🐛 fix(output): wrap gitlab sections at task level (#2806)

Previously the gitlab output wrapped each command individually, causing
two visible bugs in real GitLab pipelines:

- every section displayed a duration of 00:00, because start and end
  markers were emitted microseconds apart for instant commands
- the `task: [NAME] CMD` announcement lines were rendered outside the
  sections, because Logger.Errf bypassed the cmd-level wrapper

Fix by wrapping output at the task level via a new optional
[output.TaskWrapper] interface that GitLab implements. Task-scoped
writers are threaded via ctx so nested `task:` invocations produce
properly nested sections (GitLab supports this natively), and deps
running in parallel each get their own buffer with mutex-protected
flushes into the parent's buffer.

- `internal/output/output.go`: add TaskWrapper interface
- `internal/output/gitlab.go`: logic moved from WrapWriter to WrapTask;
  WrapWriter becomes passthrough; sync.Mutex around the buffer for
  concurrent flushes from parallel sub-task sections
- `task_output.go` (new): ctx plumbing + helpers kept out of task.go
- `task.go`: 7 lines of surgical edits — name the lambda's error
  return, wrap before the cmd loop, defer the closer with the final
  error, and swap the cmd announcement to `printCmdAnnouncement` which
  writes into the task-scoped stderr

executor.go

@@ -67,6 +67,7 @@ type (
 		Compiler           *Compiler
 		Output             output.Output
 		OutputStyle        ast.Output
+		OutputCIAuto       bool
 		TaskSorter         sort.Sorter
 		UserWorkingDir     string
 		EnableVersionCheck bool
@@ -522,6 +523,21 @@ func (o *outputStyleOption) ApplyToExecutor(e *Executor) {
 	e.OutputStyle = o.outputStyle
 }
 
+// WithOutputCIAuto enables automatic selection of a CI-aware output style
+// (e.g. "gitlab") when a supported CI environment is detected and no explicit
+// output style is configured in the Taskfile or via CLI.
+func WithOutputCIAuto(enabled bool) ExecutorOption {
+	return &outputCIAutoOption{enabled}
+}
+
+type outputCIAutoOption struct {
+	enabled bool
+}
+
+func (o *outputCIAutoOption) ApplyToExecutor(e *Executor) {
+	e.OutputCIAuto = o.enabled
+}
+
 // WithTaskSorter sets the sorter that the [Executor] will use to sort tasks. By
 // default, the sorter is set to sort tasks alphabetically, but with tasks with
 // no namespace (in the root Taskfile) first.

internal/flags/flags.go

@@ -71,6 +71,7 @@ var (
 	Dir                 string
 	Entrypoint          string
 	Output              ast.Output
+	OutputCIAuto        bool
 	Color               bool
 	Interval            time.Duration
 	Failfast            bool
@@ -143,10 +144,11 @@ func init() {
 	pflag.BoolVarP(&ExitCode, "exit-code", "x", false, "Pass-through the exit code of the task command.")
 	pflag.StringVarP(&Dir, "dir", "d", "", "Sets the directory in which Task will execute and look for a Taskfile.")
 	pflag.StringVarP(&Entrypoint, "taskfile", "t", "", `Choose which Taskfile to run. Defaults to "Taskfile.yml".`)
-	pflag.StringVarP(&Output.Name, "output", "o", "", "Sets output style: [interleaved|group|prefixed].")
+	pflag.StringVarP(&Output.Name, "output", "o", "", "Sets output style: [interleaved|group|prefixed|gitlab].")
 	pflag.StringVar(&Output.Group.Begin, "output-group-begin", "", "Message template to print before a task's grouped output.")
 	pflag.StringVar(&Output.Group.End, "output-group-end", "", "Message template to print after a task's grouped output.")
 	pflag.BoolVar(&Output.Group.ErrorOnly, "output-group-error-only", false, "Swallow output from successful tasks.")
+	OutputCIAuto = getConfig(config, "OUTPUT_CI_AUTO", func() *bool { return config.OutputCIAuto }, false)
 	pflag.BoolVarP(&Color, "color", "c", getConfig(config, "COLOR", func() *bool { return config.Color }, true), "Colored output. Enabled by default. Set flag to false or use NO_COLOR=1 to disable.")
 	pflag.IntVarP(&Concurrency, "concurrency", "C", getConfig(config, "CONCURRENCY", func() *int { return config.Concurrency }, 0), "Limit number of tasks to run concurrently.")
 	pflag.DurationVarP(&Interval, "interval", "I", 0, "Interval to watch for changes.")
@@ -305,6 +307,7 @@ func (o *flagsOption) ApplyToExecutor(e *task.Executor) {
 		task.WithConcurrency(Concurrency),
 		task.WithInterval(Interval),
 		task.WithOutputStyle(Output),
+		task.WithOutputCIAuto(OutputCIAuto),
 		task.WithTaskSorter(sorter),
 		task.WithVersionCheck(true),
 		task.WithFailfast(Failfast),

