diff --git a/lib/app/ui_feature_manifest.dart b/lib/app/ui_feature_manifest.dart
index 8991fec3..54c4af9c 100644
--- a/lib/app/ui_feature_manifest.dart
+++ b/lib/app/ui_feature_manifest.dart
@@ -7,3 +7,4 @@ import '../models/app_models.dart';
 import '../runtime/runtime_models.dart';
 
 part 'ui_feature_manifest_core.part.dart';
+part 'ui_feature_manifest_fallback.part.dart';
diff --git a/lib/app/ui_feature_manifest_core.part.dart b/lib/app/ui_feature_manifest_core.part.dart
index 0a9b803f..f13905b9 100644
--- a/lib/app/ui_feature_manifest_core.part.dart
+++ b/lib/app/ui_feature_manifest_core.part.dart
@@ -99,7 +99,7 @@ class UiFeatureFlag {
     return UiFeatureFlag(
       enabled: enabled ?? this.enabled,
       releaseTier: releaseTier ?? this.releaseTier,
-      buildModes: buildModes ?? this.buildModes,
+      buildModes: Set<UiFeatureBuildMode>.of(buildModes ?? this.buildModes),
       description: description ?? this.description,
       uiSurface: uiSurface ?? this.uiSurface,
     );
@@ -115,546 +115,7 @@ class UiFeatureManifest {
 
   static const String assetPath = 'config/feature_flags.yaml';
 
