation field is valid.
+        /// </summary>
+        public const int DmDisplayOrientation = 0x00000080;
+
+        /// <summary>
+        /// DmPelsWidth field is valid.
+        /// </summary>
+        public const int DmPelsWidth = 0x00080000;
+
+        /// <summary>
+        /// DmPelsHeight field is valid.
+        /// </summary>
+        public const int DmPelsHeight = 0x00100000;
+
+        // ==================== ChangeDisplaySettings flags ====================
+
+        /// <summary>
+        /// The settings change is temporary. Not saved to registry.
+        /// </summary>
+        public const uint CdsUpdateregistry = 0x00000001;
+
+        /// <summary>
+        /// Test the graphics mode but don't actually set it.
+        /// </summary>
+        public const uint CdsTest = 0x00000002;
+
+        /// <summary>
+        /// The mode is fullscreen.
+        /// </summary>
+        public const uint CdsFullscreen = 0x00000004;
+
+        /// <summary>
+        /// The settings apply to all users.
+        /// </summary>
+        public const uint CdsGlobal = 0x00000008;
+
+        /// <summary>
+        /// Set the primary display.
+        /// </summary>
+        public const uint CdsSetPrimary = 0x00000010;
+
+        /// <summary>
+        /// Reset the mode after a dynamic mode change.
+        /// </summary>
+        public const uint CdsReset = 0x40000000;
+
+        /// <summary>
+        /// Don't reset the mode.
+        /// </summary>
+        public const uint CdsNoreset = 0x10000000;
+
+        // ==================== ChangeDisplaySettings result codes ====================
+
+        /// <summary>
+        /// The settings change was successful.
+        /// </summary>
+        public const int DispChangeSuccessful = 0;
+
+        /// <summary>
+        /// The computer must be restarted for the graphics mode to work.
+        /// </summary>
+        public const int DispChangeRestart = 1;
+
+        /// <summary>
+        /// The display driver failed the specified graphics mode.
+        /// </summary>
+        public const int DispChangeFailed = -1;
+
+        /// <summary>
+        /// The graphics mode is not supported.
+        /// </summary>
+        public const int DispChangeBadmode = -2;
+
+        /// <summary>
+        /// Unable to write settings to the registry.
+        /// </summary>
+        public const int DispChangeNotupdated = -3;
+
+        /// <summary>
+        /// An invalid set of flags was passed in.
+        /// </summary>
+        public const int DispChangeBadflags = -4;
+
+        /// <summary>
+        /// An invalid parameter was passed in.
+        /// </summary>
+        public const int DispChangeBadparam = -5;
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/NativeDelegates.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace PowerDisplay.Common.Drivers;
+
+/// <summary>
+/// Native delegate type definitions
+/// </summary>
+public static class NativeDelegates
+{
+    /// <summary>
+    /// Monitor enumeration procedure delegate
+    /// </summary>
+    /// <param name="hMonitor">Monitor handle</param>
+    /// <param name="hdcMonitor">Monitor device context</param>
+    /// <param name="lprcMonitor">Pointer to monitor rectangle</param>
+    /// <param name="dwData">User data</param>
+    /// <returns>True to continue enumeration</returns>
+    [UnmanagedFunctionPointer(CallingConvention.StdCall)]
+    public delegate bool MonitorEnumProc(IntPtr hMonitor, IntPtr hdcMonitor, IntPtr lprcMonitor, IntPtr dwData);
+
+    /// <summary>
+    /// Thread start routine delegate
+    /// </summary>
+    /// <param name="lpParameter">Thread parameter</param>
+    /// <returns>Thread exit code</returns>
+    public delegate uint ThreadStartRoutine(IntPtr lpParameter);
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/NativeStructures.cs

@@ -0,0 +1,484 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+#pragma warning disable SA1649 // File name should match first type name - Multiple related P/Invoke structures
+
+namespace PowerDisplay.Common.Drivers
+{
+    /// <summary>
+    /// Physical monitor structure for DDC/CI
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct PhysicalMonitor
+    {
+        /// <summary>
+        /// Physical monitor handle
+        /// </summary>
+        public IntPtr HPhysicalMonitor;
+
+        /// <summary>
+        /// Physical monitor description string - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort SzPhysicalMonitorDescription[128];
+
+        /// <summary>
+        /// Helper method to get description as string
+        /// </summary>
+        public readonly string GetDescription()
+        {
+            fixed (ushort* ptr = SzPhysicalMonitorDescription)
+            {
+                return new string((char*)ptr);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Rectangle structure
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct Rect
+    {
+        public int Left;
+        public int Top;
+        public int Right;
+        public int Bottom;
+
+        public int Width => Right - Left;
+
+        public int Height => Bottom - Top;
+
+        public Rect(int left, int top, int right, int bottom)
+        {
+            Left = left;
+            Top = top;
+            Right = right;
+            Bottom = bottom;
+        }
+    }
+
+    /// <summary>
+    /// Monitor information extended structure
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct MonitorInfoEx
+    {
+        /// <summary>
+        /// Structure size
+        /// </summary>
+        public uint CbSize;
+
+        /// <summary>
+        /// Monitor rectangle area
+        /// </summary>
+        public Rect RcMonitor;
+
+        /// <summary>
+        /// Work area rectangle
+        /// </summary>
+        public Rect RcWork;
+
+        /// <summary>
+        /// Flags
+        /// </summary>
+        public uint DwFlags;
+
+        /// <summary>
+        /// Device name (e.g., "\\.\DISPLAY1") - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort SzDevice[32];
+
+        /// <summary>
+        /// Helper property to get device name as string
+        /// </summary>
+        public readonly string GetDeviceName()
+        {
+            fixed (ushort* ptr = SzDevice)
+            {
+                return new string((char*)ptr);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Display device structure
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct DisplayDevice
+    {
+        /// <summary>
+        /// Structure size
+        /// </summary>
+        public uint Cb;
+
+        /// <summary>
+        /// Device name (e.g., "\\.\DISPLAY1\Monitor0") - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DeviceName[32];
+
+        /// <summary>
+        /// Device description string - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DeviceString[128];
+
+        /// <summary>
+        /// Status flags
+        /// </summary>
+        public uint StateFlags;
+
+        /// <summary>
+        /// Device ID - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DeviceID[128];
+
+        /// <summary>
+        /// Registry device key - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DeviceKey[128];
+
+        /// <summary>
+        /// Helper method to get device name as string
+        /// </summary>
+        public readonly string GetDeviceName()
+        {
+            fixed (ushort* ptr = DeviceName)
+            {
+                return new string((char*)ptr);
+            }
+        }
+    }
+
+    /// <summary>
+    /// LUID (Locally Unique Identifier) structure
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct Luid
+    {
+        public uint LowPart;
+        public int HighPart;
+
+        public override string ToString()
+        {
+            return $"{HighPart:X8}:{LowPart:X8}";
+        }
+    }
+
+    /// <summary>
+    /// Display configuration path information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_PATH_INFO
+    {
+        public DISPLAYCONFIG_PATH_SOURCE_INFO SourceInfo;
+        public DISPLAYCONFIG_PATH_TARGET_INFO TargetInfo;
+        public uint Flags;
+    }
+
+    /// <summary>
+    /// Display configuration path source information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_PATH_SOURCE_INFO
+    {
+        public Luid AdapterId;
+        public uint Id;
+        public uint ModeInfoIdx;
+        public uint StatusFlags;
+    }
+
+    /// <summary>
+    /// Display configuration path target information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_PATH_TARGET_INFO
+    {
+        public Luid AdapterId;
+        public uint Id;
+        public uint ModeInfoIdx;
+        public uint OutputTechnology;
+        public uint Rotation;
+        public uint Scaling;
+        public DISPLAYCONFIG_RATIONAL RefreshRate;
+        public uint ScanLineOrdering;
+        public bool TargetAvailable;
+        public uint StatusFlags;
+    }
+
+    /// <summary>
+    /// Display configuration rational number
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_RATIONAL
+    {
+        public uint Numerator;
+        public uint Denominator;
+    }
+
+    /// <summary>
+    /// Display configuration mode information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_MODE_INFO
+    {
+        public uint InfoType;
+        public uint Id;
+        public Luid AdapterId;
+        public DISPLAYCONFIG_MODE_INFO_UNION ModeInfo;
+    }
+
+    /// <summary>
+    /// Display configuration mode information union
+    /// </summary>
+    [StructLayout(LayoutKind.Explicit)]
+    public struct DISPLAYCONFIG_MODE_INFO_UNION
+    {
+        [FieldOffset(0)]
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("StyleCop.CSharp.NamingRules", "SA1307:Accessible fields should begin with upper-case letter", Justification = "Native API structure field")]
+        public DISPLAYCONFIG_TARGET_MODE targetMode;
+
+        [FieldOffset(0)]
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("StyleCop.CSharp.NamingRules", "SA1307:Accessible fields should begin with upper-case letter", Justification = "Native API structure field")]
+        public DISPLAYCONFIG_SOURCE_MODE sourceMode;
+    }
+
+    /// <summary>
+    /// Display configuration target mode
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_TARGET_MODE
+    {
+        public DISPLAYCONFIG_VIDEO_SIGNAL_INFO TargetVideoSignalInfo;
+    }
+
+    /// <summary>
+    /// Display configuration source mode
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_SOURCE_MODE
+    {
+        public uint Width;
+        public uint Height;
+        public uint PixelFormat;
+        public DISPLAYCONFIG_POINT Position;
+    }
+
+    /// <summary>
+    /// Display configuration point
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_POINT
+    {
+        public int X;
+        public int Y;
+    }
+
+    /// <summary>
+    /// Display configuration video signal information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_VIDEO_SIGNAL_INFO
+    {
+        public ulong PixelRate;
+        public DISPLAYCONFIG_RATIONAL HSyncFreq;
+        public DISPLAYCONFIG_RATIONAL VSyncFreq;
+        public DISPLAYCONFIG_2DREGION ActiveSize;
+        public DISPLAYCONFIG_2DREGION TotalSize;
+        public uint VideoStandard;
+        public uint ScanLineOrdering;
+    }
+
+    /// <summary>
+    /// Display configuration 2D region
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_2DREGION
+    {
+        public uint Cx;
+        public uint Cy;
+    }
+
+    /// <summary>
+    /// Display configuration device information header
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_DEVICE_INFO_HEADER
+    {
+        public uint Type;
+        public uint Size;
+        public Luid AdapterId;
+        public uint Id;
+    }
+
+    /// <summary>
+    /// Display configuration source device name - contains GDI device name (e.g., "\\.\DISPLAY1")
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct DISPLAYCONFIG_SOURCE_DEVICE_NAME
+    {
+        public DISPLAYCONFIG_DEVICE_INFO_HEADER Header;
+
+        /// <summary>
+        /// GDI device name - fixed buffer for 32 wide characters (CCHDEVICENAME)
+        /// </summary>
+        public fixed ushort ViewGdiDeviceName[32];
+
+        /// <summary>
+        /// Helper method to get GDI device name as string
+        /// </summary>
+        public readonly string GetViewGdiDeviceName()
+        {
+            fixed (ushort* ptr = ViewGdiDeviceName)
+            {
+                return new string((char*)ptr);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Display configuration target device name
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct DISPLAYCONFIG_TARGET_DEVICE_NAME
+    {
+        public DISPLAYCONFIG_DEVICE_INFO_HEADER Header;
+        public uint Flags;
+        public uint OutputTechnology;
+        public ushort EdidManufactureId;
+        public ushort EdidProductCodeId;
+        public uint ConnectorInstance;
+
+        /// <summary>
+        /// Monitor friendly name - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort MonitorFriendlyDeviceName[64];
+
+        /// <summary>
+        /// Monitor device path - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort MonitorDevicePath[128];
+
+        /// <summary>
+        /// Helper method to get monitor friendly name as string
+        /// </summary>
+        public readonly string GetMonitorFriendlyDeviceName()
+        {
+            fixed (ushort* ptr = MonitorFriendlyDeviceName)
+            {
+                return new string((char*)ptr);
+            }
+        }
+
+        /// <summary>
+        /// Helper method to get monitor device path as string
+        /// </summary>
+        public readonly string GetMonitorDevicePath()
+        {
+            fixed (ushort* ptr = MonitorDevicePath)
+            {
+                return new string((char*)ptr);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Display configuration SDR white level
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_SDR_WHITE_LEVEL
+    {
+        public DISPLAYCONFIG_DEVICE_INFO_HEADER Header;
+        public uint SDRWhiteLevel;
+    }
+
+    /// <summary>
+    /// Display configuration advanced color information
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_GET_ADVANCED_COLOR_INFO
+    {
+        public DISPLAYCONFIG_DEVICE_INFO_HEADER Header;
+        public uint AdvancedColorSupported;
+        public uint AdvancedColorEnabled;
+        public uint BitsPerColorChannel;
+        public uint ColorEncoding;
+        public uint FormatSupport;
+    }
+
+    /// <summary>
+    /// Custom structure for setting SDR white level
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct DISPLAYCONFIG_SET_SDR_WHITE_LEVEL
+    {
+        public DISPLAYCONFIG_DEVICE_INFO_HEADER Header;
+        public uint SDRWhiteLevel;
+        public byte FinalValue;
+    }
+
+    /// <summary>
+    /// Point structure
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct POINT
+    {
+        public int X;
+        public int Y;
+
+        public POINT(int x, int y)
+        {
+            this.X = x;
+            this.Y = y;
+        }
+    }
+
+    /// <summary>
+    /// The DEVMODE structure contains information about the initialization and environment of a printer or a display device.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public unsafe struct DevMode
+    {
+        /// <summary>
+        /// Device name - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DmDeviceName[32];
+
+        public short DmSpecVersion;
+        public short DmDriverVersion;
+        public short DmSize;
+        public short DmDriverExtra;
+        public int DmFields;
+        public int DmPositionX;
+        public int DmPositionY;
+        public int DmDisplayOrientation;
+        public int DmDisplayFixedOutput;
+        public short DmColor;
+        public short DmDuplex;
+        public short DmYResolution;
+        public short DmTTOption;
+        public short DmCollate;
+
+        /// <summary>
+        /// Form name - fixed buffer for LibraryImport compatibility
+        /// </summary>
+        public fixed ushort DmFormName[32];
+
+        public short DmLogPixels;
+        public int DmBitsPerPel;
+        public int DmPelsWidth;
+        public int DmPelsHeight;
+        public int DmDisplayFlags;
+        public int DmDisplayFrequency;
+        public int DmICMMethod;
+        public int DmICMIntent;
+        public int DmMediaType;
+        public int DmDitherType;
+        public int DmReserved1;
+        public int DmReserved2;
+        public int DmPanningWidth;
+        public int DmPanningHeight;
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/PInvoke.cs

@@ -0,0 +1,151 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace PowerDisplay.Common.Drivers
+{
+    /// <summary>
+    /// P/Invoke declarations using LibraryImport source generator
+    /// </summary>
+    internal static partial class PInvoke
+    {
+        // ==================== User32.dll - Display Configuration ====================
+        [LibraryImport("user32.dll")]
+        internal static partial int GetDisplayConfigBufferSizes(
+            uint flags,
+            out uint numPathArrayElements,
+            out uint numModeInfoArrayElements);
+
+        // Use unsafe pointer to avoid runtime marshalling
+        [LibraryImport("user32.dll")]
+        internal static unsafe partial int QueryDisplayConfig(
+            uint flags,
+            ref uint numPathArrayElements,
+            DISPLAYCONFIG_PATH_INFO* pathArray,
+            ref uint numModeInfoArrayElements,
+            DISPLAYCONFIG_MODE_INFO* modeInfoArray,
+            IntPtr currentTopologyId);
+
+        [LibraryImport("user32.dll")]
+        internal static partial int DisplayConfigGetDeviceInfo(
+            ref DISPLAYCONFIG_TARGET_DEVICE_NAME deviceName);
+
+        [LibraryImport("user32.dll")]
+        internal static partial int DisplayConfigGetDeviceInfo(
+            ref DISPLAYCONFIG_SOURCE_DEVICE_NAME sourceName);
+
+        // ==================== User32.dll - Monitor Enumeration ====================
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool EnumDisplayMonitors(
+            IntPtr hdc,
+            IntPtr lprcClip,
+            NativeDelegates.MonitorEnumProc lpfnEnum,
+            IntPtr dwData);
+
+        [LibraryImport("user32.dll", EntryPoint = "GetMonitorInfoW", StringMarshalling = StringMarshalling.Utf16)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool GetMonitorInfo(
+            IntPtr hMonitor,
+            ref MonitorInfoEx lpmi);
+
+        [LibraryImport("user32.dll", EntryPoint = "EnumDisplayDevicesW", StringMarshalling = StringMarshalling.Utf16)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool EnumDisplayDevices(
+            [MarshalAs(UnmanagedType.LPWStr)] string? lpDevice,
+            uint iDevNum,
+            ref DisplayDevice lpDisplayDevice,
+            uint dwFlags);
+
+        [LibraryImport("user32.dll", EntryPoint = "EnumDisplaySettingsW", StringMarshalling = StringMarshalling.Utf16)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static unsafe partial bool EnumDisplaySettings(
+            [MarshalAs(UnmanagedType.LPWStr)] string? lpszDeviceName,
+            int iModeNum,
+            DevMode* lpDevMode);
+
+        [LibraryImport("user32.dll", EntryPoint = "ChangeDisplaySettingsExW", StringMarshalling = StringMarshalling.Utf16)]
+        internal static unsafe partial int ChangeDisplaySettingsEx(
+            [MarshalAs(UnmanagedType.LPWStr)] string? lpszDeviceName,
+            DevMode* lpDevMode,
+            IntPtr hwnd,
+            uint dwflags,
+            IntPtr lParam);
+
+        [LibraryImport("user32.dll")]
+        internal static partial IntPtr MonitorFromWindow(
+            IntPtr hwnd,
+            uint dwFlags);
+
+        [LibraryImport("user32.dll")]
+        internal static partial IntPtr MonitorFromPoint(
+            POINT pt,
+            uint dwFlags);
+
+        // ==================== Dxva2.dll - DDC/CI Monitor Control ====================
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool GetNumberOfPhysicalMonitorsFromHMONITOR(
+            IntPtr hMonitor,
+            out uint pdwNumberOfPhysicalMonitors);
+
+        // Use unsafe pointer to avoid ArraySubType limitation
+        [LibraryImport("Dxva2.dll", StringMarshalling = StringMarshalling.Utf16)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static unsafe partial bool GetPhysicalMonitorsFromHMONITOR(
+            IntPtr hMonitor,
+            uint dwPhysicalMonitorArraySize,
+            PhysicalMonitor* pPhysicalMonitorArray);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool DestroyPhysicalMonitor(IntPtr hMonitor);
+
+        // Use unsafe pointer to avoid LPArray limitation
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static unsafe partial bool DestroyPhysicalMonitors(
+            uint dwPhysicalMonitorArraySize,
+            PhysicalMonitor* pPhysicalMonitorArray);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool GetVCPFeatureAndVCPFeatureReply(
+            IntPtr hPhysicalMonitor,
+            byte bVCPCode,
+            IntPtr pvct,
+            out uint pdwCurrentValue,
+            out uint pdwMaximumValue);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool SetVCPFeature(
+            IntPtr hPhysicalMonitor,
+            byte bVCPCode,
+            uint dwNewValue);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool SaveCurrentSettings(IntPtr hPhysicalMonitor);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool GetCapabilitiesStringLength(
+            IntPtr hPhysicalMonitor,
+            out uint pdwCapabilitiesStringLengthInCharacters);
+
+        [LibraryImport("Dxva2.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static partial bool CapabilitiesRequestAndCapabilitiesReply(
+            IntPtr hPhysicalMonitor,
+            IntPtr pszASCIICapabilitiesString,
+            uint dwCapabilitiesStringLengthInCharacters);
+
+        // ==================== Kernel32.dll ====================
+        [LibraryImport("kernel32.dll")]
+        internal static partial uint GetLastError();
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/WMI/WmiController.cs

@@ -0,0 +1,376 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using PowerDisplay.Common.Interfaces;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Utils;
+using WmiLight;
+using Monitor = PowerDisplay.Common.Models.Monitor;
+
+namespace PowerDisplay.Common.Drivers.WMI
+{
+    /// <summary>
+    /// WMI monitor controller for controlling internal laptop displays.
+    /// Rewritten to use WmiLight library for Native AOT compatibility.
+    /// </summary>
+    public partial class WmiController : IMonitorController, IDisposable
+    {
+        private const string WmiNamespace = @"root\WMI";
+        private const string BrightnessQueryClass = "WmiMonitorBrightness";
+        private const string BrightnessMethodClass = "WmiMonitorBrightnessMethods";
+
+        // Common WMI error codes for classification
+        private const int WbemENotFound = unchecked((int)0x80041002);
+        private const int WbemEAccessDenied = unchecked((int)0x80041003);
+        private const int WbemEProviderFailure = unchecked((int)0x80041004);
+        private const int WbemEInvalidQuery = unchecked((int)0x80041017);
+        private const int WmiFeatureNotSupported = 0x1068;
+
+        /// <summary>
+        /// Classifies WMI exceptions into user-friendly error messages.
+        /// </summary>
+        private static MonitorOperationResult ClassifyWmiError(WmiException ex, string operation)
+        {
+            var hresult = ex.HResult;
+
+            return hresult switch
+            {
+                WbemENotFound => MonitorOperationResult.Failure($"WMI class not found during {operation}. This feature may not be supported on your system.", hresult),
+                WbemEAccessDenied => MonitorOperationResult.Failure($"Access denied during {operation}. Administrator privileges may be required.", hresult),
+                WbemEProviderFailure => MonitorOperationResult.Failure($"WMI provider failure during {operation}. The display driver may not support this feature.", hresult),
+                WbemEInvalidQuery => MonitorOperationResult.Failure($"Invalid WMI query during {operation}. This is likely a bug.", hresult),
+                WmiFeatureNotSupported => MonitorOperationResult.Failure($"WMI brightness control not supported on this system during {operation}.", hresult),
+                _ => MonitorOperationResult.Failure($"WMI error during {operation}: {ex.Message}", hresult),
+            };
+        }
+
+        /// <summary>
+        /// Escape special characters in WMI query strings.
+        /// WMI requires backslashes and single quotes to be escaped in WHERE clauses.
+        /// See: https://learn.microsoft.com/en-us/windows/win32/wmisdk/wql-sql-for-wmi
+        /// </summary>
+        /// <param name="value">The string value to escape.</param>
+        /// <returns>The escaped string safe for use in WMI queries.</returns>
+        private static string EscapeWmiString(string value)
+        {
+            if (string.IsNullOrEmpty(value))
+            {
+                return value;
+            }
+
+            // WMI requires backslashes and single quotes to be escaped in WHERE clauses
+            // Backslash must be escaped first to avoid double-escaping the quote's backslash
+            return value.Replace("\\", "\\\\").Replace("'", "\\'");
+        }
+
+        /// <summary>
+        /// Extract hardware ID from WMI InstanceName.
+        /// InstanceName format: "DISPLAY\BOE0900\4&amp;10fd3ab1&amp;0&amp;UID265988_0"
+        /// Returns the second segment (e.g., "BOE0900") which is the manufacturer+product code.
+        /// </summary>
+        /// <param name="instanceName">The WMI InstanceName.</param>
+        /// <returns>The hardware ID extracted from the InstanceName, or empty string if extraction fails.</returns>
+        private static string ExtractHardwareIdFromInstanceName(string instanceName)
+        {
+            if (string.IsNullOrEmpty(instanceName))
+            {
+                return string.Empty;
+            }
+
+            // Split by backslash: ["DISPLAY", "BOE0900", "4&10fd3ab1&0&UID265988_0"]
+            var parts = instanceName.Split('\\');
+            if (parts.Length >= 2 && !string.IsNullOrEmpty(parts[1]))
+            {
+                // Return the second part (e.g., "BOE0900")
+                return parts[1];
+            }
+
+            return string.Empty;
+        }
+
+        /// <summary>
+        /// Build a WMI query filtered by monitor instance name.
+        /// </summary>
+        /// <param name="wmiClass">The WMI class to query.</param>
+        /// <param name="instanceName">The monitor instance name to filter by.</param>
+        /// <param name="selectClause">Optional SELECT clause fields (defaults to "*").</param>
+        /// <returns>The formatted WMI query string.</returns>
+        private static string BuildInstanceNameQuery(string wmiClass, string instanceName, string selectClause = "*")
+        {
+            var escapedInstanceName = EscapeWmiString(instanceName);
+            return $"SELECT {selectClause} FROM {wmiClass} WHERE InstanceName = '{escapedInstanceName}'";
+        }
+
+        /// <summary>
+        /// Get MonitorDisplayInfo from dictionary by matching HardwareId.
+        /// Uses QueryDisplayConfig path index which matches Windows Display Settings "Identify" feature.
+        /// </summary>
+        /// <param name="hardwareId">The hardware ID to match (e.g., "LEN4038", "BOE0900").</param>
+        /// <param name="monitorDisplayInfos">Dictionary of monitor display info from QueryDisplayConfig.</param>
+        /// <returns>MonitorDisplayInfo if found, or null if not found.</returns>
+        private static Drivers.DDC.MonitorDisplayInfo? GetMonitorDisplayInfoByHardwareId(string hardwareId, Dictionary<string, Drivers.DDC.MonitorDisplayInfo> monitorDisplayInfos)
+        {
+            if (string.IsNullOrEmpty(hardwareId) || monitorDisplayInfos == null || monitorDisplayInfos.Count == 0)
+            {
+                return null;
+            }
+
+            var match = monitorDisplayInfos.Values.FirstOrDefault(
+                v => hardwareId.Equals(v.HardwareId, StringComparison.OrdinalIgnoreCase));
+
+            // Check if match was found (struct default has null/empty HardwareId)
+            if (!string.IsNullOrEmpty(match.HardwareId))
+            {
+                return match;
+            }
+
+            Logger.LogWarning($"WMI: Could not find MonitorDisplayInfo for HardwareId '{hardwareId}'");
+            return null;
+        }
+
+        public string Name => "WMI Monitor Controller";
+
+        /// <summary>
+        /// Get monitor brightness
+        /// </summary>
+        public async Task<VcpFeatureValue> GetBrightnessAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+
+            return await Task.Run(
+                () =>
+                {
+                    try
+                    {
+                        using var connection = new WmiConnection(WmiNamespace);
+                        var query = BuildInstanceNameQuery(BrightnessQueryClass, monitor.InstanceName, "CurrentBrightness");
+                        var results = connection.CreateQuery(query);
+
+                        foreach (var obj in results)
+                        {
+                            var currentBrightness = obj.GetPropertyValue<byte>("CurrentBrightness");
+                            return new VcpFeatureValue(currentBrightness, 0, 100);
+                        }
+
+                        // No match found - monitor may have been disconnected
+                    }
+                    catch (WmiException ex)
+                    {
+                        Logger.LogWarning($"WMI GetBrightness failed: {ex.Message} (HResult: 0x{ex.HResult:X})");
+                    }
+                    catch (Exception ex)
+                    {
+                        Logger.LogWarning($"WMI GetBrightness failed: {ex.Message}");
+                    }
+
+                    return VcpFeatureValue.Invalid;
+                },
+                cancellationToken);
+        }
+
+        /// <summary>
+        /// Set monitor brightness
+        /// </summary>
+        public async Task<MonitorOperationResult> SetBrightnessAsync(Monitor monitor, int brightness, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+
+            // Validate brightness range
+            brightness = Math.Clamp(brightness, 0, 100);
+
+            return await Task.Run(
+                () =>
+                {
+                    try
+                    {
+                        using var connection = new WmiConnection(WmiNamespace);
+                        var query = BuildInstanceNameQuery(BrightnessMethodClass, monitor.InstanceName);
+                        var results = connection.CreateQuery(query);
+
+                        foreach (var obj in results)
+                        {
+                            // Call WmiSetBrightness method
+                            // Parameters: Timeout (uint32), Brightness (uint8)
+                            // Note: WmiLight requires string values for method parameters
+                            using (WmiMethod method = obj.GetMethod("WmiSetBrightness"))
+                            using (WmiMethodParameters inParams = method.CreateInParameters())
+                            {
+                                inParams.SetPropertyValue("Timeout", "0");
+                                inParams.SetPropertyValue("Brightness", brightness.ToString(CultureInfo.InvariantCulture));
+
+                                uint result = obj.ExecuteMethod<uint>(
+                                    method,
+                                    inParams,
+                                    out WmiMethodParameters outParams);
+
+                                // Check return value (0 indicates success)
+                                if (result == 0)
+                                {
+                                    return MonitorOperationResult.Success();
+                                }
+
+                                return MonitorOperationResult.Failure($"WMI method returned error code: {result}", (int)result);
+                            }
+                        }
+
+                        // No match found - monitor may have been disconnected
+                        Logger.LogWarning($"WMI SetBrightness: No monitor found with InstanceName '{monitor.InstanceName}'");
+                        return MonitorOperationResult.Failure($"No WMI brightness method found for monitor '{monitor.InstanceName}'");
+                    }
+                    catch (UnauthorizedAccessException)
+                    {
+                        return MonitorOperationResult.Failure("Access denied. Administrator privileges may be required.", 5);
+                    }
+                    catch (WmiException ex)
+                    {
+                        return ClassifyWmiError(ex, "SetBrightness");
+                    }
+                    catch (Exception ex)
+                    {
+                        return MonitorOperationResult.Failure($"Unexpected error during SetBrightness: {ex.Message}");
+                    }
+                },
+                cancellationToken);
+        }
+
+        /// <summary>
+        /// Discover supported monitors.
+        /// WMI brightness control is typically only available on internal laptop displays,
+        /// which don't have meaningful UserFriendlyName in WmiMonitorID, so we use "Built-in Display".
+        /// </summary>
+        public async Task<IEnumerable<Monitor>> DiscoverMonitorsAsync(CancellationToken cancellationToken = default)
+        {
+            return await Task.Run(
+                () =>
+                {
+                var monitors = new List<Monitor>();
+
+                try
+                {
+                    using var connection = new WmiConnection(WmiNamespace);
+
+                    // Query WMI brightness support - only internal displays typically support this
+                    var brightnessQuery = $"SELECT InstanceName, CurrentBrightness FROM {BrightnessQueryClass}";
+                    var brightnessResults = connection.CreateQuery(brightnessQuery).ToList();
+
+                    if (brightnessResults.Count == 0)
+                    {
+                        return monitors;
+                    }
+
+                    // Get MonitorDisplayInfo from QueryDisplayConfig - this provides the correct monitor numbers
+                    var monitorDisplayInfos = Drivers.DDC.DdcCiNative.GetAllMonitorDisplayInfo();
+
+                    // Create monitor objects for each supported brightness instance
+                    foreach (var obj in brightnessResults)
+                    {
+                        try
+                        {
+                            var instanceName = obj.GetPropertyValue<string>("InstanceName") ?? string.Empty;
+                            var currentBrightness = obj.GetPropertyValue<byte>("CurrentBrightness");
+
+                            // Extract hardware ID from InstanceName
+                            // e.g., "DISPLAY\LEN4038\4&40f4dee&0&UID8388688_0" -> "LEN4038"
+                            var hardwareId = ExtractHardwareIdFromInstanceName(instanceName);
+
+                            // Get MonitorDisplayInfo from QueryDisplayConfig by matching hardware ID
+                            // This provides MonitorNumber and GdiDeviceName for display settings APIs
+                            var displayInfo = GetMonitorDisplayInfoByHardwareId(hardwareId, monitorDisplayInfos);
+                            int monitorNumber = displayInfo?.MonitorNumber ?? 0;
+                            string gdiDeviceName = displayInfo?.GdiDeviceName ?? string.Empty;
+
+                            // Generate unique monitor Id: "WMI_{HardwareId}_{MonitorNumber}"
+                            string monitorId = !string.IsNullOrEmpty(hardwareId)
+                                ? $"WMI_{hardwareId}_{monitorNumber}"
+                                : $"WMI_Unknown_{monitorNumber}";
+
+                            // Get display name from PnP manufacturer ID (e.g., "Lenovo Built-in Display")
+                            var displayName = PnpIdHelper.GetBuiltInDisplayName(hardwareId);
+
+                            var monitor = new Monitor
+                            {
+                                Id = monitorId,
+                                Name = displayName,
+                                CurrentBrightness = currentBrightness,
+                                MinBrightness = 0,
+                                MaxBrightness = 100,
+                                IsAvailable = true,
+                                InstanceName = instanceName,
+                                Capabilities = MonitorCapabilities.Brightness | MonitorCapabilities.Wmi,
+                                CommunicationMethod = "WMI",
+                                SupportsColorTemperature = false,
+                                MonitorNumber = monitorNumber,
+                                GdiDeviceName = gdiDeviceName,
+                            };
+
+                            monitors.Add(monitor);
+                        }
+                        catch (Exception ex)
+                        {
+                            Logger.LogWarning($"Failed to create monitor from WMI data: {ex.Message}");
+                        }
+                    }
+                }
+                catch (WmiException ex)
+                {
+                    Logger.LogError($"WMI DiscoverMonitors failed: {ex.Message} (HResult: 0x{ex.HResult:X})");
+                }
+                catch (Exception ex)
+                {
+                    Logger.LogError($"WMI DiscoverMonitors failed: {ex.Message}");
+                }
+
+                return monitors;
+            },
+                cancellationToken);
+        }
+
+        // Extended features not supported by WMI
+        public Task<MonitorOperationResult> SetContrastAsync(Monitor monitor, int contrast, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(MonitorOperationResult.Failure("Contrast control not supported via WMI"));
+        }
+
+        public Task<MonitorOperationResult> SetVolumeAsync(Monitor monitor, int volume, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(MonitorOperationResult.Failure("Volume control not supported via WMI"));
+        }
+
+        public Task<VcpFeatureValue> GetColorTemperatureAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(VcpFeatureValue.Invalid);
+        }
+
+        public Task<MonitorOperationResult> SetColorTemperatureAsync(Monitor monitor, int colorTemperature, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(MonitorOperationResult.Failure("Color temperature control not supported via WMI"));
+        }
+
+        public Task<VcpFeatureValue> GetInputSourceAsync(Monitor monitor, CancellationToken cancellationToken = default)
+        {
+            // Input source switching not supported for internal displays
+            return Task.FromResult(VcpFeatureValue.Invalid);
+        }
+
+        public Task<MonitorOperationResult> SetInputSourceAsync(Monitor monitor, int inputSource, CancellationToken cancellationToken = default)
+        {
+            // Input source switching not supported for internal displays
+            return Task.FromResult(MonitorOperationResult.Failure("Input source switching not supported via WMI"));
+        }
+
+        public void Dispose()
+        {
+            // WmiLight objects are created per-operation and disposed immediately via using statements.
+            // No instance-level resources require cleanup.
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Interfaces/IMonitorController.cs

@@ -0,0 +1,105 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using PowerDisplay.Common.Models;
+using Monitor = PowerDisplay.Common.Models.Monitor;
+
+namespace PowerDisplay.Common.Interfaces
+{
+    /// <summary>
+    /// Monitor controller interface
+    /// </summary>
+    public interface IMonitorController
+    {
+        /// <summary>
+        /// Gets controller name
+        /// </summary>
+        string Name { get; }
+
+        /// <summary>
+        /// Gets monitor brightness
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Brightness information</returns>
+        Task<VcpFeatureValue> GetBrightnessAsync(Monitor monitor, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Sets monitor brightness
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="brightness">Brightness value (0-100)</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        Task<MonitorOperationResult> SetBrightnessAsync(Monitor monitor, int brightness, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Discovers supported monitors
+        /// </summary>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>List of monitors</returns>
+        Task<IEnumerable<Monitor>> DiscoverMonitorsAsync(CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Sets monitor contrast
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="contrast">Contrast value (0-100)</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        Task<MonitorOperationResult> SetContrastAsync(Monitor monitor, int contrast, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Sets monitor volume
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="volume">Volume value (0-100)</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        Task<MonitorOperationResult> SetVolumeAsync(Monitor monitor, int volume, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Gets monitor color temperature using VCP 0x14 (Select Color Preset)
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>VCP preset value (e.g., 0x05 for 6500K), not Kelvin temperature</returns>
+        Task<VcpFeatureValue> GetColorTemperatureAsync(Monitor monitor, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Sets monitor color temperature using VCP 0x14 preset value
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="colorTemperature">VCP preset value (e.g., 0x05 for 6500K), not Kelvin temperature</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        Task<MonitorOperationResult> SetColorTemperatureAsync(Monitor monitor, int colorTemperature, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Gets current input source using VCP 0x60
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>VCP input source value (e.g., 0x11 for HDMI-1)</returns>
+        Task<VcpFeatureValue> GetInputSourceAsync(Monitor monitor, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Sets input source using VCP 0x60
+        /// </summary>
+        /// <param name="monitor">Monitor object</param>
+        /// <param name="inputSource">VCP input source value (e.g., 0x11 for HDMI-1)</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        Task<MonitorOperationResult> SetInputSourceAsync(Monitor monitor, int inputSource, CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Releases resources
+        /// </summary>
+        void Dispose();
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Interfaces/IMonitorData.cs