internal/output/gitlab.go

@@ -0,0 +1,116 @@
+package output
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"sync"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/go-task/task/v3/internal/templater"
+)
+
+// GitLab renders a task's output wrapped in [GitLab CI collapsible
+// section markers]. Section IDs are generated automatically so that
+// start and end markers always match and stay unique per invocation.
+//
+// GitLab wraps output at the task level via the [TaskWrapper] interface,
+// so each task (including its command announcements and all its cmds)
+// appears inside a single collapsible section. Nested task invocations
+// produce nested sections.
+//
+// [GitLab CI collapsible section markers]: https://docs.gitlab.com/ci/jobs/job_logs/#create-custom-collapsible-sections
+type GitLab struct {
+	Collapsed bool
+	ErrorOnly bool
+}
+
+// WrapWriter is a passthrough for GitLab: wrapping happens at the task
+// level via WrapTask, not per command.
+func (g GitLab) WrapWriter(stdOut, stdErr io.Writer, _ string, _ *templater.Cache) (io.Writer, io.Writer, CloseFunc) {
+	return stdOut, stdErr, func(error) error { return nil }
+}
+
+// WrapTask wraps an entire task's output in a single collapsible section.
+func (g GitLab) WrapTask(stdOut, _ io.Writer, cache *templater.Cache) (io.Writer, io.Writer, CloseFunc) {
+	header := ""
+	if cache != nil {
+		header = templater.Replace("{{.TASK}}", cache)
+	}
+	if header == "" {
+		header = "task"
+	}
+
+	id := fmt.Sprintf("%s_%s", gitlabSectionSlug(header), uuid.New().String()[:8])
+
+	gw := &gitlabWriter{
+		writer:    stdOut,
+		id:        id,
+		header:    header,
+		collapsed: g.Collapsed,
+		startTS:   time.Now().Unix(),
+	}
+
+	return gw, gw, func(err error) error {
+		if g.ErrorOnly && err == nil {
+			return nil
+		}
+		return gw.close()
+	}
+}
+
+type gitlabWriter struct {
+	mu        sync.Mutex
+	writer    io.Writer
+	buff      bytes.Buffer
+	id        string
+	header    string
+	collapsed bool
+	startTS   int64
+}
+
+func (gw *gitlabWriter) Write(p []byte) (int, error) {
+	gw.mu.Lock()
+	defer gw.mu.Unlock()
+	return gw.buff.Write(p)
+}
+
+func (gw *gitlabWriter) close() error {
+	gw.mu.Lock()
+	defer gw.mu.Unlock()
+
+	if gw.buff.Len() == 0 {
+		return nil
+	}
+
+	var b bytes.Buffer
+	b.WriteString(gitlabSectionStart(gw.startTS, gw.id, gw.header, gw.collapsed))
+	if _, err := io.Copy(&b, &gw.buff); err != nil {
+		return err
+	}
+	b.WriteString(gitlabSectionEnd(time.Now().Unix(), gw.id))
+
+	_, err := io.Copy(gw.writer, &b)
+	return err
+}
+
+func gitlabSectionStart(ts int64, id, header string, collapsed bool) string {
+	options := ""
+	if collapsed {
+		options = "[collapsed=true]"
+	}
+	return fmt.Sprintf("\x1b[0Ksection_start:%d:%s%s\r\x1b[0K%s\n", ts, id, options, header)
+}
+
+func gitlabSectionEnd(ts int64, id string) string {
+	return fmt.Sprintf("\x1b[0Ksection_end:%d:%s\r\x1b[0K\n", ts, id)
+}
+
+var gitlabSlugDisallowed = regexp.MustCompile(`[^a-zA-Z0-9_.-]`)
+
+func gitlabSectionSlug(s string) string {
+	return gitlabSlugDisallowed.ReplaceAllString(s, "_")
+}

internal/output/output.go

@@ -13,6 +13,14 @@ type Output interface {
 	WrapWriter(stdOut, stdErr io.Writer, prefix string, cache *templater.Cache) (io.Writer, io.Writer, CloseFunc)
 }
 
+// TaskWrapper is an optional interface that Output implementations can satisfy
+// to wrap an entire task's execution in a single enclosing block — including
+// the task's command announcements and all its commands' output — instead of
+// wrapping each command individually via WrapWriter.
+type TaskWrapper interface {
+	WrapTask(stdOut, stdErr io.Writer, cache *templater.Cache) (io.Writer, io.Writer, CloseFunc)
+}
+
 type CloseFunc func(err error) error
 
