Enable inline sub-agents by default and deprecate features.inline-agents with auto-removal codemod (#30661)

* Enable inline-agents by default and add deprecation codemod

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Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Plan remove inline-agents constant

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Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Revert accidental lockfile-only update commit

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* Remove deprecated InlineAgentsFeatureFlag constant

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Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Simplify inline-agents test flag literal

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---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot

.github/aw/subagents.md

@@ -1,5 +1,5 @@
 ---
-description: Guide for defining inline sub-agents in workflow markdown files — syntax, feature flag, engine placement, frontmatter fields, and best practices.
+description: Guide for defining inline sub-agents in workflow markdown files — syntax, engine placement, frontmatter fields, and best practices.
 ---
 
 # Inline Sub-Agents
@@ -12,17 +12,15 @@ Inline sub-agents let you define specialised agents directly inside a workflow m
 
 ## Enabling the Feature
 
-Inline sub-agent extraction and restoration steps are **only compiled in when the `inline-agents` feature flag is set**:
+Inline sub-agent extraction and restoration steps are enabled by default:
 
 ```yaml
 ---
 engine: copilot
-features:
-  inline-agents: true
 ---
 ```
 
-Without this flag the `## agent:` sections are stripped from the prompt at compile time but no upload or restore steps are generated, so the sub-agent files will not be available during the agent job.
+> `features.inline-agents` is deprecated and no longer needed. Existing workflows may still include it, but it has no effect.
 
 ---
 
@@ -99,8 +97,6 @@ For sub-agents to perform useful work they typically need access to the file sys
 ```yaml
 ---
 engine: copilot
-features:
-  inline-agents: true
 tools:
   github:
     mode: gh-proxy
@@ -172,8 +168,6 @@ Extract a repetitive sub-task (file summarisation, commit-message generation, co
 ```markdown
 ---
 engine: copilot
-features:
-  inline-agents: true
 tools:
   github:
     mode: gh-proxy
@@ -205,5 +199,5 @@ changes. Return a bulleted list, one bullet per file.
 
 - Sub-agents do not support `engine:`, `tools:`, `network:`, or `mcp-servers:` fields — those are stripped at runtime.
 - Sub-agents cannot define their own safe-output jobs.
-- The feature requires `features.inline-agents: true` — without it the upload/restore steps are not generated.
+- `features.inline-agents` is deprecated and has no effect; inline sub-agent upload/restore is always generated.
 - Sub-agent blocks must appear in the main workflow file body; they are not resolved inside imported shared files.

pkg/cli/codemod_inline_agents.go

@@ -0,0 +1,19 @@
+package cli
+
+import "github.com/github/gh-aw/pkg/logger"
+
+var inlineAgentsCodemodLog = logger.New("cli:codemod_inline_agents")
+
+// getInlineAgentsFeatureRemovalCodemod removes deprecated features.inline-agents.
+func getInlineAgentsFeatureRemovalCodemod() Codemod {
+	return newFieldRemovalCodemod(fieldRemovalCodemodConfig{
+		ID:           "features-inline-agents-removal",
+		Name:         "Remove deprecated features.inline-agents",
+		Description:  "Removes deprecated features.inline-agents. Inline sub-agents are now enabled by default.",
+		IntroducedIn: "1.0.0",
+		ParentKey:    "features",
+		FieldKey:     "inline-agents",
+		LogMsg:       "Removed deprecated features.inline-agents",
+		Log:          inlineAgentsCodemodLog,
+	})
+}