@@ -0,0 +1,56 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace PowerDisplay.Common.Interfaces
+{
+    /// <summary>
+    /// Core interface representing monitor hardware data.
+    /// This interface defines the actual hardware values for a monitor.
+    /// Implementations can add UI-specific properties and use converters for display formatting.
+    /// </summary>
+    public interface IMonitorData
+    {
+        /// <summary>
+        /// Gets or sets the unique identifier for the monitor.
+        /// </summary>
+        string Id { get; set; }
+
+        /// <summary>
+        /// Gets or sets the display name of the monitor.
+        /// </summary>
+        string Name { get; set; }
+
+        /// <summary>
+        /// Gets or sets the current brightness value (0-100).
+        /// </summary>
+        int Brightness { get; set; }
+
+        /// <summary>
+        /// Gets or sets the current contrast value (0-100).
+        /// </summary>
+        int Contrast { get; set; }
+
+        /// <summary>
+        /// Gets or sets the current volume value (0-100).
+        /// </summary>
+        int Volume { get; set; }
+
+        /// <summary>
+        /// Gets or sets the color temperature VCP preset value (raw DDC/CI value from VCP code 0x14).
+        /// This stores the raw VCP value (e.g., 0x05 for 6500K preset), not the Kelvin temperature.
+        /// Use MonitorValueConverter to convert to/from human-readable Kelvin values.
+        /// </summary>
+        int ColorTemperatureVcp { get; set; }
+
+        /// <summary>
+        /// Gets or sets the monitor number (1, 2, 3...) as assigned by the OS.
+        /// </summary>
+        int MonitorNumber { get; set; }
+
+        /// <summary>
+        /// Gets or sets the monitor orientation (0=0, 1=90, 2=180, 3=270).
+        /// </summary>
+        int Orientation { get; set; }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Interfaces/IProfileService.cs

@@ -0,0 +1,62 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using PowerDisplay.Common.Models;
+
+namespace PowerDisplay.Common.Interfaces
+{
+    /// <summary>
+    /// Interface for profile management service.
+    /// Provides abstraction for loading, saving, and managing PowerDisplay profiles.
+    /// Enables dependency injection and unit testing.
+    /// </summary>
+    public interface IProfileService
+    {
+        /// <summary>
+        /// Loads PowerDisplay profiles from disk.
+        /// </summary>
+        /// <returns>PowerDisplayProfiles object, or a new empty instance if file doesn't exist or load fails.</returns>
+        PowerDisplayProfiles LoadProfiles();
+
+        /// <summary>
+        /// Saves PowerDisplay profiles to disk.
+        /// </summary>
+        /// <param name="profiles">The profiles collection to save.</param>
+        /// <returns>True if save was successful, false otherwise.</returns>
+        bool SaveProfiles(PowerDisplayProfiles profiles);
+
+        /// <summary>
+        /// Adds or updates a profile in the collection and persists to disk.
+        /// </summary>
+        /// <param name="profile">The profile to add or update.</param>
+        /// <returns>True if operation was successful, false otherwise.</returns>
+        bool AddOrUpdateProfile(PowerDisplayProfile profile);
+
+        /// <summary>
+        /// Removes a profile by name and persists to disk.
+        /// </summary>
+        /// <param name="profileName">The name of the profile to remove.</param>
+        /// <returns>True if profile was found and removed, false otherwise.</returns>
+        bool RemoveProfile(string profileName);
+
+        /// <summary>
+        /// Gets a profile by name.
+        /// </summary>
+        /// <param name="profileName">The name of the profile to retrieve.</param>
+        /// <returns>The profile if found, null otherwise.</returns>
+        PowerDisplayProfile? GetProfile(string profileName);
+
+        /// <summary>
+        /// Checks if the profiles file exists.
+        /// </summary>
+        /// <returns>True if profiles file exists, false otherwise.</returns>
+        bool ProfilesFileExists();
+
+        /// <summary>
+        /// Gets the path to the profiles file.
+        /// </summary>
+        /// <returns>The full path to the profiles file.</returns>
+        string GetProfilesFilePath();
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/ColorPresetItem.cs

@@ -0,0 +1,86 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Represents a color temperature preset item for VCP code 0x14.
+    /// Used to display available color temperature presets in UI components.
+    /// </summary>
+    public partial class ColorPresetItem : INotifyPropertyChanged
+    {
+        private int _vcpValue;
+        private string _displayName = string.Empty;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ColorPresetItem"/> class.
+        /// </summary>
+        public ColorPresetItem()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ColorPresetItem"/> class.
+        /// </summary>
+        /// <param name="vcpValue">The VCP value for the color temperature preset.</param>
+        /// <param name="displayName">The display name for UI.</param>
+        public ColorPresetItem(int vcpValue, string displayName)
+        {
+            _vcpValue = vcpValue;
+            _displayName = displayName;
+        }
+
+        /// <summary>
+        /// Occurs when a property value changes.
+        /// </summary>
+        public event PropertyChangedEventHandler? PropertyChanged;
+
+        /// <summary>
+        /// Gets or sets the VCP value for this color temperature preset.
+        /// </summary>
+        [JsonPropertyName("vcpValue")]
+        public int VcpValue
+        {
+            get => _vcpValue;
+            set
+            {
+                if (_vcpValue != value)
+                {
+                    _vcpValue = value;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the display name for UI.
+        /// </summary>
+        [JsonPropertyName("displayName")]
+        public string DisplayName
+        {
+            get => _displayName;
+            set
+            {
+                if (_displayName != value)
+                {
+                    _displayName = value;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Raises the PropertyChanged event.
+        /// </summary>
+        /// <param name="propertyName">The name of the property that changed.</param>
+        protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/ColorTemperatureOperation.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Represents a pending color temperature change operation
+    /// </summary>
+    public class ColorTemperatureOperation
+    {
+        [JsonPropertyName("monitor_id")]
+        public string MonitorId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the color temperature VCP preset value.
+        /// JSON property name kept as "color_temperature" for IPC compatibility.
+        /// </summary>
+        [JsonPropertyName("color_temperature")]
+        public int ColorTemperatureVcp { get; set; }
+
+        public ColorTemperatureOperation()
+        {
+            MonitorId = string.Empty;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/Monitor.cs

@@ -0,0 +1,352 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using PowerDisplay.Common.Interfaces;
+using PowerDisplay.Common.Utils;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Monitor model that implements property change notification.
+    /// Implements IMonitorData to provide a common interface for monitor hardware values.
+    /// </summary>
+    /// <remarks>
+    /// <para><see cref="Id"/> is the unique identifier used for all purposes: UI lookups, IPC, persistent storage, and handle management.</para>
+    /// <para>Format: "{Source}_{EdidId}_{MonitorNumber}" (e.g., "DDC_GSM5C6D_1", "WMI_BOE0900_2").</para>
+    /// </remarks>
+    public partial class Monitor : INotifyPropertyChanged, IMonitorData
+    {
+        private int _currentBrightness;
+        private int _currentColorTemperature = 0x05; // Default to 6500K preset (VCP 0x14 value)
+        private int _currentInputSource; // VCP 0x60 value
+        private bool _isAvailable = true;
+        private int _orientation;
+
+        /// <summary>
+        /// Gets or sets unique identifier for all purposes: UI lookups, IPC, persistent storage, and handle management.
+        /// </summary>
+        /// <remarks>
+        /// Format: "{Source}_{EdidId}_{MonitorNumber}" where Source is "DDC" or "WMI".
+        /// Examples: "DDC_GSM5C6D_1", "WMI_BOE0900_2".
+        /// Stable across reboots and unique even for multiple identical monitors.
+        /// </remarks>
+        public string Id { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets display name
+        /// </summary>
+        public string Name { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets current brightness (0-100)
+        /// </summary>
+        public int CurrentBrightness
+        {
+            get => _currentBrightness;
+            set
+            {
+                var clamped = Math.Clamp(value, MinBrightness, MaxBrightness);
+                if (_currentBrightness != clamped)
+                {
+                    _currentBrightness = clamped;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets minimum brightness value
+        /// </summary>
+        public int MinBrightness { get; set; }
+
+        /// <summary>
+        /// Gets or sets maximum brightness value
+        /// </summary>
+        public int MaxBrightness { get; set; } = 100;
+
+        /// <summary>
+        /// Gets or sets current color temperature VCP preset value (from VCP code 0x14).
+        /// This stores the raw VCP value (e.g., 0x05 for 6500K), not Kelvin temperature.
+        /// Use ColorTemperaturePresetName to get human-readable name.
+        /// </summary>
+        public int CurrentColorTemperature
+        {
+            get => _currentColorTemperature;
+            set
+            {
+                if (_currentColorTemperature != value)
+                {
+                    _currentColorTemperature = value;
+                    OnPropertyChanged();
+                    OnPropertyChanged(nameof(ColorTemperaturePresetName));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets human-readable color temperature preset name (e.g., "6500K (0x05)", "sRGB (0x01)")
+        /// </summary>
+        public string ColorTemperaturePresetName =>
+            VcpNames.GetFormattedValueName(0x14, CurrentColorTemperature);
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the monitor supports color temperature adjustment via VCP 0x14
+        /// </summary>
+        public bool SupportsColorTemperature { get; set; }
+
+        /// <summary>
+        /// Gets or sets current input source VCP value (from VCP code 0x60).
+        /// This stores the raw VCP value (e.g., 0x11 for HDMI-1).
+        /// Use InputSourceName to get human-readable name.
+        /// </summary>
+        public int CurrentInputSource
+        {
+            get => _currentInputSource;
+            set
+            {
+                if (_currentInputSource != value)
+                {
+                    _currentInputSource = value;
+                    OnPropertyChanged();
+                    OnPropertyChanged(nameof(InputSourceName));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets human-readable input source name (e.g., "HDMI-1", "DisplayPort-1")
+        /// Returns just the name without hex value for cleaner UI display.
+        /// </summary>
+        public string InputSourceName =>
+            VcpNames.GetValueName(0x60, CurrentInputSource) ?? $"Source 0x{CurrentInputSource:X2}";
+
+        /// <summary>
+        /// Gets a value indicating whether the monitor supports input source switching via VCP 0x60
+        /// </summary>
+        public bool SupportsInputSource => VcpCapabilitiesInfo?.SupportsVcpCode(0x60) ?? false;
+
+        /// <summary>
+        /// Gets get supported input sources from capabilities (as list of VCP values)
+        /// </summary>
+        public System.Collections.Generic.IReadOnlyList<int>? SupportedInputSources =>
+            VcpCapabilitiesInfo?.GetSupportedValues(0x60);
+
+        /// <summary>
+        /// Gets a value indicating whether the monitor supports contrast adjustment
+        /// </summary>
+        public bool SupportsContrast => Capabilities.HasFlag(MonitorCapabilities.Contrast);
+
+        /// <summary>
+        /// Gets a value indicating whether the monitor supports volume adjustment (for audio-capable monitors)
+        /// </summary>
+        public bool SupportsVolume => Capabilities.HasFlag(MonitorCapabilities.Volume);
+
+        private int _currentContrast = 50;
+        private int _currentVolume = 50;
+
+        /// <summary>
+        /// Gets or sets current contrast (0-100)
+        /// </summary>
+        public int CurrentContrast
+        {
+            get => _currentContrast;
+            set
+            {
+                var clamped = Math.Clamp(value, MinContrast, MaxContrast);
+                if (_currentContrast != clamped)
+                {
+                    _currentContrast = clamped;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets minimum contrast value
+        /// </summary>
+        public int MinContrast { get; set; }
+
+        /// <summary>
+        /// Gets or sets maximum contrast value
+        /// </summary>
+        public int MaxContrast { get; set; } = 100;
+
+        /// <summary>
+        /// Gets or sets current volume (0-100)
+        /// </summary>
+        public int CurrentVolume
+        {
+            get => _currentVolume;
+            set
+            {
+                var clamped = Math.Clamp(value, MinVolume, MaxVolume);
+                if (_currentVolume != clamped)
+                {
+                    _currentVolume = clamped;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets minimum volume value
+        /// </summary>
+        public int MinVolume { get; set; }
+
+        /// <summary>
+        /// Gets or sets maximum volume value
+        /// </summary>
+        public int MaxVolume { get; set; } = 100;
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the monitor is available/online
+        /// </summary>
+        public bool IsAvailable
+        {
+            get => _isAvailable;
+            set
+            {
+                if (_isAvailable != value)
+                {
+                    _isAvailable = value;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets physical monitor handle (for DDC/CI)
+        /// </summary>
+        public IntPtr Handle { get; set; } = IntPtr.Zero;
+
+        /// <summary>
+        /// Gets or sets instance name (used by WMI)
+        /// </summary>
+        public string InstanceName { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets communication method (DDC/CI, WMI, HDR API, etc.)
+        /// </summary>
+        public string CommunicationMethod { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets supported control methods
+        /// </summary>
+        public MonitorCapabilities Capabilities { get; set; } = MonitorCapabilities.None;
+
+        /// <summary>
+        /// Gets or sets raw DDC/CI capabilities string (MCCS format)
+        /// </summary>
+        public string? CapabilitiesRaw { get; set; }
+
+        /// <summary>
+        /// Gets or sets parsed VCP capabilities information
+        /// </summary>
+        public VcpCapabilities? VcpCapabilitiesInfo { get; set; }
+
+        /// <summary>
+        /// Gets or sets last update time
+        /// </summary>
+        public DateTime LastUpdate { get; set; } = DateTime.Now;
+
+        public event PropertyChangedEventHandler? PropertyChanged;
+
+        protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+
+        public override string ToString()
+        {
+            return $"{Name} ({CommunicationMethod}) - {CurrentBrightness}%";
+        }
+
+        /// <summary>
+        /// Update monitor status
+        /// </summary>
+        public void UpdateStatus(int brightness, bool isAvailable = true)
+        {
+            IsAvailable = isAvailable;
+            if (isAvailable)
+            {
+                CurrentBrightness = brightness;
+                LastUpdate = DateTime.Now;
+            }
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.Brightness
+        {
+            get => CurrentBrightness;
+            set => CurrentBrightness = value;
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.Contrast
+        {
+            get => CurrentContrast;
+            set => CurrentContrast = value;
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.Volume
+        {
+            get => CurrentVolume;
+            set => CurrentVolume = value;
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.ColorTemperatureVcp
+        {
+            get => CurrentColorTemperature;
+            set => CurrentColorTemperature = value;
+        }
+
+        /// <summary>
+        /// Gets or sets monitor number (1, 2, 3...)
+        /// </summary>
+        public int MonitorNumber { get; set; }
+
+        /// <summary>
+        /// Gets or sets the GDI device name (e.g., "\\.\DISPLAY1").
+        /// This is obtained from QueryDisplayConfig during discovery and should be used
+        /// for display settings APIs (EnumDisplaySettings, ChangeDisplaySettingsEx).
+        /// </summary>
+        public string GdiDeviceName { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets monitor orientation (0=0, 1=90, 2=180, 3=270).
+        /// Fires PropertyChanged when value changes.
+        /// </summary>
+        public int Orientation
+        {
+            get => _orientation;
+            set
+            {
+                if (_orientation != value)
+                {
+                    _orientation = value;
+                    OnPropertyChanged();
+                }
+            }
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.MonitorNumber
+        {
+            get => MonitorNumber;
+            set => MonitorNumber = value;
+        }
+
+        /// <inheritdoc />
+        int IMonitorData.Orientation
+        {
+            get => Orientation;
+            set => Orientation = value;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/MonitorCapabilities.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Monitor control capabilities flags
+    /// </summary>
+    [Flags]
+    public enum MonitorCapabilities
+    {
+        None = 0,
+
+        /// <summary>
+        /// Supports brightness control
+        /// </summary>
+        Brightness = 1 << 0,
+
+        /// <summary>
+        /// Supports contrast control
+        /// </summary>
+        Contrast = 1 << 1,
+
+        /// <summary>
+        /// Supports DDC/CI protocol
+        /// </summary>
+        DdcCi = 1 << 2,
+
+        /// <summary>
+        /// Supports WMI control
+        /// </summary>
+        Wmi = 1 << 3,
+
+        /// <summary>
+        /// Supports HDR
+        /// </summary>
+        Hdr = 1 << 4,
+
+        /// <summary>
+        /// Supports high-level monitor API
+        /// </summary>
+        HighLevel = 1 << 5,
+
+        /// <summary>
+        /// Supports volume control
+        /// </summary>
+        Volume = 1 << 6,
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/MonitorOperationResult.cs

@@ -0,0 +1,58 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Monitor operation result
+    /// </summary>
+    public readonly struct MonitorOperationResult
+    {
+        /// <summary>
+        /// Gets a value indicating whether the operation was successful
+        /// </summary>
+        public bool IsSuccess { get; }
+
+        /// <summary>
+        /// Gets error message
+        /// </summary>
+        public string? ErrorMessage { get; }
+
+        /// <summary>
+        /// Gets system error code
+        /// </summary>
+        public int? ErrorCode { get; }
+
+        /// <summary>
+        /// Gets operation timestamp
+        /// </summary>
+        public DateTime Timestamp { get; }
+
+        private MonitorOperationResult(bool isSuccess, string? errorMessage = null, int? errorCode = null)
+        {
+            IsSuccess = isSuccess;
+            ErrorMessage = errorMessage;
+            ErrorCode = errorCode;
+            Timestamp = DateTime.Now;
+        }
+
+        /// <summary>
+        /// Creates a successful result
+        /// </summary>
+        public static MonitorOperationResult Success() => new(true);
+
+        /// <summary>
+        /// Creates a failed result
+        /// </summary>
+        public static MonitorOperationResult Failure(string errorMessage, int? errorCode = null)
+            => new(false, errorMessage, errorCode);
+
+        public override string ToString()
+        {
+            return IsSuccess ? "Success" : $"Failed: {ErrorMessage}";
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/MonitorStateEntry.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Individual monitor state entry for JSON persistence.
+    /// Stores the current state of a monitor's adjustable parameters.
+    /// </summary>
+    public sealed class MonitorStateEntry
+    {
+        /// <summary>
+        /// Gets or sets the brightness level (0-100).
+        /// </summary>
+        [JsonPropertyName("brightness")]
+        public int Brightness { get; set; }
+
+        /// <summary>
+        /// Gets or sets the color temperature VCP value.
+        /// </summary>
+        [JsonPropertyName("colorTemperature")]
+        public int ColorTemperatureVcp { get; set; }
+
+        /// <summary>
+        /// Gets or sets the contrast level (0-100).
+        /// </summary>
+        [JsonPropertyName("contrast")]
+        public int Contrast { get; set; }
+
+        /// <summary>
+        /// Gets or sets the volume level (0-100).
+        /// </summary>
+        [JsonPropertyName("volume")]
+        public int Volume { get; set; }
+
+        /// <summary>
+        /// Gets or sets the raw capabilities string from DDC/CI.
+        /// </summary>
+        [JsonPropertyName("capabilitiesRaw")]
+        public string? CapabilitiesRaw { get; set; }
+
+        /// <summary>
+        /// Gets or sets when this entry was last updated.
+        /// </summary>
+        [JsonPropertyName("lastUpdated")]
+        public DateTime LastUpdated { get; set; }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/MonitorStateFile.cs

@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Monitor state file structure for JSON persistence.
+    /// Contains all monitor states indexed by Monitor.Id.
+    /// </summary>
+    public sealed class MonitorStateFile
+    {
+        /// <summary>
+        /// Gets or sets the monitor states dictionary.
+        /// Key is the monitor's unique Id (e.g., "DDC_GSM5C6D_1", "WMI_BOE0900_2").
+        /// </summary>
+        [JsonPropertyName("monitors")]
+        public Dictionary<string, MonitorStateEntry> Monitors { get; set; } = new();
+
+        /// <summary>
+        /// Gets or sets when the file was last updated.
+        /// </summary>
+        [JsonPropertyName("lastUpdated")]
+        public DateTime LastUpdated { get; set; }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/PowerDisplayProfile.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Represents a PowerDisplay profile containing monitor settings
+    /// </summary>
+    public class PowerDisplayProfile
+    {
+        [JsonPropertyName("name")]
+        public string Name { get; set; }
+
+        [JsonPropertyName("monitorSettings")]
+        public List<ProfileMonitorSetting> MonitorSettings { get; set; }
+
+        [JsonPropertyName("createdDate")]
+        public DateTime CreatedDate { get; set; }
+
+        [JsonPropertyName("lastModified")]
+        public DateTime LastModified { get; set; }
+
+        public PowerDisplayProfile()
+        {
+            Name = string.Empty;
+            MonitorSettings = new List<ProfileMonitorSetting>();
+            CreatedDate = DateTime.UtcNow;
+            LastModified = DateTime.UtcNow;
+        }
+
+        public PowerDisplayProfile(string name, List<ProfileMonitorSetting> monitorSettings)
+        {
+            Name = name;
+            MonitorSettings = monitorSettings ?? new List<ProfileMonitorSetting>();
+            CreatedDate = DateTime.UtcNow;
+            LastModified = DateTime.UtcNow;
+        }
+
+        /// <summary>
+        /// Validates that the profile has at least one monitor configured
+        /// </summary>
+        public bool IsValid()
+        {
+            return !string.IsNullOrWhiteSpace(Name) && MonitorSettings != null && MonitorSettings.Count > 0;
+        }
+
+        /// <summary>
+        /// Updates the last modified timestamp
+        /// </summary>
+        public void Touch()
+        {
+            LastModified = DateTime.UtcNow;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/PowerDisplayProfiles.cs

@@ -0,0 +1,100 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Container for all PowerDisplay profiles
+    /// </summary>
+    public class PowerDisplayProfiles
+    {
+        // NOTE: Custom profile concept has been removed. Profiles are now templates, not states.
+        // This constant is kept for backward compatibility (cleaning up legacy Custom profiles).
+        public const string CustomProfileName = "Custom";
+
+        [JsonPropertyName("profiles")]
+        public List<PowerDisplayProfile> Profiles { get; set; }
+
+        [JsonPropertyName("lastUpdated")]
+        public DateTime LastUpdated { get; set; }
+
+        public PowerDisplayProfiles()
+        {
+            Profiles = new List<PowerDisplayProfile>();
+            LastUpdated = DateTime.UtcNow;
+        }
+
+        /// <summary>
+        /// Gets the profile by name
+        /// </summary>
+        public PowerDisplayProfile? GetProfile(string name)
+        {
+            return Profiles.FirstOrDefault(p => p.Name.Equals(name, StringComparison.OrdinalIgnoreCase));
+        }
+
+        /// <summary>
+        /// Adds or updates a profile
+        /// </summary>
+        public void SetProfile(PowerDisplayProfile profile)
+        {
+            if (profile == null || !profile.IsValid())
+            {
+                throw new ArgumentException("Profile is invalid");
+            }
+
+            var existing = GetProfile(profile.Name);
+            if (existing != null)
+            {
+                Profiles.Remove(existing);
+            }
+
+            profile.Touch();
+            Profiles.Add(profile);
+            LastUpdated = DateTime.UtcNow;
+        }
+
+        /// <summary>
+        /// Removes a profile by name
+        /// </summary>
+        public bool RemoveProfile(string name)
+        {
+            var profile = GetProfile(name);
+            if (profile != null)
+            {
+                Profiles.Remove(profile);
+                LastUpdated = DateTime.UtcNow;
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Checks if a profile name is valid and available
+        /// </summary>
+        public bool IsNameAvailable(string name, string? excludeName = null)
+        {
+            if (string.IsNullOrWhiteSpace(name))
+            {
+                return false;
+            }
+
+            // Check if name is already used (excluding the profile being renamed)
+            var existing = GetProfile(name);
+            if (existing != null && (excludeName == null || !existing.Name.Equals(excludeName, StringComparison.OrdinalIgnoreCase)))
+            {
+                return false;
+            }
+
+            return true;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/ProfileMonitorSetting.cs

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Monitor settings for a specific profile
+    /// </summary>
+    public class ProfileMonitorSetting
+    {
+        /// <summary>
+        /// Gets or sets the monitor's unique identifier.
+        /// Format: "{Source}_{EdidId}_{MonitorNumber}" (e.g., "DDC_GSM5C6D_1").
+        /// </summary>
+        [JsonPropertyName("monitorId")]
+        public string MonitorId { get; set; }
+
+        [JsonPropertyName("brightness")]
+        public int? Brightness { get; set; }
+
+        [JsonPropertyName("contrast")]
+        public int? Contrast { get; set; }
+
+        [JsonPropertyName("volume")]
+        public int? Volume { get; set; }
+
+        /// <summary>
+        /// Gets or sets the color temperature VCP preset value.
+        /// JSON property name kept as "colorTemperature" for backward compatibility.
+        /// </summary>
+        [JsonPropertyName("colorTemperature")]
+        public int? ColorTemperatureVcp { get; set; }
+
+        public ProfileMonitorSetting()
+        {
+            MonitorId = string.Empty;
+        }
+
+        public ProfileMonitorSetting(string monitorId, int? brightness = null, int? colorTemperatureVcp = null, int? contrast = null, int? volume = null)
+        {
+            MonitorId = monitorId;
+            Brightness = brightness;
+            ColorTemperatureVcp = colorTemperatureVcp;
+            Contrast = contrast;
+            Volume = volume;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/ProfileOperation.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// Represents a pending profile operation to be applied by PowerDisplay
+    /// </summary>
+    public class ProfileOperation
+    {
+        [JsonPropertyName("profileName")]
+        public string ProfileName { get; set; }
+
+        [JsonPropertyName("monitorSettings")]
+        public List<ProfileMonitorSetting> MonitorSettings { get; set; }
+
+        public ProfileOperation()
+        {
+            ProfileName = string.Empty;
+            MonitorSettings = new List<ProfileMonitorSetting>();
+        }
+
+        public ProfileOperation(string profileName, List<ProfileMonitorSetting> monitorSettings)
+        {
+            ProfileName = profileName;
+            MonitorSettings = monitorSettings ?? new List<ProfileMonitorSetting>();
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/VcpCapabilities.cs

@@ -0,0 +1,314 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// DDC/CI VCP capabilities information
+    /// </summary>
+    public class VcpCapabilities
+    {
+        /// <summary>
+        /// Gets or sets raw capabilities string (MCCS format)
+        /// </summary>
+        public string Raw { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Gets or sets monitor model name from capabilities
+        /// </summary>
+        public string? Model { get; set; }
+
+        /// <summary>
+        /// Gets or sets monitor type from capabilities (e.g., "LCD")
+        /// </summary>
+        public string? Type { get; set; }
+
+        /// <summary>
+        /// Gets or sets mCCS protocol version
+        /// </summary>
+        public string? Protocol { get; set; }
+
+        /// <summary>
+        /// Gets or sets mCCS version (e.g., "2.2", "2.1")
+        /// </summary>
+        public string? MccsVersion { get; set; }
+
+        /// <summary>
+        /// Gets or sets supported command codes
+        /// </summary>
+        public List<byte> SupportedCommands { get; set; } = new();
+
+        /// <summary>
+        /// Gets or sets supported VCP codes with their information
+        /// </summary>
+        public Dictionary<byte, VcpCodeInfo> SupportedVcpCodes { get; set; } = new();
+
+        /// <summary>
+        /// Gets or sets window capabilities for PIP/PBP support
+        /// </summary>
+        public List<WindowCapability> Windows { get; set; } = new();
+
+        /// <summary>
+        /// Gets a value indicating whether check if display supports PIP/PBP windows
+        /// </summary>
+        public bool HasWindowSupport => Windows.Count > 0;
+
+        /// <summary>
+        /// Check if a specific VCP code is supported
+        /// </summary>
+        public bool SupportsVcpCode(byte code) => SupportedVcpCodes.ContainsKey(code);
+
+        /// <summary>
+        /// Get VCP code information
+        /// </summary>
+        public VcpCodeInfo? GetVcpCodeInfo(byte code)
+        {
+            return SupportedVcpCodes.TryGetValue(code, out var info) ? info : null;
+        }
+
+        /// <summary>
+        /// Check if a VCP code supports discrete values
+        /// </summary>
+        public bool HasDiscreteValues(byte code)
+        {
+            var info = GetVcpCodeInfo(code);
+            return info?.HasDiscreteValues ?? false;
+        }
+
+        /// <summary>
+        /// Get supported values for a VCP code
+        /// </summary>
+        public IReadOnlyList<int>? GetSupportedValues(byte code)
+        {
+            return GetVcpCodeInfo(code)?.SupportedValues;
+        }
+
+        /// <summary>
+        /// Get all VCP codes as hex strings, sorted by code value.
+        /// </summary>
+        /// <returns>List of hex strings like ["0x10", "0x12", "0x14"]</returns>
+        public List<string> GetVcpCodesAsHexStrings()
+        {
+            var result = new List<string>(SupportedVcpCodes.Count);
+            foreach (var kvp in SupportedVcpCodes)
+            {
+                result.Add($"0x{kvp.Key:X2}");
+            }
+
+            result.Sort(StringComparer.Ordinal);
+            return result;
+        }
+
+        /// <summary>
+        /// Get all VCP codes sorted by code value.
+        /// </summary>
+        /// <returns>Sorted list of VcpCodeInfo</returns>
+        public IEnumerable<VcpCodeInfo> GetSortedVcpCodes()
+        {
+            var sortedKeys = new List<byte>(SupportedVcpCodes.Keys);
+            sortedKeys.Sort();
+
+            foreach (var key in sortedKeys)
+            {
+                yield return SupportedVcpCodes[key];
+            }
+        }
+
+        /// <summary>
+        /// Gets creates an empty capabilities object
+        /// </summary>
+        public static VcpCapabilities Empty => new();
+
+        public override string ToString()
+        {
+            return $"Model: {Model}, VCP Codes: {SupportedVcpCodes.Count}";
+        }
+    }
+
+    /// <summary>
+    /// Information about a single VCP code
+    /// </summary>
+    public readonly struct VcpCodeInfo
+    {
+        /// <summary>
+        /// Gets vCP code (e.g., 0x10 for brightness)
+        /// </summary>
+        public byte Code { get; }
+
+        /// <summary>
+        /// Gets human-readable name of the VCP code
+        /// </summary>
+        public string Name { get; }
+
+        /// <summary>
+        /// Gets supported discrete values (empty if continuous range)
+        /// </summary>
+        public IReadOnlyList<int> SupportedValues { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether this VCP code has discrete values
+        /// </summary>
+        public bool HasDiscreteValues => SupportedValues.Count > 0;
+
+        /// <summary>
+        /// Gets a value indicating whether this VCP code supports a continuous range
+        /// </summary>
+        public bool IsContinuous => SupportedValues.Count == 0;
+
+        /// <summary>
+        /// Gets the VCP code formatted as a hex string (e.g., "0x10").
+        /// </summary>
+        public string FormattedCode => $"0x{Code:X2}";
+
+        /// <summary>
+        /// Gets the VCP code formatted with its name (e.g., "Brightness (0x10)").
+        /// </summary>
+        public string FormattedTitle => $"{Name} ({FormattedCode})";
+
+        public VcpCodeInfo(byte code, string name, IReadOnlyList<int>? supportedValues = null)
+        {
+            Code = code;
+            Name = name;
+            SupportedValues = supportedValues ?? Array.Empty<int>();
+        }
+
+        public override string ToString()
+        {
+            if (HasDiscreteValues)
+            {
+                return $"0x{Code:X2} ({Name}): {string.Join(", ", SupportedValues)}";
+            }
+
+            return $"0x{Code:X2} ({Name}): Continuous";
+        }
+    }
+
+    /// <summary>
+    /// Window size (width and height)
+    /// </summary>
+    public readonly struct WindowSize
+    {
+        /// <summary>
+        /// Gets width in pixels
+        /// </summary>
+        public int Width { get; }
+
+        /// <summary>
+        /// Gets height in pixels
+        /// </summary>
+        public int Height { get; }
+
+        public WindowSize(int width, int height)
+        {
+            Width = width;
+            Height = height;
+        }
+
+        public override string ToString() => $"{Width}x{Height}";
+    }
+
+    /// <summary>
+    /// Window area coordinates (top-left and bottom-right)
+    /// </summary>
+    public readonly struct WindowArea
+    {
+        /// <summary>
+        /// Gets top-left X coordinate
+        /// </summary>
+        public int X1 { get; }
+
+        /// <summary>
+        /// Gets top-left Y coordinate
+        /// </summary>
+        public int Y1 { get; }
+
+        /// <summary>
+        /// Gets bottom-right X coordinate
+        /// </summary>
+        public int X2 { get; }
+
+        /// <summary>
+        /// Gets bottom-right Y coordinate
+        /// </summary>
+        public int Y2 { get; }
+
+        /// <summary>
+        /// Gets width of the area
+        /// </summary>
+        public int Width => X2 - X1;
+
+        /// <summary>
+        /// Gets height of the area
+        /// </summary>
+        public int Height => Y2 - Y1;
+
+        public WindowArea(int x1, int y1, int x2, int y2)
+        {
+            X1 = x1;
+            Y1 = y1;
+            X2 = x2;
+            Y2 = y2;
+        }
+
+        public override string ToString() => $"({X1},{Y1})-({X2},{Y2})";
+    }
+
+    /// <summary>
+    /// Window capability information for PIP/PBP displays
+    /// </summary>
+    public readonly struct WindowCapability
+    {
+        /// <summary>
+        /// Gets window number (1, 2, 3, etc.)
+        /// </summary>
+        public int WindowNumber { get; }
+
+        /// <summary>
+        /// Gets window type (e.g., "PIP", "PBP")
+        /// </summary>
+        public string Type { get; }
+
+        /// <summary>
+        /// Gets window area coordinates
+        /// </summary>
+        public WindowArea Area { get; }
+
+        /// <summary>
+        /// Gets maximum window size
+        /// </summary>
+        public WindowSize MaxSize { get; }
+
+        /// <summary>
+        /// Gets minimum window size
+        /// </summary>
+        public WindowSize MinSize { get; }
+
+        /// <summary>
+        /// Gets window identifier
+        /// </summary>
+        public int WindowId { get; }
+
+        public WindowCapability(
+            int windowNumber,
+            string type,
+            WindowArea area,
+            WindowSize maxSize,
+            WindowSize minSize,
+            int windowId)
+        {
+            WindowNumber = windowNumber;
+            Type = type ?? string.Empty;
+            Area = area;
+            MaxSize = maxSize;
+            MinSize = minSize;
+            WindowId = windowId;
+        }
+
+        public override string ToString() =>
+            $"Window{WindowNumber}: Type={Type}, Area={Area}, Max={MaxSize}, Min={MinSize}";
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Models/VcpFeatureValue.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace PowerDisplay.Common.Models
+{
+    /// <summary>
+    /// VCP feature value information structure.
+    /// Represents the current, minimum, and maximum values for a VCP (Virtual Control Panel) feature.
+    /// </summary>
+    public readonly struct VcpFeatureValue
+    {
+        /// <summary>
+        /// Gets current value
+        /// </summary>
+        public int Current { get; }
+
+        /// <summary>
+        /// Gets minimum value
+        /// </summary>
+        public int Minimum { get; }
+
+        /// <summary>
+        /// Gets maximum value
+        /// </summary>
+        public int Maximum { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether the value information is valid
+        /// </summary>
+        public bool IsValid { get; }
+
+        /// <summary>
+        /// Gets timestamp when the value information was obtained
+        /// </summary>
+        public DateTime Timestamp { get; }
+
+        public VcpFeatureValue(int current, int minimum, int maximum)
+        {
+            Current = current;
+            Minimum = minimum;
+            Maximum = maximum;
+            IsValid = current >= minimum && current <= maximum && maximum > minimum;
+            Timestamp = DateTime.Now;
+        }
+
+        public VcpFeatureValue(int current, int maximum)
+            : this(current, 0, maximum)
+        {
+        }
+
+        /// <summary>
+        /// Gets creates invalid value information
+        /// </summary>
+        public static VcpFeatureValue Invalid => new(-1, -1, -1);
+
+        /// <summary>
+        /// Converts value to percentage (0-100)
+        /// </summary>
+        public int ToPercentage()
+        {
+            if (!IsValid || Maximum == Minimum)
+            {
+                return 0;
+            }
+
+            return (int)Math.Round((double)(Current - Minimum) * 100 / (Maximum - Minimum));
+        }
+
+        public override string ToString()
+        {
+            return IsValid ? $"{Current}/{Maximum} ({ToPercentage()}%)" : "Invalid";
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/PathConstants.cs