 // Build the Output for the requested ast.Output.
@@ -34,6 +42,14 @@ func BuildFor(o *ast.Output, logger *logger.Logger) (Output, error) {
 			return nil, err
 		}
 		return NewPrefixed(logger), nil
+	case "gitlab":
+		if err := checkOutputGroupUnset(o); err != nil {
+			return nil, err
+		}
+		return GitLab{
+			Collapsed: o.GitLab.Collapsed,
+			ErrorOnly: o.GitLab.ErrorOnly,
+		}, nil
 	default:
 		return nil, fmt.Errorf(`task: output style %q not recognized`, o.Name)
 	}

internal/output/output_test.go

@@ -5,7 +5,12 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
 	"testing"
+	"time"
 
 	"github.com/fatih/color"
 	"github.com/stretchr/testify/assert"
@@ -121,6 +126,238 @@ func TestGroupErrorOnlyShowsOutputOnError(t *testing.T) {
 	assert.Equal(t, "std-out\nstd-err\n", b.String())
 }
 
+func gitlabTaskCache(taskName string) *templater.Cache {
+	return &templater.Cache{
+		Vars: ast.NewVars(
+			&ast.VarElement{
+				Key:   "TASK",
+				Value: ast.Var{Value: taskName},
+			},
+		),
+	}
+}
+
+var gitlabMarkerPattern = regexp.MustCompile(
+	`\x1b\[0Ksection_start:(\d+):(\S+?)(\[[^\]]+\])?\r\x1b\[0K(.*)\n` +
+		`(?s)(.*)` +
+		`\x1b\[0Ksection_end:(\d+):(\S+)\r\x1b\[0K\n$`,
+)
+
+func TestGitLab(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+
+	fmt.Fprintln(w, "hello")
+	assert.Equal(t, "", b.String(), "output must be buffered until close")
+	require.NoError(t, cleanup(nil))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m, "output should match GitLab section markers, got: %q", b.String())
+	assert.Equal(t, m[2], m[7], "start and end section IDs must match")
+	assert.Empty(t, m[3], "collapsed option should not be present by default")
+	assert.Equal(t, "build", m[4], "section header should be the task name")
+	assert.Equal(t, "hello\n", m[5], "wrapped content must be preserved")
+	assert.Contains(t, m[2], "build_", "section ID should be prefixed with slugged task name")
+}
+
+func TestGitLabUniqueSectionIDs(t *testing.T) {
+	t.Parallel()
+
+	o := output.GitLab{}
+
+	ids := make([]string, 3)
+	for i := range ids {
+		var b bytes.Buffer
+		w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+		fmt.Fprintln(w, "x")
+		require.NoError(t, cleanup(nil))
+		m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+		require.NotNil(t, m)
+		ids[i] = m[2]
+	}
+
+	assert.NotEqual(t, ids[0], ids[1])
+	assert.NotEqual(t, ids[1], ids[2])
+	assert.NotEqual(t, ids[0], ids[2])
+}
+
+func TestGitLabCollapsed(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{Collapsed: true}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+	fmt.Fprintln(w, "x")
+	require.NoError(t, cleanup(nil))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m)
+	assert.Equal(t, "[collapsed=true]", m[3])
+}
+
+func TestGitLabErrorOnlySwallowsOutputOnNoError(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{ErrorOnly: true}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+	fmt.Fprintln(w, "hello")
+	require.NoError(t, cleanup(nil))
+	assert.Empty(t, b.String())
+}
+
+func TestGitLabErrorOnlyShowsOutputOnError(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{ErrorOnly: true}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+	fmt.Fprintln(w, "hello")
+	require.NoError(t, cleanup(errors.New("boom")))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m)
+	assert.Equal(t, "hello\n", m[5])
+}
+
+func TestGitLabSlugSanitizesTaskName(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("my task:with spaces"))
+	fmt.Fprintln(w, "x")
+	require.NoError(t, cleanup(nil))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m)
+	assert.Regexp(t, `^[a-zA-Z0-9_.-]+$`, m[2], "section ID must only contain GitLab-allowed chars")
+}
+
+func TestGitLabWrapWriterIsPassthrough(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{}
+	w, _, cleanup := o.WrapWriter(&b, io.Discard, "", nil)
+
+	fmt.Fprintln(w, "hello")
