diff --git a/backend/open_webui/routers/files.py b/backend/open_webui/routers/files.py
index 9022ca66ff..5fbbbf3cc4 100644
--- a/backend/open_webui/routers/files.py
+++ b/backend/open_webui/routers/files.py
@@ -121,6 +121,27 @@ def has_access_to_file(
 ############################
 
 
+def _is_text_file(file_path: str, chunk_size: int = 8192) -> bool:
+    """Check if a file is likely a text file by reading a chunk and validating UTF-8.
+
+    This catches files whose extensions are mis-mapped by mimetypes/browsers
+    (e.g. TypeScript .ts → video/mp2t) without maintaining an extension whitelist.
+    """
+    try:
+        resolved = Storage.get_file(file_path)
+        with open(resolved, "rb") as f:
+            chunk = f.read(chunk_size)
+        if not chunk:
+            return False
+        # Null bytes are a strong indicator of binary content
+        if b"\x00" in chunk:
+            return False
+        chunk.decode("utf-8")
+        return True
+    except (UnicodeDecodeError, Exception):
+        return False
+
+
 def process_uploaded_file(
     request,
     file,
@@ -132,13 +153,20 @@ def process_uploaded_file(
 ):
     def _process_handler(db_session):
         try:
-            if file.content_type:
+            content_type = file.content_type
+
+            # Detect mis-labeled text files (e.g. .ts → video/mp2t)
+            if content_type and content_type.startswith(("image/", "video/")):
+                if _is_text_file(file_path):
+                    content_type = "text/plain"
+
+            if content_type:
                 stt_supported_content_types = getattr(
                     request.app.state.config, "STT_SUPPORTED_CONTENT_TYPES", []
                 )
 
                 if strict_match_mime_type(
-                    stt_supported_content_types, file.content_type
+                    stt_supported_content_types, content_type
                 ):
                     file_path_processed = Storage.get_file(file_path)
                     result = transcribe(
@@ -153,7 +181,7 @@ def process_uploaded_file(
                         user=user,
                         db=db_session,
                     )
-                elif (not file.content_type.startswith(("image/", "video/"))) or (
+                elif (not content_type.startswith(("image/", "video/"))) or (
                     request.app.state.config.CONTENT_EXTRACTION_ENGINE == "external"
                 ):
                     process_file(
@@ -164,7 +192,7 @@ def process_uploaded_file(
                     )
                 else:
                     raise Exception(
-                        f"File type {file.content_type} is not supported for processing"
+                        f"File type {content_type} is not supported for processing"
                     )
             else:
                 log.info(