@@ -0,0 +1,122 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+
+namespace PowerDisplay.Common
+{
+    /// <summary>
+    /// Centralized path constants for PowerDisplay module.
+    /// Provides unified access to all file and folder paths used by PowerDisplay and related integrations.
+    /// </summary>
+    public static class PathConstants
+    {
+        private static readonly Lazy<string> _localAppDataPath = new Lazy<string>(
+            () => Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData));
+
+        private static readonly Lazy<string> _powerToysBasePath = new Lazy<string>(
+            () => Path.Combine(_localAppDataPath.Value, "Microsoft", "PowerToys"));
+
+        /// <summary>
+        /// Gets the base PowerToys settings folder path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys
+        /// </summary>
+        public static string PowerToysBasePath => _powerToysBasePath.Value;
+
+        /// <summary>
+        /// Gets the PowerDisplay module folder path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\PowerDisplay
+        /// </summary>
+        public static string PowerDisplayFolderPath => Path.Combine(PowerToysBasePath, "PowerDisplay");
+
+        /// <summary>
+        /// Gets the PowerDisplay profiles file path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\PowerDisplay\profiles.json
+        /// </summary>
+        public static string ProfilesFilePath => Path.Combine(PowerDisplayFolderPath, ProfilesFileName);
+
+        /// <summary>
+        /// Gets the PowerDisplay settings file path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\PowerDisplay\settings.json
+        /// </summary>
+        public static string SettingsFilePath => Path.Combine(PowerDisplayFolderPath, SettingsFileName);
+
+        /// <summary>
+        /// Gets the LightSwitch module folder path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\LightSwitch
+        /// </summary>
+        public static string LightSwitchFolderPath => Path.Combine(PowerToysBasePath, "LightSwitch");
+
+        /// <summary>
+        /// Gets the LightSwitch settings file path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\LightSwitch\settings.json
+        /// </summary>
+        public static string LightSwitchSettingsFilePath => Path.Combine(LightSwitchFolderPath, SettingsFileName);
+
+        /// <summary>
+        /// The name of the profiles file.
+        /// </summary>
+        public const string ProfilesFileName = "profiles.json";
+
+        /// <summary>
+        /// The name of the settings file.
+        /// </summary>
+        public const string SettingsFileName = "settings.json";
+
+        /// <summary>
+        /// The name of the monitor state file.
+        /// </summary>
+        public const string MonitorStateFileName = "monitor_state.json";
+
+        /// <summary>
+        /// Gets the monitor state file path.
+        /// Example: C:\Users\{User}\AppData\Local\Microsoft\PowerToys\PowerDisplay\monitor_state.json
+        /// </summary>
+        public static string MonitorStateFilePath => Path.Combine(PowerDisplayFolderPath, MonitorStateFileName);
+
+        /// <summary>
+        /// Event name for LightSwitch light theme change notifications.
+        /// Signaled when LightSwitch switches to light mode.
+        /// Must match CommonSharedConstants::LIGHT_SWITCH_LIGHT_THEME_EVENT in shared_constants.h.
+        /// </summary>
+        public const string LightSwitchLightThemeEventName = "Local\\PowerToysLightSwitch-LightThemeEvent-50077121-2ffc-4841-9c86-ab1bd3f9baca";
+
+        /// <summary>
+        /// Event name for LightSwitch dark theme change notifications.
+        /// Signaled when LightSwitch switches to dark mode.
+        /// Must match CommonSharedConstants::LIGHT_SWITCH_DARK_THEME_EVENT in shared_constants.h.
+        /// </summary>
+        public const string LightSwitchDarkThemeEventName = "Local\\PowerToysLightSwitch-DarkThemeEvent-b3a835c0-eaa2-49b0-b8eb-f793e3df3368";
+
+        /// <summary>
+        /// Ensures the PowerDisplay folder exists. Creates it if necessary.
+        /// </summary>
+        /// <returns>The PowerDisplay folder path</returns>
+        public static string EnsurePowerDisplayFolderExists()
+            => EnsureFolderExists(PowerDisplayFolderPath);
+
+        /// <summary>
+        /// Ensures the LightSwitch folder exists. Creates it if necessary.
+        /// </summary>
+        /// <returns>The LightSwitch folder path</returns>
+        public static string EnsureLightSwitchFolderExists()
+            => EnsureFolderExists(LightSwitchFolderPath);
+
+        /// <summary>
+        /// Ensures the specified folder exists. Creates it if necessary.
+        /// </summary>
+        /// <param name="folderPath">The folder path to ensure exists</param>
+        /// <returns>The folder path</returns>
+        private static string EnsureFolderExists(string folderPath)
+        {
+            if (!Directory.Exists(folderPath))
+            {
+                Directory.CreateDirectory(folderPath);
+            }
+
+            return folderPath;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/PowerDisplay.Lib.csproj

@@ -0,0 +1,40 @@
+<!-- Copyright (c) Microsoft Corporation. All rights reserved. -->
+<!-- Licensed under the MIT License. See LICENSE file in the project root for license information. -->
+<Project Sdk="Microsoft.NET.Sdk">
+  <!-- Look at Directory.Build.props in root for common stuff as well -->
+  <Import Project="..\..\..\Common.Dotnet.CsWinRT.props" />
+  <Import Project="..\..\..\Common.Dotnet.AotCompatibility.props" />
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <RootNamespace>PowerDisplay.Common</RootNamespace>
+    <Platforms>x64;ARM64</Platforms>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
+    <AssemblyName>PowerDisplay.Lib</AssemblyName>
+  </PropertyGroup>
+  <!-- Native AOT Configuration -->
+  <PropertyGroup>
+    <PublishSingleFile>false</PublishSingleFile>
+    <DisableRuntimeMarshalling>false</DisableRuntimeMarshalling>
+    <IsAotCompatible>true</IsAotCompatible>
+    <TrimmerSingleWarn>false</TrimmerSingleWarn>
+    <SuppressTrimAnalysisWarnings>false</SuppressTrimAnalysisWarnings>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Polly.Core" />
+    <PackageReference Include="WmiLight" />
+    <PackageReference Include="System.Collections.Immutable" />
+  </ItemGroup>
+  <ItemGroup>
+    <!-- Hide build log files from Solution Explorer -->
+    <None Remove="*.log" />
+    <None Remove="*.binlog" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\common\ManagedCommon\ManagedCommon.csproj" />
+    <ProjectReference Include="..\..\..\common\ManagedCsWin32\ManagedCsWin32.csproj" />
+    <ProjectReference Include="..\..\..\common\interop\PowerToys.Interop.vcxproj" />
+  </ItemGroup>
+</Project>

src/modules/powerdisplay/PowerDisplay.Lib/Serialization/ProfileSerializationContext.cs

@@ -0,0 +1,38 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+using PowerDisplay.Common.Models;
+
+namespace PowerDisplay.Common.Serialization
+{
+    /// <summary>
+    /// JSON serialization context for PowerDisplay Profile types.
+    /// Provides source-generated serialization for Native AOT compatibility.
+    /// </summary>
+    [JsonSourceGenerationOptions(
+        WriteIndented = false,
+        DefaultIgnoreCondition = JsonIgnoreCondition.Never,
+        IncludeFields = true)]
+
+    // Profile Types
+    [JsonSerializable(typeof(ProfileMonitorSetting))]
+    [JsonSerializable(typeof(List<ProfileMonitorSetting>))]
+    [JsonSerializable(typeof(PowerDisplayProfile))]
+    [JsonSerializable(typeof(List<PowerDisplayProfile>))]
+    [JsonSerializable(typeof(PowerDisplayProfiles))]
+    [JsonSerializable(typeof(ProfileOperation))]
+    [JsonSerializable(typeof(List<ProfileOperation>))]
+    [JsonSerializable(typeof(ColorTemperatureOperation))]
+    [JsonSerializable(typeof(List<ColorTemperatureOperation>))]
+
+    // Monitor State Types
+    [JsonSerializable(typeof(MonitorStateEntry))]
+    [JsonSerializable(typeof(MonitorStateFile))]
+    [JsonSerializable(typeof(Dictionary<string, MonitorStateEntry>))]
+    public partial class ProfileSerializationContext : JsonSerializerContext
+    {
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Services/DisplayRotationService.cs

@@ -0,0 +1,174 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using ManagedCommon;
+using PowerDisplay.Common.Models;
+using static PowerDisplay.Common.Drivers.NativeConstants;
+using static PowerDisplay.Common.Drivers.PInvoke;
+
+using DevMode = PowerDisplay.Common.Drivers.DevMode;
+
+namespace PowerDisplay.Common.Services
+{
+    /// <summary>
+    /// Service for controlling display rotation/orientation.
+    /// Uses ChangeDisplaySettingsEx API to change display orientation.
+    /// </summary>
+    public class DisplayRotationService
+    {
+        /// <summary>
+        /// Set display rotation for a specific monitor.
+        /// Uses GdiDeviceName from the Monitor object for accurate adapter targeting.
+        /// </summary>
+        /// <param name="monitor">Monitor object with GdiDeviceName</param>
+        /// <param name="newOrientation">New orientation: 0=normal, 1=90°, 2=180°, 3=270°</param>
+        /// <returns>Operation result</returns>
+        public MonitorOperationResult SetRotation(Monitor monitor, int newOrientation)
+        {
+            ArgumentNullException.ThrowIfNull(monitor);
+
+            if (newOrientation < 0 || newOrientation > 3)
+            {
+                return MonitorOperationResult.Failure($"Invalid orientation value: {newOrientation}. Must be 0-3.");
+            }
+
+            if (string.IsNullOrEmpty(monitor.GdiDeviceName))
+            {
+                return MonitorOperationResult.Failure("Monitor has no GdiDeviceName");
+            }
+
+            return SetRotationByGdiDeviceName(monitor.GdiDeviceName, newOrientation);
+        }
+
+        /// <summary>
+        /// Set display rotation by GDI device name.
+        /// </summary>
+        /// <param name="gdiDeviceName">GDI device name (e.g., "\\.\DISPLAY1")</param>
+        /// <param name="newOrientation">New orientation: 0=normal, 1=90°, 2=180°, 3=270°</param>
+        /// <returns>Operation result</returns>
+        public unsafe MonitorOperationResult SetRotationByGdiDeviceName(string gdiDeviceName, int newOrientation)
+        {
+            if (string.IsNullOrEmpty(gdiDeviceName))
+            {
+                return MonitorOperationResult.Failure("GDI device name is required");
+            }
+
+            try
+            {
+                Logger.LogInfo($"SetRotation: Setting {gdiDeviceName} to orientation {newOrientation}");
+
+                // 1. Get current display settings
+                DevMode devMode = default;
+                devMode.DmSize = (short)sizeof(DevMode);
+
+                if (!EnumDisplaySettings(gdiDeviceName, EnumCurrentSettings, &devMode))
+                {
+                    var error = GetLastError();
+                    Logger.LogError($"SetRotation: EnumDisplaySettings failed for {gdiDeviceName}, error: {error}");
+                    return MonitorOperationResult.Failure($"Failed to get current display settings for {gdiDeviceName}", (int)error);
+                }
+
+                int currentOrientation = devMode.DmDisplayOrientation;
+
+                // If already at target orientation, return success
+                if (currentOrientation == newOrientation)
+                {
+                    return MonitorOperationResult.Success();
+                }
+
+                // 2. Determine if we need to swap width and height
+                // When switching between landscape (0°/180°) and portrait (90°/270°), swap dimensions
+                bool currentIsLandscape = currentOrientation == DmdoDefault || currentOrientation == Dmdo180;
+                bool newIsLandscape = newOrientation == DmdoDefault || newOrientation == Dmdo180;
+
+                if (currentIsLandscape != newIsLandscape)
+                {
+                    // Swap width and height
+                    int temp = devMode.DmPelsWidth;
+                    devMode.DmPelsWidth = devMode.DmPelsHeight;
+                    devMode.DmPelsHeight = temp;
+                }
+
+                // 3. Set new orientation
+                devMode.DmDisplayOrientation = newOrientation;
+                devMode.DmFields = DmDisplayOrientation | DmPelsWidth | DmPelsHeight;
+
+                // 4. Test the settings first using CDS_TEST flag
+                int testResult = ChangeDisplaySettingsEx(gdiDeviceName, &devMode, IntPtr.Zero, CdsTest, IntPtr.Zero);
+                if (testResult != DispChangeSuccessful)
+                {
+                    string errorMsg = GetChangeDisplaySettingsErrorMessage(testResult);
+                    Logger.LogError($"SetRotation: Test failed for {gdiDeviceName}: {errorMsg}");
+                    return MonitorOperationResult.Failure($"Display settings test failed: {errorMsg}", testResult);
+                }
+
+                // 5. Apply the settings (without CDS_UPDATEREGISTRY to make it temporary)
+                int result = ChangeDisplaySettingsEx(gdiDeviceName, &devMode, IntPtr.Zero, 0, IntPtr.Zero);
+                if (result != DispChangeSuccessful)
+                {
+                    string errorMsg = GetChangeDisplaySettingsErrorMessage(result);
+                    Logger.LogError($"SetRotation: Apply failed for {gdiDeviceName}: {errorMsg}");
+                    return MonitorOperationResult.Failure($"Failed to apply display settings: {errorMsg}", result);
+                }
+
+                Logger.LogInfo($"SetRotation: Successfully set {gdiDeviceName} to orientation {newOrientation}");
+                return MonitorOperationResult.Success();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"SetRotation: Exception for {gdiDeviceName}: {ex.Message}");
+                return MonitorOperationResult.Failure($"Exception while setting rotation: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Get current orientation for a GDI device name.
+        /// </summary>
+        /// <param name="gdiDeviceName">GDI device name (e.g., "\\.\DISPLAY1")</param>
+        /// <returns>Current orientation (0-3), or -1 if query failed</returns>
+        public unsafe int GetCurrentOrientation(string gdiDeviceName)
+        {
+            if (string.IsNullOrEmpty(gdiDeviceName))
+            {
+                return -1;
+            }
+
+            try
+            {
+                DevMode devMode = default;
+                devMode.DmSize = (short)sizeof(DevMode);
+
+                if (!EnumDisplaySettings(gdiDeviceName, EnumCurrentSettings, &devMode))
+                {
+                    return -1;
+                }
+
+                return devMode.DmDisplayOrientation;
+            }
+            catch
+            {
+                return -1;
+            }
+        }
+
+        /// <summary>
+        /// Get human-readable error message for ChangeDisplaySettings result code.
+        /// </summary>
+        private static string GetChangeDisplaySettingsErrorMessage(int resultCode)
+        {
+            return resultCode switch
+            {
+                DispChangeSuccessful => "Success",
+                DispChangeRestart => "Computer must be restarted",
+                DispChangeFailed => "Display driver failed the specified graphics mode",
+                DispChangeBadmode => "Graphics mode is not supported",
+                DispChangeNotupdated => "Unable to write settings to registry",
+                DispChangeBadflags => "Invalid flags",
+                DispChangeBadparam => "Invalid parameter",
+                _ => $"Unknown error code: {resultCode}",
+            };
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Services/MonitorStateManager.cs

@@ -0,0 +1,300 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.IO;
+using System.Text.Json;
+using System.Threading.Tasks;
+using ManagedCommon;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Serialization;
+using PowerDisplay.Common.Utils;
+
+namespace PowerDisplay.Common.Services
+{
+    /// <summary>
+    /// Manages monitor parameter state in a separate file from main settings.
+    /// This avoids FileSystemWatcher feedback loops by separating read-only config (settings.json)
+    /// from frequently updated state (monitor_state.json).
+    /// Simplified to use direct save strategy for reliability and simplicity (KISS principle).
+    /// </summary>
+    public partial class MonitorStateManager : IDisposable
+    {
+        private readonly string _stateFilePath;
+        private readonly ConcurrentDictionary<string, MonitorState> _states = new();
+        private readonly object _statesLock = new();
+        private readonly SimpleDebouncer _saveDebouncer;
+
+        private bool _disposed;
+        private bool _isDirty; // Track pending changes for flush on dispose
+        private const int SaveDebounceMs = 2000; // Save 2 seconds after last update
+
+        /// <summary>
+        /// Monitor state data (internal tracking, not serialized)
+        /// </summary>
+        private sealed class MonitorState
+        {
+            public int Brightness { get; set; }
+
+            public int ColorTemperatureVcp { get; set; }
+
+            public int Contrast { get; set; }
+
+            public int Volume { get; set; }
+
+            public string? CapabilitiesRaw { get; set; }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MonitorStateManager"/> class.
+        /// Uses PathConstants for consistent path management.
+        /// </summary>
+        public MonitorStateManager()
+        {
+            // Use PathConstants for consistent path management
+            PathConstants.EnsurePowerDisplayFolderExists();
+            _stateFilePath = PathConstants.MonitorStateFilePath;
+
+            // Initialize debouncer for batching rapid updates (e.g., slider drag)
+            _saveDebouncer = new SimpleDebouncer(SaveDebounceMs);
+
+            // Load existing state if available
+            LoadStateFromDisk();
+
+            Logger.LogInfo($"MonitorStateManager initialized with debounced-save strategy (debounce: {SaveDebounceMs}ms), state file: {_stateFilePath}");
+        }
+
+        /// <summary>
+        /// Update monitor parameter and schedule debounced save to disk.
+        /// Uses Monitor.Id as the stable key (e.g., "DDC_GSM5C6D_1", "WMI_BOE0900_2").
+        /// Debounced-save strategy reduces disk I/O by batching rapid updates (e.g., during slider drag).
+        /// </summary>
+        /// <param name="monitorId">The monitor's unique Id (e.g., "DDC_GSM5C6D_1").</param>
+        /// <param name="property">The property name to update (Brightness, ColorTemperature, Contrast, or Volume).</param>
+        /// <param name="value">The new value.</param>
+        public void UpdateMonitorParameter(string monitorId, string property, int value)
+        {
+            try
+            {
+                if (string.IsNullOrEmpty(monitorId))
+                {
+                    Logger.LogWarning($"Cannot update monitor parameter: monitorId is empty");
+                    return;
+                }
+
+                var state = _states.GetOrAdd(monitorId, _ => new MonitorState());
+
+                // Update the specific property
+                bool shouldSave = true;
+                switch (property)
+                {
+                    case "Brightness":
+                        state.Brightness = value;
+                        break;
+                    case "ColorTemperature":
+                        state.ColorTemperatureVcp = value;
+                        break;
+                    case "Contrast":
+                        state.Contrast = value;
+                        break;
+                    case "Volume":
+                        state.Volume = value;
+                        break;
+                    default:
+                        Logger.LogWarning($"Unknown property: {property}");
+                        shouldSave = false;
+                        break;
+                }
+
+                if (shouldSave)
+                {
+                    // Mark dirty for flush on dispose
+                    _isDirty = true;
+                }
+
+                // Schedule debounced save (SimpleDebouncer handles cancellation of previous calls)
+                if (shouldSave)
+                {
+                    _saveDebouncer.Debounce(SaveStateToDiskAsync);
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Failed to update monitor parameter: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Get saved parameters for a monitor using Monitor.Id.
+        /// </summary>
+        /// <param name="monitorId">The monitor's unique Id (e.g., "DDC_GSM5C6D_1").</param>
+        /// <returns>A tuple of (Brightness, ColorTemperatureVcp, Contrast, Volume) or null if not found.</returns>
+        public (int Brightness, int ColorTemperatureVcp, int Contrast, int Volume)? GetMonitorParameters(string monitorId)
+        {
+            if (string.IsNullOrEmpty(monitorId))
+            {
+                return null;
+            }
+
+            if (_states.TryGetValue(monitorId, out var state))
+            {
+                return (state.Brightness, state.ColorTemperatureVcp, state.Contrast, state.Volume);
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Load state from disk.
+        /// </summary>
+        private void LoadStateFromDisk()
+        {
+            try
+            {
+                if (!File.Exists(_stateFilePath))
+                {
+                    Logger.LogInfo("[State] No existing state file found, starting fresh");
+                    return;
+                }
+
+                var json = File.ReadAllText(_stateFilePath);
+                var stateFile = JsonSerializer.Deserialize(json, ProfileSerializationContext.Default.MonitorStateFile);
+
+                if (stateFile?.Monitors != null)
+                {
+                    foreach (var kvp in stateFile.Monitors)
+                    {
+                        var monitorKey = kvp.Key; // Should be HardwareId (e.g., "GSM5C6D")
+                        var entry = kvp.Value;
+
+                        _states[monitorKey] = new MonitorState
+                        {
+                            Brightness = entry.Brightness,
+                            ColorTemperatureVcp = entry.ColorTemperatureVcp,
+                            Contrast = entry.Contrast,
+                            Volume = entry.Volume,
+                            CapabilitiesRaw = entry.CapabilitiesRaw,
+                        };
+                    }
+
+                    Logger.LogInfo($"[State] Loaded state for {stateFile.Monitors.Count} monitors from {_stateFilePath}");
+                    Logger.LogInfo($"[State] Monitor keys in state file: {string.Join(", ", stateFile.Monitors.Keys)}");
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Failed to load monitor state: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Save current state to disk immediately (async).
+        /// Called by timer after debounce period.
+        /// </summary>
+        private async Task SaveStateToDiskAsync()
+        {
+            try
+            {
+                if (_disposed)
+                {
+                    return;
+                }
+
+                var (json, monitorCount) = BuildStateJson();
+
+                // Write to disk asynchronously
+                await File.WriteAllTextAsync(_stateFilePath, json);
+
+                // Clear dirty flag after successful save
+                _isDirty = false;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Failed to save monitor state: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Save current state to disk synchronously.
+        /// Called during Dispose to flush pending changes without risk of deadlock.
+        /// </summary>
+        private void SaveStateToDiskSync()
+        {
+            try
+            {
+                var (json, monitorCount) = BuildStateJson();
+
+                // Write to disk synchronously - safe for Dispose
+                File.WriteAllText(_stateFilePath, json);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Failed to save monitor state (sync): {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Build the JSON string for state file.
+        /// Shared logic between async and sync save methods.
+        /// </summary>
+        /// <returns>Tuple of (JSON string, monitor count)</returns>
+        private (string Json, int MonitorCount) BuildStateJson()
+        {
+            var now = DateTime.Now;
+            var stateFile = new MonitorStateFile
+            {
+                LastUpdated = now,
+            };
+
+            foreach (var kvp in _states)
+            {
+                var monitorId = kvp.Key;
+                var state = kvp.Value;
+
+                stateFile.Monitors[monitorId] = new MonitorStateEntry
+                {
+                    Brightness = state.Brightness,
+                    ColorTemperatureVcp = state.ColorTemperatureVcp,
+                    Contrast = state.Contrast,
+                    Volume = state.Volume,
+                    CapabilitiesRaw = state.CapabilitiesRaw,
+                    LastUpdated = now,
+                };
+            }
+
+            var json = JsonSerializer.Serialize(stateFile, ProfileSerializationContext.Default.MonitorStateFile);
+            return (json, stateFile.Monitors.Count);
+        }
+
+        /// <summary>
+        /// Disposes the MonitorStateManager, flushing any pending state changes.
+        /// </summary>
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            bool wasDirty = _isDirty;
+            _disposed = true;
+            _isDirty = false;
+
+            // Dispose debouncer first to cancel any pending saves
+            _saveDebouncer?.Dispose();
+
+            // Flush any pending changes before disposing using sync method to avoid deadlock
+            if (wasDirty)
+            {
+                Logger.LogInfo("Flushing pending state changes before dispose");
+                SaveStateToDiskSync();
+            }
+
+            Logger.LogInfo("MonitorStateManager disposed");
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Services/ProfileService.cs

@@ -0,0 +1,261 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+using System.Text.Json;
+using ManagedCommon;
+using PowerDisplay.Common.Interfaces;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Serialization;
+
+namespace PowerDisplay.Common.Services
+{
+    /// <summary>
+    /// Centralized service for managing PowerDisplay profiles storage and retrieval.
+    /// Provides unified access to profile data for PowerDisplay, Settings UI, and LightSwitch modules.
+    /// Thread-safe and AOT-compatible.
+    /// </summary>
+    public class ProfileService : IProfileService
+    {
+        private const string LogPrefix = "[ProfileService]";
+        private static readonly object _lock = new object();
+
+        /// <summary>
+        /// Gets the singleton instance of the ProfileService.
+        /// Use this for dependency injection or when interface-based access is needed.
+        /// </summary>
+        public static IProfileService Instance { get; } = new ProfileService();
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ProfileService"/> class.
+        /// Private constructor to enforce singleton pattern for instance-based access.
+        /// Static methods remain available for backward compatibility.
+        /// </summary>
+        private ProfileService()
+        {
+        }
+
+        /// <summary>
+        /// Loads PowerDisplay profiles from disk.
+        /// Thread-safe operation with automatic legacy profile cleanup.
+        /// </summary>
+        /// <returns>PowerDisplayProfiles object, or a new empty instance if file doesn't exist or load fails</returns>
+        public static PowerDisplayProfiles LoadProfiles()
+        {
+            lock (_lock)
+            {
+                var (profiles, _) = LoadProfilesInternal();
+                return profiles;
+            }
+        }
+
+        /// <summary>
+        /// Saves PowerDisplay profiles to disk.
+        /// Thread-safe operation with automatic timestamp update and legacy profile cleanup.
+        /// </summary>
+        /// <param name="profiles">The profiles collection to save</param>
+        /// <returns>True if save was successful, false otherwise</returns>
+        public static bool SaveProfiles(PowerDisplayProfiles profiles)
+        {
+            lock (_lock)
+            {
+                if (profiles == null)
+                {
+                    Logger.LogWarning($"{LogPrefix} Cannot save null profiles");
+                    return false;
+                }
+
+                var (success, _) = SaveProfilesInternal(profiles);
+                return success;
+            }
+        }
+
+        /// <summary>
+        /// Adds or updates a profile in the collection and persists to disk.
+        /// Thread-safe operation.
+        /// </summary>
+        /// <param name="profile">The profile to add or update</param>
+        /// <returns>True if operation was successful, false otherwise</returns>
+        public static bool AddOrUpdateProfile(PowerDisplayProfile profile)
+        {
+            lock (_lock)
+            {
+                if (profile == null || !profile.IsValid())
+                {
+                    Logger.LogWarning($"{LogPrefix} Cannot add invalid profile");
+                    return false;
+                }
+
+                var (profiles, _) = LoadProfilesInternal();
+                profiles.SetProfile(profile);
+
+                var (success, _) = SaveProfilesInternal(profiles);
+
+                if (success)
+                {
+                    Logger.LogInfo($"{LogPrefix} Profile '{profile.Name}' added/updated with {profile.MonitorSettings.Count} monitors");
+                }
+
+                return success;
+            }
+        }
+
+        /// <summary>
+        /// Removes a profile by name and persists to disk.
+        /// Thread-safe operation.
+        /// </summary>
+        /// <param name="profileName">The name of the profile to remove</param>
+        /// <returns>True if profile was found and removed, false otherwise</returns>
+        public static bool RemoveProfile(string profileName)
+        {
+            lock (_lock)
+            {
+                var (profiles, _) = LoadProfilesInternal();
+                bool removed = profiles.RemoveProfile(profileName);
+
+                if (removed)
+                {
+                    SaveProfilesInternal(profiles);
+                    Logger.LogInfo($"{LogPrefix} Profile '{profileName}' removed");
+                }
+                else
+                {
+                    Logger.LogWarning($"{LogPrefix} Profile '{profileName}' not found or cannot be removed");
+                }
+
+                return removed;
+            }
+        }
+
+        /// <summary>
+        /// Gets a profile by name.
+        /// Thread-safe operation.
+        /// </summary>
+        /// <param name="profileName">The name of the profile to retrieve</param>
+        /// <returns>The profile if found, null otherwise</returns>
+        public static PowerDisplayProfile? GetProfile(string profileName)
+        {
+            lock (_lock)
+            {
+                var (profiles, _) = LoadProfilesInternal();
+                return profiles.GetProfile(profileName);
+            }
+        }
+
+        /// <summary>
+        /// Checks if the profiles file exists.
+        /// </summary>
+        /// <returns>True if profiles file exists, false otherwise</returns>
+        public static bool ProfilesFileExists()
+        {
+            try
+            {
+                return File.Exists(PathConstants.ProfilesFilePath);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"{LogPrefix} Error checking if profiles file exists: {ex.Message}");
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Gets the path to the profiles file.
+        /// </summary>
+        /// <returns>The full path to the profiles file</returns>
+        public static string GetProfilesFilePath()
+        {
+            return PathConstants.ProfilesFilePath;
+        }
+
+        // Internal methods without lock for use within already-locked contexts
+        // Returns tuple with result and optional log message
+        private static (PowerDisplayProfiles Profiles, string? Message) LoadProfilesInternal()
+        {
+            try
+            {
+                var filePath = PathConstants.ProfilesFilePath;
+
+                PathConstants.EnsurePowerDisplayFolderExists();
+
+                if (File.Exists(filePath))
+                {
+                    var json = File.ReadAllText(filePath);
+                    var profiles = JsonSerializer.Deserialize(json, ProfileSerializationContext.Default.PowerDisplayProfiles);
+
+                    if (profiles != null)
+                    {
+                        profiles.Profiles.RemoveAll(p => p.Name.Equals(PowerDisplayProfiles.CustomProfileName, StringComparison.OrdinalIgnoreCase));
+                        return (profiles, $"Loaded {profiles.Profiles.Count} profiles from {filePath}");
+                    }
+                }
+                else
+                {
+                    return (new PowerDisplayProfiles(), $"No profiles file found at {filePath}, returning empty collection");
+                }
+
+                return (new PowerDisplayProfiles(), null);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"{LogPrefix} Failed to load profiles: {ex.Message}");
+                return (new PowerDisplayProfiles(), null);
+            }
+        }
+
+        // Returns tuple with success status and optional log message
+        private static (bool Success, string? Message) SaveProfilesInternal(PowerDisplayProfiles profiles)
+        {
+            try
+            {
+                if (profiles == null)
+                {
+                    return (false, null);
+                }
+
+                PathConstants.EnsurePowerDisplayFolderExists();
+
+                profiles.Profiles.RemoveAll(p => p.Name.Equals(PowerDisplayProfiles.CustomProfileName, StringComparison.OrdinalIgnoreCase));
+                profiles.LastUpdated = DateTime.UtcNow;
+
+                var json = JsonSerializer.Serialize(profiles, ProfileSerializationContext.Default.PowerDisplayProfiles);
+                var filePath = PathConstants.ProfilesFilePath;
+                File.WriteAllText(filePath, json);
+
+                return (true, $"Saved {profiles.Profiles.Count} profiles to {filePath}");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"{LogPrefix} Failed to save profiles: {ex.Message}");
+                return (false, null);
+            }
+        }
+
+        // IProfileService Implementation
+        // Explicit interface implementation to satisfy IProfileService
+        // These methods delegate to the static methods for backward compatibility
+
+        /// <inheritdoc/>
+        PowerDisplayProfiles IProfileService.LoadProfiles() => LoadProfiles();
+
+        /// <inheritdoc/>
+        bool IProfileService.SaveProfiles(PowerDisplayProfiles profiles) => SaveProfiles(profiles);
+
+        /// <inheritdoc/>
+        bool IProfileService.AddOrUpdateProfile(PowerDisplayProfile profile) => AddOrUpdateProfile(profile);
+
+        /// <inheritdoc/>
+        bool IProfileService.RemoveProfile(string profileName) => RemoveProfile(profileName);
+
+        /// <inheritdoc/>
+        PowerDisplayProfile? IProfileService.GetProfile(string profileName) => GetProfile(profileName);
+
+        /// <inheritdoc/>
+        bool IProfileService.ProfilesFileExists() => ProfilesFileExists();
+
+        /// <inheritdoc/>
+        string IProfileService.GetProfilesFilePath() => GetProfilesFilePath();
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/ColorTemperatureHelper.cs

@@ -0,0 +1,79 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Linq;
+using PowerDisplay.Common.Drivers;
+using PowerDisplay.Common.Models;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Helper class for color temperature preset computation.
+    /// Provides shared logic for computing available color presets from VCP capabilities.
+    /// </summary>
+    public static class ColorTemperatureHelper
+    {
+        /// <summary>
+        /// Computes available color temperature presets from VCP value data.
+        /// </summary>
+        /// <param name="colorTemperatureValues">
+        /// Collection of tuples containing (VcpValue, Name) for each color temperature preset.
+        /// The VcpValue is the VCP value, Name is the name from capabilities string if available.
+        /// </param>
+        /// <returns>Sorted list of ColorPresetItem objects.</returns>
+        public static List<ColorPresetItem> ComputeColorPresets(IEnumerable<(int VcpValue, string? Name)> colorTemperatureValues)
+        {
+            if (colorTemperatureValues == null)
+            {
+                return new List<ColorPresetItem>();
+            }
+
+            var presetList = new List<ColorPresetItem>();
+
+            foreach (var item in colorTemperatureValues)
+            {
+                var displayName = FormatColorTemperatureDisplayName(item.VcpValue, item.Name);
+                presetList.Add(new ColorPresetItem(item.VcpValue, displayName));
+            }
+
+            // Sort by VCP value for consistent ordering
+            return presetList.OrderBy(p => p.VcpValue).ToList();
+        }
+
+        /// <summary>
+        /// Formats a color temperature display name.
+        /// Uses VcpNames for standard VCP value mappings if no custom name is provided.
+        /// </summary>
+        /// <param name="vcpValue">The VCP value.</param>
+        /// <param name="customName">Optional custom name from capabilities string.</param>
+        /// <returns>Formatted display name.</returns>
+        public static string FormatColorTemperatureDisplayName(int vcpValue, string? customName = null)
+        {
+            // Priority: use name from VCP capabilities if available
+            if (!string.IsNullOrEmpty(customName))
+            {
+                return customName;
+            }
+
+            // Fall back to standard VCP value name from shared library
+            return VcpNames.GetValueName(NativeConstants.VcpCodeSelectColorPreset, vcpValue)
+                   ?? "Manufacturer Defined";
+        }
+
+        /// <summary>
+        /// Formats a display name for a custom (non-preset) color temperature value.
+        /// Used when the current value is not in the available preset list.
+        /// </summary>
+        /// <param name="vcpValue">The VCP value.</param>
+        /// <returns>Formatted display name with "Custom" indicator.</returns>
+        public static string FormatCustomColorTemperatureDisplayName(int vcpValue)
+        {
+            var standardName = VcpNames.GetValueName(NativeConstants.VcpCodeSelectColorPreset, vcpValue);
+            return string.IsNullOrEmpty(standardName)
+                ? "Custom"
+                : $"{standardName} (Custom)";
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/EventHelper.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using ManagedCommon;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Helper class for Windows named event operations.
+    /// Provides unified event signaling with consistent error handling and logging.
+    /// </summary>
+    public static class EventHelper
+    {
+        /// <summary>
+        /// Signals a named event. Creates the event if it doesn't exist.
+        /// </summary>
+        /// <param name="eventName">The name of the event to signal.</param>
+        /// <returns>True if the event was signaled successfully, false otherwise.</returns>
+        public static bool SignalEvent(string eventName)
+        {
+            if (string.IsNullOrEmpty(eventName))
+            {
+                Logger.LogWarning("[EventHelper] SignalEvent called with null or empty event name");
+                return false;
+            }
+
+            try
+            {
+                using var eventHandle = new EventWaitHandle(
+                    false,
+                    EventResetMode.AutoReset,
+                    eventName);
+                eventHandle.Set();
+                return true;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[EventHelper] Failed to signal event '{eventName}': {ex.Message}");
+                return false;
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/MccsCapabilitiesParser.cs