+	assert.Equal(t, "hello\n", b.String(), "WrapWriter must be a passthrough for GitLab")
+	assert.NoError(t, cleanup(nil))
+	assert.Equal(t, "hello\n", b.String(), "closer must be a no-op")
+}
+
+func TestGitLabWrapTaskSingleSection(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("build"))
+
+	// Simulate multiple cmd outputs being written during a task's execution.
+	fmt.Fprintln(w, "cmd 1 output")
+	fmt.Fprintln(w, "cmd 2 output")
+	fmt.Fprintln(w, "cmd 3 output")
+	require.NoError(t, cleanup(nil))
+
+	// There must be exactly one section_start and one section_end.
+	assert.Equal(t, 1, strings.Count(b.String(), "section_start:"))
+	assert.Equal(t, 1, strings.Count(b.String(), "section_end:"))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m)
+	assert.Equal(t, "cmd 1 output\ncmd 2 output\ncmd 3 output\n", m[5])
+}
+
+func TestGitLabWrapTaskDurationElapsed(t *testing.T) {
+	t.Parallel()
+
+	var b bytes.Buffer
+	o := output.GitLab{}
+	w, _, cleanup := o.WrapTask(&b, io.Discard, gitlabTaskCache("slow"))
+
+	fmt.Fprintln(w, "started")
+	time.Sleep(1100 * time.Millisecond)
+	fmt.Fprintln(w, "done")
+	require.NoError(t, cleanup(nil))
+
+	m := gitlabMarkerPattern.FindStringSubmatch(b.String())
+	require.NotNil(t, m)
+	startTS, err := strconv.ParseInt(m[1], 10, 64)
+	require.NoError(t, err)
+	endTS, err := strconv.ParseInt(m[6], 10, 64)
+	require.NoError(t, err)
+	assert.GreaterOrEqual(t, endTS-startTS, int64(1),
+		"end TS must be at least 1 second after start TS when task takes >1s")
+}
+
+func TestGitLabWrapTaskNested(t *testing.T) {
+	t.Parallel()
+
+	var root bytes.Buffer
+	parent := output.GitLab{}
+	parentW, _, parentClose := parent.WrapTask(&root, io.Discard, gitlabTaskCache("parent"))
+
+	fmt.Fprintln(parentW, "before child")
+
+	child := output.GitLab{}
+	childW, _, childClose := child.WrapTask(parentW, io.Discard, gitlabTaskCache("child"))
+	fmt.Fprintln(childW, "inside child")
+	require.NoError(t, childClose(nil))
+
+	fmt.Fprintln(parentW, "after child")
+	require.NoError(t, parentClose(nil))
+
+	out := root.String()
+	// Two section_start and two section_end
+	assert.Equal(t, 2, strings.Count(out, "section_start:"))
+	assert.Equal(t, 2, strings.Count(out, "section_end:"))
+
+	// Order: parent start → child start → child end → parent end
+	parentStart := strings.Index(out, "section_start:") // first
+	childStart := strings.Index(out[parentStart+1:], "section_start:") + parentStart + 1
+	childEnd := strings.Index(out, "section_end:")
+	parentEnd := strings.LastIndex(out, "section_end:")
+	assert.Less(t, parentStart, childStart, "child_start must come after parent_start")
+	assert.Less(t, childStart, childEnd, "child_end must come after child_start")
+	assert.Less(t, childEnd, parentEnd, "parent_end must come after child_end")
+}
+
+func TestGitLabWrapTaskConcurrentWrites(t *testing.T) {
+	t.Parallel()
+
+	var root bytes.Buffer
+	parent := output.GitLab{}
+	parentW, _, parentClose := parent.WrapTask(&root, io.Discard, gitlabTaskCache("parent"))
+
+	const numChildren = 10
+	var wg sync.WaitGroup
+	for i := 0; i < numChildren; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			child := output.GitLab{}
+			childW, _, childClose := child.WrapTask(parentW, io.Discard, gitlabTaskCache(fmt.Sprintf("child%d", i)))
+			fmt.Fprintf(childW, "child %d output\n", i)
+			_ = childClose(nil)
+		}(i)
+	}
+	wg.Wait()
+	require.NoError(t, parentClose(nil))
+
+	out := root.String()
+	// 1 parent + 10 children = 11 section_start and 11 section_end
+	assert.Equal(t, 11, strings.Count(out, "section_start:"))
+	assert.Equal(t, 11, strings.Count(out, "section_end:"))
+	// All 10 child outputs present
+	for i := 0; i < numChildren; i++ {
+		assert.Contains(t, out, fmt.Sprintf("child %d output", i))
+	}
+}
+
 func TestPrefixed(t *testing.T) { //nolint:paralleltest // cannot run in parallel
 	var b bytes.Buffer
 	l := &logger.Logger{