pkg/cli/codemod_inline_agents_test.go

@@ -0,0 +1,70 @@
+//go:build !integration
+
+package cli
+
+import (
+	"testing"
+
+	"github.com/github/gh-aw/pkg/parser"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInlineAgentsFeatureRemovalCodemod(t *testing.T) {
+	codemod := getInlineAgentsFeatureRemovalCodemod()
+
+	tests := []struct {
+		name        string
+		input       string
+		expectApply bool
+	}{
+		{
+			name: "removes inline-agents when true",
+			input: `---
+name: Test Workflow
+features:
+  inline-agents: true
+  mcp-gateway: true
+---
+# Test workflow`,
+			expectApply: true,
+		},
+		{
+			name: "removes inline-agents when false",
+			input: `---
+name: Test Workflow
+features:
+  inline-agents: false
+---
+# Test workflow`,
+			expectApply: true,
+		},
+		{
+			name: "does not modify when inline-agents is absent",
+			input: `---
+name: Test Workflow
+features:
+  mcp-gateway: true
+---
+# Test workflow`,
+			expectApply: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := parser.ExtractFrontmatterFromContent(tt.input)
+			require.NoError(t, err, "Failed to parse test input frontmatter")
+
+			output, applied, err := codemod.Apply(tt.input, result.Frontmatter)
+			require.NoError(t, err, "Codemod apply should not error")
+			assert.Equal(t, tt.expectApply, applied, "Applied status mismatch")
+
+			if tt.expectApply {
+				assert.NotContains(t, output, "inline-agents:", "Codemod should remove deprecated inline-agents flag")
+			} else {
+				assert.Equal(t, tt.input, output, "Output should be unchanged when codemod does not apply")
+			}
+		})
+	}
+}

pkg/cli/fix_codemods.go

@@ -58,6 +58,7 @@ func GetAllCodemods() []Codemod {
 		getDependabotPermissionsCodemod(),             // Add vulnerability-alerts: read when dependabot toolset is used
 		getGitHubReposToAllowedReposCodemod(),         // Rename deprecated tools.github.repos to tools.github.allowed-repos
 		getByokCopilotFeatureRemovalCodemod(),         // Remove deprecated features.byok-copilot (Copilot BYOK is default)
+		getInlineAgentsFeatureRemovalCodemod(),        // Remove deprecated features.inline-agents (inline sub-agents now default)
 		getCliProxyFeatureToGitHubModeCodemod(),       // Migrate features.cli-proxy: true to tools.github.mode: gh-proxy
 		getDIFCProxyToIntegrityProxyCodemod(),         // Migrate deprecated features.difc-proxy to tools.github.integrity-proxy
 		getMountAsCLIsToCLIProxyCodemod(),             // Rename tools.mount-as-clis to tools.cli-proxy and remove features.mcp-cli

pkg/cli/fix_codemods_test.go

@@ -88,6 +88,7 @@ func TestGetAllCodemods_ContainsExpectedCodemods(t *testing.T) {
 		"pull-request-target-checkout-false",
 		"dependabot-toolset-permissions",
 		"features-byok-copilot-removal",
+		"features-inline-agents-removal",
 		"mount-as-clis-to-cli-proxy",
 	}
 
@@ -149,6 +150,7 @@ func TestGetAllCodemods_InExpectedOrder(t *testing.T) {
 		"dependabot-toolset-permissions",
 		"github-repos-to-allowed-repos",
 		"features-byok-copilot-removal",
+		"features-inline-agents-removal",
 		"features-cli-proxy-to-tools-github-mode",
 		"features-difc-proxy-to-tools-github",
 		"mount-as-clis-to-cli-proxy",

pkg/constants/feature_constants.go

@@ -72,14 +72,4 @@ const (
 	//	features:
 	//	  integrity-reactions: true
 	IntegrityReactionsFeatureFlag FeatureFlag = "integrity-reactions"
-	// InlineAgentsFeatureFlag enables the generation of inline sub-agent extraction and
-	// restoration steps in the compiled workflow. When enabled, the compiler adds a runtime
-	// step to extract `## agent: \`name\`` sections from the workflow markdown and write them
-	// to the engine-specific agents directory after the base branch restore step.
-	//
-	// Workflow frontmatter usage:
-	//
-	//	features:
-	//	  inline-agents: true
-	InlineAgentsFeatureFlag FeatureFlag = "inline-agents"
 )