@@ -0,0 +1,860 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using ManagedCommon;
+using PowerDisplay.Common.Models;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Recursive descent parser for DDC/CI MCCS capabilities strings.
+    ///
+    /// MCCS Capabilities String Grammar (BNF):
+    /// <code>
+    /// capabilities     ::= '(' segment* ')'
+    /// segment          ::= identifier '(' segment_content ')'
+    /// segment_content  ::= text | vcp_entries | hex_list
+    /// vcp_entries      ::= vcp_entry*
+    /// vcp_entry        ::= hex_byte [ '(' hex_list ')' ]
+    /// hex_list         ::= hex_byte*
+    /// hex_byte         ::= [0-9A-Fa-f]{2}
+    /// identifier       ::= [a-z_]+
+    /// text             ::= [^()]+
+    /// </code>
+    ///
+    /// Example input:
+    /// (prot(monitor)type(lcd)model(PD3220U)cmds(01 02 03)vcp(10 12 14(04 05) 60(11 12))mccs_ver(2.2))
+    /// </summary>
+    public ref struct MccsCapabilitiesParser
+    {
+        private readonly List<ParseError> _errors;
+        private ReadOnlySpan<char> _input;
+        private int _position;
+
+        /// <summary>
+        /// Parse a capabilities string into structured VcpCapabilities.
+        /// </summary>
+        /// <param name="capabilitiesString">Raw MCCS capabilities string</param>
+        /// <returns>Parsed capabilities object with any parse errors</returns>
+        public static MccsParseResult Parse(string? capabilitiesString)
+        {
+            if (string.IsNullOrWhiteSpace(capabilitiesString))
+            {
+                return new MccsParseResult(VcpCapabilities.Empty, new List<ParseError>());
+            }
+
+            var parser = new MccsCapabilitiesParser(capabilitiesString);
+            return parser.ParseCapabilities();
+        }
+
+        private MccsCapabilitiesParser(string input)
+        {
+            _input = input.AsSpan();
+            _position = 0;
+            _errors = new List<ParseError>();
+        }
+
+        /// <summary>
+        /// Main entry point: parse the entire capabilities string.
+        /// capabilities ::= '(' segment* ')' | segment*
+        /// </summary>
+        private MccsParseResult ParseCapabilities()
+        {
+            var capabilities = new VcpCapabilities
+            {
+                Raw = _input.ToString(),
+            };
+
+            SkipWhitespace();
+
+            // Handle optional outer parentheses (some monitors omit them)
+            bool hasOuterParens = Peek() == '(';
+            if (hasOuterParens)
+            {
+                Advance(); // consume '('
+            }
+
+            // Parse segments until end or closing paren
+            while (!IsAtEnd())
+            {
+                SkipWhitespace();
+
+                if (IsAtEnd())
+                {
+                    break;
+                }
+
+                if (Peek() == ')')
+                {
+                    if (hasOuterParens)
+                    {
+                        Advance(); // consume closing ')'
+                    }
+
+                    break;
+                }
+
+                // Parse a segment: identifier(content)
+                var segment = ParseSegment();
+                if (segment.HasValue)
+                {
+                    ApplySegment(capabilities, segment.Value);
+                }
+            }
+
+            return new MccsParseResult(capabilities, _errors);
+        }
+
+        /// <summary>
+        /// Parse a single segment: identifier '(' content ')'
+        /// </summary>
+        private ParsedSegment? ParseSegment()
+        {
+            SkipWhitespace();
+
+            int startPos = _position;
+
+            // Parse identifier
+            var identifier = ParseIdentifier();
+            if (identifier.IsEmpty)
+            {
+                // Not a valid segment start - skip this character and continue
+                if (!IsAtEnd())
+                {
+                    Advance();
+                }
+
+                return null;
+            }
+
+            SkipWhitespace();
+
+            // Expect '('
+            if (Peek() != '(')
+            {
+                AddError($"Expected '(' after identifier '{identifier.ToString()}' at position {_position}");
+                return null;
+            }
+
+            Advance(); // consume '('
+
+            // Parse content until matching ')'
+            var content = ParseBalancedContent();
+
+            // Expect ')'
+            if (Peek() != ')')
+            {
+                AddError($"Expected ')' to close segment '{identifier.ToString()}' at position {_position}");
+            }
+            else
+            {
+                Advance(); // consume ')'
+            }
+
+            return new ParsedSegment(identifier.ToString(), content);
+        }
+
+        /// <summary>
+        /// Parse content between balanced parentheses.
+        /// Handles nested parentheses correctly.
+        /// </summary>
+        private string ParseBalancedContent()
+        {
+            int start = _position;
+            int depth = 1;
+
+            while (!IsAtEnd() && depth > 0)
+            {
+                char c = Peek();
+                if (c == '(')
+                {
+                    depth++;
+                }
+                else if (c == ')')
+                {
+                    depth--;
+                    if (depth == 0)
+                    {
+                        break; // Don't consume the closing paren
+                    }
+                }
+
+                Advance();
+            }
+
+            return _input.Slice(start, _position - start).ToString();
+        }
+
+        /// <summary>
+        /// Parse an identifier (letters, digits, and underscores).
+        /// identifier ::= [a-zA-Z0-9_]+
+        /// Note: MCCS uses identifiers like window1, window2, etc.
+        /// </summary>
+        private ReadOnlySpan<char> ParseIdentifier()
+        {
+            int start = _position;
+
+            while (!IsAtEnd() && IsIdentifierChar(Peek()))
+            {
+                Advance();
+            }
+
+            return _input.Slice(start, _position - start);
+        }
+
+        /// <summary>
+        /// Apply a parsed segment to the capabilities object.
+        /// </summary>
+        private void ApplySegment(VcpCapabilities capabilities, ParsedSegment segment)
+        {
+            switch (segment.Name.ToLowerInvariant())
+            {
+                case "prot":
+                    capabilities.Protocol = segment.Content.Trim();
+                    break;
+
+                case "type":
+                    capabilities.Type = segment.Content.Trim();
+                    break;
+
+                case "model":
+                    capabilities.Model = segment.Content.Trim();
+                    break;
+
+                case "mccs_ver":
+                    capabilities.MccsVersion = segment.Content.Trim();
+                    break;
+
+                case "cmds":
+                    capabilities.SupportedCommands = ParseHexList(segment.Content);
+                    break;
+
+                case "vcp":
+                    capabilities.SupportedVcpCodes = ParseVcpEntries(segment.Content);
+                    break;
+
+                case "vcpname":
+                    ParseVcpNames(segment.Content, capabilities);
+                    break;
+
+                default:
+                    // Check for windowN pattern (window1, window2, etc.)
+                    if (segment.Name.Length > 6 &&
+                        segment.Name.StartsWith("window", StringComparison.OrdinalIgnoreCase) &&
+                        int.TryParse(segment.Name.AsSpan(6), out int windowNum))
+                    {
+                        var windowParser = new WindowParser(segment.Content);
+                        var windowCap = windowParser.Parse(windowNum);
+                        capabilities.Windows.Add(windowCap);
+                    }
+                    else
+                    {
+                        // Unknown segments are silently ignored
+                    }
+
+                    break;
+            }
+        }
+
+        /// <summary>
+        /// Parse VCP entries: vcp_entry*
+        /// vcp_entry ::= hex_byte [ '(' hex_list ')' ]
+        /// </summary>
+        private Dictionary<byte, VcpCodeInfo> ParseVcpEntries(string content)
+        {
+            var vcpCodes = new Dictionary<byte, VcpCodeInfo>();
+            var parser = new VcpEntryParser(content);
+
+            while (parser.TryParseEntry(out var entry))
+            {
+                var name = VcpNames.GetCodeName(entry.Code);
+                vcpCodes[entry.Code] = new VcpCodeInfo(entry.Code, name, entry.Values);
+            }
+
+            return vcpCodes;
+        }
+
+        /// <summary>
+        /// Parse a hex byte list: hex_byte*
+        /// Handles both space-separated (01 02 03) and concatenated (010203) formats.
+        /// </summary>
+        private static List<byte> ParseHexList(string content)
+        {
+            var result = new List<byte>();
+            var span = content.AsSpan();
+            int i = 0;
+
+            while (i < span.Length)
+            {
+                // Skip whitespace
+                while (i < span.Length && char.IsWhiteSpace(span[i]))
+                {
+                    i++;
+                }
+
+                if (i >= span.Length)
+                {
+                    break;
+                }
+
+                // Try to read two hex digits
+                if (i + 1 < span.Length && IsHexDigit(span[i]) && IsHexDigit(span[i + 1]))
+                {
+                    if (byte.TryParse(span.Slice(i, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var value))
+                    {
+                        result.Add(value);
+                    }
+
+                    i += 2;
+                }
+                else
+                {
+                    i++; // Skip invalid character
+                }
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Parse vcpname entries: hex_byte '(' name ')'
+        /// </summary>
+        private void ParseVcpNames(string content, VcpCapabilities capabilities)
+        {
+            // vcpname format: F0(Custom Name 1) F1(Custom Name 2)
+            var parser = new VcpNameParser(content);
+
+            while (parser.TryParseEntry(out var code, out var name))
+            {
+                if (capabilities.SupportedVcpCodes.TryGetValue(code, out var existingInfo))
+                {
+                    // Update existing entry with custom name
+                    capabilities.SupportedVcpCodes[code] = new VcpCodeInfo(code, name, existingInfo.SupportedValues);
+                }
+                else
+                {
+                    // Add new entry with custom name
+                    capabilities.SupportedVcpCodes[code] = new VcpCodeInfo(code, name, Array.Empty<int>());
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private char Peek() => IsAtEnd() ? '\0' : _input[_position];
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void Advance() => _position++;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private bool IsAtEnd() => _position >= _input.Length;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void SkipWhitespace()
+        {
+            while (!IsAtEnd() && char.IsWhiteSpace(Peek()))
+            {
+                Advance();
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsIdentifierChar(char c) =>
+            (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_';
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsHexDigit(char c) =>
+            (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
+
+        private void AddError(string message)
+        {
+            _errors.Add(new ParseError(_position, message));
+            Logger.LogWarning($"[MccsParser] {message}");
+        }
+    }
+
+    /// <summary>
+    /// Sub-parser for VCP entries within the vcp() segment.
+    /// </summary>
+    internal ref struct VcpEntryParser
+    {
+        private ReadOnlySpan<char> _content;
+        private int _position;
+
+        public VcpEntryParser(string content)
+        {
+            _content = content.AsSpan();
+            _position = 0;
+        }
+
+        /// <summary>
+        /// Try to parse the next VCP entry.
+        /// vcp_entry ::= hex_byte [ '(' hex_list ')' ]
+        /// </summary>
+        public bool TryParseEntry(out VcpEntry entry)
+        {
+            entry = default;
+            SkipWhitespace();
+
+            if (IsAtEnd())
+            {
+                return false;
+            }
+
+            // Parse hex byte (VCP code)
+            if (!TryParseHexByte(out var code))
+            {
+                // Skip invalid character and try again
+                _position++;
+                return TryParseEntry(out entry);
+            }
+
+            var values = new List<int>();
+
+            SkipWhitespace();
+
+            // Check for optional value list
+            if (!IsAtEnd() && Peek() == '(')
+            {
+                _position++; // consume '('
+
+                // Parse values until ')'
+                while (!IsAtEnd() && Peek() != ')')
+                {
+                    SkipWhitespace();
+
+                    if (Peek() == ')')
+                    {
+                        break;
+                    }
+
+                    if (TryParseHexByte(out var value))
+                    {
+                        values.Add(value);
+                    }
+                    else
+                    {
+                        _position++; // Skip invalid character
+                    }
+                }
+
+                if (!IsAtEnd() && Peek() == ')')
+                {
+                    _position++; // consume ')'
+                }
+            }
+
+            entry = new VcpEntry(code, values);
+            return true;
+        }
+
+        private bool TryParseHexByte(out byte value)
+        {
+            value = 0;
+
+            if (_position + 1 >= _content.Length)
+            {
+                return false;
+            }
+
+            if (!IsHexDigit(_content[_position]) || !IsHexDigit(_content[_position + 1]))
+            {
+                return false;
+            }
+
+            if (byte.TryParse(_content.Slice(_position, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out value))
+            {
+                _position += 2;
+                return true;
+            }
+
+            return false;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private char Peek() => IsAtEnd() ? '\0' : _content[_position];
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private bool IsAtEnd() => _position >= _content.Length;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void SkipWhitespace()
+        {
+            while (!IsAtEnd() && char.IsWhiteSpace(Peek()))
+            {
+                _position++;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsHexDigit(char c) =>
+            (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
+    }
+
+    /// <summary>
+    /// Sub-parser for vcpname entries.
+    /// </summary>
+    internal ref struct VcpNameParser
+    {
+        private ReadOnlySpan<char> _content;
+        private int _position;
+
+        public VcpNameParser(string content)
+        {
+            _content = content.AsSpan();
+            _position = 0;
+        }
+
+        /// <summary>
+        /// Try to parse the next vcpname entry.
+        /// vcpname_entry ::= hex_byte '(' name ')'
+        /// </summary>
+        public bool TryParseEntry(out byte code, out string name)
+        {
+            code = 0;
+            name = string.Empty;
+
+            SkipWhitespace();
+
+            if (IsAtEnd())
+            {
+                return false;
+            }
+
+            // Parse hex byte
+            if (!TryParseHexByte(out code))
+            {
+                _position++;
+                return TryParseEntry(out code, out name);
+            }
+
+            SkipWhitespace();
+
+            // Expect '('
+            if (IsAtEnd() || Peek() != '(')
+            {
+                return false;
+            }
+
+            _position++; // consume '('
+
+            // Parse name until ')'
+            int start = _position;
+            while (!IsAtEnd() && Peek() != ')')
+            {
+                _position++;
+            }
+
+            name = _content.Slice(start, _position - start).ToString().Trim();
+
+            if (!IsAtEnd() && Peek() == ')')
+            {
+                _position++; // consume ')'
+            }
+
+            return true;
+        }
+
+        private bool TryParseHexByte(out byte value)
+        {
+            value = 0;
+
+            if (_position + 1 >= _content.Length)
+            {
+                return false;
+            }
+
+            if (!IsHexDigit(_content[_position]) || !IsHexDigit(_content[_position + 1]))
+            {
+                return false;
+            }
+
+            if (byte.TryParse(_content.Slice(_position, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out value))
+            {
+                _position += 2;
+                return true;
+            }
+
+            return false;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private char Peek() => IsAtEnd() ? '\0' : _content[_position];
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private bool IsAtEnd() => _position >= _content.Length;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void SkipWhitespace()
+        {
+            while (!IsAtEnd() && char.IsWhiteSpace(Peek()))
+            {
+                _position++;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsHexDigit(char c) =>
+            (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
+    }
+
+    /// <summary>
+    /// Sub-parser for window segment content.
+    /// Parses: type(PIP) area(25 25 1895 1175) max(640 480) min(10 10) window(10)
+    /// </summary>
+    internal ref struct WindowParser
+    {
+        private ReadOnlySpan<char> _content;
+        private int _position;
+
+        public WindowParser(string content)
+        {
+            _content = content.AsSpan();
+            _position = 0;
+        }
+
+        /// <summary>
+        /// Parse window segment content into a WindowCapability.
+        /// </summary>
+        public WindowCapability Parse(int windowNumber)
+        {
+            string type = string.Empty;
+            var area = default(WindowArea);
+            var maxSize = default(WindowSize);
+            var minSize = default(WindowSize);
+            int windowId = 0;
+
+            // Parse sub-segments: type(...) area(...) max(...) min(...) window(...)
+            while (!IsAtEnd())
+            {
+                SkipWhitespace();
+                if (IsAtEnd())
+                {
+                    break;
+                }
+
+                var subSegment = ParseSubSegment();
+                if (subSegment.HasValue)
+                {
+                    switch (subSegment.Value.Name.ToLowerInvariant())
+                    {
+                        case "type":
+                            type = subSegment.Value.Content.Trim();
+                            break;
+                        case "area":
+                            area = ParseArea(subSegment.Value.Content);
+                            break;
+                        case "max":
+                            maxSize = ParseSize(subSegment.Value.Content);
+                            break;
+                        case "min":
+                            minSize = ParseSize(subSegment.Value.Content);
+                            break;
+                        case "window":
+                            _ = int.TryParse(subSegment.Value.Content.Trim(), out windowId);
+                            break;
+                    }
+                }
+            }
+
+            return new WindowCapability(windowNumber, type, area, maxSize, minSize, windowId);
+        }
+
+        private (string Name, string Content)? ParseSubSegment()
+        {
+            int start = _position;
+
+            // Parse identifier
+            while (!IsAtEnd() && IsIdentifierChar(Peek()))
+            {
+                _position++;
+            }
+
+            if (_position == start)
+            {
+                // No identifier found, skip character
+                if (!IsAtEnd())
+                {
+                    _position++;
+                }
+
+                return null;
+            }
+
+            var name = _content.Slice(start, _position - start).ToString();
+
+            SkipWhitespace();
+
+            // Expect '('
+            if (IsAtEnd() || Peek() != '(')
+            {
+                return null;
+            }
+
+            _position++; // consume '('
+
+            // Parse content with balanced parentheses
+            int contentStart = _position;
+            int depth = 1;
+
+            while (!IsAtEnd() && depth > 0)
+            {
+                char c = Peek();
+                if (c == '(')
+                {
+                    depth++;
+                }
+                else if (c == ')')
+                {
+                    depth--;
+                    if (depth == 0)
+                    {
+                        break;
+                    }
+                }
+
+                _position++;
+            }
+
+            var content = _content.Slice(contentStart, _position - contentStart).ToString();
+
+            if (!IsAtEnd() && Peek() == ')')
+            {
+                _position++; // consume ')'
+            }
+
+            return (name, content);
+        }
+
+        private static WindowArea ParseArea(string content)
+        {
+            var values = ParseIntList(content);
+            if (values.Length >= 4)
+            {
+                return new WindowArea(values[0], values[1], values[2], values[3]);
+            }
+
+            return default;
+        }
+
+        private static WindowSize ParseSize(string content)
+        {
+            var values = ParseIntList(content);
+            if (values.Length >= 2)
+            {
+                return new WindowSize(values[0], values[1]);
+            }
+
+            return default;
+        }
+
+        private static int[] ParseIntList(string content)
+        {
+            var parts = content.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+            var result = new List<int>(parts.Length);
+
+            foreach (var part in parts)
+            {
+                if (int.TryParse(part.Trim(), out int value))
+                {
+                    result.Add(value);
+                }
+            }
+
+            return result.ToArray();
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private char Peek() => IsAtEnd() ? '\0' : _content[_position];
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private bool IsAtEnd() => _position >= _content.Length;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void SkipWhitespace()
+        {
+            while (!IsAtEnd() && char.IsWhiteSpace(Peek()))
+            {
+                _position++;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsIdentifierChar(char c) =>
+            (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_';
+    }
+
+    /// <summary>
+    /// Represents a parsed segment from the capabilities string.
+    /// </summary>
+    internal readonly struct ParsedSegment
+    {
+        public string Name { get; }
+
+        public string Content { get; }
+
+        public ParsedSegment(string name, string content)
+        {
+            Name = name;
+            Content = content;
+        }
+    }
+
+    /// <summary>
+    /// Represents a parsed VCP entry.
+    /// </summary>
+    internal readonly struct VcpEntry
+    {
+        public byte Code { get; }
+
+        public IReadOnlyList<int> Values { get; }
+
+        public VcpEntry(byte code, IReadOnlyList<int> values)
+        {
+            Code = code;
+            Values = values;
+        }
+    }
+
+    /// <summary>
+    /// Represents a parse error with position information.
+    /// </summary>
+    public readonly struct ParseError
+    {
+        public int Position { get; }
+
+        public string Message { get; }
+
+        public ParseError(int position, string message)
+        {
+            Position = position;
+            Message = message;
+        }
+
+        public override string ToString() => $"[{Position}] {Message}";
+    }
+
+    /// <summary>
+    /// Result of parsing MCCS capabilities string.
+    /// </summary>
+    public sealed class MccsParseResult
+    {
+        public VcpCapabilities Capabilities { get; }
+
+        public IReadOnlyList<ParseError> Errors { get; }
+
+        public bool HasErrors => Errors.Count > 0;
+
+        public bool IsValid => !HasErrors && Capabilities.SupportedVcpCodes.Count > 0;
+
+        public MccsParseResult(VcpCapabilities capabilities, IReadOnlyList<ParseError> errors)
+        {
+            Capabilities = capabilities;
+            Errors = errors;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/MonitorFeatureHelper.cs

@@ -0,0 +1,108 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using PowerDisplay.Common.Drivers;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Unified helper class for parsing monitor feature support from VCP capabilities.
+    /// This eliminates duplicate VCP parsing logic across PowerDisplay.exe and Settings.UI.
+    /// </summary>
+    public static class MonitorFeatureHelper
+    {
+        /// <summary>
+        /// Result of parsing monitor feature support from VCP capabilities
+        /// </summary>
+        public readonly struct FeatureSupportResult
+        {
+            public bool SupportsBrightness { get; init; }
+
+            public bool SupportsContrast { get; init; }
+
+            public bool SupportsColorTemperature { get; init; }
+
+            public bool SupportsVolume { get; init; }
+
+            public bool SupportsInputSource { get; init; }
+
+            public static FeatureSupportResult Unavailable => new()
+            {
+                SupportsBrightness = false,
+                SupportsContrast = false,
+                SupportsColorTemperature = false,
+                SupportsVolume = false,
+                SupportsInputSource = false,
+            };
+        }
+
+        /// <summary>
+        /// Parse feature support from a list of VCP code strings.
+        /// This is the single source of truth for determining monitor capabilities.
+        /// </summary>
+        /// <param name="vcpCodes">List of VCP codes as strings (e.g., "0x10", "10", "0x12")</param>
+        /// <param name="capabilitiesRaw">Raw capabilities string, used to determine availability status</param>
+        /// <returns>Feature support result</returns>
+        public static FeatureSupportResult ParseFeatureSupport(IReadOnlyList<string>? vcpCodes, string? capabilitiesRaw)
+        {
+            // Check capabilities availability
+            if (string.IsNullOrEmpty(capabilitiesRaw))
+            {
+                return FeatureSupportResult.Unavailable;
+            }
+
+            // Convert all VCP codes to integers for comparison
+            var vcpCodeInts = ParseVcpCodesToIntegers(vcpCodes);
+
+            // Determine feature support based on VCP codes
+            return new FeatureSupportResult
+            {
+                SupportsBrightness = vcpCodeInts.Contains(NativeConstants.VcpCodeBrightness),
+                SupportsContrast = vcpCodeInts.Contains(NativeConstants.VcpCodeContrast),
+                SupportsColorTemperature = vcpCodeInts.Contains(NativeConstants.VcpCodeSelectColorPreset),
+                SupportsVolume = vcpCodeInts.Contains(NativeConstants.VcpCodeVolume),
+                SupportsInputSource = vcpCodeInts.Contains(NativeConstants.VcpCodeInputSource),
+            };
+        }
+
+        /// <summary>
+        /// Parse VCP codes from string list to integer set
+        /// Handles both hex formats: "0x10" and "10"
+        /// </summary>
+        private static HashSet<int> ParseVcpCodesToIntegers(IReadOnlyList<string>? vcpCodes)
+        {
+            var result = new HashSet<int>();
+
+            if (vcpCodes == null)
+            {
+                return result;
+            }
+
+            foreach (var code in vcpCodes)
+            {
+                if (string.IsNullOrWhiteSpace(code))
+                {
+                    continue;
+                }
+
+                // Remove "0x" prefix if present and parse as hex
+                var cleanCode = code.Trim();
+                if (cleanCode.StartsWith("0x", StringComparison.OrdinalIgnoreCase))
+                {
+                    cleanCode = cleanCode[2..];
+                }
+
+                if (int.TryParse(cleanCode, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out int codeInt))
+                {
+                    result.Add(codeInt);
+                }
+            }
+
+            return result;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/MonitorMatchingHelper.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using PowerDisplay.Common.Interfaces;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Helper class for monitor matching and identification.
+    /// Provides consistent logic for matching monitors across different data sources.
+    /// </summary>
+    public static class MonitorMatchingHelper
+    {
+        /// <summary>
+        /// Generate a unique key for monitor matching based on Id.
+        /// </summary>
+        /// <param name="monitor">The monitor data to generate a key for.</param>
+        /// <returns>A unique string key for the monitor.</returns>
+        public static string GetMonitorKey(IMonitorData? monitor)
+            => monitor?.Id ?? string.Empty;
+
+        /// <summary>
+        /// Check if two monitors are considered the same based on their Ids.
+        /// </summary>
+        /// <param name="monitor1">First monitor.</param>
+        /// <param name="monitor2">Second monitor.</param>
+        /// <returns>True if the monitors have the same Id.</returns>
+        public static bool AreMonitorsSame(IMonitorData monitor1, IMonitorData monitor2)
+        {
+            if (monitor1 == null || monitor2 == null)
+            {
+                return false;
+            }
+
+            return !string.IsNullOrEmpty(monitor1.Id) && monitor1.Id == monitor2.Id;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/MonitorValueConverter.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Provides conversion utilities for monitor hardware values.
+    /// Use this class to convert between raw hardware values and display-friendly formats.
+    /// </summary>
+    public static class MonitorValueConverter
+    {
+        /// <summary>
+        /// Formats a VCP color temperature value as a display name.
+        /// </summary>
+        /// <param name="vcpValue">The VCP preset value (e.g., 0x05).</param>
+        /// <returns>Display name like "6500K" or "sRGB".</returns>
+        public static string FormatColorTemperatureDisplay(int vcpValue)
+        {
+            return ColorTemperatureHelper.FormatColorTemperatureDisplayName(vcpValue);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/PnpIdHelper.cs

@@ -0,0 +1,86 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Frozen;
+using System.Collections.Generic;
+
+namespace PowerDisplay.Common.Utils;
+
+/// <summary>
+/// Helper class for mapping PnP (Plug and Play) manufacturer IDs to display names.
+/// PnP IDs are 3-character codes assigned by Microsoft to hardware manufacturers.
+/// See: https://uefi.org/pnp_id_list
+/// </summary>
+public static class PnpIdHelper
+{
+    /// <summary>
+    /// Map of common laptop/monitor manufacturer PnP IDs to display names.
+    /// Only includes manufacturers known to produce laptops with internal displays.
+    /// </summary>
+    private static readonly FrozenDictionary<string, string> ManufacturerNames = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
+    {
+        // Major laptop manufacturers
+        { "ACR", "Acer" },
+        { "AUO", "AU Optronics" },
+        { "BOE", "BOE" },
+        { "CMN", "Chi Mei Innolux" },
+        { "DEL", "Dell" },
+        { "HWP", "HP" },
+        { "IVO", "InfoVision" },
+        { "LEN", "Lenovo" },
+        { "LGD", "LG Display" },
+        { "NCP", "Nanjing CEC Panda" },
+        { "SAM", "Samsung" },
+        { "SDC", "Samsung Display" },
+        { "SEC", "Samsung Electronics" },
+        { "SHP", "Sharp" },
+        { "AUS", "ASUS" },
+        { "MSI", "MSI" },
+        { "APP", "Apple" },
+        { "SNY", "Sony" },
+        { "PHL", "Philips" },
+        { "HSD", "HannStar" },
+        { "CPT", "Chunghwa Picture Tubes" },
+        { "QDS", "Quanta Display" },
+        { "TMX", "Tianma Microelectronics" },
+        { "CSO", "CSOT" },
+
+        // Microsoft Surface
+        { "MSF", "Microsoft" },
+    }.ToFrozenDictionary(StringComparer.OrdinalIgnoreCase);
+
+    /// <summary>
+    /// Extract the 3-character PnP manufacturer ID from a hardware ID.
+    /// </summary>
+    /// <param name="hardwareId">Hardware ID like "LEN4038" or "BOE0900".</param>
+    /// <returns>The 3-character PnP ID (e.g., "LEN"), or null if invalid.</returns>
+    public static string? ExtractPnpId(string? hardwareId)
+    {
+        if (string.IsNullOrEmpty(hardwareId) || hardwareId.Length < 3)
+        {
+            return null;
+        }
+
+        // PnP ID is the first 3 characters
+        return hardwareId.Substring(0, 3).ToUpperInvariant();
+    }
+
+    /// <summary>
+    /// Get a user-friendly display name for an internal display based on its hardware ID.
+    /// </summary>
+    /// <param name="hardwareId">Hardware ID like "LEN4038" or "BOE0900".</param>
+    /// <returns>Display name like "Lenovo Built-in Display" or "Built-in Display" as fallback.</returns>
+    public static string GetBuiltInDisplayName(string? hardwareId)
+    {
+        var pnpId = ExtractPnpId(hardwareId);
+
+        if (pnpId != null && ManufacturerNames.TryGetValue(pnpId, out var manufacturer))
+        {
+            return $"{manufacturer} Built-in Display";
+        }
+
+        return "Built-in Display";
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/ProfileHelper.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Helper class for profile management operations.
+    /// Provides utilities for profile name generation and validation.
+    /// </summary>
+    public static class ProfileHelper
+    {
+        private const string DefaultProfileBaseName = "Profile";
+
+        /// <summary>
+        /// Generate a unique profile name that doesn't conflict with existing names.
+        /// </summary>
+        /// <param name="existingNames">Set of existing profile names.</param>
+        /// <param name="baseName">The base name to use (default: "Profile").</param>
+        /// <returns>A unique profile name like "Profile 1", "Profile 2", etc.</returns>
+        public static string GenerateUniqueProfileName(ISet<string>? existingNames, string baseName = DefaultProfileBaseName)
+        {
+            if (existingNames == null || existingNames.Count == 0)
+            {
+                return $"{baseName} 1";
+            }
+
+            int counter = 1;
+            string name;
+            do
+            {
+                name = $"{baseName} {counter}";
+                counter++;
+            }
+            while (existingNames.Contains(name));
+
+            return name;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/SimpleDebouncer.cs

@@ -0,0 +1,127 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Simple debouncer that delays execution of an action until a quiet period.
+    /// Replaces the complex PropertyUpdateQueue with a much simpler approach (KISS principle).
+    /// </summary>
+    public partial class SimpleDebouncer : IDisposable
+    {
+        private readonly int _delayMs;
+        private readonly object _lock = new object();
+        private CancellationTokenSource? _cts;
+        private bool _disposed;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SimpleDebouncer"/> class.
+        /// Create a debouncer with specified delay
+        /// </summary>
+        /// <param name="delayMs">Delay in milliseconds before executing action</param>
+        public SimpleDebouncer(int delayMs = 300)
+        {
+            _delayMs = delayMs;
+        }
+
+        /// <summary>
+        /// Debounce an async action. Cancels previous invocation if still pending.
+        /// </summary>
+        /// <param name="action">Async action to execute after delay</param>
+        public void Debounce(Func<Task> action)
+        {
+            _ = DebounceAsync(action);
+        }
+
+        /// <summary>
+        /// Debounce a synchronous action
+        /// </summary>
+        public void Debounce(Action action)
+        {
+            _ = DebounceAsync(() =>
+            {
+                action();
+                return Task.CompletedTask;
+            });
+        }
+
+        private async Task DebounceAsync(Func<Task> action)
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            CancellationTokenSource cts;
+            CancellationTokenSource? oldCts = null;
+
+            lock (_lock)
+            {
+                // Store old CTS to dispose later
+                oldCts = _cts;
+
+                // Create new CTS
+                _cts = new CancellationTokenSource();
+                cts = _cts;
+            }
+
+            // Dispose old CTS outside the lock to avoid blocking
+            if (oldCts != null)
+            {
+                try
+                {
+                    oldCts.Cancel();
+                    oldCts.Dispose();
+                }
+                catch (ObjectDisposedException)
+                {
+                    // Expected if CTS was already disposed
+                }
+            }
+
+            try
+            {
+                // Wait for quiet period
+                await Task.Delay(_delayMs, cts.Token).ConfigureAwait(false);
+
+                // Execute action if not cancelled
+                if (!cts.Token.IsCancellationRequested)
+                {
+                    await action().ConfigureAwait(false);
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                // Expected when debouncing - a newer call cancelled this one
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Debounced action failed: {ex.Message}");
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            lock (_lock)
+            {
+                _disposed = true;
+                _cts?.Cancel();
+                _cts?.Dispose();
+                _cts = null;
+            }
+
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Utils/VcpNames.cs