setup.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"slices"
+	"strconv"
 	"strings"
 	"sync"
 
@@ -202,12 +203,27 @@ func (e *Executor) setupOutput() error {
 	if !e.OutputStyle.IsSet() {
 		e.OutputStyle = e.Taskfile.Output
 	}
+	if !e.OutputStyle.IsSet() && e.OutputCIAuto {
+		if name := detectCIOutput(); name != "" {
+			e.OutputStyle.Name = name
+		}
+	}
 
 	var err error
 	e.Output, err = output.BuildFor(&e.OutputStyle, e.Logger)
 	return err
 }
 
+// detectCIOutput returns the name of a CI-aware output style to use based
+// on environment variables set by common CI runners. Returns an empty string
+// when no supported CI environment is detected.
+func detectCIOutput() string {
+	if isGitLab, _ := strconv.ParseBool(os.Getenv("GITLAB_CI")); isGitLab {
+		return "gitlab"
+	}
+	return ""
+}
+
 func (e *Executor) setupCompiler() error {
 	if e.UserWorkingDir == "" {
 		var err error

setup_test.go

@@ -0,0 +1,97 @@
+package task
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/go-task/task/v3/internal/logger"
+	"github.com/go-task/task/v3/taskfile/ast"
+)
+
+func TestDetectCIOutput(t *testing.T) {
+	cases := []struct {
+		name string
+		env  map[string]string
+		want string
+	}{
+		{name: "no CI detected", env: nil, want: ""},
+		{name: "GITLAB_CI=true", env: map[string]string{"GITLAB_CI": "true"}, want: "gitlab"},
+		{name: "GITLAB_CI=1", env: map[string]string{"GITLAB_CI": "1"}, want: "gitlab"},
+		{name: "GITLAB_CI=false", env: map[string]string{"GITLAB_CI": "false"}, want: ""},
+		{name: "GITLAB_CI empty", env: map[string]string{"GITLAB_CI": ""}, want: ""},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("GITLAB_CI", "") // reset
+			for k, v := range tc.env {
+				t.Setenv(k, v)
+			}
+			assert.Equal(t, tc.want, detectCIOutput())
+		})
+	}
+}
+
+func TestSetupOutputPriority(t *testing.T) {
+	cases := []struct {
+		name          string
+		cliStyle      ast.Output
+		taskfileStyle ast.Output
+		ciAuto        bool
+		gitlabEnv     string
+		wantName      string
+	}{
+		{
+			name:     "CLI wins over everything",
+			cliStyle: ast.Output{Name: "prefixed"},
+			taskfileStyle: ast.Output{Name: "group", Group: ast.OutputGroup{
+				Begin: "b", End: "e",
+			}},
+			ciAuto:    true,
+			gitlabEnv: "true",
+			wantName:  "prefixed",
+		},
+		{
+			name:          "Taskfile wins over auto-detect",
+			taskfileStyle: ast.Output{Name: "prefixed"},
+			ciAuto:        true,
+			gitlabEnv:     "true",
+			wantName:      "prefixed",
+		},
+		{
+			name:      "auto-detect activates when nothing explicit",
+			ciAuto:    true,
+			gitlabEnv: "true",
+			wantName:  "gitlab",
+		},
+		{
+			name:      "auto-detect disabled does nothing",
+			ciAuto:    false,
+			gitlabEnv: "true",
+			wantName:  "",
+		},
+		{
+			name:      "auto-detect without CI env does nothing",
+			ciAuto:    true,
+			gitlabEnv: "",
+			wantName:  "",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("GITLAB_CI", tc.gitlabEnv)
+
+			e := &Executor{
+				OutputStyle:  tc.cliStyle,
+				OutputCIAuto: tc.ciAuto,
+				Taskfile:     &ast.Taskfile{Output: tc.taskfileStyle},
+				Logger:       &logger.Logger{},
+			}
+			require.NoError(t, e.setupOutput())
+			assert.Equal(t, tc.wantName, e.OutputStyle.Name)
+		})
+	}
+}

task.go

@@ -204,9 +204,9 @@ func (e *Executor) RunTask(ctx context.Context, call *Call) error {
 	release := e.acquireConcurrencyLimit()
 	defer release()
 
-	if err = e.startExecution(ctx, t, func(ctx context.Context) error {
+	if err = e.startExecution(ctx, t, func(ctx context.Context) (err error) {
 		e.Logger.VerboseErrf(logger.Magenta, "task: %q started\n", call.Task)
-		if err := e.runDeps(ctx, t); err != nil {
+		if err = e.runDeps(ctx, t); err != nil {
 			return err
 		}
 
@@ -266,6 +266,9 @@ func (e *Executor) RunTask(ctx context.Context, call *Call) error {
 
 		var deferredExitCode uint8
 
+		ctx, taskOutCloser := e.wrapTaskOutput(ctx, t, call)
+		defer func() { taskOutCloser(err) }()
+
 		for i := range t.Cmds {
 			if t.Cmds[i].Defer {
 				defer e.runDeferred(t, call, i, t.Vars, &deferredExitCode)
@@ -393,7 +396,7 @@ func (e *Executor) runCommand(ctx context.Context, t *ast.Task, call *Call, i in
 		}
 
 		if e.Verbose || (!call.Silent && !cmd.Silent && !t.IsSilent() && !e.Taskfile.Silent && !e.Silent) {
-			e.Logger.Errf(logger.Green, "task: [%s] %s\n", t.Name(), cmd.Cmd)
+			e.printCmdAnnouncement(ctx, t, cmd.Cmd)
 		}
 