pkg/workflow/compiler_activation_job_builder.go

@@ -463,17 +463,14 @@ func (c *Compiler) addActivationArtifactUploadStep(ctx *activationJobBuildContex
 	ctx.steps = append(ctx.steps, "            /tmp/gh-aw/aw-prompts/prompt-import-tree.json\n")
 	ctx.steps = append(ctx.steps, "            /tmp/gh-aw/"+constants.GithubRateLimitsFilename+"\n")
 	ctx.steps = append(ctx.steps, "            /tmp/gh-aw/base\n")
-	// Include the engine-specific sub-agents staging directory when inline-agents is enabled
-	// so inline sub-agent files written during the activation job are available to the agent job.
-	if v, ok := ctx.data.Features[string(constants.InlineAgentsFeatureFlag)]; ok {
-		if enabled, isBool := v.(bool); isBool && enabled {
-			engineID := ""
-			if ctx.data.EngineConfig != nil {
-				engineID = ctx.data.EngineConfig.ID
-			}
-			subAgentDir := parser.GetEngineSubAgentDir(engineID)
-			ctx.steps = append(ctx.steps, fmt.Sprintf("            /tmp/gh-aw/%s\n", subAgentDir))
+	// Include the engine-specific sub-agents staging directory (inline sub-agents are enabled by default).
+	if isFeatureEnabled(constants.FeatureFlag("inline-agents"), ctx.data) {
+		engineID := ""
+		if ctx.data.EngineConfig != nil {
+			engineID = ctx.data.EngineConfig.ID
 		}
+		subAgentDir := parser.GetEngineSubAgentDir(engineID)
+		ctx.steps = append(ctx.steps, fmt.Sprintf("            /tmp/gh-aw/%s\n", subAgentDir))
 	}
 	ctx.steps = append(ctx.steps, "          if-no-files-found: ignore\n")
 	ctx.steps = append(ctx.steps, "          retention-days: 1\n")

pkg/workflow/compiler_yaml_main_job.go

@@ -418,11 +418,9 @@ func (c *Compiler) generateEngineInstallAndPreAgentSteps(yaml *strings.Builder,
 
 	// Restore inline sub-agents written during the activation job.
 	// This step runs AFTER the base-branch restore so the engine-specific agent directory
-	// is not clobbered. It is guarded by the features.inline-agents flag.
-	if v, ok := data.Features[string(constants.InlineAgentsFeatureFlag)]; ok {
-		if enabled, isBool := v.(bool); isBool && enabled {
-			generateRestoreInlineSubAgentsStep(yaml, data)
-		}
+	// is not clobbered. Inline sub-agents are enabled by default.
+	if isFeatureEnabled(constants.FeatureFlag("inline-agents"), data) {
+		generateRestoreInlineSubAgentsStep(yaml, data)
 	}
 
 	// Add pre-agent-steps (if any) after base-branch restore but before MCP setup.

pkg/workflow/features.go

@@ -22,6 +22,15 @@ func isFeatureEnabled(flag constants.FeatureFlag, workflowData *WorkflowData) bo
 		featuresLog.Printf("Checking if feature is enabled: %s", flagLower)
 	}
 
+	// Inline sub-agents are now enabled by default and the corresponding
+	// frontmatter flag is deprecated/no-op.
+	if flagLower == "inline-agents" {
+		if logEnabled {
+			featuresLog.Printf("Feature %s is deprecated and always enabled", flagLower)
+		}
+		return true
+	}
+
 	// First, check if the feature is explicitly set in frontmatter.
 	// Frontmatter values always take precedence.
 	if enabled, found := getFeatureValueFromFrontmatter(flagLower, workflowData, logEnabled); found {

pkg/workflow/features_test.go

@@ -293,3 +293,39 @@ func TestMergedFeaturesTopLevelPrecedence(t *testing.T) {
 		t.Errorf("isFeatureEnabled(\"import-only\") = %v, want true (from import)", importOnlyResult)
 	}
 }
+
+func TestInlineAgentsFeatureAlwaysEnabled(t *testing.T) {
+	t.Setenv("GH_AW_FEATURES", "")
+
+	tests := []struct {
+		name     string
+		features map[string]any
+	}{
+		{
+			name:     "enabled when feature absent",
+			features: map[string]any{},
+		},
+		{
+			name: "enabled when explicitly true",
+			features: map[string]any{
+				"inline-agents": true,
+			},
+		},
+		{
+			name: "enabled when explicitly false",
+			features: map[string]any{
+				"inline-agents": false,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			workflowData := &WorkflowData{Features: tt.features}
+			result := isFeatureEnabled("inline-agents", workflowData)
+			if !result {
+				t.Errorf("isFeatureEnabled(%q, %+v) = %v, want true", "inline-agents", tt.features, result)
+			}
+		})
+	}
+}