@@ -0,0 +1,427 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Provides human-readable names for VCP codes and their values based on MCCS v2.2a specification.
+    /// Combines VCP code names (e.g., 0x10 = "Brightness") and VCP value names (e.g., 0x14:0x05 = "6500K").
+    /// </summary>
+    public static class VcpNames
+    {
+        /// <summary>
+        /// VCP code to name mapping
+        /// </summary>
+        private static readonly Dictionary<byte, string> CodeNames = new()
+        {
+            // Control codes (0x00-0x0F)
+            { 0x00, "Code Page" },
+            { 0x01, "Degauss" },
+            { 0x02, "New Control Value" },
+            { 0x03, "Soft Controls" },
+
+            // Preset operations (0x04-0x0A)
+            { 0x04, "Restore Factory Defaults" },
+            { 0x05, "Restore Brightness and Contrast" },
+            { 0x06, "Restore Factory Geometry" },
+            { 0x08, "Restore Color Defaults" },
+            { 0x0A, "Restore Factory TV Defaults" },
+
+            // Color temperature codes
+            { 0x0B, "Color Temperature Increment" },
+            { 0x0C, "Color Temperature Request" },
+            { 0x0E, "Clock" },
+            { 0x0F, "Color Saturation" },
+
+            // Image adjustment codes
+            { 0x10, "Brightness" },
+            { 0x11, "Flesh Tone Enhancement" },
+            { 0x12, "Contrast" },
+            { 0x13, "Backlight Control" },
+            { 0x14, "Select Color Preset" },
+            { 0x16, "Video Gain: Red" },
+            { 0x17, "User Color Vision Compensation" },
+            { 0x18, "Video Gain: Green" },
+            { 0x1A, "Video Gain: Blue" },
+            { 0x1C, "Focus" },
+            { 0x1E, "Auto Setup" },
+            { 0x1F, "Auto Color Setup" },
+
+            // Geometry controls (0x20-0x4C)
+            { 0x20, "Horizontal Position" },
+            { 0x22, "Horizontal Size" },
+            { 0x24, "Horizontal Pincushion" },
+            { 0x26, "Horizontal Pincushion Balance" },
+            { 0x28, "Horizontal Convergence R/B" },
+            { 0x29, "Horizontal Convergence M/G" },
+            { 0x2A, "Horizontal Linearity" },
+            { 0x2C, "Horizontal Linearity Balance" },
+            { 0x2E, "Gray Scale Expansion" },
+            { 0x30, "Vertical Position" },
+            { 0x32, "Vertical Size" },
+            { 0x34, "Vertical Pincushion" },
+            { 0x36, "Vertical Pincushion Balance" },
+            { 0x38, "Vertical Convergence R/B" },
+            { 0x39, "Vertical Convergence M/G" },
+            { 0x3A, "Vertical Linearity" },
+            { 0x3C, "Vertical Linearity Balance" },
+            { 0x3E, "Clock Phase" },
+
+            // Miscellaneous codes
+            { 0x40, "Horizontal Parallelogram" },
+            { 0x41, "Vertical Parallelogram" },
+            { 0x42, "Horizontal Keystone" },
+            { 0x43, "Vertical Keystone" },
+            { 0x44, "Rotation" },
+            { 0x46, "Top Corner Flare" },
+            { 0x48, "Top Corner Hook" },
+            { 0x4A, "Bottom Corner Flare" },
+            { 0x4C, "Bottom Corner Hook" },
+
+            // Advanced codes
+            { 0x52, "Active Control" },
+            { 0x54, "Performance Preservation" },
+            { 0x56, "Horizontal Moire" },
+            { 0x58, "Vertical Moire" },
+            { 0x59, "6 Axis Saturation: Red" },
+            { 0x5A, "6 Axis Saturation: Yellow" },
+            { 0x5B, "6 Axis Saturation: Green" },
+            { 0x5C, "6 Axis Saturation: Cyan" },
+            { 0x5D, "6 Axis Saturation: Blue" },
+            { 0x5E, "6 Axis Saturation: Magenta" },
+
+            // Input source codes
+            { 0x60, "Input Source" },
+            { 0x62, "Audio Speaker Volume" },
+            { 0x63, "Speaker Select" },
+            { 0x64, "Audio: Microphone Volume" },
+            { 0x66, "Ambient Light Sensor" },
+            { 0x6B, "Backlight Level: White" },
+            { 0x6C, "Video Black Level: Red" },
+            { 0x6D, "Backlight Level: Red" },
+            { 0x6E, "Video Black Level: Green" },
+            { 0x6F, "Backlight Level: Green" },
+            { 0x70, "Video Black Level: Blue" },
+            { 0x71, "Backlight Level: Blue" },
+            { 0x72, "Gamma" },
+            { 0x73, "LUT Size" },
+            { 0x74, "Single Point LUT Operation" },
+            { 0x75, "Block LUT Operation" },
+            { 0x76, "Remote Procedure Call" },
+            { 0x78, "Display Identification Data Operation" },
+            { 0x7A, "Adjust Focal Plane" },
+            { 0x7C, "Adjust Zoom" },
+            { 0x7E, "Trapezoid" },
+            { 0x80, "Keystone" },
+            { 0x82, "Horizontal Mirror (Flip)" },
+            { 0x84, "Vertical Mirror (Flip)" },
+
+            // Image adjustment codes (0x86-0x9F)
+            { 0x86, "Display Scaling" },
+            { 0x87, "Sharpness" },
+            { 0x88, "Velocity Scan Modulation" },
+            { 0x8A, "Color Saturation" },
+            { 0x8B, "TV Channel Up/Down" },
+            { 0x8C, "TV Sharpness" },
+            { 0x8D, "Audio Mute/Screen Blank" },
+            { 0x8E, "TV Contrast" },
+            { 0x8F, "Audio Treble" },
+            { 0x90, "Hue" },
+            { 0x91, "Audio Bass" },
+            { 0x92, "TV Black Level/Luminance" },
+            { 0x93, "Audio Balance L/R" },
+            { 0x94, "Audio Processor Mode" },
+            { 0x95, "Window Position(TL_X)" },
+            { 0x96, "Window Position(TL_Y)" },
+            { 0x97, "Window Position(BR_X)" },
+            { 0x98, "Window Position(BR_Y)" },
+            { 0x99, "Window Background" },
+            { 0x9A, "6 Axis Hue Control: Red" },
+            { 0x9B, "6 Axis Hue Control: Yellow" },
+            { 0x9C, "6 Axis Hue Control: Green" },
+            { 0x9D, "6 Axis Hue Control: Cyan" },
+            { 0x9E, "6 Axis Hue Control: Blue" },
+            { 0x9F, "6 Axis Hue Control: Magenta" },
+
+            // Window control codes
+            { 0xA0, "Auto Setup On/Off" },
+            { 0xA2, "Auto Color Setup On/Off" },
+            { 0xA4, "Window Mask Control" },
+            { 0xA5, "Window Select" },
+            { 0xA6, "Window Size" },
+            { 0xA7, "Window Transparency" },
+            { 0xA8, "Window Control" },
+            { 0xAA, "Screen Orientation" },
+            { 0xAC, "Horizontal Frequency" },
+            { 0xAE, "Vertical Frequency" },
+
+            // Misc advanced codes
+            { 0xB0, "Settings" },
+            { 0xB2, "Flat Panel Sub-Pixel Layout" },
+            { 0xB4, "Source Timing Mode" },
+            { 0xB6, "Display Technology Type" },
+            { 0xB7, "Monitor Status" },
+            { 0xB8, "Packet Count" },
+            { 0xB9, "Monitor X Origin" },
+            { 0xBA, "Monitor Y Origin" },
+            { 0xBB, "Header Error Count" },
+            { 0xBC, "Body CRC Error Count" },
+            { 0xBD, "Client ID" },
+            { 0xBE, "Link Control" },
+
+            // Display controller codes
+            { 0xC0, "Display Usage Time" },
+            { 0xC2, "Display Firmware Level" },
+            { 0xC4, "Display Descriptor Length" },
+            { 0xC5, "Transmit Display Descriptor" },
+            { 0xC6, "Enable Display of 'Display Descriptor'" },
+            { 0xC8, "Display Controller Type" },
+            { 0xC9, "Display Firmware Level" },
+            { 0xCA, "OSD" },
+            { 0xCC, "OSD Language" },
+            { 0xCD, "Status Indicators" },
+            { 0xCE, "Auxiliary Display Size" },
+            { 0xCF, "Auxiliary Display Data" },
+            { 0xD0, "Output Select" },
+            { 0xD2, "Asset Tag" },
+            { 0xD4, "Stereo Video Mode" },
+            { 0xD6, "Power Mode" },
+            { 0xD7, "Auxiliary Power Output" },
+            { 0xD8, "Scan Mode" },
+            { 0xD9, "Image Mode" },
+            { 0xDA, "On Screen Display" },
+            { 0xDB, "Backlight Level: White" },
+            { 0xDC, "Display Application" },
+            { 0xDD, "Application Enable Key" },
+            { 0xDE, "Scratch Pad" },
+            { 0xDF, "VCP Version" },
+
+            // Manufacturer specific codes (0xE0-0xFF)
+            // Per MCCS 2.2a: "The 32 control codes E0h through FFh have been
+            // allocated to allow manufacturers to issue their own specific controls."
+            { 0xE0, "Manufacturer Specific" },
+            { 0xE1, "Manufacturer Specific" },
+            { 0xE2, "Manufacturer Specific" },
+            { 0xE3, "Manufacturer Specific" },
+            { 0xE4, "Manufacturer Specific" },
+            { 0xE5, "Manufacturer Specific" },
+            { 0xE6, "Manufacturer Specific" },
+            { 0xE7, "Manufacturer Specific" },
+            { 0xE8, "Manufacturer Specific" },
+            { 0xE9, "Manufacturer Specific" },
+            { 0xEA, "Manufacturer Specific" },
+            { 0xEB, "Manufacturer Specific" },
+            { 0xEC, "Manufacturer Specific" },
+            { 0xED, "Manufacturer Specific" },
+            { 0xEE, "Manufacturer Specific" },
+            { 0xEF, "Manufacturer Specific" },
+            { 0xF0, "Manufacturer Specific" },
+            { 0xF1, "Manufacturer Specific" },
+            { 0xF2, "Manufacturer Specific" },
+            { 0xF3, "Manufacturer Specific" },
+            { 0xF4, "Manufacturer Specific" },
+            { 0xF5, "Manufacturer Specific" },
+            { 0xF6, "Manufacturer Specific" },
+            { 0xF7, "Manufacturer Specific" },
+            { 0xF8, "Manufacturer Specific" },
+            { 0xF9, "Manufacturer Specific" },
+            { 0xFA, "Manufacturer Specific" },
+            { 0xFB, "Manufacturer Specific" },
+            { 0xFC, "Manufacturer Specific" },
+            { 0xFD, "Manufacturer Specific" },
+            { 0xFE, "Manufacturer Specific" },
+            { 0xFF, "Manufacturer Specific" },
+        };
+
+        /// <summary>
+        /// Get the friendly name for a VCP code
+        /// </summary>
+        /// <param name="code">VCP code (e.g., 0x10)</param>
+        /// <returns>Friendly name, or hex representation if unknown</returns>
+        public static string GetCodeName(byte code)
+        {
+            return CodeNames.TryGetValue(code, out var name) ? name : $"Unknown (0x{code:X2})";
+        }
+
+        // Dictionary<VcpCode, Dictionary<Value, Name>>
+        private static readonly Dictionary<byte, Dictionary<int, string>> ValueNames = new()
+        {
+            // 0x14: Select Color Preset
+            [0x14] = new Dictionary<int, string>
+            {
+                [0x01] = "sRGB",
+                [0x02] = "Display Native",
+                [0x03] = "4000K",
+                [0x04] = "5000K",
+                [0x05] = "6500K",
+                [0x06] = "7500K",
+                [0x08] = "9300K",
+                [0x09] = "10000K",
+                [0x0A] = "11500K",
+                [0x0B] = "User 1",
+                [0x0C] = "User 2",
+                [0x0D] = "User 3",
+            },
+
+            // 0x60: Input Source
+            [0x60] = new Dictionary<int, string>
+            {
+                [0x01] = "VGA-1",
+                [0x02] = "VGA-2",
+                [0x03] = "DVI-1",
+                [0x04] = "DVI-2",
+                [0x05] = "Composite Video 1",
+                [0x06] = "Composite Video 2",
+                [0x07] = "S-Video-1",
+                [0x08] = "S-Video-2",
+                [0x09] = "Tuner-1",
+                [0x0A] = "Tuner-2",
+                [0x0B] = "Tuner-3",
+                [0x0C] = "Component Video 1",
+                [0x0D] = "Component Video 2",
+                [0x0E] = "Component Video 3",
+                [0x0F] = "DisplayPort-1",
+                [0x10] = "DisplayPort-2",
+                [0x11] = "HDMI-1",
+                [0x12] = "HDMI-2",
+                [0x1B] = "USB-C",
+            },
+
+            // 0xD6: Power Mode
+            [0xD6] = new Dictionary<int, string>
+            {
+                [0x01] = "On",
+                [0x02] = "Standby",
+                [0x03] = "Suspend",
+                [0x04] = "Off (DPM)",
+                [0x05] = "Off (Hard)",
+            },
+
+            // 0x8D: Audio Mute
+            [0x8D] = new Dictionary<int, string>
+            {
+                [0x01] = "Muted",
+                [0x02] = "Unmuted",
+            },
+
+            // 0xDC: Display Application
+            [0xDC] = new Dictionary<int, string>
+            {
+                [0x00] = "Standard/Default",
+                [0x01] = "Productivity",
+                [0x02] = "Mixed",
+                [0x03] = "Movie",
+                [0x04] = "User Defined",
+                [0x05] = "Games",
+                [0x06] = "Sports",
+                [0x07] = "Professional (calibration)",
+                [0x08] = "Standard/Default with intermediate power consumption",
+                [0x09] = "Standard/Default with low power consumption",
+                [0x0A] = "Demonstration",
+                [0xF0] = "Dynamic Contrast",
+            },
+
+            // 0xCC: OSD Language
+            [0xCC] = new Dictionary<int, string>
+            {
+                [0x01] = "Chinese (traditional, Hantai)",
+                [0x02] = "English",
+                [0x03] = "French",
+                [0x04] = "German",
+                [0x05] = "Italian",
+                [0x06] = "Japanese",
+                [0x07] = "Korean",
+                [0x08] = "Portuguese (Portugal)",
+                [0x09] = "Russian",
+                [0x0A] = "Spanish",
+                [0x0B] = "Swedish",
+                [0x0C] = "Turkish",
+                [0x0D] = "Chinese (simplified, Kantai)",
+                [0x0E] = "Portuguese (Brazil)",
+                [0x0F] = "Arabic",
+                [0x10] = "Bulgarian",
+                [0x11] = "Croatian",
+                [0x12] = "Czech",
+                [0x13] = "Danish",
+                [0x14] = "Dutch",
+                [0x15] = "Estonian",
+                [0x16] = "Finnish",
+                [0x17] = "Greek",
+                [0x18] = "Hebrew",
+                [0x19] = "Hindi",
+                [0x1A] = "Hungarian",
+                [0x1B] = "Latvian",
+                [0x1C] = "Lithuanian",
+                [0x1D] = "Norwegian",
+                [0x1E] = "Polish",
+                [0x1F] = "Romanian",
+                [0x20] = "Serbian",
+                [0x21] = "Slovak",
+                [0x22] = "Slovenian",
+                [0x23] = "Thai",
+                [0x24] = "Ukrainian",
+                [0x25] = "Vietnamese",
+            },
+
+            // 0x62: Audio Speaker Volume
+            [0x62] = new Dictionary<int, string>
+            {
+                [0x00] = "Mute",
+
+                // Other values are continuous
+            },
+
+            // 0xDB: Image Mode (Dell monitors)
+            [0xDB] = new Dictionary<int, string>
+            {
+                [0x00] = "Standard",
+                [0x01] = "Multimedia",
+                [0x02] = "Movie",
+                [0x03] = "Game",
+                [0x04] = "Sports",
+                [0x05] = "Color Temperature",
+                [0x06] = "Custom Color",
+                [0x07] = "ComfortView",
+            },
+        };
+
+        /// <summary>
+        /// Get human-readable name for a VCP value
+        /// </summary>
+        /// <param name="vcpCode">VCP code (e.g., 0x14)</param>
+        /// <param name="value">Value to translate</param>
+        /// <returns>Name string like "sRGB" or null if unknown</returns>
+        public static string? GetValueName(byte vcpCode, int value)
+        {
+            if (ValueNames.TryGetValue(vcpCode, out var codeValues))
+            {
+                if (codeValues.TryGetValue(value, out var name))
+                {
+                    return name;
+                }
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Get formatted display name for a VCP value (with hex value in parentheses)
+        /// </summary>
+        /// <param name="vcpCode">VCP code (e.g., 0x14)</param>
+        /// <param name="value">Value to translate</param>
+        /// <returns>Formatted string like "sRGB (0x01)" or "0x01" if unknown</returns>
+        public static string GetFormattedValueName(byte vcpCode, int value)
+        {
+            var name = GetValueName(vcpCode, value);
+            if (name != null)
+            {
+                return $"{name} (0x{value:X2})";
+            }
+
+            return $"0x{value:X2}";
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Configuration/AppConstants.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace PowerDisplay.Configuration
+{
+    /// <summary>
+    /// Application-wide constants and configuration values
+    /// </summary>
+    public static class AppConstants
+    {
+        /// <summary>
+        /// UI layout and timing constants
+        /// </summary>
+        public static class UI
+        {
+            // Window dimensions
+            public const int WindowWidth = 362;
+            public const int MinWindowHeight = 100;
+            public const int MaxWindowHeight = 650;
+            public const int WindowRightMargin = 12;
+
+            /// <summary>
+            /// Debounce delay for slider controls in milliseconds
+            /// </summary>
+            public const int SliderDebounceDelayMs = 300;
+
+            /// <summary>
+            /// Icon glyph for internal/laptop displays (WMI)
+            /// </summary>
+            public const string InternalMonitorGlyph = "\uE7F8";
+
+            /// <summary>
+            /// Icon glyph for external monitors (DDC/CI)
+            /// </summary>
+            public const string ExternalMonitorGlyph = "\uE7F4";
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/GlobalUsings.cs

@@ -0,0 +1,9 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+// Enable compile-time marshalling for all P/Invoke declarations
+// This allows LibraryImport to handle array marshalling and achieve 100% coverage
+[assembly: DisableRuntimeMarshalling]

src/modules/powerdisplay/PowerDisplay/Helpers/DisplayChangeWatcher.cs

@@ -0,0 +1,268 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Microsoft.UI.Dispatching;
+using Windows.Devices.Display;
+using Windows.Devices.Enumeration;
+
+namespace PowerDisplay.Helpers;
+
+/// <summary>
+/// Watches for display/monitor connection changes using WinRT DeviceWatcher.
+/// Triggers DisplayChanged event when monitors are added, removed, or updated.
+/// </summary>
+public sealed partial class DisplayChangeWatcher : IDisposable
+{
+    private readonly DispatcherQueue _dispatcherQueue;
+    private readonly TimeSpan _debounceDelay = TimeSpan.FromSeconds(1);
+
+    private DeviceWatcher? _deviceWatcher;
+    private CancellationTokenSource? _debounceCts;
+    private bool _isRunning;
+    private bool _disposed;
+    private bool _initialEnumerationComplete;
+
+    /// <summary>
+    /// Event triggered when display configuration changes (after debounce period).
+    /// </summary>
+    public event EventHandler? DisplayChanged;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="DisplayChangeWatcher"/> class.
+    /// </summary>
+    /// <param name="dispatcherQueue">The dispatcher queue for UI thread marshalling.</param>
+    public DisplayChangeWatcher(DispatcherQueue dispatcherQueue)
+    {
+        _dispatcherQueue = dispatcherQueue ?? throw new ArgumentNullException(nameof(dispatcherQueue));
+    }
+
+    /// <summary>
+    /// Gets a value indicating whether the watcher is currently running.
+    /// </summary>
+    public bool IsRunning => _isRunning;
+
+    /// <summary>
+    /// Starts watching for display changes.
+    /// </summary>
+    public void Start()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+
+        if (_isRunning)
+        {
+            return;
+        }
+
+        try
+        {
+            // Get the device selector for display monitors
+            string selector = DisplayMonitor.GetDeviceSelector();
+            Logger.LogInfo($"[DisplayChangeWatcher] Using device selector: {selector}");
+
+            // Create the device watcher
+            _deviceWatcher = DeviceInformation.CreateWatcher(selector);
+
+            // Subscribe to events
+            _deviceWatcher.Added += OnDeviceAdded;
+            _deviceWatcher.Removed += OnDeviceRemoved;
+            _deviceWatcher.Updated += OnDeviceUpdated;
+            _deviceWatcher.EnumerationCompleted += OnEnumerationCompleted;
+            _deviceWatcher.Stopped += OnWatcherStopped;
+
+            // Reset state before starting (must be before Start() to avoid race)
+            _initialEnumerationComplete = false;
+            _isRunning = true;
+
+            // Start watching
+            _deviceWatcher.Start();
+
+            Logger.LogInfo("[DisplayChangeWatcher] Started watching for display changes");
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[DisplayChangeWatcher] Failed to start: {ex.Message}");
+            _isRunning = false;
+        }
+    }
+
+    /// <summary>
+    /// Stops watching for display changes.
+    /// </summary>
+    public void Stop()
+    {
+        if (!_isRunning || _deviceWatcher == null)
+        {
+            return;
+        }
+
+        try
+        {
+            // Cancel any pending debounce
+            CancelDebounce();
+
+            // Stop the watcher
+            _deviceWatcher.Stop();
+
+            Logger.LogInfo("[DisplayChangeWatcher] Stopped watching for display changes");
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[DisplayChangeWatcher] Error stopping watcher: {ex.Message}");
+        }
+    }
+
+    private void OnDeviceAdded(DeviceWatcher sender, DeviceInformation args)
+    {
+        // Dispatch to UI thread to ensure thread-safe state access
+        _dispatcherQueue.TryEnqueue(() =>
+        {
+            // Ignore events during initial enumeration or after disposal
+            if (_disposed || !_initialEnumerationComplete)
+            {
+                return;
+            }
+
+            Logger.LogInfo($"[DisplayChangeWatcher] Display added: {args.Name}");
+            ScheduleDisplayChanged();
+        });
+    }
+
+    private void OnDeviceRemoved(DeviceWatcher sender, DeviceInformationUpdate args)
+    {
+        // Dispatch to UI thread to ensure thread-safe state access
+        _dispatcherQueue.TryEnqueue(() =>
+        {
+            // Ignore events during initial enumeration or after disposal
+            if (_disposed || !_initialEnumerationComplete)
+            {
+                return;
+            }
+
+            Logger.LogInfo("[DisplayChangeWatcher] Display removed");
+            ScheduleDisplayChanged();
+        });
+    }
+
+    private void OnDeviceUpdated(DeviceWatcher sender, DeviceInformationUpdate args)
+    {
+        // Only trigger refresh for significant updates, not every property change.
+        // For now, we'll skip updates to avoid excessive refreshes.
+        // The Added and Removed events are the primary triggers for monitor changes.
+    }
+
+    private void OnEnumerationCompleted(DeviceWatcher sender, object args)
+    {
+        // Dispatch to UI thread to ensure thread-safe state access
+        _dispatcherQueue.TryEnqueue(() =>
+        {
+            _initialEnumerationComplete = true;
+            Logger.LogInfo("[DisplayChangeWatcher] Initial enumeration completed, now responding to display changes");
+        });
+    }
+
+    private void OnWatcherStopped(DeviceWatcher sender, object args)
+    {
+        // Dispatch to UI thread to ensure thread-safe state access
+        _dispatcherQueue.TryEnqueue(() =>
+        {
+            _isRunning = false;
+            _initialEnumerationComplete = false;
+            Logger.LogInfo("[DisplayChangeWatcher] Watcher stopped");
+        });
+    }
+
+    /// <summary>
+    /// Schedules a DisplayChanged event with debouncing.
+    /// Multiple rapid changes will only trigger one event after the debounce period.
+    /// </summary>
+    private void ScheduleDisplayChanged()
+    {
+        // Cancel any pending debounce
+        CancelDebounce();
+
+        // Create new cancellation token
+        _debounceCts = new CancellationTokenSource();
+        var token = _debounceCts.Token;
+
+        // Schedule the event after debounce delay
+        Task.Run(async () =>
+        {
+            try
+            {
+                await Task.Delay(_debounceDelay, token);
+
+                if (!token.IsCancellationRequested)
+                {
+                    // Dispatch to UI thread
+                    _dispatcherQueue.TryEnqueue(() =>
+                    {
+                        if (!_disposed)
+                        {
+                            Logger.LogInfo("[DisplayChangeWatcher] Triggering DisplayChanged event");
+                            DisplayChanged?.Invoke(this, EventArgs.Empty);
+                        }
+                    });
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                // Debounce was cancelled by a newer event, this is expected
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[DisplayChangeWatcher] Error in debounce task: {ex.Message}");
+            }
+        });
+    }
+
+    private void CancelDebounce()
+    {
+        try
+        {
+            _debounceCts?.Cancel();
+            _debounceCts?.Dispose();
+            _debounceCts = null;
+        }
+        catch (ObjectDisposedException)
+        {
+            // Already disposed, ignore
+        }
+    }
+
+    /// <summary>
+    /// Disposes resources used by the watcher.
+    /// </summary>
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        _disposed = true;
+
+        // Stop watching
+        Stop();
+
+        // Unsubscribe from events
+        if (_deviceWatcher != null)
+        {
+            _deviceWatcher.Added -= OnDeviceAdded;
+            _deviceWatcher.Removed -= OnDeviceRemoved;
+            _deviceWatcher.Updated -= OnDeviceUpdated;
+            _deviceWatcher.EnumerationCompleted -= OnEnumerationCompleted;
+            _deviceWatcher.Stopped -= OnWatcherStopped;
+            _deviceWatcher = null;
+        }
+
+        // Cancel debounce
+        CancelDebounce();
+
+        Logger.LogInfo("[DisplayChangeWatcher] Disposed");
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/HotkeyService.cs

@@ -0,0 +1,188 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Library;
+using WinRT.Interop;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// Service for handling hotkey registration in-process.
+    /// Uses RegisterHotKey Win32 API instead of Runner's centralized mechanism
+    /// to avoid IPC timing issues (CmdPal pattern).
+    /// </summary>
+    internal sealed partial class HotkeyService : IDisposable
+    {
+        private const int HotkeyId = 9001;
+
+        private readonly SettingsUtils _settingsUtils;
+        private readonly Action _hotkeyAction;
+
+        private nint _hwnd;
+        private nint _originalWndProc;
+
+        // Must keep delegate reference to prevent GC collection
+        private WndProcDelegate? _hotkeyWndProc;
+        private bool _isRegistered;
+        private bool _disposed;
+
+        public HotkeyService(SettingsUtils settingsUtils, Action hotkeyAction)
+        {
+            _settingsUtils = settingsUtils;
+            _hotkeyAction = hotkeyAction;
+        }
+
+        /// <summary>
+        /// Initialize the hotkey service with a window handle.
+        /// Must be called after window is created.
+        /// </summary>
+        /// <param name="window">The WinUI window to attach to.</param>
+        public void Initialize(Microsoft.UI.Xaml.Window window)
+        {
+            _hwnd = WindowNative.GetWindowHandle(window);
+            Logger.LogTrace($"[HotkeyService] Initialize: hwnd=0x{_hwnd:X}");
+
+            // LOAD BEARING: If you don't stick the pointer to the WndProc into a
+            // member (and instead use a local), then the pointer we marshal
+            // into the WindowLongPtr will be useless after we leave this function,
+            // and our WndProc will explode.
+            _hotkeyWndProc = HotkeyWndProc;
+            var wndProcPointer = Marshal.GetFunctionPointerForDelegate(_hotkeyWndProc);
+            _originalWndProc = SetWindowLongPtrNative(_hwnd, GwlWndProc, wndProcPointer);
+
+            Logger.LogTrace($"[HotkeyService] WndProc hooked, original=0x{_originalWndProc:X}");
+
+            // Register hotkey based on current settings
+            ReloadSettings();
+        }
+
+        /// <summary>
+        /// Reload settings and re-register hotkey.
+        /// Call this when settings change.
+        /// </summary>
+        public void ReloadSettings()
+        {
+            Logger.LogTrace("[HotkeyService] ReloadSettings called");
+            UnregisterHotkey();
+
+            var settings = _settingsUtils.GetSettingsOrDefault<PowerDisplaySettings>(PowerDisplaySettings.ModuleName);
+            var hotkey = settings?.Properties?.ActivationShortcut;
+
+            if (hotkey == null || !hotkey.IsValid())
+            {
+                Logger.LogInfo("[HotkeyService] No valid hotkey configured");
+                return;
+            }
+
+            RegisterHotkey(hotkey);
+        }
+
+        private void RegisterHotkey(HotkeySettings hotkey)
+        {
+            if (_hwnd == 0)
+            {
+                Logger.LogWarning("[HotkeyService] Cannot register hotkey: window handle not set");
+                return;
+            }
+
+            // Build modifiers using bit flags
+            uint modifiers = ModNoRepeat
+                | (hotkey.Win ? ModWin : 0)
+                | (hotkey.Ctrl ? ModControl : 0)
+                | (hotkey.Alt ? ModAlt : 0)
+                | (hotkey.Shift ? ModShift : 0);
+
+            if (RegisterHotKeyNative(_hwnd, HotkeyId, modifiers, (uint)hotkey.Code))
+            {
+                _isRegistered = true;
+                Logger.LogInfo($"[HotkeyService] Hotkey registered: {hotkey}");
+            }
+            else
+            {
+                Logger.LogError($"[HotkeyService] Failed to register hotkey: {hotkey}, error={Marshal.GetLastWin32Error()}");
+            }
+        }
+
+        private void UnregisterHotkey()
+        {
+            if (!_isRegistered || _hwnd == 0)
+            {
+                return;
+            }
+
+            bool success = UnregisterHotKeyNative(_hwnd, HotkeyId);
+
+            if (success)
+            {
+                Logger.LogTrace("[HotkeyService] Hotkey unregistered");
+            }
+            else
+            {
+                var error = Marshal.GetLastWin32Error();
+                Logger.LogWarning($"[HotkeyService] Failed to unregister hotkey, error={error}");
+            }
+
+            _isRegistered = false;
+        }
+
+        private nint HotkeyWndProc(nint hwnd, uint uMsg, nuint wParam, nint lParam)
+        {
+            if (uMsg == WmHotkey && (int)wParam == HotkeyId)
+            {
+                Logger.LogInfo("[HotkeyService] WM_HOTKEY received, invoking action");
+                try
+                {
+                    _hotkeyAction?.Invoke();
+                }
+                catch (Exception ex)
+                {
+                    Logger.LogError($"[HotkeyService] Hotkey action failed: {ex.Message}");
+                }
+
+                return 0;
+            }
+
+            return CallWindowProcNative(_originalWndProc, hwnd, uMsg, wParam, lParam);
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            UnregisterHotkey();
+            _disposed = true;
+        }
+
+        // P/Invoke constants
+        private const int GwlWndProc = -4;
+        private const uint WmHotkey = 0x0312;
+
+        // HOT_KEY_MODIFIERS flags
+        private const uint ModAlt = 0x0001;
+        private const uint ModControl = 0x0002;
+        private const uint ModShift = 0x0004;
+        private const uint ModWin = 0x0008;
+        private const uint ModNoRepeat = 0x4000;
+
+        [LibraryImport("user32.dll", EntryPoint = "SetWindowLongPtrW")]
+        private static partial nint SetWindowLongPtrNative(nint hWnd, int nIndex, nint dwNewLong);
+
+        [LibraryImport("user32.dll", EntryPoint = "CallWindowProcW")]
+        private static partial nint CallWindowProcNative(nint lpPrevWndFunc, nint hWnd, uint msg, nuint wParam, nint lParam);
+
+        [LibraryImport("user32.dll", EntryPoint = "RegisterHotKey", SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool RegisterHotKeyNative(nint hWnd, int id, uint fsModifiers, uint vk);
+
+        [LibraryImport("user32.dll", EntryPoint = "UnregisterHotKey", SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool UnregisterHotKeyNative(nint hWnd, int id);
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/MonitorManager.cs

@@ -0,0 +1,448 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using PowerDisplay.Common.Drivers;
+using PowerDisplay.Common.Drivers.DDC;
+using PowerDisplay.Common.Drivers.WMI;
+using PowerDisplay.Common.Interfaces;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Common.Services;
+using PowerDisplay.Common.Utils;
+using Monitor = PowerDisplay.Common.Models.Monitor;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// Monitor manager for unified control of all monitors
+    /// No interface abstraction - KISS principle (only one implementation needed)
+    /// </summary>
+    public partial class MonitorManager : IDisposable
+    {
+        private readonly List<Monitor> _monitors = new();
+        private readonly Dictionary<string, Monitor> _monitorLookup = new();
+        private readonly SemaphoreSlim _discoveryLock = new(1, 1);
+        private readonly DisplayRotationService _rotationService = new();
+
+        // Controllers stored by type for O(1) lookup based on CommunicationMethod
+        private DdcCiController? _ddcController;
+        private WmiController? _wmiController;
+        private bool _disposed;
+
+        public IReadOnlyList<Monitor> Monitors => _monitors.AsReadOnly();
+
+        public MonitorManager()
+        {
+            // Initialize controllers
+            InitializeControllers();
+        }
+
+        /// <summary>
+        /// Initialize controllers
+        /// </summary>
+        private void InitializeControllers()
+        {
+            try
+            {
+                // DDC/CI controller (external monitors)
+                _ddcController = new DdcCiController();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogWarning($"Failed to initialize DDC/CI controller: {ex.Message}");
+            }
+
+            try
+            {
+                // WMI controller (internal monitors)
+                // Always create - DiscoverMonitorsAsync returns empty list if WMI is unavailable
+                _wmiController = new WmiController();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogWarning($"Failed to initialize WMI controller: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Discover all monitors from all controllers.
+        /// Each controller is responsible for fully initializing its monitors
+        /// (including brightness, capabilities, input source, color temperature, etc.)
+        /// </summary>
+        public async Task<IReadOnlyList<Monitor>> DiscoverMonitorsAsync(CancellationToken cancellationToken = default)
+        {
+            await _discoveryLock.WaitAsync(cancellationToken);
+
+            try
+            {
+                var discoveredMonitors = await DiscoverFromAllControllersAsync(cancellationToken);
+
+                // Update collections
+                _monitors.Clear();
+                _monitorLookup.Clear();
+
+                var sortedMonitors = discoveredMonitors
+                    .OrderBy(m => m.MonitorNumber)
+                    .ToList();
+
+                _monitors.AddRange(sortedMonitors);
+                foreach (var monitor in sortedMonitors)
+                {
+                    _monitorLookup[monitor.Id] = monitor;
+                }
+
+                return _monitors.AsReadOnly();
+            }
+            finally
+            {
+                _discoveryLock.Release();
+            }
+        }
+
+        /// <summary>
+        /// Discover monitors from all registered controllers in parallel.
+        /// </summary>
+        private async Task<List<Monitor>> DiscoverFromAllControllersAsync(CancellationToken cancellationToken)
+        {
+            var tasks = new List<Task<IEnumerable<Monitor>>>();
+
+            if (_ddcController != null)
+            {
+                tasks.Add(SafeDiscoverAsync(_ddcController, cancellationToken));
+            }
+
+            if (_wmiController != null)
+            {
+                tasks.Add(SafeDiscoverAsync(_wmiController, cancellationToken));
+            }
+
+            var results = await Task.WhenAll(tasks);
+            return results.SelectMany(m => m).ToList();
+        }
+
+        /// <summary>
+        /// Safely discover monitors from a controller, returning empty list on failure.
+        /// </summary>
+        private static async Task<IEnumerable<Monitor>> SafeDiscoverAsync(
+            IMonitorController controller,
+            CancellationToken cancellationToken)
+        {
+            try
+            {
+                return await controller.DiscoverMonitorsAsync(cancellationToken);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogWarning($"Controller {controller.Name} discovery failed: {ex.Message}");
+                return Enumerable.Empty<Monitor>();
+            }
+        }
+
+        /// <summary>
+        /// Get brightness of the specified monitor
+        /// </summary>
+        public async Task<VcpFeatureValue> GetBrightnessAsync(string monitorId, CancellationToken cancellationToken = default)
+        {
+            var monitor = GetMonitor(monitorId);
+            if (monitor == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            var controller = GetControllerForMonitor(monitor);
+            if (controller == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            try
+            {
+                var brightnessInfo = await controller.GetBrightnessAsync(monitor, cancellationToken);
+
+                // Update cached brightness value
+                if (brightnessInfo.IsValid)
+                {
+                    monitor.UpdateStatus(brightnessInfo.ToPercentage(), true);
+                }
+
+                return brightnessInfo;
+            }
+            catch (Exception ex)
+            {
+                // Mark monitor as unavailable
+                Logger.LogError($"Failed to get brightness for monitor {monitorId}: {ex.Message}");
+                monitor.IsAvailable = false;
+                return VcpFeatureValue.Invalid;
+            }
+        }
+
+        /// <summary>
+        /// Set brightness of the specified monitor
+        /// </summary>
+        public Task<MonitorOperationResult> SetBrightnessAsync(string monitorId, int brightness, CancellationToken cancellationToken = default)
+            => ExecuteMonitorOperationAsync(
+                monitorId,
+                brightness,
+                (ctrl, mon, val, ct) => ctrl.SetBrightnessAsync(mon, val, ct),
+                (mon, val) => mon.UpdateStatus(val, true),
+                cancellationToken);
+
+        /// <summary>
+        /// Set contrast of the specified monitor
+        /// </summary>
+        public Task<MonitorOperationResult> SetContrastAsync(string monitorId, int contrast, CancellationToken cancellationToken = default)
+            => ExecuteMonitorOperationAsync(
+                monitorId,
+                contrast,
+                (ctrl, mon, val, ct) => ctrl.SetContrastAsync(mon, val, ct),
+                (mon, val) => mon.CurrentContrast = val,
+                cancellationToken);
+
+        /// <summary>
+        /// Set volume of the specified monitor
+        /// </summary>
+        public Task<MonitorOperationResult> SetVolumeAsync(string monitorId, int volume, CancellationToken cancellationToken = default)
+            => ExecuteMonitorOperationAsync(
+                monitorId,
+                volume,
+                (ctrl, mon, val, ct) => ctrl.SetVolumeAsync(mon, val, ct),
+                (mon, val) => mon.CurrentVolume = val,
+                cancellationToken);
+
+        /// <summary>
+        /// Get monitor color temperature
+        /// </summary>
+        public async Task<VcpFeatureValue> GetColorTemperatureAsync(string monitorId, CancellationToken cancellationToken = default)
+        {
+            var monitor = GetMonitor(monitorId);
+            if (monitor == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            var controller = GetControllerForMonitor(monitor);
+            if (controller == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            try
+            {
+                return await controller.GetColorTemperatureAsync(monitor, cancellationToken);
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+        }
+
+        /// <summary>
+        /// Set monitor color temperature
+        /// </summary>
+        public Task<MonitorOperationResult> SetColorTemperatureAsync(string monitorId, int colorTemperature, CancellationToken cancellationToken = default)
+            => ExecuteMonitorOperationAsync(
+                monitorId,
+                colorTemperature,
+                (ctrl, mon, val, ct) => ctrl.SetColorTemperatureAsync(mon, val, ct),
+                (mon, val) => mon.CurrentColorTemperature = val,
+                cancellationToken);
+
+        /// <summary>
+        /// Get current input source for a monitor
+        /// </summary>
+        public async Task<VcpFeatureValue> GetInputSourceAsync(string monitorId, CancellationToken cancellationToken = default)
+        {
+            var monitor = GetMonitor(monitorId);
+            if (monitor == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            var controller = GetControllerForMonitor(monitor);
+            if (controller == null)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+
+            try
+            {
+                return await controller.GetInputSourceAsync(monitor, cancellationToken);
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException)
+            {
+                return VcpFeatureValue.Invalid;
+            }
+        }
+
+        /// <summary>
+        /// Set input source for a monitor
+        /// </summary>
+        public Task<MonitorOperationResult> SetInputSourceAsync(string monitorId, int inputSource, CancellationToken cancellationToken = default)
+            => ExecuteMonitorOperationAsync(
+                monitorId,
+                inputSource,
+                (ctrl, mon, val, ct) => ctrl.SetInputSourceAsync(mon, val, ct),
+                (mon, val) => mon.CurrentInputSource = val,
+                cancellationToken);
+
+        /// <summary>
+        /// Set rotation/orientation for a monitor.
+        /// Uses Windows ChangeDisplaySettingsEx API (not DDC/CI).
+        /// After successful rotation, refreshes orientation for all monitors sharing the same GdiDeviceName
+        /// (important for mirror/clone mode where multiple monitors share one display source).
+        /// </summary>
+        /// <param name="monitorId">Monitor ID</param>
+        /// <param name="orientation">Orientation: 0=normal, 1=90°, 2=180°, 3=270°</param>
+        /// <param name="cancellationToken">Cancellation token</param>
+        /// <returns>Operation result</returns>
+        public Task<MonitorOperationResult> SetRotationAsync(string monitorId, int orientation, CancellationToken cancellationToken = default)
+        {
+            var monitor = GetMonitor(monitorId);
+            if (monitor == null)
+            {
+                Logger.LogError($"[MonitorManager] SetRotation: Monitor not found: {monitorId}");
+                return Task.FromResult(MonitorOperationResult.Failure("Monitor not found"));
+            }
+
+            // Rotation uses Windows display settings API, not DDC/CI controller
+            // Prefer using Monitor object which contains GdiDeviceName for accurate adapter targeting
+            var result = _rotationService.SetRotation(monitor, orientation);
+
+            if (result.IsSuccess)
+            {
+                // Refresh orientation for all monitors - rotation affects the GdiDeviceName (display source),
+                // and in mirror mode multiple monitors may share the same GdiDeviceName
+                RefreshAllOrientations();
+                Logger.LogInfo($"[MonitorManager] SetRotation: Successfully set {monitorId} to orientation {orientation}");
+            }
+            else
+            {
+                Logger.LogError($"[MonitorManager] SetRotation: Failed for {monitorId}: {result.ErrorMessage}");
+            }
+
+            return Task.FromResult(result);
+        }
+
+        /// <summary>
+        /// Refresh orientation values for all monitors by querying current display settings.
+        /// This ensures all monitors reflect the actual system state, which is important
+        /// in mirror mode where multiple monitors share the same GdiDeviceName.
+        /// </summary>
+        public void RefreshAllOrientations()
+        {
+            foreach (var monitor in _monitors)
+            {
+                if (string.IsNullOrEmpty(monitor.GdiDeviceName))
+                {
+                    continue;
+                }
+
+                var currentOrientation = _rotationService.GetCurrentOrientation(monitor.GdiDeviceName);
+                if (currentOrientation >= 0 && currentOrientation != monitor.Orientation)
+                {
+                    monitor.Orientation = currentOrientation;
+                    monitor.LastUpdate = DateTime.Now;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Get monitor by ID. Uses dictionary lookup for O(1) performance.
+        /// </summary>
+        public Monitor? GetMonitor(string monitorId)
+        {
+            return _monitorLookup.TryGetValue(monitorId, out var monitor) ? monitor : null;
+        }
+
+        /// <summary>
+        /// Get controller for the monitor based on CommunicationMethod.
+        /// O(1) lookup - no async validation needed since controller type is determined at discovery.
+        /// </summary>
+        private IMonitorController? GetControllerForMonitor(Monitor monitor)
+        {
+            return monitor.CommunicationMethod switch
+            {
+                "WMI" => _wmiController,
+                "DDC/CI" => _ddcController,
+                _ => null,
+            };
+        }
+
+        /// <summary>
+        /// Generic helper to execute monitor operations with common error handling.
+        /// Eliminates code duplication across Set* methods.
+        /// </summary>
+        private async Task<MonitorOperationResult> ExecuteMonitorOperationAsync<T>(
+            string monitorId,
+            T value,
+            Func<IMonitorController, Monitor, T, CancellationToken, Task<MonitorOperationResult>> operation,
+            Action<Monitor, T> onSuccess,
+            CancellationToken cancellationToken = default)
+        {
+            var monitor = GetMonitor(monitorId);
+            if (monitor == null)
+            {
+                Logger.LogError($"[MonitorManager] Monitor not found: {monitorId}");
+                return MonitorOperationResult.Failure("Monitor not found");
+            }
+
+            var controller = GetControllerForMonitor(monitor);
+            if (controller == null)
+            {
+                Logger.LogError($"[MonitorManager] No controller available for monitor {monitorId}");
+                return MonitorOperationResult.Failure("No controller available for this monitor");
+            }
+
+            try
+            {
+                var result = await operation(controller, monitor, value, cancellationToken);
+
+                if (result.IsSuccess)
+                {
+                    onSuccess(monitor, value);
+                    monitor.LastUpdate = DateTime.Now;
+                }
+                else
+                {
+                    monitor.IsAvailable = false;
+                }
+
+                return result;
+            }
+            catch (Exception ex)
+            {
+                monitor.IsAvailable = false;
+                Logger.LogError($"[MonitorManager] Operation failed for {monitorId}: {ex.Message}");
+                return MonitorOperationResult.Failure($"Exception: {ex.Message}");
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed && disposing)
+            {
+                _discoveryLock?.Dispose();
+
+                // Release controllers
+                _ddcController?.Dispose();
+                _wmiController?.Dispose();
+
+                _monitors.Clear();
+                _monitorLookup.Clear();
+                _disposed = true;
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/NativeEventWaiter.cs