 		if e.Dry {
@@ -409,7 +412,8 @@ func (e *Executor) runCommand(ctx context.Context, t *ast.Task, call *Call, i in
 		if err != nil {
 			return fmt.Errorf("task: failed to get variables: %w", err)
 		}
-		stdOut, stdErr, closer := outputWrapper.WrapWriter(e.Stdout, e.Stderr, t.Prefix, outputTemplater)
+		taskStdOut, taskStdErr := e.writersFromCtx(ctx)
+		stdOut, stdErr, closer := outputWrapper.WrapWriter(taskStdOut, taskStdErr, t.Prefix, outputTemplater)
 
 		err = execext.RunCommand(ctx, &execext.RunCommandOptions{
 			Command:   cmd.Cmd,

task_output.go

@@ -0,0 +1,70 @@
+package task
+
+import (
+	"context"
+	"io"
+
+	"github.com/fatih/color"
+
+	"github.com/go-task/task/v3/internal/logger"
+	"github.com/go-task/task/v3/internal/output"
+	"github.com/go-task/task/v3/internal/templater"
+	"github.com/go-task/task/v3/taskfile/ast"
+)
+
+type taskWritersKey struct{}
+
+type taskWriters struct {
+	stdout, stderr io.Writer
+}
+
+// writersFromCtx returns the task-scoped writers if set, otherwise the
+// Executor's own stdout/stderr.
+func (e *Executor) writersFromCtx(ctx context.Context) (io.Writer, io.Writer) {
+	if tw, ok := ctx.Value(taskWritersKey{}).(*taskWriters); ok && tw != nil {
+		return tw.stdout, tw.stderr
+	}
+	return e.Stdout, e.Stderr
+}
+
+// wrapTaskOutput wraps a task's output in a task-scoped block if e.Output
+// implements [output.TaskWrapper] and the task is not interactive. Returns
+// the (possibly updated) ctx and a closer that flushes the block. The closer
+// is always safe to call — it is a no-op when no wrapping took place.
+func (e *Executor) wrapTaskOutput(ctx context.Context, t *ast.Task, call *Call) (context.Context, func(error)) {
+	noop := func(error) {}
+	if t.Interactive {
+		return ctx, noop
+	}
+	tw, ok := e.Output.(output.TaskWrapper)
+	if !ok {
+		return ctx, noop
+	}
+	stdOut, stdErr := e.writersFromCtx(ctx)
+	vars, err := e.Compiler.FastGetVariables(t, call)
+	if err != nil {
+		e.Logger.VerboseErrf(logger.Yellow, "task: output setup: %v\n", err)
+		return ctx, noop
+	}
+	wOut, wErr, closer := tw.WrapTask(stdOut, stdErr, &templater.Cache{Vars: vars})
+	ctx = context.WithValue(ctx, taskWritersKey{}, &taskWriters{stdout: wOut, stderr: wErr})
+	return ctx, func(loopErr error) {
+		if err := closer(loopErr); err != nil {
+			e.Logger.Errf(logger.Red, "task: output close: %v\n", err)
+		}
+	}
+}
+
+// printCmdAnnouncement prints the "task: [NAME] CMD" line using the
+// task-scoped stderr if available, so the announcement ends up inside the
+// task's output block.
+func (e *Executor) printCmdAnnouncement(ctx context.Context, t *ast.Task, cmdStr string) {
+	_, stdErr := e.writersFromCtx(ctx)
+	if stdErr == e.Stderr {
+		// No task-scoped writer — fall back to the Logger to preserve existing
+		// behavior (respects Logger's color config, etc.).
+		e.Logger.Errf(logger.Green, "task: [%s] %s\n", t.Name(), cmdStr)
+		return
+	}
+	_, _ = color.New(color.FgGreen).Fprintf(stdErr, "task: [%s] %s\n", t.Name(), cmdStr)
+}

taskfile/ast/output.go

@@ -12,6 +12,8 @@ type Output struct {
 	Name string `yaml:"-"`
 	// Group specific style
 	Group OutputGroup
+	// GitLab specific style
+	GitLab OutputGitLab
 }
 
 // IsSet returns true if and only if a custom output style is set.
@@ -32,19 +34,30 @@ func (s *Output) UnmarshalYAML(node *yaml.Node) error {
 
 	case yaml.MappingNode:
 		var tmp struct {
-			Group *OutputGroup
+			Group  *OutputGroup
+			GitLab *OutputGitLab `yaml:"gitlab"`
 		}
 		if err := node.Decode(&tmp); err != nil {
 			return errors.NewTaskfileDecodeError(err, node)
 		}
-		if tmp.Group == nil {
-			return errors.NewTaskfileDecodeError(nil, node).WithMessage(`output style must have the "group" key when in mapping form`)
+		switch {
+		case tmp.Group != nil && tmp.GitLab != nil:
+			return errors.NewTaskfileDecodeError(nil, node).WithMessage(`output style cannot set both "group" and "gitlab"`)
+		case tmp.Group != nil:
+			*s = Output{
+				Name:  "group",
+				Group: *tmp.Group,
+			}
+			return nil
+		case tmp.GitLab != nil:
+			*s = Output{
+				Name:   "gitlab",
+				GitLab: *tmp.GitLab,
+			}
+			return nil
+		default:
+			return errors.NewTaskfileDecodeError(nil, node).WithMessage(`output style must have the "group" or "gitlab" key when in mapping form`)
 		}
-		*s = Output{
-			Name:  "group",
-			Group: *tmp.Group,
-		}
-		return nil
 	}
 