@@ -0,0 +1,89 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using ManagedCommon;
+using Microsoft.UI.Dispatching;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// Helper class for waiting on Windows Named Events (Awake pattern)
+    /// Based on Peek.UI implementation
+    /// </summary>
+    public static class NativeEventWaiter
+    {
+        /// <summary>
+        /// Wait for a Windows Event in a background thread and invoke callback on UI thread when signaled
+        /// </summary>
+        /// <param name="eventName">Name of the Windows Event to wait for</param>
+        /// <param name="callback">Callback to invoke when event is signaled</param>
+        /// <param name="cancellationToken">Token to cancel the wait loop</param>
+        public static void WaitForEventLoop(string eventName, Action callback, CancellationToken cancellationToken)
+        {
+            Logger.LogTrace($"[NativeEventWaiter] Setting up event loop for event: {eventName}");
+            var dispatcherQueue = DispatcherQueue.GetForCurrentThread();
+
+            if (dispatcherQueue == null)
+            {
+                Logger.LogError($"[NativeEventWaiter] DispatcherQueue is null for event: {eventName}");
+                return;
+            }
+
+            Logger.LogTrace($"[NativeEventWaiter] DispatcherQueue obtained for event: {eventName}");
+
+            var t = new Thread(() =>
+            {
+                Logger.LogInfo($"[NativeEventWaiter] Background thread started for event: {eventName}");
+                try
+                {
+                    Logger.LogTrace($"[NativeEventWaiter] Creating EventWaitHandle for event: {eventName}");
+                    using var eventHandle = new EventWaitHandle(false, EventResetMode.AutoReset, eventName);
+                    Logger.LogInfo($"[NativeEventWaiter] EventWaitHandle created successfully for event: {eventName}");
+
+                    int waitCount = 0;
+                    while (!cancellationToken.IsCancellationRequested)
+                    {
+                        // Use 500ms timeout for polling
+                        if (eventHandle.WaitOne(500))
+                        {
+                            waitCount++;
+                            Logger.LogInfo($"[NativeEventWaiter] Event SIGNALED: {eventName} (signal count: {waitCount})");
+                            bool enqueued = dispatcherQueue.TryEnqueue(() =>
+                            {
+                                Logger.LogTrace($"[NativeEventWaiter] Executing callback on UI thread for event: {eventName}");
+                                try
+                                {
+                                    callback();
+                                    Logger.LogTrace($"[NativeEventWaiter] Callback completed for event: {eventName}");
+                                }
+                                catch (Exception callbackEx)
+                                {
+                                    Logger.LogError($"[NativeEventWaiter] Callback exception for event {eventName}: {callbackEx.Message}");
+                                }
+                            });
+
+                            if (!enqueued)
+                            {
+                                Logger.LogError($"[NativeEventWaiter] Failed to enqueue callback to UI thread for event: {eventName}");
+                            }
+                        }
+                    }
+
+                    Logger.LogInfo($"[NativeEventWaiter] Event loop ending for event: {eventName} (cancellation requested)");
+                }
+                catch (Exception ex)
+                {
+                    Logger.LogError($"[NativeEventWaiter] Exception in event loop for {eventName}: {ex.Message}\n{ex.StackTrace}");
+                }
+            });
+
+            t.IsBackground = true;
+            t.Name = $"NativeEventWaiter_{eventName}";
+            t.Start();
+            Logger.LogTrace($"[NativeEventWaiter] Background thread started with name: {t.Name}");
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/ResourceLoaderInstance.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Windows.ApplicationModel.Resources;
+
+namespace PowerDisplay.Helpers
+{
+    public static class ResourceLoaderInstance
+    {
+        public static ResourceLoader ResourceLoader { get; private set; }
+
+        static ResourceLoaderInstance()
+        {
+            ResourceLoader = new ResourceLoader("PowerToys.PowerDisplay.pri");
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/SettingsDeepLink.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.IO;
+
+namespace PowerDisplay.Helpers
+{
+    public static class SettingsDeepLink
+    {
+        public enum SettingsWindow
+        {
+            PowerDisplay,
+        }
+
+        public static void OpenSettings(SettingsWindow window, bool mainExecutableIsOnTheParentFolder)
+        {
+            try
+            {
+                var directoryPath = System.AppContext.BaseDirectory;
+                if (mainExecutableIsOnTheParentFolder)
+                {
+                    // Need to go into parent folder for PowerToys.exe. Likely a WinUI3 App SDK application.
+                    directoryPath = Path.Combine(directoryPath, "..");
+                    directoryPath = Path.Combine(directoryPath, "PowerToys.exe");
+                }
+                else
+                {
+                    // PowerToys.exe is in the same path as the application.
+                    directoryPath = Path.Combine(directoryPath, "PowerToys.exe");
+                }
+
+                Process.Start(new ProcessStartInfo(directoryPath) { Arguments = "--open-settings=PowerDisplay" });
+            }
+            catch
+            {
+                // Silently ignore errors opening settings
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/TrayIconService.cs

@@ -0,0 +1,328 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Runtime.InteropServices;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.UI.Xaml;
+using Windows.Win32;
+using Windows.Win32.Foundation;
+using Windows.Win32.UI.Shell;
+using Windows.Win32.UI.WindowsAndMessaging;
+using WinRT.Interop;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// Window procedure delegate for handling window messages.
+    /// Uses primitive types to avoid accessibility issues with CsWin32-generated types.
+    /// </summary>
+    /// <param name="hwnd">Handle to the window.</param>
+    /// <param name="msg">The message.</param>
+    /// <param name="wParam">Additional message information.</param>
+    /// <param name="lParam">Additional message.</param>
+    /// <returns>The result of the message processing.</returns>
+    internal delegate nint WndProcDelegate(nint hwnd, uint msg, nuint wParam, nint lParam);
+
+    [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore", Justification = "Stylistically, window messages are WM_*")]
+    [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1306:Field names should begin with lower-case letter", Justification = "Stylistically, window messages are WM_*")]
+    internal sealed partial class TrayIconService
+    {
+        private const uint MY_NOTIFY_ID = 1001;
+        private const uint WM_TRAY_ICON = PInvoke.WM_USER + 1;
+
+        private readonly SettingsUtils _settingsUtils;
+        private readonly Action _toggleWindowAction;
+        private readonly Action _exitAction;
+        private readonly Action _openSettingsAction;
+        private readonly uint WM_TASKBAR_RESTART;
+
+        private Window? _window;
+        private nint _hwnd;
+        private nint _originalWndProc;
+        private WndProcDelegate? _trayWndProc;
+        private NOTIFYICONDATAW? _trayIconData;
+        private nint _largeIcon;
+        private nint _popupMenu;
+
+        public TrayIconService(
+            SettingsUtils settingsUtils,
+            Action toggleWindowAction,
+            Action exitAction,
+            Action openSettingsAction)
+        {
+            _settingsUtils = settingsUtils;
+            _toggleWindowAction = toggleWindowAction;
+            _exitAction = exitAction;
+            _openSettingsAction = openSettingsAction;
+
+            // TaskbarCreated is the message that's broadcast when explorer.exe
+            // restarts. We need to know when that happens to be able to bring our
+            // notification area icon back
+            WM_TASKBAR_RESTART = RegisterWindowMessageNative("TaskbarCreated");
+        }
+
+        public void SetupTrayIcon(bool? showSystemTrayIcon = null)
+        {
+            var settings = _settingsUtils.GetSettingsOrDefault<PowerDisplaySettings>(PowerDisplaySettings.ModuleName);
+            bool shouldShow = showSystemTrayIcon ?? settings.Properties.ShowSystemTrayIcon;
+
+            if (shouldShow)
+            {
+                if (_window is null)
+                {
+                    _window = new Window();
+                    _hwnd = WindowNative.GetWindowHandle(_window);
+
+                    // LOAD BEARING: If you don't stick the pointer to HotKeyPrc into a
+                    // member (and instead like, use a local), then the pointer we marshal
+                    // into the WindowLongPtr will be useless after we leave this function,
+                    // and our **WindProc will explode**.
+                    _trayWndProc = WindowProc;
+                    var hotKeyPrcPointer = Marshal.GetFunctionPointerForDelegate(_trayWndProc);
+                    _originalWndProc = SetWindowLongPtrNative(_hwnd, GWL_WNDPROC, hotKeyPrcPointer);
+                }
+
+                if (_trayIconData is null)
+                {
+                    // We need to stash this handle, so it doesn't clean itself up. If
+                    // explorer restarts, we'll come back through here, and we don't
+                    // really need to re-load the icon in that case. We can just use
+                    // the handle from the first time.
+                    _largeIcon = GetAppIconHandle();
+                    unsafe
+                    {
+                        _trayIconData = new NOTIFYICONDATAW()
+                        {
+                            cbSize = (uint)sizeof(NOTIFYICONDATAW),
+                            hWnd = new HWND(_hwnd),
+                            uID = MY_NOTIFY_ID,
+                            uFlags = NOTIFY_ICON_DATA_FLAGS.NIF_MESSAGE | NOTIFY_ICON_DATA_FLAGS.NIF_ICON | NOTIFY_ICON_DATA_FLAGS.NIF_TIP,
+                            uCallbackMessage = WM_TRAY_ICON,
+                            hIcon = new HICON(_largeIcon),
+                            szTip = GetString("AppName"),
+                        };
+                    }
+                }
+
+                var d = (NOTIFYICONDATAW)_trayIconData;
+
+                // Add the notification icon
+                unsafe
+                {
+                    bool success = Shell_NotifyIconNative((uint)NOTIFY_ICON_MESSAGE.NIM_ADD, &d);
+                    if (!success)
+                    {
+                        // Shell_NotifyIcon can fail if explorer.exe isn't ready yet (e.g., during system startup)
+                        // Reset _trayIconData to allow retry via WM_WINDOWPOSCHANGING or WM_TASKBAR_RESTART
+                        Logger.LogWarning("[TrayIcon] Shell_NotifyIcon(NIM_ADD) failed, will retry later");
+                        _trayIconData = null;
+                        return;
+                    }
+
+                    Logger.LogInfo("[TrayIcon] Tray icon created successfully");
+                }
+
+                if (_popupMenu == 0)
+                {
+                    _popupMenu = CreatePopupMenu();
+                    InsertMenuNative(_popupMenu, 0, (uint)(MENU_ITEM_FLAGS.MF_BYPOSITION | MENU_ITEM_FLAGS.MF_STRING), PInvoke.WM_USER + 1, GetString("TrayMenu_Settings"));
+                    InsertMenuNative(_popupMenu, 1, (uint)(MENU_ITEM_FLAGS.MF_BYPOSITION | MENU_ITEM_FLAGS.MF_STRING), PInvoke.WM_USER + 2, GetString("TrayMenu_Exit"));
+                }
+            }
+            else
+            {
+                Destroy();
+            }
+        }
+
+        public void Destroy()
+        {
+            if (_trayIconData is not null)
+            {
+                var d = (NOTIFYICONDATAW)_trayIconData;
+                unsafe
+                {
+                    if (Shell_NotifyIconNative((uint)NOTIFY_ICON_MESSAGE.NIM_DELETE, &d))
+                    {
+                        _trayIconData = null;
+                    }
+                }
+            }
+
+            if (_popupMenu != 0)
+            {
+                DestroyMenu(_popupMenu);
+                _popupMenu = 0;
+            }
+
+            if (_largeIcon != 0)
+            {
+                DestroyIcon(_largeIcon);
+                _largeIcon = 0;
+            }
+
+            if (_window is not null)
+            {
+                _window.Close();
+                _window = null;
+                _hwnd = 0;
+            }
+        }
+
+        private static string GetString(string key)
+        {
+            try
+            {
+                return ResourceLoaderInstance.ResourceLoader.GetString(key);
+            }
+            catch
+            {
+                return "unknown";
+            }
+        }
+
+        private nint GetAppIconHandle()
+        {
+            var exePath = Path.Combine(AppContext.BaseDirectory, "PowerToys.PowerDisplay.exe");
+            ExtractIconExNative(exePath, 0, out var largeIcon, out _, 1);
+            return largeIcon;
+        }
+
+        private nint WindowProc(
+            nint hwnd,
+            uint uMsg,
+            nuint wParam,
+            nint lParam)
+        {
+            switch (uMsg)
+            {
+                case PInvoke.WM_COMMAND:
+                    {
+                        if (wParam == PInvoke.WM_USER + 1)
+                        {
+                            // Settings menu item
+                            Logger.LogInfo("[TrayIcon] Settings menu clicked");
+                            _openSettingsAction?.Invoke();
+                        }
+                        else if (wParam == PInvoke.WM_USER + 2)
+                        {
+                            // Exit menu item
+                            Logger.LogInfo("[TrayIcon] Exit menu clicked");
+                            _exitAction?.Invoke();
+                        }
+                    }
+
+                    break;
+
+                // Shell_NotifyIcon can fail when we invoke it during the time explorer.exe isn't present/ready to handle it.
+                // We'll also never receive WM_TASKBAR_RESTART message if the first call to Shell_NotifyIcon failed, so we use
+                // WM_WINDOWPOSCHANGING which is always received on explorer startup sequence.
+                case PInvoke.WM_WINDOWPOSCHANGING:
+                    {
+                        if (_trayIconData is null)
+                        {
+                            SetupTrayIcon();
+                        }
+                    }
+
+                    break;
+                default:
+                    // WM_TASKBAR_RESTART isn't a compile-time constant, so we can't
+                    // use it in a case label
+                    if (uMsg == WM_TASKBAR_RESTART)
+                    {
+                        // Handle the case where explorer.exe restarts.
+                        // Even if we created it before, do it again
+                        Logger.LogInfo("[TrayIcon] Taskbar restarted, recreating tray icon");
+                        SetupTrayIcon();
+                    }
+                    else if (uMsg == WM_TRAY_ICON)
+                    {
+                        switch ((uint)lParam)
+                        {
+                            case PInvoke.WM_RBUTTONUP:
+                                {
+                                    if (_popupMenu != 0)
+                                    {
+                                        GetCursorPos(out var cursorPos);
+                                        SetForegroundWindow(_hwnd);
+                                        TrackPopupMenuExNative(_popupMenu, (uint)TRACK_POPUP_MENU_FLAGS.TPM_LEFTALIGN | (uint)TRACK_POPUP_MENU_FLAGS.TPM_BOTTOMALIGN, cursorPos.X, cursorPos.Y, _hwnd, 0);
+                                    }
+                                }
+
+                                break;
+                            case PInvoke.WM_LBUTTONUP:
+                            case PInvoke.WM_LBUTTONDBLCLK:
+                                Logger.LogInfo("[TrayIcon] Left click/double click - toggling window");
+                                _toggleWindowAction?.Invoke();
+                                break;
+                        }
+                    }
+
+                    break;
+            }
+
+            return CallWindowProcIntPtr(_originalWndProc, hwnd, uMsg, wParam, lParam);
+        }
+
+        [LibraryImport("user32.dll", EntryPoint = "CallWindowProcW")]
+        private static partial nint CallWindowProcIntPtr(IntPtr lpPrevWndFunc, nint hWnd, uint msg, nuint wParam, nint lParam);
+
+        [LibraryImport("user32.dll", EntryPoint = "RegisterWindowMessageW", StringMarshalling = StringMarshalling.Utf16)]
+        private static partial uint RegisterWindowMessageNative(string lpString);
+
+        [LibraryImport("user32.dll", EntryPoint = "SetWindowLongPtrW")]
+        private static partial nint SetWindowLongPtrNative(nint hWnd, int nIndex, nint dwNewLong);
+
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool GetCursorPos(out POINT lpPoint);
+
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool SetForegroundWindow(nint hWnd);
+
+        // Shell APIs - use uint for enums and unsafe pointer for struct
+        [LibraryImport("shell32.dll", EntryPoint = "Shell_NotifyIconW")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static unsafe partial bool Shell_NotifyIconNative(uint dwMessage, NOTIFYICONDATAW* lpData);
+
+        [LibraryImport("shell32.dll", EntryPoint = "ExtractIconExW", StringMarshalling = StringMarshalling.Utf16)]
+        private static partial uint ExtractIconExNative(string lpszFile, int nIconIndex, out nint phiconLarge, out nint phiconSmall, uint nIcons);
+
+        // Menu APIs
+        [LibraryImport("user32.dll")]
+        private static partial nint CreatePopupMenu();
+
+        [LibraryImport("user32.dll", EntryPoint = "InsertMenuW", StringMarshalling = StringMarshalling.Utf16)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool InsertMenuNative(nint hMenu, uint uPosition, uint uFlags, nuint uIDNewItem, string? lpNewItem);
+
+        [LibraryImport("user32.dll", EntryPoint = "TrackPopupMenuEx")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool TrackPopupMenuExNative(nint hMenu, uint uFlags, int x, int y, nint hwnd, nint lptpm);
+
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool DestroyMenu(nint hMenu);
+
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool DestroyIcon(nint hIcon);
+
+        [StructLayout(LayoutKind.Sequential)]
+        private struct POINT
+        {
+            public int X;
+            public int Y;
+        }
+
+        // GWL_WNDPROC constant
+        private const int GWL_WNDPROC = -4;
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/TypePreservation.cs

@@ -0,0 +1,81 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// This class ensures types used in XAML are preserved during AOT compilation.
+    /// Framework types cannot have attributes added directly to their definitions since they're external types.
+    /// Use DynamicDependency to preserve all members of these WinUI3 framework types.
+    /// </summary>
+    internal static class TypePreservation
+    {
+        // Core WinUI3 Controls used in XAML
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Window))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Application))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.Grid))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.Border))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ScrollViewer))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.StackPanel))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ItemsControl))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.Slider))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.TextBlock))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.Button))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.FontIcon))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ProgressRing))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.InfoBar))]
+
+        // Animation and Transform types
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.Storyboard))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.DoubleAnimation))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.CubicEase))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.TranslateTransform))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.TransitionCollection))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.EntranceThemeTransition))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.RepositionThemeTransition))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Animation.EasingFunctionBase))]
+
+        // Template and Resource types
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.DataTemplate))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ItemsPanelTemplate))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Style))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.FontIconSource))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.ResourceDictionary))]
+
+        // Text and Document types
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Documents.Run))]
+
+        // Layout types
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.RowDefinition))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ColumnDefinition))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.RowDefinitionCollection))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ColumnDefinitionCollection))]
+
+        // Media types for brushes and visuals
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.SolidColorBrush))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Brush))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Media.Transform))]
+
+        // Core UI element types
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.UIElement))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.FrameworkElement))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.DependencyObject))]
+
+        // Thickness and other value types used in XAML (structs, not enums)
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Thickness))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.CornerRadius))]
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.GridLength))]
+
+        // ToolTip service used in buttons
+        [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Microsoft.UI.Xaml.Controls.ToolTipService))]
+
+        public static void PreserveTypes()
+        {
+            // This method exists only to hold the DynamicDependency attributes above.
+            // It must be called to ensure the types are not trimmed during AOT compilation.
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/VisibilityConverter.cs

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.UI.Xaml;
+
+namespace PowerDisplay.Helpers
+{
+    /// <summary>
+    /// Provides conversion utilities for Visibility binding in x:Bind scenarios.
+    /// AOT-compatible alternative to IValueConverter implementations.
+    /// </summary>
+    public static class VisibilityConverter
+    {
+        /// <summary>
+        /// Converts a boolean value to a Visibility value.
+        /// </summary>
+        /// <param name="value">The boolean value to convert.</param>
+        /// <returns>Visibility.Visible if true, Visibility.Collapsed if false.</returns>
+        public static Visibility BoolToVisibility(bool value) => value ? Visibility.Visible : Visibility.Collapsed;
+    }
+}

src/modules/powerdisplay/PowerDisplay/Helpers/WindowHelper.cs

@@ -0,0 +1,261 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Microsoft.UI;
+using Microsoft.UI.Windowing;
+using WinUIEx;
+
+namespace PowerDisplay.Helpers
+{
+    internal static partial class WindowHelper
+    {
+        // Cursor position structure for GetCursorPos
+        [StructLayout(LayoutKind.Sequential)]
+        private struct POINT
+        {
+            public int X;
+            public int Y;
+        }
+
+        // Cursor position for detecting the monitor with the mouse
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool GetCursorPos(out POINT lpPoint);
+
+        // Window Styles
+        private const int GwlStyle = -16;
+        private const int WsCaption = 0x00C00000;
+        private const int WsThickframe = 0x00040000;
+        private const int WsMinimizebox = 0x00020000;
+        private const int WsMaximizebox = 0x00010000;
+        private const int WsSysmenu = 0x00080000;
+
+        // Extended Window Styles
+        private const int GwlExstyle = -20;
+        private const int WsExDlgmodalframe = 0x00000001;
+        private const int WsExWindowedge = 0x00000100;
+        private const int WsExClientedge = 0x00000200;
+        private const int WsExStaticedge = 0x00020000;
+        private const int WsExToolwindow = 0x00000080;
+
+        private const uint SwpNosize = 0x0001;
+        private const uint SwpNomove = 0x0002;
+        private const uint SwpFramechanged = 0x0020;
+        private const nint HwndTopmost = -1;
+        private const nint HwndNotopmost = -2;
+
+        // ShowWindow commands
+        private const int SwHide = 0;
+        private const int SwShow = 5;
+
+        // P/Invoke declarations (64-bit only - PowerToys only builds for x64/ARM64)
+        [LibraryImport("user32.dll", EntryPoint = "GetWindowLongPtrW")]
+        private static partial nint GetWindowLongPtr(nint hWnd, int nIndex);
+
+        [LibraryImport("user32.dll", EntryPoint = "SetWindowLongPtrW")]
+        private static partial nint SetWindowLong(nint hWnd, int nIndex, nint dwNewLong);
+
+        [LibraryImport("user32.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool SetWindowPos(
+            nint hWnd,
+            nint hWndInsertAfter,
+            int x,
+            int y,
+            int cx,
+            int cy,
+            uint uFlags);
+
+        [LibraryImport("user32.dll", EntryPoint = "ShowWindow")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool ShowWindowNative(nint hWnd, int nCmdShow);
+
+        [LibraryImport("user32.dll", EntryPoint = "IsWindowVisible")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static partial bool IsWindowVisibleNative(nint hWnd);
+
+        /// <summary>
+        /// Check if window is visible
+        /// </summary>
+        public static bool IsWindowVisible(nint hWnd)
+        {
+            return IsWindowVisibleNative(hWnd);
+        }
+
+        /// <summary>
+        /// Disable window moving and resizing functionality
+        /// </summary>
+        public static void DisableWindowMovingAndResizing(nint hWnd)
+        {
+            // Get current window style
+            nint style = GetWindowLongPtr(hWnd, GwlStyle);
+
+            // Remove resizable borders, title bar, and system menu
+            style &= ~WsThickframe;
+            style &= ~WsMaximizebox;
+            style &= ~WsMinimizebox;
+            style &= ~WsCaption;  // Remove entire title bar
+            style &= ~WsSysmenu;   // Remove system menu
+
+            // Set new window style
+            _ = SetWindowLong(hWnd, GwlStyle, style);
+
+            // Get extended style and remove related borders
+            nint exStyle = GetWindowLongPtr(hWnd, GwlExstyle);
+            exStyle &= ~WsExDlgmodalframe;
+            exStyle &= ~WsExWindowedge;
+            exStyle &= ~WsExClientedge;
+            exStyle &= ~WsExStaticedge;
+            _ = SetWindowLong(hWnd, GwlExstyle, exStyle);
+
+            // Refresh window frame
+            SetWindowPos(
+                hWnd,
+                0,
+                0,
+                0,
+                0,
+                0,
+                SwpNomove | SwpNosize | SwpFramechanged);
+        }
+
+        /// <summary>
+        /// Set whether window is topmost
+        /// </summary>
+        public static void SetWindowTopmost(nint hWnd, bool topmost)
+        {
+            SetWindowPos(
+                hWnd,
+                topmost ? HwndTopmost : HwndNotopmost,
+                0,
+                0,
+                0,
+                0,
+                SwpNomove | SwpNosize);
+        }
+
+        /// <summary>
+        /// Show or hide window
+        /// </summary>
+        public static void ShowWindow(nint hWnd, bool show)
+        {
+            ShowWindowNative(hWnd, show ? SwShow : SwHide);
+        }
+
+        /// <summary>
+        /// Hide window from taskbar
+        /// </summary>
+        public static void HideFromTaskbar(nint hWnd)
+        {
+            // Get current extended style
+            nint exStyle = GetWindowLongPtr(hWnd, GwlExstyle);
+
+            // Add WS_EX_TOOLWINDOW style to hide window from taskbar
+            exStyle |= WsExToolwindow;
+
+            // Set new extended style
+            _ = SetWindowLong(hWnd, GwlExstyle, exStyle);
+
+            // Refresh window frame
+            SetWindowPos(
+                hWnd,
+                0,
+                0,
+                0,
+                0,
+                0,
+                SwpNomove | SwpNosize | SwpFramechanged);
+        }
+
+        /// <summary>
+        /// Get the DPI scale factor for a window (relative to standard 96 DPI)
+        /// </summary>
+        /// <param name="window">WinUIEx window</param>
+        /// <returns>DPI scale factor (1.0 = 100%, 1.25 = 125%, 1.5 = 150%, 2.0 = 200%)</returns>
+        public static double GetDpiScale(WindowEx window)
+        {
+            return (float)window.GetDpiForWindow() / 96.0;
+        }
+
+        /// <summary>
+        /// Convert device-independent units (DIU) to physical pixels
+        /// </summary>
+        /// <param name="diu">Device-independent unit value</param>
+        /// <param name="dpiScale">DPI scale factor</param>
+        /// <returns>Physical pixel value</returns>
+        public static int ScaleToPhysicalPixels(int diu, double dpiScale)
+        {
+            return (int)Math.Ceiling(diu * dpiScale);
+        }
+
+        /// <summary>
+        /// Position a window at the bottom-right corner of the monitor where the mouse cursor is located.
+        /// Uses WinUIEx MonitorInfo API which correctly handles all edge cases:
+        /// - Multi-monitor setups
+        /// - Taskbar at any position (top/bottom/left/right)
+        /// - Different DPI settings
+        /// </summary>
+        /// <param name="window">WinUIEx window to position</param>
+        /// <param name="width">Window width in device-independent units (DIU)</param>
+        /// <param name="height">Window height in device-independent units (DIU)</param>
+        /// <param name="rightMargin">Right margin in device-independent units (DIU)</param>
+        public static void PositionWindowBottomRight(
+            WindowEx window,
+            int width,
+            int height,
+            int rightMargin = 0)
+        {
+            // Use WinUIEx MonitorInfo - RectWork already includes correct offsets for taskbar position
+            var monitors = MonitorInfo.GetDisplayMonitors();
+            if (monitors == null || monitors.Count == 0)
+            {
+                ManagedCommon.Logger.LogWarning("PositionWindowBottomRight: No monitors found, skipping positioning");
+                return;
+            }
+
+            // Find the monitor where the mouse cursor is located
+            var targetMonitor = GetMonitorAtCursor(monitors);
+            var workArea = targetMonitor.RectWork;
+            double dpiScale = GetDpiScale(window);
+
+            // Calculate bottom-right position
+            // RectWork.Right/Bottom already account for taskbar position
+            double x = workArea.Right - (dpiScale * (width + rightMargin));
+            double y = workArea.Bottom - (dpiScale * height);
+
+            window.MoveAndResize(x, y, width, height);
+        }
+
+        /// <summary>
+        /// Get the monitor where the mouse cursor is currently located.
+        /// Falls back to primary monitor if cursor position cannot be determined.
+        /// </summary>
+        /// <param name="monitors">List of available monitors</param>
+        /// <returns>MonitorInfo of the monitor containing the cursor</returns>
+        private static MonitorInfo GetMonitorAtCursor(IList<MonitorInfo> monitors)
+        {
+            // Try to get cursor position using Win32 API
+            if (GetCursorPos(out var cursorPos))
+            {
+                // Find the monitor that contains the cursor point
+                foreach (var monitor in monitors)
+                {
+                    if (cursorPos.X >= monitor.RectMonitor.Left &&
+                        cursorPos.X < monitor.RectMonitor.Right &&
+                        cursorPos.Y >= monitor.RectMonitor.Top &&
+                        cursorPos.Y < monitor.RectMonitor.Bottom)
+                    {
+                        return monitor;
+                    }
+                }
+            }
+
+            // Fallback to first monitor (typically primary)
+            return monitors[0];
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/NativeMethods.json

@@ -0,0 +1,5 @@
+{
+  "$schema": "https://aka.ms/CsWin32.schema.json",
+  "public": true,
+  "allowMarshaling": false
+}

src/modules/powerdisplay/PowerDisplay/NativeMethods.txt

@@ -0,0 +1,17 @@
+// Structs and types only - functions use LibraryImport for AOT compatibility
+NOTIFYICONDATAW
+NOTIFY_ICON_MESSAGE
+NOTIFY_ICON_DATA_FLAGS
+MENU_ITEM_FLAGS
+TRACK_POPUP_MENU_FLAGS
+
+// Window message constants (used by TrayIconService)
+WM_USER
+WM_COMMAND
+WM_RBUTTONUP
+WM_LBUTTONUP
+WM_LBUTTONDBLCLK
+WM_WINDOWPOSCHANGING
+
+// COM wait flags for single instance redirection (constants only)
+CWMO_FLAGS

src/modules/powerdisplay/PowerDisplay/PowerDisplay.csproj

@@ -0,0 +1,104 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <!-- Look at Directory.Build.props in root for common stuff as well -->
+  <Import Project="..\..\..\Common.Dotnet.CsWinRT.props" />
+  <Import Project="..\..\..\Common.SelfContained.props" />
+  <Import Project="..\..\..\Common.Dotnet.AotCompatibility.props" />
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <RootNamespace>PowerDisplay</RootNamespace>
+    <ApplicationManifest>app.manifest</ApplicationManifest>
+    <ApplicationIcon>Assets\PowerDisplay\PowerDisplay.ico</ApplicationIcon>
+    <Platforms>x64;ARM64</Platforms>
+    <UseWinUI>true</UseWinUI>
+    <EnableMsixTooling>true</EnableMsixTooling>
+    <EnablePreviewMsixTooling>true</EnablePreviewMsixTooling>
+    <WindowsPackageType>None</WindowsPackageType>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
+    <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
+    <OutputPath>..\..\..\..\$(Platform)\$(Configuration)\WinUI3Apps</OutputPath>
+    <AssemblyName>PowerToys.PowerDisplay</AssemblyName>
+    <!-- MRT from windows app sdk will search for a pri file with the same name of the module before defaulting to resources.pri -->
+    <ProjectPriFileName>PowerToys.PowerDisplay.pri</ProjectPriFileName>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
+    <!-- Disable XAML-generated Main method, use custom Program.cs -->
+    <DefineConstants>DISABLE_XAML_GENERATED_MAIN</DefineConstants>
+  </PropertyGroup>
+  <!-- Native AOT Configuration -->
+  <PropertyGroup>
+    <PublishSingleFile>false</PublishSingleFile>
+    <DisableRuntimeMarshalling>false</DisableRuntimeMarshalling>
+    <PublishAot>true</PublishAot>
+    <TrimmerSingleWarn>false</TrimmerSingleWarn>
+    <SuppressTrimAnalysisWarnings>false</SuppressTrimAnalysisWarnings>
+  </PropertyGroup>
+  <ItemGroup>
+    <!-- Hide build log files from Solution Explorer -->
+    <None Remove="*.log" />
+    <None Remove="*.binlog" />
+  </ItemGroup>
+  <ItemGroup>
+    <!-- Add WindowsDesktop.App framework reference to align Microsoft.VisualBasic.dll version
+         with other projects that use UseWPF/UseWindowsForms. This does NOT enable WPF/WinForms,
+         it only ensures consistent runtime DLL versions across all WinUI3Apps. -->
+    <FrameworkReference Include="Microsoft.WindowsDesktop.App" />
+  </ItemGroup>
+  <ItemGroup>
+    <Page Remove="PowerDisplayXAML\App.xaml" />
+  </ItemGroup>
+  <ItemGroup>
+    <ApplicationDefinition Include="PowerDisplayXAML\App.xaml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Folder Include="PowerDisplayXAML\" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.WindowsAppSDK" />
+    <PackageReference Include="Microsoft.Windows.SDK.BuildTools" />
+    <PackageReference Include="WmiLight" />
+	<PackageReference Include="WinUIEx" />
+    <PackageReference Include="System.Collections.Immutable" />
+    <PackageReference Include="CommunityToolkit.WinUI.Controls.SettingsControls" />
+    <PackageReference Include="CommunityToolkit.WinUI.Animations" />
+    <PackageReference Include="CommunityToolkit.WinUI.Extensions" />
+    <PackageReference Include="CommunityToolkit.WinUI.Controls.Segmented" />
+    <PackageReference Include="CommunityToolkit.WinUI.Controls.Sizers" />
+    <PackageReference Include="CommunityToolkit.WinUI.Converters" />
+    <PackageReference Include="CommunityToolkit.Mvvm" />
+    <PackageReference Include="Microsoft.Windows.CsWin32">
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <Manifest Include="$(ApplicationManifest)" />
+  </ItemGroup>
+  <!--
+    Defining the "Msix" ProjectCapability here allows the Single-project MSIX Packaging
+    Tools extension to be activated for this project even if the Windows App SDK Nuget
+    package has not yet been restored.
+  -->
+  <ItemGroup Condition="'$(DisableMsixProjectCapabilityAddedByProject)'!='true' and '$(EnableMsixTooling)'=='true'">
+    <ProjectCapability Include="Msix" />
+  </ItemGroup>
+  <ItemGroup>
+    <!-- Removed Common.UI dependency - SettingsDeepLink is now implemented locally -->
+    <ProjectReference Include="..\..\..\common\ManagedCommon\ManagedCommon.csproj" />
+    <!-- Removed ManagedCsWin32 - using CsWin32 directly for TrayIcon APIs -->
+    <ProjectReference Include="..\..\..\common\interop\PowerToys.Interop.vcxproj" />
+    <ProjectReference Include="..\..\..\settings-ui\Settings.UI.Library\Settings.UI.Library.csproj" />
+    <ProjectReference Include="..\PowerDisplay.Lib\PowerDisplay.Lib.csproj" />
+  </ItemGroup>
+  <!-- Copy Assets folder to output directory -->
+  <ItemGroup>
+    <Content Include="Assets\PowerDisplay\*">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+  <!--
+    Defining the "HasPackageAndPublishMenuAddedByProject" property here allows the Solution
+    Explorer "Package and Publish" context menu entry to be enabled for this project even if
+    the Windows App SDK Nuget package has not yet been restored.
+  -->
+  <PropertyGroup Condition="'$(DisableHasPackageAndPublishMenuAddedByProject)'!='true' and '$(EnableMsixTooling)'=='true'">
+    <HasPackageAndPublishMenu>true</HasPackageAndPublishMenu>
+  </PropertyGroup>
+</Project>

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/App.xaml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Application
+    x:Class="PowerDisplay.App"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:toolkit="using:CommunityToolkit.WinUI">
+    <Application.Resources>
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <!--  WinUI 3 System Resources  -->
+                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
+    </Application.Resources>
+</Application>

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/App.xaml.cs

@@ -0,0 +1,333 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.PowerToys.Telemetry;
+using Microsoft.UI.Dispatching;
+using Microsoft.UI.Xaml;
+using Microsoft.Windows.AppLifecycle;
+using PowerDisplay.Common;
+using PowerDisplay.Helpers;
+using PowerDisplay.Serialization;
+using PowerToys.Interop;
+
+namespace PowerDisplay
+{
+    /// <summary>
+    /// PowerDisplay application main class
+    /// </summary>
+#pragma warning disable CA1001 // CancellationTokenSource is disposed in Shutdown/ForceExit methods
+    public partial class App : Application
+#pragma warning restore CA1001
+    {
+        private readonly SettingsUtils _settingsUtils = SettingsUtils.Default;
+        private Window? _mainWindow;
+        private int _powerToysRunnerPid;
+        private TrayIconService? _trayIconService;
+
+        public App(int runnerPid)
+        {
+            Logger.LogInfo($"App constructor: Starting with runnerPid={runnerPid}");
+            _powerToysRunnerPid = runnerPid;
+
+            Logger.LogTrace("App constructor: Calling InitializeComponent");
+            this.InitializeComponent();
+
+            // Ensure types used in XAML are preserved for AOT compilation
+            TypePreservation.PreserveTypes();
+
+            // Note: Logger is already initialized in Program.cs before App constructor
+            Logger.LogTrace("App constructor: InitializeComponent completed");
+
+            // Initialize PowerToys telemetry
+            try
+            {
+                PowerToysTelemetry.Log.WriteEvent(new Telemetry.Events.PowerDisplayStartEvent());
+                Logger.LogTrace("App constructor: Telemetry event sent");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogWarning($"App constructor: Telemetry failed: {ex.Message}");
+            }
+
+            // Initialize language settings
+            string appLanguage = LanguageHelper.LoadLanguage();
+            if (!string.IsNullOrEmpty(appLanguage))
+            {
+                Microsoft.Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride = appLanguage;
+                Logger.LogTrace($"App constructor: Language set to {appLanguage}");
+            }
+
+            // Handle unhandled exceptions
+            this.UnhandledException += OnUnhandledException;
+            Logger.LogInfo("App constructor: Completed");
+        }
+
+        /// <summary>
+        /// Handle unhandled exceptions
+        /// </summary>
+        private void OnUnhandledException(object sender, Microsoft.UI.Xaml.UnhandledExceptionEventArgs e)
+        {
+            Logger.LogError("Unhandled exception", e.Exception);
+        }
+
+        /// <summary>
+        /// Called when the application is launched
+        /// </summary>
+        /// <param name="args">Launch arguments</param>
+        protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
+        {
+            Logger.LogInfo("OnLaunched: Application launching");
+            try
+            {
+                // Single instance is already ensured by AppInstance.FindOrRegisterForKey() in Program.cs
+                // PID is already parsed in Program.cs and passed to constructor
+
+                // Set up Windows Events monitoring (Awake pattern)
+                // Note: PowerDisplay.exe should NOT listen to RefreshMonitorsEvent
+                // That event is sent BY PowerDisplay TO Settings UI for one-way notification
+                Logger.LogInfo("OnLaunched: Registering Windows Events for IPC...");
+                RegisterWindowEvent(Constants.TogglePowerDisplayEvent(), mw => mw.ToggleWindow(), "Toggle");
+                Logger.LogTrace($"OnLaunched: Registered Toggle event: {Constants.TogglePowerDisplayEvent()}");
+                RegisterEvent(Constants.TerminatePowerDisplayEvent(), () => Environment.Exit(0), "Terminate");
+                Logger.LogTrace($"OnLaunched: Registered Terminate event: {Constants.TerminatePowerDisplayEvent()}");
+                RegisterWindowEvent(
+                    Constants.SettingsUpdatedPowerDisplayEvent(),
+                    mw =>
+                    {
+                        mw.ViewModel.ApplySettingsFromUI();
+
+                        // Refresh tray icon based on updated settings
+                        _trayIconService?.SetupTrayIcon();
+                    },
+                    "SettingsUpdated");
+                RegisterWindowEvent(
+                    Constants.HotkeyUpdatedPowerDisplayEvent(),
+                    mw => mw.ReloadHotkeySettings(),
+                    "HotkeyUpdated");
+                RegisterViewModelEvent(Constants.ApplyColorTemperaturePowerDisplayEvent(), vm => vm.ApplyColorTemperatureFromSettings(), "ApplyColorTemperature");
+                RegisterViewModelEvent(Constants.ApplyProfilePowerDisplayEvent(), vm => vm.ApplyProfileFromSettings(), "ApplyProfile");
+                RegisterViewModelEvent(Constants.PowerDisplaySendSettingsTelemetryEvent(), vm => vm.SendSettingsTelemetry(), "SendSettingsTelemetry");
+
+                // LightSwitch integration - apply profiles when theme changes
+                RegisterViewModelEvent(PathConstants.LightSwitchLightThemeEventName, vm => vm.ApplyLightSwitchProfile(isLightMode: true), "LightSwitch-Light");
+                RegisterViewModelEvent(PathConstants.LightSwitchDarkThemeEventName, vm => vm.ApplyLightSwitchProfile(isLightMode: false), "LightSwitch-Dark");
+                Logger.LogInfo("OnLaunched: All Windows Events registered");
+
+                // Monitor Runner process (backup exit mechanism)
+                if (_powerToysRunnerPid > 0)
+                {
+                    Logger.LogInfo($"OnLaunched: PowerDisplay started from PowerToys Runner. Runner pid={_powerToysRunnerPid}");
+
+                    RunnerHelper.WaitForPowerToysRunner(_powerToysRunnerPid, () =>
+                    {
+                        Logger.LogInfo("OnLaunched: PowerToys Runner exited. Exiting PowerDisplay");
+                        Environment.Exit(0);
+                    });
+                }
+                else
+                {
+                    Logger.LogInfo("OnLaunched: PowerDisplay started in standalone mode (no runner PID)");
+                }
+
+                // Create main window
+                Logger.LogInfo("OnLaunched: Creating MainWindow");
+                _mainWindow = new MainWindow();
+                Logger.LogInfo("OnLaunched: MainWindow created");
+
+                // Initialize tray icon service
+                Logger.LogTrace("OnLaunched: Initializing TrayIconService");
+                _trayIconService = new TrayIconService(
+                    _settingsUtils,
+                    ToggleMainWindow,
+                    () => Environment.Exit(0),
+                    OpenSettings);
+                _trayIconService.SetupTrayIcon();
+                Logger.LogTrace("OnLaunched: TrayIconService initialized");
+
+                // Window visibility depends on launch mode
+                bool isStandaloneMode = _powerToysRunnerPid <= 0;
+                Logger.LogInfo($"OnLaunched: isStandaloneMode={isStandaloneMode}");
+
+                if (isStandaloneMode)
+                {
+                    // Standalone mode - activate and show window immediately
+                    Logger.LogInfo("OnLaunched: Activating window (standalone mode)");
+                    _mainWindow.Activate();
+                    Logger.LogInfo("OnLaunched: Window activated (standalone mode)");
+                }
+                else
+                {
+                    // PowerToys mode - window remains hidden until show event received
+                    // Background initialization runs automatically via MainWindow constructor
+                    Logger.LogInfo("OnLaunched: Window created but hidden, waiting for show/toggle event (PowerToys mode)");
+                }
+
+                Logger.LogInfo("OnLaunched: Application launch completed");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"OnLaunched: PowerDisplay startup failed: {ex.Message}\n{ex.StackTrace}");
+            }
+        }
+
+        /// <summary>
+        /// Register a simple event handler (no window access needed)
+        /// </summary>
+        private void RegisterEvent(string eventName, Action action, string logName)
+        {
+            Logger.LogTrace($"RegisterEvent: Setting up event listener for '{logName}' on event '{eventName}'");
+            NativeEventWaiter.WaitForEventLoop(
+                eventName,
+                () =>
+                {
+                    Logger.LogInfo($"[EVENT] {logName} event received from event '{eventName}'");
+                    try
+                    {
+                        action();
+                        Logger.LogTrace($"[EVENT] {logName} action completed");
+                    }
+                    catch (Exception ex)
+                    {
+                        Logger.LogError($"[EVENT] {logName} action failed: {ex.Message}");
+                    }
+                },
+                CancellationToken.None);
+        }
+
+        /// <summary>
+        /// Register an event handler that operates on MainWindow directly
+        /// NativeEventWaiter already marshals to UI thread
+        /// </summary>
+        private void RegisterWindowEvent(string eventName, Action<MainWindow> action, string logName)
+        {
+            Logger.LogTrace($"RegisterWindowEvent: Setting up window event listener for '{logName}' on event '{eventName}'");
+            NativeEventWaiter.WaitForEventLoop(
+                eventName,
+                () =>
+                {
+                    Logger.LogInfo($"[EVENT] {logName} window event received from event '{eventName}'");
+                    if (_mainWindow is MainWindow mainWindow)
+                    {
+                        Logger.LogTrace($"[EVENT] {logName}: MainWindow is valid, invoking action");
+                        try
+                        {
+                            action(mainWindow);
+                            Logger.LogTrace($"[EVENT] {logName}: Window action completed");
+                        }
+                        catch (Exception ex)
+                        {
+                            Logger.LogError($"[EVENT] {logName}: Window action failed: {ex.Message}");
+                        }
+                    }
+                    else
+                    {
+                        Logger.LogError($"[EVENT] {logName}: _mainWindow is null or not MainWindow type");
+                    }
+                },
+                CancellationToken.None);
+        }
+
+        /// <summary>
+        /// Register an event handler that operates on ViewModel via DispatcherQueue
+        /// Used for Settings UI IPC events that need ViewModel access
+        /// </summary>
+        private void RegisterViewModelEvent(string eventName, Action<ViewModels.MainViewModel> action, string logName)
+        {
+            NativeEventWaiter.WaitForEventLoop(
+                eventName,
+                () =>
+                {
+                    Logger.LogInfo($"[EVENT] {logName} event received");
+                    _mainWindow?.DispatcherQueue.TryEnqueue(() =>
+                    {
+                        if (_mainWindow is MainWindow mainWindow && mainWindow.ViewModel != null)
+                        {
+                            action(mainWindow.ViewModel);
+                        }
+                    });
+                },
+                CancellationToken.None);
+        }
+
+        /// <summary>
+        /// Gets the main window instance
+        /// </summary>
+        public Window? MainWindow => _mainWindow;
+
+        /// <summary>
+        /// Show the main window
+        /// </summary>
+        private void ShowMainWindow()
+        {
+            Logger.LogInfo("ShowMainWindow: Called");
+            if (_mainWindow is MainWindow mainWindow)
+            {
+                Logger.LogTrace("ShowMainWindow: MainWindow is valid, calling ShowWindow");
+                mainWindow.ShowWindow();
+            }
+            else
+            {
+                Logger.LogError("ShowMainWindow: _mainWindow is null or not MainWindow type");
+            }
+        }
+
+        /// <summary>
+        /// Toggle the main window visibility
+        /// </summary>
+        private void ToggleMainWindow()
+        {
+            Logger.LogInfo("ToggleMainWindow: Called");
+            if (_mainWindow is MainWindow mainWindow)
+            {
+                Logger.LogTrace($"ToggleMainWindow: MainWindow is valid, current visibility={mainWindow.IsWindowVisible()}");
+                mainWindow.ToggleWindow();
+            }
+            else
+            {
+                Logger.LogError("ToggleMainWindow: _mainWindow is null or not MainWindow type");
+            }
+        }
+
+        /// <summary>
+        /// Open PowerDisplay settings in PowerToys Settings UI
+        /// </summary>
+        private void OpenSettings()
+        {
+            // mainExecutableIsOnTheParentFolder = true because PowerDisplay is a WinUI 3 app
+            // deployed in a subfolder (PowerDisplay\) while PowerToys.exe is in the parent folder
+            SettingsDeepLink.OpenSettings(SettingsDeepLink.SettingsWindow.PowerDisplay, true);
+        }
+
+        /// <summary>
+        /// Refresh tray icon based on current settings
+        /// </summary>
+        public void RefreshTrayIcon()
+        {
+            _trayIconService?.SetupTrayIcon();
+        }
+
+        /// <summary>
+        /// Check if running standalone (not launched from PowerToys Runner)
+        /// </summary>
+        public bool IsRunningDetachedFromPowerToys()
+        {
+            return _powerToysRunnerPid == -1;
+        }
+
+        /// <summary>
+        /// Shutdown application (Awake pattern - simple and clean)
+        /// </summary>
+        public void Shutdown()
+        {
+            Logger.LogInfo("PowerDisplay shutting down");
+            _trayIconService?.Destroy();
+            Environment.Exit(0);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/IdentifyWindow.xaml

@@ -0,0 +1,25 @@
+<winuiex:WindowEx
+    x:Class="PowerDisplay.PowerDisplayXAML.IdentifyWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:winuiex="using:WinUIEx"
+    IsMaximizable="False"
+    IsMinimizable="False"
+    IsResizable="False"
+    IsShownInSwitchers="False"
+    IsTitleBarVisible="False"
+    mc:Ignorable="d">
+    <Grid Background="#1A000000">
+        <TextBlock
+            x:Name="NumberText"
+            HorizontalAlignment="Center"
+            VerticalAlignment="Center"
+            FontFamily="Segoe UI"
+            FontSize="200"
+            FontWeight="Bold"
+            Foreground="White"
+            Text="1" />
+    </Grid>
+</winuiex:WindowEx>

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/IdentifyWindow.xaml.cs

@@ -0,0 +1,78 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Microsoft.UI.Windowing;
+using Windows.Graphics;
+using WinUIEx;
+
+namespace PowerDisplay.PowerDisplayXAML
+{
+    /// <summary>
+    /// Interaction logic for IdentifyWindow.xaml
+    /// </summary>
+    public sealed partial class IdentifyWindow : WindowEx
+    {
+        // Window size in device-independent units (DIU)
+        private const int WindowWidthDiu = 300;
+        private const int WindowHeightDiu = 280;
+
+        private double _dpiScale = 1.0;
+
+        public IdentifyWindow(string displayText)
+        {
+            InitializeComponent();
+            NumberText.Text = displayText;
+
+            // Configure window style
+            ConfigureWindow();
+
+            // Auto close after 3 seconds
+            Task.Delay(3000).ContinueWith(_ =>
+            {
+                DispatcherQueue.TryEnqueue(() =>
+                {
+                    Close();
+                });
+            });
+        }
+
+        private void ConfigureWindow()
+        {
+            // Get DPI scale using WinUIEx API
+            _dpiScale = this.GetDpiForWindow() / 96.0;
+
+            // Set window size scaled for DPI
+            // AppWindow.Resize expects physical pixels
+            int physicalWidth = (int)(WindowWidthDiu * _dpiScale);
+            int physicalHeight = (int)(WindowHeightDiu * _dpiScale);
+            this.AppWindow.Resize(new SizeInt32 { Width = physicalWidth, Height = physicalHeight });
+
+            // Window properties (IsResizable, IsMinimizable, IsMaximizable,
+            // IsTitleBarVisible, IsShownInSwitchers) are set in XAML
+
+            // Set window topmost using WinUIEx API
+            this.IsAlwaysOnTop = true;
+        }
+
+        /// <summary>
+        /// Position the window at the center of the specified display area
+        /// </summary>
+        public void PositionOnDisplay(DisplayArea displayArea)
+        {
+            var workArea = displayArea.WorkArea;
+
+            // Window size in physical pixels (already scaled for DPI)
+            int physicalWidth = (int)(WindowWidthDiu * _dpiScale);
+            int physicalHeight = (int)(WindowHeightDiu * _dpiScale);
+
+            // Calculate center position (WorkArea coordinates are in physical pixels)
+            int x = workArea.X + ((workArea.Width - physicalWidth) / 2);
+            int y = workArea.Y + ((workArea.Height - physicalHeight) / 2);
+
+            // Use WindowEx's AppWindow property
+            this.AppWindow.Move(new PointInt32(x, y));
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/MainWindow.xaml

@@ -0,0 +1,427 @@
+<winuiex:WindowEx
+    x:Class="PowerDisplay.MainWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:animatedVisuals="using:Microsoft.UI.Xaml.Controls.AnimatedVisuals"
+    xmlns:animations="using:CommunityToolkit.WinUI.Animations"
+    xmlns:helpers="using:PowerDisplay.Helpers"
+    xmlns:local="using:PowerDisplay"
+    xmlns:models="using:PowerDisplay.Common.Models"
+    xmlns:toolkit="using:CommunityToolkit.WinUI.Controls"
+    xmlns:ui="using:CommunityToolkit.WinUI"
+    xmlns:vm="using:PowerDisplay.ViewModels"
+    xmlns:winuiex="using:WinUIEx"
+    MinWidth="0"
+    MinHeight="0"
+    IsMaximizable="False"
+    IsMinimizable="False"
+    IsResizable="False"
+    IsShownInSwitchers="False"
+    IsTitleBarVisible="False">
+    <winuiex:WindowEx.SystemBackdrop>
+        <DesktopAcrylicBackdrop />
+    </winuiex:WindowEx.SystemBackdrop>
+
+    <Grid x:Name="RootGrid" IsTabStop="True">
+        <Grid.Resources>
+            <Style
+                x:Key="FlyoutButtonStyle"
+                BasedOn="{StaticResource SubtleButtonStyle}"
+                TargetType="Button">
+                <Setter Property="Padding" Value="6" />
+                <Setter Property="Width" Value="32" />
+                <Setter Property="Height" Value="32" />
+                <Setter Property="FontFamily" Value="{ThemeResource SymbolThemeFontFamily}" />
+            </Style>
+        </Grid.Resources>
+        <Border x:Name="MainContainer">
+            <Grid>
+                <Grid.RowDefinitions>
+                    <RowDefinition Height="Auto" />
+                    <RowDefinition Height="48" />
+                </Grid.RowDefinitions>
+
+                <!--  Main Content Area with modern design  -->
+                <Border
+                    x:Name="ContentArea"
+                    Background="{ThemeResource LayerOnAcrylicFillColorDefaultBrush}"
+                    BorderBrush="{ThemeResource CardStrokeColorDefaultBrush}"
+                    BorderThickness="0,0,0,1">
+                    <Grid>
+                        <StackPanel
+                            Margin="0,16,0,16"
+                            HorizontalAlignment="Center"
+                            VerticalAlignment="Center"
+                            Orientation="Vertical"
+                            Spacing="16"
+                            Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ViewModel.IsScanning), Mode=OneWay}">
+                            <ProgressRing
+                                Width="24"
+                                Height="24"
+                                Foreground="{ThemeResource AccentFillColorDefaultBrush}"
+                                IsActive="True" />
+                            <TextBlock
+                                x:Name="ScanningMonitorsTextBlock"
+                                x:Uid="ScanningMonitorsText"
+                                HorizontalAlignment="Center"
+                                FontSize="12"
+                                Foreground="{ThemeResource TextFillColorSecondaryBrush}"
+                                TextAlignment="Center" />
+                        </StackPanel>
+
+                        <!--  No Monitors State with InfoBar  -->
+                        <InfoBar
+                            x:Name="NoMonitorsInfoBar"
+                            x:Uid="NoMonitorsText"
+                            IconSource="{ui:FontIconSource Glyph=&#xE7F4;}"
+                            IsClosable="False"
+                            IsOpen="{x:Bind ViewModel.ShowNoMonitorsMessage, Mode=OneWay}"
+                            Severity="Informational"
+                            Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ViewModel.ShowNoMonitorsMessage), Mode=OneWay}" />
+
+                        <!--  Content Area  -->
+                        <ScrollViewer
+                            x:Name="MainScrollViewer"
+                            Padding="16,16,16,16"
+                            VerticalAlignment="Stretch"
+                            HorizontalScrollBarVisibility="Disabled"
+                            HorizontalScrollMode="Disabled"
+                            VerticalScrollBarVisibility="Auto"
+                            ZoomMode="Disabled">
+                            <!--  Monitors List with modern card design  -->
+                            <ItemsRepeater
+                                x:Name="MonitorsRepeater"
+                                HorizontalAlignment="Stretch"
+                                ItemsSource="{x:Bind ViewModel.Monitors, Mode=OneWay}"
+                                Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ViewModel.HasMonitors), Mode=OneWay}">
+                                <ItemsRepeater.Layout>
+                                    <StackLayout Orientation="Vertical" Spacing="32" />
+                                </ItemsRepeater.Layout>
+                                <ItemsRepeater.ItemTemplate>
+                                    <DataTemplate x:DataType="vm:MonitorViewModel">
+                                        <StackPanel HorizontalAlignment="Stretch" Spacing="4">
+                                            <!--  Monitor Name with Icon  -->
+                                            <Grid Margin="2,0,0,0" HorizontalAlignment="Stretch">
+                                                <Grid.ColumnDefinitions>
+                                                    <ColumnDefinition Width="22" />
+                                                    <ColumnDefinition Width="16" />
+                                                    <!--  Spacing  -->
+                                                    <ColumnDefinition Width="*" />
+                                                </Grid.ColumnDefinitions>
+                                                <local:MonitorIcon
+                                                    VerticalAlignment="Center"
+                                                    IsBuiltIn="{x:Bind IsInternal, Mode=OneWay}"
+                                                    MonitorNumber="{x:Bind MonitorNumber, Mode=OneWay}" />
+                                                <TextBlock
+                                                    Grid.Column="2"
+                                                    Margin="0,0,0,2"
+                                                    VerticalAlignment="Center"
+                                                    Text="{x:Bind DisplayName, Mode=OneWay}" />
+                                                <Button
+                                                    Grid.Column="2"
+                                                    HorizontalAlignment="Right"
+                                                    Content="{ui:FontIcon Glyph=&#xE712;,
+                                                                          FontSize=16}"
+                                                    Style="{StaticResource SubtleButtonStyle}"
+                                                    Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ShowInputSource), Mode=OneWay}">
+                                                    <Button.Flyout>
+                                                        <Flyout>
+                                                            <StackPanel Orientation="Vertical">
+                                                                <ListView
+                                                                    ItemsSource="{x:Bind AvailableInputSources, Mode=OneWay}"
+                                                                    SelectionChanged="InputSourceListView_SelectionChanged"
+                                                                    SelectionMode="Single">
+                                                                    <ListView.Header>
+                                                                        <TextBlock
+                                                                            Margin="16,0,8,0"
+                                                                            FontSize="12"
+                                                                            Foreground="{ThemeResource TextFillColorSecondaryBrush}"
+                                                                            Text="Input source" />
+                                                                    </ListView.Header>
+                                                                    <ListView.ItemTemplate>
+                                                                        <DataTemplate x:DataType="vm:InputSourceItem">
+                                                                            <Grid Padding="0,4">
+                                                                                <Grid.ColumnDefinitions>
+                                                                                    <ColumnDefinition Width="*" />
+                                                                                    <ColumnDefinition Width="Auto" />
+                                                                                </Grid.ColumnDefinitions>
+                                                                                <TextBlock VerticalAlignment="Center" Text="{x:Bind Name}" />
+                                                                                <FontIcon
+                                                                                    Grid.Column="1"
+                                                                                    Margin="8,0,0,0"
+                                                                                    FontSize="12"
+                                                                                    Glyph="&#xE73E;"
+                                                                                    Visibility="{x:Bind SelectionVisibility}" />
+                                                                            </Grid>
+                                                                        </DataTemplate>
+                                                                    </ListView.ItemTemplate>
+                                                                </ListView>
+                                                            </StackPanel>
+                                                        </Flyout>
+                                                    </Button.Flyout>
+                                                </Button>
+                                            </Grid>
+                                            <StackPanel
+                                                Margin="0,8,0,0"
+                                                Padding="8,0,16,8"
+                                                Background="{ThemeResource LayerOnAcrylicFillColorDefaultBrush}"
+                                                BorderBrush="{ThemeResource CardStrokeColorDefaultBrush}"
+                                                BorderThickness="1"
+                                                CornerRadius="{StaticResource OverlayCornerRadius}">
+                                                <!--  Brightness Control  -->
+                                                <Grid Margin="0,8,0,0" HorizontalAlignment="Stretch">
+                                                    <Grid.ColumnDefinitions>
+                                                        <ColumnDefinition Width="16" />
+                                                        <ColumnDefinition Width="16" />
+                                                        <!--  Spacing  -->
+                                                        <ColumnDefinition Width="*" />
+                                                    </Grid.ColumnDefinitions>
+                                                    <FontIcon
+                                                        x:Uid="BrightnessTooltip"
+                                                        VerticalAlignment="Center"
+                                                        AutomationProperties.AccessibilityView="Raw"
+                                                        FontSize="18"
+                                                        Glyph="&#xEC8A;" />
+                                                    <Slider
+                                                        x:Uid="BrightnessAutomation"
+                                                        Grid.Column="2"
+                                                        HorizontalAlignment="Stretch"
+                                                        VerticalAlignment="Center"
+                                                        DataContext="{x:Bind}"
+                                                        IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                        Maximum="{x:Bind MaxBrightness, Mode=OneWay}"
+                                                        Minimum="{x:Bind MinBrightness, Mode=OneWay}"
+                                                        PointerCaptureLost="Slider_PointerCaptureLost"
+                                                        Tag="Brightness"
+                                                        Value="{x:Bind Brightness, Mode=OneWay}" />
+                                                </Grid>
+
+                                                <!--  Contrast Control  -->
+                                                <Grid
+                                                    Margin="0,8,0,0"
+                                                    HorizontalAlignment="Stretch"
+                                                    Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ShowContrast), Mode=OneWay}">
+                                                    <Grid.ColumnDefinitions>
+                                                        <ColumnDefinition Width="16" />
+                                                        <ColumnDefinition Width="16" />
+                                                        <!--  Spacing  -->
+                                                        <ColumnDefinition Width="*" />
+                                                    </Grid.ColumnDefinitions>
+
+                                                    <FontIcon
+                                                        x:Uid="ContrastTooltip"
+                                                        VerticalAlignment="Center"
+                                                        AutomationProperties.AccessibilityView="Raw"
+                                                        FontSize="12"
+                                                        Glyph="&#xE7A1;" />
+
+                                                    <Slider
+                                                        x:Uid="ContrastAutomation"
+                                                        Grid.Column="2"
+                                                        VerticalAlignment="Center"
+                                                        DataContext="{x:Bind}"
+                                                        IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                        Maximum="100"
+                                                        Minimum="0"
+                                                        PointerCaptureLost="Slider_PointerCaptureLost"
+                                                        Tag="Contrast"
+                                                        Value="{x:Bind ContrastPercent, Mode=OneWay}" />
+                                                </Grid>
+
+                                                <!--  Volume Control  -->
+                                                <Grid
+                                                    Margin="0,8,0,0"
+                                                    HorizontalAlignment="Stretch"
+                                                    Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ShowVolume), Mode=OneWay}">
+                                                    <Grid.ColumnDefinitions>
+                                                        <ColumnDefinition Width="16" />
+                                                        <ColumnDefinition Width="16" />
+                                                        <!--  Spacing  -->
+                                                        <ColumnDefinition Width="*" />
+                                                    </Grid.ColumnDefinitions>
+
+                                                    <FontIcon
+                                                        x:Uid="VolumeTooltip"
+                                                        Margin="2,0,0,0"
+                                                        VerticalAlignment="Center"
+                                                        AutomationProperties.AccessibilityView="Raw"
+                                                        FontSize="16"
+                                                        Glyph="&#xE993;" />
+                                                    <Slider
+                                                        x:Uid="VolumeAutomation"
+                                                        Grid.Column="2"
+                                                        HorizontalAlignment="Stretch"
+                                                        VerticalAlignment="Center"
+                                                        DataContext="{x:Bind}"
+                                                        IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                        Maximum="{x:Bind MaxVolume, Mode=OneWay}"
+                                                        Minimum="{x:Bind MinVolume, Mode=OneWay}"
+                                                        PointerCaptureLost="Slider_PointerCaptureLost"
+                                                        Tag="Volume"
+                                                        Value="{x:Bind Volume, Mode=OneWay}" />
+                                                </Grid>
+
+                                                <!--  Rotation Controls  -->
+                                                <Grid
+                                                    Margin="0,8,0,0"
+                                                    HorizontalAlignment="Stretch"
+                                                    Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ShowRotation), Mode=OneWay}">
+                                                    <Grid.ColumnDefinitions>
+                                                        <ColumnDefinition Width="16" />
+                                                        <ColumnDefinition Width="16" />
+                                                        <!--  Spacing  -->
+                                                        <ColumnDefinition Width="*" />
+                                                    </Grid.ColumnDefinitions>
+
+                                                    <FontIcon
+                                                        x:Uid="RotationTooltip"
+                                                        VerticalAlignment="Center"
+                                                        AutomationProperties.AccessibilityView="Raw"
+                                                        FontSize="16"
+                                                        Glyph="&#xE7AD;" />
+
+                                                    <Grid Grid.Column="2" HorizontalAlignment="Stretch">
+                                                        <Grid.ColumnDefinitions>
+                                                            <ColumnDefinition Width="*" />
+                                                            <ColumnDefinition Width="4" />
+                                                            <ColumnDefinition Width="*" />
+                                                            <ColumnDefinition Width="4" />
+                                                            <ColumnDefinition Width="*" />
+                                                            <ColumnDefinition Width="4" />
+                                                            <ColumnDefinition Width="*" />
+                                                        </Grid.ColumnDefinitions>
+                                                        <!--  Normal (0°)  -->
+                                                        <ToggleButton
+                                                            x:Uid="RotateNormalTooltip"
+                                                            Grid.Column="0"
+                                                            HorizontalAlignment="Stretch"
+                                                            Click="RotationButton_Click"
+                                                            DataContext="{x:Bind}"
+                                                            IsChecked="{x:Bind IsRotation0, Mode=OneWay}"
+                                                            IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                            Tag="0">
+                                                            <FontIcon FontSize="14" Glyph="&#xE74A;" />
+                                                        </ToggleButton>
+                                                        <!--  Left (270°)  -->
+                                                        <ToggleButton
+                                                            x:Uid="RotateLeftTooltip"
+                                                            Grid.Column="2"
+                                                            HorizontalAlignment="Stretch"
+                                                            Click="RotationButton_Click"
+                                                            DataContext="{x:Bind}"
+                                                            IsChecked="{x:Bind IsRotation3, Mode=OneWay}"
+                                                            IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                            Tag="3">
+                                                            <FontIcon FontSize="14" Glyph="&#xE76B;" />
+                                                        </ToggleButton>
+                                                        <!--  Right (90°)  -->
+                                                        <ToggleButton
+                                                            x:Uid="RotateRightTooltip"
+                                                            Grid.Column="4"
+                                                            HorizontalAlignment="Stretch"
+                                                            Click="RotationButton_Click"
+                                                            DataContext="{x:Bind}"
+                                                            IsChecked="{x:Bind IsRotation1, Mode=OneWay}"
+                                                            IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                            Tag="1">
+                                                            <FontIcon FontSize="14" Glyph="&#xE76C;" />
+                                                        </ToggleButton>
+                                                        <!--  Inverted (180°)  -->
+                                                        <ToggleButton
+                                                            x:Uid="RotateInvertedTooltip"
+                                                            Grid.Column="6"
+                                                            HorizontalAlignment="Stretch"
+                                                            Click="RotationButton_Click"
+                                                            DataContext="{x:Bind}"
+                                                            IsChecked="{x:Bind IsRotation2, Mode=OneWay}"
+                                                            IsEnabled="{x:Bind IsInteractionEnabled, Mode=OneWay}"
+                                                            Tag="2">
+                                                            <FontIcon FontSize="14" Glyph="&#xE74B;" />
+                                                        </ToggleButton>
+                                                    </Grid>
+                                                </Grid>
+                                            </StackPanel>
+                                        </StackPanel>
+                                    </DataTemplate>
+                                </ItemsRepeater.ItemTemplate>
+                            </ItemsRepeater>
+                        </ScrollViewer>
+                    </Grid>
+                </Border>
+
+                <Grid x:Name="StatusBar" Grid.Row="1">
+                    <!--  Action Buttons  -->
+                    <StackPanel
+                        Margin="0,0,8,8"
+                        HorizontalAlignment="Right"
+                        VerticalAlignment="Center"
+                        Orientation="Horizontal"
+                        Spacing="8">
+                        <Button
+                            x:Name="ProfilesButton"
+                            x:Uid="ProfilesTooltip"
+                            Content="{ui:FontIcon Glyph=&#xE748;,
+                                                  FontSize=16}"
+                            Style="{StaticResource SubtleButtonStyle}"
+                            Visibility="{x:Bind helpers:VisibilityConverter.BoolToVisibility(ViewModel.HasProfiles), Mode=OneWay}">
+                            <Button.Flyout>
+                                <Flyout x:Name="ProfilesFlyout">
+                                    <ListView
+                                        x:Name="ProfilesListView"
+                                        ItemsSource="{x:Bind ViewModel.Profiles, Mode=OneWay}"
+                                        SelectionChanged="ProfileListView_SelectionChanged"
+                                        SelectionMode="Single">
+                                        <ListView.Header>
+                                            <TextBlock
+                                                Margin="16,0,8,0"
+                                                FontSize="12"
+                                                Foreground="{ThemeResource TextFillColorSecondaryBrush}"
+                                                Text="Profiles" />
+                                        </ListView.Header>
+                                        <ListView.ItemTemplate>
+                                            <DataTemplate x:DataType="models:PowerDisplayProfile">
+                                                <TextBlock Padding="0,4" Text="{x:Bind Name}" />
+                                            </DataTemplate>
+                                        </ListView.ItemTemplate>
+                                    </ListView>
+                                </Flyout>
+                            </Button.Flyout>
+                        </Button>
+                        <Button
+                            x:Name="RefreshButton"
+                            x:Uid="RefreshTooltip"
+                            Click="OnRefreshClick"
+                            Content="{ui:FontIcon Glyph=&#xE72C;,
+                                                  FontSize=16}"
+                            Style="{StaticResource SubtleButtonStyle}" />
+                        <Button
+                            x:Name="IdentifyButton"
+                            x:Uid="IdentifyTooltip"
+                            Command="{x:Bind ViewModel.IdentifyMonitorsCommand}"
+                            Content="{ui:FontIcon Glyph=&#xE9D9;,
+                                                  FontSize=16}"
+                            Style="{StaticResource SubtleButtonStyle}" />
+                        <Button
+                            x:Name="SettingsBtn"
+                            x:Uid="SettingsTooltip"
+                            Padding="6"
+                            Click="OnSettingsClick"
+                            Style="{StaticResource FlyoutButtonStyle}">
+                            <ToolTipService.ToolTip>
+                                <TextBlock x:Uid="SettingsTooltip" />
+                            </ToolTipService.ToolTip>
+                            <AnimatedIcon x:Name="SearchAnimatedIcon">
+                                <AnimatedIcon.Source>
+                                    <animatedVisuals:AnimatedSettingsVisualSource />
+                                </AnimatedIcon.Source>
+                                <AnimatedIcon.FallbackIconSource>
+                                    <SymbolIconSource Symbol="Setting" />
+                                </AnimatedIcon.FallbackIconSource>
+                            </AnimatedIcon>
+                        </Button>
+                    </StackPanel>
+                </Grid>
+            </Grid>
+        </Border>
+    </Grid>
+</winuiex:WindowEx>