 	return errors.NewTaskfileDecodeError(nil, node).WithTypeMessage("output")
@@ -63,3 +76,9 @@ func (g *OutputGroup) IsSet() bool {
 	}
 	return g.Begin != "" || g.End != ""
 }
+
+// OutputGitLab is the style options specific to the GitLab style.
+type OutputGitLab struct {
+	Collapsed bool
+	ErrorOnly bool `yaml:"error_only"`
+}

taskrc/ast/taskrc.go

@@ -17,6 +17,7 @@ type TaskRC struct {
 	DisableFuzzy *bool           `yaml:"disable-fuzzy"`
 	Concurrency  *int            `yaml:"concurrency"`
 	Interactive  *bool           `yaml:"interactive"`
+	OutputCIAuto *bool           `yaml:"output-ci-auto"`
 	Remote       Remote          `yaml:"remote"`
 	Failfast     bool            `yaml:"failfast"`
 	Experiments  map[string]int  `yaml:"experiments"`
@@ -69,5 +70,6 @@ func (t *TaskRC) Merge(other *TaskRC) {
 	t.DisableFuzzy = cmp.Or(other.DisableFuzzy, t.DisableFuzzy)
 	t.Concurrency = cmp.Or(other.Concurrency, t.Concurrency)
 	t.Interactive = cmp.Or(other.Interactive, t.Interactive)
+	t.OutputCIAuto = cmp.Or(other.OutputCIAuto, t.OutputCIAuto)
 	t.Failfast = cmp.Or(other.Failfast, t.Failfast)
 }

taskrc/taskrc_test.go

@@ -306,4 +306,27 @@ remote:
 		assert.Equal(t, &cacheExpiry, base.Remote.CacheExpiry)
 		assert.Equal(t, []string{"github.com", "gitlab.com"}, base.Remote.TrustedHosts)
 	})
+
+	t.Run("output-ci-auto merge", func(t *testing.T) { //nolint:paralleltest // parent test cannot run in parallel
+		trueVal := true
+		falseVal := false
+
+		t.Run("other overrides nil base", func(t *testing.T) { //nolint:paralleltest
+			base := &ast.TaskRC{}
+			base.Merge(&ast.TaskRC{OutputCIAuto: &trueVal})
+			assert.Equal(t, &trueVal, base.OutputCIAuto)
+		})
+
+		t.Run("other overrides base", func(t *testing.T) { //nolint:paralleltest
+			base := &ast.TaskRC{OutputCIAuto: &falseVal}
+			base.Merge(&ast.TaskRC{OutputCIAuto: &trueVal})
+			assert.Equal(t, &trueVal, base.OutputCIAuto)
+		})
+
+		t.Run("nil other does not override base", func(t *testing.T) { //nolint:paralleltest
+			base := &ast.TaskRC{OutputCIAuto: &trueVal}
+			base.Merge(&ast.TaskRC{})
+			assert.Equal(t, &trueVal, base.OutputCIAuto)
+		})
+	})
 }

website/src/docs/guide.md

@@ -2426,12 +2426,13 @@ the shell in real-time. This is good for having live feedback for logging
 printed by commands, but the output can become messy if you have multiple
 commands running simultaneously and printing lots of stuff.
 
-To make this more customizable, there are currently three different output
+To make this more customizable, there are currently four different output
 options you can choose:
 
 - `interleaved` (default)
 - `group`
 - `prefixed`
+- `gitlab`
 
 To choose another one, just set it to root in the Taskfile:
 