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/MainWindow.xaml.cs

@@ -0,0 +1,563 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.UI.Windowing;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using PowerDisplay.Common.Models;
+using PowerDisplay.Configuration;
+using PowerDisplay.Helpers;
+using PowerDisplay.ViewModels;
+using Windows.Graphics;
+using WinUIEx;
+using Monitor = PowerDisplay.Common.Models.Monitor;
+
+namespace PowerDisplay
+{
+    /// <summary>
+    /// PowerDisplay main window
+    /// </summary>
+    [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicProperties | DynamicallyAccessedMemberTypes.PublicMethods)]
+    public sealed partial class MainWindow : WindowEx, IDisposable
+    {
+        private readonly SettingsUtils _settingsUtils = SettingsUtils.Default;
+        private MainViewModel? _viewModel;
+        private HotkeyService? _hotkeyService;
+
+        // Expose ViewModel as property for x:Bind
+        public MainViewModel ViewModel => _viewModel ?? throw new InvalidOperationException("ViewModel not initialized");
+
+        public MainWindow()
+        {
+            Logger.LogInfo("MainWindow constructor: Starting");
+            try
+            {
+                // 1. Create ViewModel BEFORE InitializeComponent to avoid x:Bind failures
+                // x:Bind evaluates during InitializeComponent, so ViewModel must exist first
+                Logger.LogTrace("MainWindow constructor: Creating MainViewModel");
+                _viewModel = new MainViewModel();
+                Logger.LogTrace("MainWindow constructor: MainViewModel created");
+
+                Logger.LogTrace("MainWindow constructor: Calling InitializeComponent");
+                this.InitializeComponent();
+                Logger.LogTrace("MainWindow constructor: InitializeComponent completed");
+
+                // 2. Configure window immediately (synchronous, no data dependency)
+                Logger.LogTrace("MainWindow constructor: Configuring window");
+                ConfigureWindow();
+
+                // 3. Set up data context and update bindings
+                RootGrid.DataContext = _viewModel;
+                Bindings.Update();
+                Logger.LogTrace("MainWindow constructor: Data context set and bindings updated");
+
+                // 4. Register event handlers
+                RegisterEventHandlers();
+                Logger.LogTrace("MainWindow constructor: Event handlers registered");
+
+                // 5. Initialize HotkeyService for in-process hotkey handling (CmdPal pattern)
+                // This avoids IPC timing issues with Runner's centralized hotkey mechanism
+                Logger.LogTrace("MainWindow constructor: Initializing HotkeyService");
+                _hotkeyService = new HotkeyService(_settingsUtils, ToggleWindow);
+                _hotkeyService.Initialize(this);
+                Logger.LogTrace("MainWindow constructor: HotkeyService initialized");
+
+                // Note: ViewModel handles all async initialization internally.
+                // We listen to InitializationCompleted event to know when data is ready.
+                // No duplicate initialization here - single responsibility in ViewModel.
+                Logger.LogInfo("MainWindow constructor: Completed");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"MainWindow constructor: Initialization failed: {ex.Message}\n{ex.StackTrace}");
+                ShowError($"Unable to start main window: {ex.Message}");
+            }
+        }
+
+        /// <summary>
+        /// Register all event handlers for window and ViewModel
+        /// </summary>
+        private void RegisterEventHandlers()
+        {
+            // Window events
+            this.Closed += OnWindowClosed;
+            this.Activated += OnWindowActivated;
+
+            // ViewModel events - _viewModel is guaranteed non-null here as this is called after initialization
+            if (_viewModel != null)
+            {
+                _viewModel.InitializationCompleted += OnViewModelInitializationCompleted;
+                _viewModel.UIRefreshRequested += OnUIRefreshRequested;
+                _viewModel.Monitors.CollectionChanged += OnMonitorsCollectionChanged;
+                _viewModel.PropertyChanged += OnViewModelPropertyChanged;
+            }
+        }
+
+        /// <summary>
+        /// Called when ViewModel completes initial monitor discovery.
+        /// This is the single source of truth for initialization state.
+        /// </summary>
+        private void OnViewModelInitializationCompleted(object? sender, EventArgs e)
+        {
+            _hasInitialized = true;
+            Logger.LogInfo("MainWindow: Initialization completed via ViewModel event, _hasInitialized=true");
+            AdjustWindowSizeToContent();
+        }
+
+        private bool _hasInitialized;
+
+        private void ShowError(string message)
+        {
+            Logger.LogError($"Error: {message}");
+        }
+
+        private void OnWindowActivated(object sender, WindowActivatedEventArgs args)
+        {
+            Logger.LogTrace($"OnWindowActivated: WindowActivationState={args.WindowActivationState}");
+
+            // Auto-hide window when it loses focus (deactivated)
+            if (args.WindowActivationState == WindowActivationState.Deactivated)
+            {
+                Logger.LogInfo("OnWindowActivated: Window deactivated, hiding window");
+                HideWindow();
+            }
+        }
+
+        private void OnWindowClosed(object sender, WindowEventArgs args)
+        {
+            // If only user operation (although we hide close button), just hide window
+            args.Handled = true; // Prevent window closing
+            HideWindow();
+        }
+
+        public void ShowWindow()
+        {
+            Logger.LogInfo($"ShowWindow: Called, _hasInitialized={_hasInitialized}");
+            try
+            {
+                // If not initialized, log warning but continue showing
+                if (!_hasInitialized)
+                {
+                    Logger.LogWarning("ShowWindow: Window not fully initialized yet, showing anyway");
+                }
+
+                // Adjust size BEFORE showing to prevent flicker
+                // This measures content and positions window at correct size
+                Logger.LogTrace("ShowWindow: Adjusting window size to content");
+                AdjustWindowSizeToContent();
+
+                // CRITICAL: WinUI3 windows must be Activated at least once to display properly.
+                // In PowerToys mode, window is created but never activated until first show.
+                // Without Activate(), Show() may not actually render the window on screen.
+                Logger.LogTrace("ShowWindow: Calling this.Activate()");
+                this.Activate();
+
+                // Now show the window - it should appear at the correct size (WinUIEx simplified)
+                Logger.LogTrace("ShowWindow: Calling this.Show()");
+                this.Show();
+
+                // Ensure window stays on top of other windows
+                this.IsAlwaysOnTop = true;
+                Logger.LogTrace("ShowWindow: IsAlwaysOnTop set to true");
+
+                // Clear focus from any interactive element (e.g., Slider) to prevent
+                // showing the value tooltip when the window opens
+                RootGrid.Focus(FocusState.Programmatic);
+
+                // Verify window is visible
+                bool isVisible = IsWindowVisible();
+                Logger.LogInfo($"ShowWindow: Window visibility after show: {isVisible}");
+                if (!isVisible)
+                {
+                    Logger.LogError("ShowWindow: Window not visible after show attempt, forcing visibility");
+                    this.Activate();
+                    this.Show();
+                    this.BringToFront();
+                    Logger.LogInfo($"ShowWindow: After forced show, visibility: {IsWindowVisible()}");
+                }
+                else
+                {
+                    Logger.LogInfo("ShowWindow: Window shown successfully");
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"ShowWindow: Failed to show window: {ex.Message}\n{ex.StackTrace}");
+                throw;
+            }
+        }
+
+        public void HideWindow()
+        {
+            Logger.LogInfo("HideWindow: Hiding window");
+
+            // Hide window using WinUIEx simplified API
+            this.Hide();
+
+            Logger.LogTrace($"HideWindow: Window hidden, visibility now: {IsWindowVisible()}");
+        }
+
+        /// <summary>
+        /// Check if window is currently visible
+        /// </summary>
+        /// <returns>True if window is visible, false otherwise</returns>
+        public bool IsWindowVisible()
+        {
+            // Use WinUIEx Visible property
+            bool visible = this.Visible;
+            Logger.LogTrace($"IsWindowVisible: Returning {visible}");
+            return visible;
+        }
+
+        /// <summary>
+        /// Toggle window visibility (show if hidden, hide if visible)
+        /// </summary>
+        public void ToggleWindow()
+        {
+            bool currentlyVisible = IsWindowVisible();
+            Logger.LogInfo($"ToggleWindow: Called, current visibility={currentlyVisible}");
+            try
+            {
+                if (currentlyVisible)
+                {
+                    Logger.LogInfo("ToggleWindow: Window is visible, hiding");
+                    HideWindow();
+                }
+                else
+                {
+                    Logger.LogInfo("ToggleWindow: Window is hidden, showing");
+                    ShowWindow();
+                }
+
+                Logger.LogInfo($"ToggleWindow: Completed, new visibility={IsWindowVisible()}");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"ToggleWindow: Failed to toggle window: {ex.Message}\n{ex.StackTrace}");
+                throw;
+            }
+        }
+
+        private void OnUIRefreshRequested(object? sender, EventArgs e)
+        {
+            // Adjust window size when UI configuration changes (feature visibility toggles)
+            DispatcherQueue.TryEnqueue(() => AdjustWindowSizeToContent());
+        }
+
+        private void OnMonitorsCollectionChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
+        {
+            // Adjust window size when monitors collection changes (event-driven!)
+            // The UI binding will update first, then we adjust size
+            DispatcherQueue.TryEnqueue(Microsoft.UI.Dispatching.DispatcherQueuePriority.Low, () =>
+            {
+                AdjustWindowSizeToContent();
+            });
+        }
+
+        private void OnViewModelPropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
+        {
+            // Adjust window size when relevant properties change (event-driven!)
+            if (e.PropertyName == nameof(_viewModel.IsScanning) ||
+                e.PropertyName == nameof(_viewModel.HasMonitors) ||
+                e.PropertyName == nameof(_viewModel.ShowNoMonitorsMessage))
+            {
+                // Use Low priority to ensure UI bindings update first
+                DispatcherQueue.TryEnqueue(Microsoft.UI.Dispatching.DispatcherQueuePriority.Low, () =>
+                {
+                    AdjustWindowSizeToContent();
+                });
+            }
+        }
+
+        private void OnRefreshClick(object sender, RoutedEventArgs e)
+        {
+            try
+            {
+                // Refresh monitor list
+                if (_viewModel?.RefreshCommand?.CanExecute(null) == true)
+                {
+                    _viewModel.RefreshCommand.Execute(null);
+
+                    // Window size will be adjusted automatically by OnMonitorsCollectionChanged event!
+                    // No delay needed - event-driven design
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"OnRefreshClick failed: {ex}");
+            }
+        }
+
+        private void OnSettingsClick(object sender, RoutedEventArgs e)
+        {
+            // Open PowerDisplay settings in PowerToys Settings UI
+            // mainExecutableIsOnTheParentFolder = true because PowerDisplay is a WinUI 3 app
+            // deployed in a subfolder (PowerDisplay\) while PowerToys.exe is in the parent folder
+            SettingsDeepLink.OpenSettings(SettingsDeepLink.SettingsWindow.PowerDisplay, true);
+        }
+
+        /// <summary>
+        /// Configure window properties (synchronous, no data dependency)
+        /// </summary>
+        private void ConfigureWindow()
+        {
+            try
+            {
+                // Window properties (IsResizable, IsMaximizable, IsMinimizable,
+                // IsTitleBarVisible, IsShownInSwitchers) are set in XAML
+
+                // Set minimal initial window size - will be adjusted before showing
+                // Using minimal height to prevent "large window shrinking" flicker
+                this.AppWindow.Resize(new SizeInt32 { Width = AppConstants.UI.WindowWidth, Height = 100 });
+
+                // Position window at bottom right corner
+                PositionWindowAtBottomRight();
+
+                // Set window title
+                this.AppWindow.Title = "PowerDisplay";
+
+                // Custom title bar - completely remove all buttons
+                var titleBar = this.AppWindow.TitleBar;
+                if (titleBar != null)
+                {
+                    // Extend content into title bar area
+                    titleBar.ExtendsContentIntoTitleBar = true;
+
+                    // Completely remove title bar height
+                    titleBar.PreferredHeightOption = TitleBarHeightOption.Collapsed;
+
+                    // Set all button colors to transparent
+                    titleBar.ButtonBackgroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonInactiveBackgroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonForegroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonHoverBackgroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonHoverForegroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonPressedBackgroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonPressedForegroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+                    titleBar.ButtonInactiveForegroundColor = Windows.UI.Color.FromArgb(0, 0, 0, 0);
+
+                    // Disable title bar interaction area
+                    titleBar.SetDragRectangles(Array.Empty<Windows.Graphics.RectInt32>());
+                }
+
+                // Use Win32 API to further disable window moving (removes WS_CAPTION, WS_SYSMENU, etc.)
+                var hWnd = this.GetWindowHandle();
+                WindowHelper.DisableWindowMovingAndResizing(hWnd);
+            }
+            catch (Exception ex)
+            {
+                // Ignore window setup errors
+                Logger.LogWarning($"Window configuration error: {ex.Message}");
+            }
+        }
+
+        private void AdjustWindowSizeToContent()
+        {
+            try
+            {
+                if (RootGrid == null)
+                {
+                    return;
+                }
+
+                // Force layout update and measure content height
+                RootGrid.UpdateLayout();
+                MainContainer?.Measure(new Windows.Foundation.Size(AppConstants.UI.WindowWidth, double.PositiveInfinity));
+                var contentHeight = (int)Math.Ceiling(MainContainer?.DesiredSize.Height ?? 0);
+
+                // Apply min/max height limits and reposition (WindowEx handles DPI automatically)
+                // Min height ensures window is visible even if content hasn't loaded yet
+                var finalHeight = Math.Max(AppConstants.UI.MinWindowHeight, Math.Min(contentHeight, AppConstants.UI.MaxWindowHeight));
+                Logger.LogTrace($"AdjustWindowSizeToContent: contentHeight={contentHeight}, finalHeight={finalHeight}");
+                WindowHelper.PositionWindowBottomRight(this, AppConstants.UI.WindowWidth, finalHeight, AppConstants.UI.WindowRightMargin);
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Error adjusting window size: {ex.Message}");
+            }
+        }
+
+        private void PositionWindowAtBottomRight()
+        {
+            try
+            {
+                var windowSize = this.AppWindow.Size;
+                WindowHelper.PositionWindowBottomRight(
+                    this,  // MainWindow inherits from WindowEx
+                    AppConstants.UI.WindowWidth,
+                    windowSize.Height,
+                    AppConstants.UI.WindowRightMargin);
+            }
+            catch (Exception)
+            {
+                // Window positioning failures are non-critical, silently ignore
+            }
+        }
+
+        /// <summary>
+        /// Slider PointerCaptureLost event handler - updates ViewModel when drag completes
+        /// This is the WinUI3 recommended way to detect drag completion
+        /// </summary>
+        private void Slider_PointerCaptureLost(object sender, Microsoft.UI.Xaml.Input.PointerRoutedEventArgs e)
+        {
+            var slider = sender as Slider;
+            if (slider == null)
+            {
+                return;
+            }
+
+            var propertyName = slider.Tag as string;
+            var monitorVm = slider.DataContext as MonitorViewModel;
+
+            if (monitorVm == null || propertyName == null)
+            {
+                return;
+            }
+
+            // Get final value after drag completes
+            int finalValue = (int)slider.Value;
+
+            // Now update the ViewModel, which will trigger hardware operation
+            switch (propertyName)
+            {
+                case "Brightness":
+                    monitorVm.Brightness = finalValue;
+                    break;
+
+                // ColorTemperature case removed - now controlled via Settings UI
+                case "Contrast":
+                    monitorVm.ContrastPercent = finalValue;
+                    break;
+                case "Volume":
+                    monitorVm.Volume = finalValue;
+                    break;
+            }
+        }
+
+        /// <summary>
+        /// Input source ListView selection changed handler - switches the monitor input source
+        /// </summary>
+        private async void InputSourceListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            if (sender is not ListView listView)
+            {
+                return;
+            }
+
+            // Get the selected input source item
+            var selectedItem = listView.SelectedItem as InputSourceItem;
+            if (selectedItem == null)
+            {
+                return;
+            }
+
+            Logger.LogInfo($"[UI] InputSourceListView_SelectionChanged: Selected {selectedItem.Name} (0x{selectedItem.Value:X2}) for monitor {selectedItem.MonitorId}");
+
+            // Find the monitor by ID
+            MonitorViewModel? monitorVm = null;
+            if (!string.IsNullOrEmpty(selectedItem.MonitorId) && _viewModel != null)
+            {
+                monitorVm = _viewModel.Monitors.FirstOrDefault(m => m.Id == selectedItem.MonitorId);
+            }
+
+            if (monitorVm == null)
+            {
+                Logger.LogWarning("[UI] InputSourceListView_SelectionChanged: Could not find MonitorViewModel");
+                return;
+            }
+
+            // Set the input source
+            await monitorVm.SetInputSourceAsync(selectedItem.Value);
+        }
+
+        /// <summary>
+        /// Rotation button click handler - changes monitor orientation
+        /// </summary>
+        private async void RotationButton_Click(object sender, RoutedEventArgs e)
+        {
+            if (sender is not Microsoft.UI.Xaml.Controls.Primitives.ToggleButton toggleButton)
+            {
+                return;
+            }
+
+            // Get the orientation from the Tag
+            if (toggleButton.Tag is not string tagStr || !int.TryParse(tagStr, out int orientation))
+            {
+                Logger.LogWarning("[UI] RotationButton_Click: Invalid Tag");
+                return;
+            }
+
+            var monitorVm = toggleButton.DataContext as MonitorViewModel;
+            if (monitorVm == null)
+            {
+                Logger.LogWarning("[UI] RotationButton_Click: Could not find MonitorViewModel");
+                return;
+            }
+
+            // If clicking the current orientation, restore the checked state and do nothing
+            if (monitorVm.CurrentRotation == orientation)
+            {
+                toggleButton.IsChecked = true;
+                return;
+            }
+
+            Logger.LogInfo($"[UI] RotationButton_Click: Setting rotation for {monitorVm.Name} to {orientation}");
+
+            // Set the rotation
+            await monitorVm.SetRotationAsync(orientation);
+        }
+
+        /// <summary>
+        /// Profile selection changed handler - applies the selected profile
+        /// </summary>
+        private void ProfileListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            if (sender is not ListView listView)
+            {
+                return;
+            }
+
+            var selectedProfile = listView.SelectedItem as PowerDisplayProfile;
+            if (selectedProfile == null || !selectedProfile.IsValid())
+            {
+                return;
+            }
+
+            Logger.LogInfo($"[UI] ProfileListView_SelectionChanged: Applying profile '{selectedProfile.Name}'");
+
+            // Apply profile via ViewModel command
+            if (_viewModel?.ApplyProfileCommand?.CanExecute(selectedProfile) == true)
+            {
+                _viewModel.ApplyProfileCommand.Execute(selectedProfile);
+            }
+
+            // Close the flyout after selection
+            ProfilesFlyout?.Hide();
+
+            // Clear selection to allow reselecting the same profile
+            listView.SelectedItem = null;
+        }
+
+        public void Dispose()
+        {
+            _hotkeyService?.Dispose();
+            _viewModel?.Dispose();
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Reload hotkey settings. Call this when settings change.
+        /// </summary>
+        public void ReloadHotkeySettings()
+        {
+            _hotkeyService?.ReloadSettings();
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/MonitorIcon.xaml

@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<UserControl
+    x:Class="PowerDisplay.MonitorIcon"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:local="using:PowerDisplay"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d">
+
+    <Grid>
+        <Viewbox>
+            <Grid>
+                <Grid x:Name="MonitorGrid">
+                    <FontIcon
+                        x:Uid="MonitorTooltip"
+                        VerticalAlignment="Center"
+                        AutomationProperties.AccessibilityView="Raw"
+                        FontSize="22"
+                        Glyph="&#xE7F4;" />
+                    <TextBlock
+                        Margin="0,0,0,4"
+                        HorizontalAlignment="Center"
+                        VerticalAlignment="Center"
+                        FontSize="10"
+                        FontWeight="SemiBold"
+                        Text="{x:Bind MonitorNumber, Mode=OneWay}" />
+                </Grid>
+
+                <Grid
+                    x:Name="BuiltInDisplayGrid"
+                    Padding="0,0,0,-4"
+                    Visibility="Collapsed">
+                    <FontIcon
+                        x:Uid="MonitorTooltip"
+                        Margin="0,0,0,0"
+                        VerticalAlignment="Center"
+                        AutomationProperties.AccessibilityView="Raw"
+                        FontSize="22"
+                        Glyph="&#xE7FB;" />
+                    <TextBlock
+                        Margin="0,0,0,6"
+                        HorizontalAlignment="Center"
+                        VerticalAlignment="Center"
+                        FontSize="10"
+                        FontWeight="SemiBold"
+                        Text="{x:Bind MonitorNumber, Mode=OneWay}" />
+                </Grid>
+            </Grid>
+        </Viewbox>
+        <VisualStateManager.VisualStateGroups>
+            <VisualStateGroup x:Name="CommonStates">
+                <VisualState x:Name="Monitor" />
+                <VisualState x:Name="BuiltIn">
+                    <VisualState.Setters>
+                        <Setter Target="BuiltInDisplayGrid.Visibility" Value="Visible" />
+                        <Setter Target="MonitorGrid.Visibility" Value="Collapsed" />
+                    </VisualState.Setters>
+                </VisualState>
+            </VisualStateGroup>
+        </VisualStateManager.VisualStateGroups>
+    </Grid>
+</UserControl>

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/MonitorIcon.xaml.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace PowerDisplay;
+
+public sealed partial class MonitorIcon : UserControl
+{
+    public MonitorIcon()
+    {
+        InitializeComponent();
+    }
+
+    public bool IsBuiltIn
+    {
+        get => (bool)GetValue(IsBuiltInProperty);
+        set => SetValue(IsBuiltInProperty, value);
+    }
+
+    public static readonly DependencyProperty IsBuiltInProperty = DependencyProperty.Register(nameof(IsBuiltIn), typeof(bool), typeof(MonitorIcon), new PropertyMetadata(false, OnPropertyChanged));
+
+    public int MonitorNumber
+    {
+        get => (int)GetValue(MonitorNumberProperty);
+        set => SetValue(MonitorNumberProperty, value);
+    }
+
+    public static readonly DependencyProperty MonitorNumberProperty = DependencyProperty.Register(nameof(MonitorNumber), typeof(int), typeof(MonitorIcon), new PropertyMetadata(0, OnPropertyChanged));
+
+    private static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        var monIcon = (MonitorIcon)d;
+        if (monIcon.IsBuiltIn)
+        {
+            VisualStateManager.GoToState(monIcon, "BuiltIn", true);
+        }
+        else
+        {
+            VisualStateManager.GoToState(monIcon, "Monitor", true);
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Program.cs

@@ -0,0 +1,163 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Microsoft.UI.Dispatching;
+using Microsoft.Windows.AppLifecycle;
+
+namespace PowerDisplay
+{
+    public static partial class Program
+    {
+        private static App? _app;
+
+        // LibraryImport for AOT compatibility - COM wait constants
+        private const uint CowaitDefault = 0;
+        private const uint InfiniteTimeout = 0xFFFFFFFF;
+
+        [LibraryImport("ole32.dll")]
+        private static partial int CoWaitForMultipleObjects(
+            uint dwFlags,
+            uint dwTimeout,
+            int cHandles,
+            nint[] pHandles,
+            out uint lpdwIndex);
+
+        [STAThread]
+        public static int Main(string[] args)
+        {
+            // Initialize COM wrappers first (needed for AppInstance)
+            WinRT.ComWrappersSupport.InitializeComWrappers();
+
+            // Single instance check BEFORE logger initialization to avoid creating extra log files
+            // Command Palette pattern: check for existing instance first
+            var activationArgs = AppInstance.GetCurrent().GetActivatedEventArgs();
+            var keyInstance = AppInstance.FindOrRegisterForKey("PowerToys_PowerDisplay_Instance");
+
+            if (!keyInstance.IsCurrent)
+            {
+                // Another instance exists - redirect and exit WITHOUT initializing logger
+                // This prevents creation of extra log files for short-lived redirect processes
+                RedirectActivationTo(activationArgs, keyInstance);
+                return 0;
+            }
+
+            // This is the primary instance - now initialize logger
+            Logger.InitializeLogger("\\PowerDisplay\\Logs");
+            Logger.LogInfo("=== PowerDisplay Process Starting (Primary Instance) ===");
+            Logger.LogInfo($"Main: Process ID = {Environment.ProcessId}");
+            Logger.LogInfo($"Main: Command line args count = {args.Length}");
+
+            for (int i = 0; i < args.Length; i++)
+            {
+                Logger.LogInfo($"Main: args[{i}] = '{args[i]}'");
+            }
+
+            // Register activation handler for future redirects
+            keyInstance.Activated += OnActivated;
+
+            // Parse command line arguments: args[0] = runner_pid (Awake pattern)
+            int runnerPid = -1;
+
+            if (args.Length >= 1)
+            {
+                if (int.TryParse(args[0], out int parsedPid))
+                {
+                    runnerPid = parsedPid;
+                    Logger.LogInfo($"Main: Parsed runner_pid={runnerPid} from args[0]");
+                }
+                else
+                {
+                    Logger.LogWarning($"Main: Failed to parse PID from args[0]: '{args[0]}'");
+                }
+            }
+            else
+            {
+                Logger.LogWarning("Main: No command line args provided. Running in standalone mode.");
+            }
+
+            Logger.LogInfo("Main: Starting application");
+            Microsoft.UI.Xaml.Application.Start((p) =>
+            {
+                Logger.LogTrace("Main: Application.Start callback - setting up SynchronizationContext");
+                var context = new DispatcherQueueSynchronizationContext(DispatcherQueue.GetForCurrentThread());
+                SynchronizationContext.SetSynchronizationContext(context);
+                Logger.LogTrace("Main: Creating App instance");
+                _app = new App(runnerPid);
+                Logger.LogTrace("Main: App instance created");
+            });
+
+            Logger.LogInfo("Main: Application.Start returned, process ending");
+            return 0;
+        }
+
+        /// <summary>
+        /// Redirect activation to existing instance (Command Palette pattern)
+        /// Called BEFORE logger is initialized, so no logging here
+        /// </summary>
+        private static void RedirectActivationTo(AppActivationArguments args, AppInstance keyInstance)
+        {
+            // Do the redirection on another thread, and use a non-blocking
+            // wait method to wait for the redirection to complete.
+            using var redirectSemaphore = new Semaphore(0, 1);
+            var redirectTimeout = TimeSpan.FromSeconds(10);
+
+            _ = Task.Run(() =>
+            {
+                using var cts = new CancellationTokenSource(redirectTimeout);
+                try
+                {
+                    keyInstance.RedirectActivationToAsync(args)
+                        .AsTask(cts.Token)
+                        .GetAwaiter()
+                        .GetResult();
+                }
+                catch
+                {
+                    // Silently ignore errors - logger not initialized yet
+                }
+                finally
+                {
+                    redirectSemaphore.Release();
+                }
+            });
+
+            // Use CoWaitForMultipleObjects to pump COM messages while waiting
+            nint[] handles = [redirectSemaphore.SafeWaitHandle.DangerousGetHandle()];
+            _ = CoWaitForMultipleObjects(
+                CowaitDefault,
+                InfiniteTimeout,
+                1,
+                handles,
+                out _);
+        }
+
+        /// <summary>
+        /// Called when an existing instance is activated by another process
+        /// </summary>
+        private static void OnActivated(object? sender, AppActivationArguments args)
+        {
+            Logger.LogInfo("OnActivated: Received activation from another instance");
+
+            // Toggle the window visibility when activated by another instance
+            if (_app?.MainWindow is MainWindow mainWindow)
+            {
+                Logger.LogInfo("OnActivated: Showing/toggling main window");
+                mainWindow.DispatcherQueue.TryEnqueue(() =>
+                {
+                    Logger.LogTrace("OnActivated: Executing ShowWindow on UI thread");
+                    mainWindow.ShowWindow();
+                });
+            }
+            else
+            {
+                Logger.LogWarning("OnActivated: MainWindow not available");
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Serialization/JsonSourceGenerationContext.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.PowerToys.Settings.UI.Library;
+using PowerDisplay.Common.Models;
+
+#pragma warning disable SA1402 // File may only contain a single type - Related JSON serialization types grouped together
+
+namespace PowerDisplay.Serialization
+{
+    /// <summary>
+    /// JSON source generation context for AOT compatibility.
+    /// Eliminates reflection-based JSON serialization.
+    /// Note: MonitorStateFile and MonitorStateEntry are now in PowerDisplay.Lib
+    /// and should be serialized using ProfileSerializationContext from the Lib.
+    /// </summary>
+    [JsonSerializable(typeof(MonitorInfoData))]
+    [JsonSerializable(typeof(IPCMessageAction))]
+    [JsonSerializable(typeof(PowerDisplaySettings))]
+    [JsonSerializable(typeof(ColorTemperatureOperation))]
+    [JsonSerializable(typeof(ProfileOperation))]
+    [JsonSerializable(typeof(PowerDisplayProfiles))]
+    [JsonSerializable(typeof(PowerDisplayProfile))]
+    [JsonSerializable(typeof(ProfileMonitorSetting))]
+
+    // MonitorInfo and related types (Settings.UI.Library)
+    [JsonSerializable(typeof(MonitorInfo))]
+    [JsonSerializable(typeof(VcpCodeDisplayInfo))]
+    [JsonSerializable(typeof(VcpValueInfo))]
+
+    // Generic collection types
+    [JsonSerializable(typeof(List<string>))]
+    [JsonSerializable(typeof(List<MonitorInfo>))]
+    [JsonSerializable(typeof(List<VcpCodeDisplayInfo>))]
+    [JsonSerializable(typeof(List<VcpValueInfo>))]
+    [JsonSerializable(typeof(List<PowerDisplayProfile>))]
+    [JsonSerializable(typeof(List<ProfileMonitorSetting>))]
+
+    [JsonSourceGenerationOptions(
+        WriteIndented = true,
+        PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase,
+        DefaultIgnoreCondition = JsonIgnoreCondition.Never)]
+    internal sealed partial class AppJsonContext : JsonSerializerContext
+    {
+    }
+
+    /// <summary>
+    /// IPC message wrapper for parsing action-based messages.
+    /// Used in App.xaml.cs for dynamic IPC command handling.
+    /// </summary>
+    internal sealed class IPCMessageAction
+    {
+        [JsonPropertyName("action")]
+        public string? Action { get; set; }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Services/LightSwitchService.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Library;
+using Settings.UI.Library;
+
+namespace PowerDisplay.Services
+{
+    /// <summary>
+    /// Service for handling LightSwitch theme change events.
+    /// Reads LightSwitch settings using the standard PowerToys settings pattern.
+    /// </summary>
+    public static class LightSwitchService
+    {
+        private const string LogPrefix = "[LightSwitch]";
+
+        /// <summary>
+        /// Get the profile name to apply for the given theme.
+        /// </summary>
+        /// <param name="isLightMode">Whether the theme changed to light mode.</param>
+        /// <returns>The profile name to apply, or null if no profile is configured.</returns>
+        public static string? GetProfileForTheme(bool isLightMode)
+        {
+            try
+            {
+                Logger.LogInfo($"{LogPrefix} Processing theme change to {(isLightMode ? "light" : "dark")} mode");
+
+                var settings = SettingsUtils.Default.GetSettingsOrDefault<LightSwitchSettings>(LightSwitchSettings.ModuleName);
+
+                if (settings?.Properties == null)
+                {
+                    Logger.LogWarning($"{LogPrefix} LightSwitch settings not found");
+                    return null;
+                }
+
+                string? profileName;
+                if (isLightMode)
+                {
+                    if (!settings.Properties.EnableLightModeProfile.Value)
+                    {
+                        Logger.LogInfo($"{LogPrefix} Light mode profile is disabled");
+                        return null;
+                    }
+
+                    profileName = settings.Properties.LightModeProfile.Value;
+                }
+                else
+                {
+                    if (!settings.Properties.EnableDarkModeProfile.Value)
+                    {
+                        Logger.LogInfo($"{LogPrefix} Dark mode profile is disabled");
+                        return null;
+                    }
+
+                    profileName = settings.Properties.DarkModeProfile.Value;
+                }
+
+                if (string.IsNullOrEmpty(profileName) || profileName == "(None)")
+                {
+                    Logger.LogInfo($"{LogPrefix} No profile configured for {(isLightMode ? "light" : "dark")} mode");
+                    return null;
+                }
+
+                Logger.LogInfo($"{LogPrefix} Profile to apply: {profileName}");
+                return profileName;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"{LogPrefix} Failed to get profile for theme: {ex.Message}");
+                return null;
+            }
+        }
+    }
+}