@@ -2535,6 +2536,44 @@ $ task default
 [print-baz] baz
 ```
 
+The `gitlab` output wraps each task's output in
+[GitLab CI collapsible section markers](https://docs.gitlab.com/ci/jobs/job_logs/#create-custom-collapsible-sections).
+Section names are generated automatically so that start and end markers always
+match and stay unique per invocation — even when the same task runs multiple
+times in the same job.
+
+```yaml
+version: '3'
+
+output: gitlab
+```
+
+Two options are available:
+
+- `collapsed`: maps to GitLab's native
+  [`[collapsed=true]`](https://docs.gitlab.com/ci/jobs/job_logs/#create-custom-collapsible-sections)
+  option, which tells GitLab to fold the section by default in the UI.
+- `error_only`: a Task-level option (same as in the [`group`](#output-syntax)
+  style) that swallows the command output — markers included — for tasks that
+  exit with a zero status code.
+
+```yaml
+version: '3'
+
+output:
+  gitlab:
+    collapsed: true
+    error_only: true
+```
+
+::: tip
+
+Rather than hard-coding `output: gitlab` in your Taskfile (which also affects
+local development), consider using [`output-ci-auto`](#automatic-ci-output) so
+the mode is only activated in CI.
+
+:::
+
 ::: tip
 
 The `output` option can also be specified by the `--output` or `-o` flags.
@@ -2563,6 +2602,28 @@ summary, making it easier to spot failures without scrolling through logs.
 
 This feature requires no configuration and works automatically.
 
+### Automatic CI output
+
+When `output-ci-auto: true` is set in a [`.taskrc.yml`](./taskrc.md) file, Task
+will automatically select a CI-aware [output style](#output-syntax) based on
+the environment it is running in, but only when no output style is configured
+explicitly (via the Taskfile, `--output`, or `TASK_X_OUTPUT`).
+
+Currently supported:
+
+| Environment variable | Output style selected |
+| -------------------- | --------------------- |
+| `GITLAB_CI=true`     | `gitlab`              |
+
+This lets you keep your Taskfile neutral — local developers get the default
+`interleaved` output, while CI runs get their matching CI-flavored output
+without any per-job configuration.
+
+```yaml
+# .taskrc.yml
+output-ci-auto: true
+```
+
 ## Interactive CLI application
 
 When running interactive CLI applications inside Task they can sometimes behave

website/src/docs/reference/cli.md

@@ -224,7 +224,8 @@ task backup --global
 
 #### `-o, --output <mode>`
 
-Set output style. Available modes: `interleaved`, `group`, `prefixed`.
+Set output style. Available modes: `interleaved`, `group`, `prefixed`,
+`gitlab`.
 
 ```bash
 task test --output group

website/src/docs/reference/config.md

@@ -166,6 +166,21 @@ failfast: true
 interactive: true
 ```
 
+### `output-ci-auto`
+
+- **Type**: `boolean`
+- **Default**: `false`
+- **Description**: Automatically select a CI-aware
+  [output style](../guide.md#output-syntax) when a supported CI environment
+  is detected and no output style is explicitly configured (via the Taskfile
+  or `--output`). Currently maps `GITLAB_CI=true` to the `gitlab` output
+  style.
+- **Environment variable**: [`TASK_OUTPUT_CI_AUTO`](./environment.md#task-output-ci-auto)
+
+```yaml
+output-ci-auto: true
+```
+
 ## Example Configuration
 
 Here's a complete example of a `.taskrc.yml` file with all available options:

website/src/docs/reference/environment.md

@@ -81,6 +81,16 @@ variables. The priority order is: CLI flags > environment variables > config fil
 - **Default**: `false`
 - **Description**: Prompt for missing required variables
 
+### `TASK_OUTPUT_CI_AUTO`
+
+- **Type**: `boolean` (`true`, `false`, `1`, `0`)
+- **Default**: `false`
+- **Description**: Automatically select a CI-aware output style when a
+  supported CI environment is detected and no output style is explicitly
+  configured. See [output syntax](../guide.md#output-syntax) and
+  [automatic CI output](../guide.md#automatic-ci-output).
+- **Config equivalent**: [`output-ci-auto`](./config.md#output-ci-auto)
+
 ### `TASK_TEMP_DIR`
 
 Defines the location of Task's temporary directory which is used for storing

website/src/docs/reference/schema.md

@@ -29,7 +29,7 @@ version: '3'
 
 - **Type**: `string` or `object`
 - **Default**: `interleaved`
-- **Options**: `interleaved`, `group`, `prefixed`
+- **Options**: `interleaved`, `group`, `prefixed`, `gitlab`
 - **Description**: Controls how task output is displayed
 
 ```yaml

website/src/public/schema.json

@@ -595,7 +595,7 @@
     },
     "outputString": {
       "type": "string",
-      "enum": ["interleaved", "prefixed", "group"],
+      "enum": ["interleaved", "prefixed", "group", "gitlab"],
       "default": "interleaved"
     },
     "outputObject": {
@@ -616,6 +616,22 @@
               "default": false
             }
           }
+        },
+        "gitlab": {
+          "type": "object",
+          "description": "Wraps each task's output in GitLab CI collapsible section markers",
+          "properties": {
+            "collapsed": {
+              "description": "Passes the native GitLab [collapsed=true] option so sections are folded by default in the GitLab CI UI",
+              "type": "boolean",
+              "default": false
+            },
+            "error_only": {
+              "description": "Swallows command output on zero exit code (Task-level behavior, identical to group.error_only)",
+              "type": "boolean",
+              "default": false
+            }
+          }
         }
       },
       "additionalProperties": false