-  static const String fallbackYaml = '''
-release_policy:
-  debug: [stable, beta, experimental]
-  profile: [stable, beta]
-  release: [stable]
-
-mobile:
-  navigation:
-    assistant:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile assistant destination
-      ui_surface: mobile_shell
-    tasks:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile tasks destination
-      ui_surface: mobile_shell
-    workspace:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace hub destination
-      ui_surface: mobile_shell
-    secrets:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile secrets destination
-      ui_surface: mobile_shell
-    settings:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings destination
-      ui_surface: mobile_shell
-  workspace:
-    skills:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace skills launcher
-      ui_surface: mobile_workspace_hub
-    nodes:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace nodes launcher
-      ui_surface: mobile_workspace_hub
-    agents:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace agents launcher
-      ui_surface: mobile_workspace_hub
-    mcp_server:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace MCP launcher
-      ui_surface: mobile_workspace_hub
-    claw_hub:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile workspace ClawHub launcher
-      ui_surface: mobile_workspace_hub
-    connectors:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile workspace connectors launcher
-      ui_surface: mobile_workspace_hub
-    ai_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace LLM API launcher
-      ui_surface: mobile_workspace_hub
-    account:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile workspace account launcher
-      ui_surface: mobile_workspace_hub
-  assistant:
-    direct_ai:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Mobile does not expose direct AI assistant mode
-      ui_surface: assistant_page
-    local_gateway:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Mobile does not expose local gateway assistant mode
-      ui_surface: assistant_page
-    relay_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile relay gateway assistant mode
-      ui_surface: assistant_page
-    file_attachments:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile file attachment action in assistant composer
-      ui_surface: assistant_page
-    multi_agent:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile multi-agent toggle in assistant composer
-      ui_surface: assistant_page
-    local_runtime:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Mobile does not expose desktop runtime controls
-      ui_surface: assistant_page
-  settings:
-    general:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings general tab
-      ui_surface: settings_page
-    workspace:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings workspace tab
-      ui_surface: settings_page
-    gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings gateway tab
-      ui_surface: settings_page
-    account_access:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile account access section
-      ui_surface: settings_page
-    vault_server:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile Vault server integration section
-      ui_surface: settings_page
-    gateway_setup_code:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile gateway setup code editor
-      ui_surface: settings_page
-    agents:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile settings multi-agent tab
-      ui_surface: settings_page
-    appearance:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings appearance tab
-      ui_surface: settings_page
-    diagnostics:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings diagnostics tab
-      ui_surface: settings_page
-    experimental:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile settings experimental tab
-      ui_surface: settings_page
-    about:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Mobile settings about tab
-      ui_surface: settings_page
-    experimental_canvas:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile experimental canvas host toggle
-      ui_surface: settings_page
-    experimental_bridge:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile experimental bridge toggle
-      ui_surface: settings_page
-    experimental_debug:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Mobile experimental debug runtime toggle
-      ui_surface: settings_page
-
-desktop:
-  navigation:
-    assistant:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop assistant destination
-      ui_surface: sidebar_navigation
-    tasks:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop tasks destination
-      ui_surface: sidebar_navigation
-    skills:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop skills destination
-      ui_surface: sidebar_navigation
-    nodes:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop nodes destination
-      ui_surface: sidebar_navigation
-    agents:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop agents destination
-      ui_surface: sidebar_navigation
-    mcp_server:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop MCP Hub destination
-      ui_surface: sidebar_navigation
-    claw_hub:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop ClawHub destination
-      ui_surface: sidebar_navigation
-    secrets:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop secrets destination
-      ui_surface: sidebar_navigation
-    ai_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop LLM API destination
-      ui_surface: sidebar_navigation
-    settings:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings destination
-      ui_surface: sidebar_navigation
-    account:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop account destination
-      ui_surface: sidebar_navigation
-  workspace:
-    claw_hub:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop workspace ClawHub tab
-      ui_surface: modules_page
-    connectors:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop workspace connectors tab
-      ui_surface: modules_page
-  assistant:
-    direct_ai:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop direct AI assistant mode
-      ui_surface: assistant_page
-    local_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop local gateway assistant mode
-      ui_surface: assistant_page
-    relay_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop relay gateway assistant mode
-      ui_surface: assistant_page
-    file_attachments:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop file attachment action in assistant composer
-      ui_surface: assistant_page
-    multi_agent:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop multi-agent toggle in assistant composer
-      ui_surface: assistant_page
-    local_runtime:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop local runtime and gateway orchestration entry
-      ui_surface: assistant_page
-  settings:
-    general:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings general tab
-      ui_surface: settings_page
-    workspace:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings workspace tab
-      ui_surface: settings_page
-    gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings gateway tab
-      ui_surface: settings_page
-    account_access:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop account access section
-      ui_surface: settings_page
-    vault_server:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop Vault server integration section
-      ui_surface: settings_page
-    gateway_setup_code:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop gateway setup code editor
-      ui_surface: settings_page
-    agents:
-      enabled: false
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop settings multi-agent tab
-      ui_surface: settings_page
-    appearance:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings appearance tab
-      ui_surface: settings_page
-    diagnostics:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings diagnostics tab
-      ui_surface: settings_page
-    experimental:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop settings experimental tab
-      ui_surface: settings_page
-    about:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Desktop settings about tab
-      ui_surface: settings_page
-    experimental_canvas:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop experimental canvas host toggle
-      ui_surface: settings_page
-    experimental_bridge:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop experimental bridge toggle
-      ui_surface: settings_page
-    experimental_debug:
-      enabled: true
-      release_tier: experimental
-      build_modes: [debug, profile, release]
-      description: Desktop experimental debug runtime toggle
-      ui_surface: settings_page
-
-web:
-  navigation:
-    assistant:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web assistant destination
-      ui_surface: web_shell
-    tasks:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web tasks destination
-      ui_surface: web_shell
-    skills:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web skills destination
-      ui_surface: web_shell
-    nodes:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web nodes destination
-      ui_surface: web_shell
-    secrets:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web secrets destination
-      ui_surface: web_shell
-    ai_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web LLM API destination
-      ui_surface: web_shell
-    settings:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web settings destination
-      ui_surface: web_shell
-  assistant:
-    direct_ai:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web direct AI assistant mode
-      ui_surface: web_assistant_page
-    relay_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web relay gateway assistant mode
-      ui_surface: web_assistant_page
-    file_attachments:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web file attachment action in assistant composer
-      ui_surface: web_assistant_page
-    multi_agent:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web multi-agent toggle in assistant composer
-      ui_surface: web_assistant_page
-    local_gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web local gateway assistant mode
-      ui_surface: web_assistant_page
-    local_runtime:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Web does not expose desktop runtime controls
-      ui_surface: web_assistant_page
-  settings:
-    general:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web settings general tab
-      ui_surface: web_settings_page
-    gateway:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web settings gateway tab
-      ui_surface: web_settings_page
-    account_access:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Web does not expose account access section
-      ui_surface: web_settings_page
-    vault_server:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Web does not expose vault server integration
-      ui_surface: web_settings_page
-    gateway_setup_code:
-      enabled: false
-      release_tier: experimental
-      build_modes: []
-      description: Web does not expose gateway setup code editor
-      ui_surface: web_settings_page
-    appearance:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web settings appearance tab
-      ui_surface: web_settings_page
-    about:
-      enabled: true
-      release_tier: stable
-      build_modes: [debug, profile, release]
-      description: Web settings about tab
-      ui_surface: web_settings_page
-''';
-
+  static const String fallbackYaml = _fallbackUiFeatureManifestYaml;
   final Map<UiFeatureBuildMode, Set<UiFeatureReleaseTier>> releasePolicy;
   final Map<UiFeaturePlatform, Map<String, Map<String, UiFeatureFlag>>>
   _flagsByPlatform;
diff --git a/lib/app/ui_feature_manifest_fallback.part.dart b/lib/app/ui_feature_manifest_fallback.part.dart
new file mode 100644
index 00000000..c93fd99b
--- /dev/null
+++ b/lib/app/ui_feature_manifest_fallback.part.dart
@@ -0,0 +1,541 @@
+part of 'ui_feature_manifest.dart';
+
+const String _fallbackUiFeatureManifestYaml = '''
+release_policy:
+  debug: [stable, beta, experimental]
+  profile: [stable, beta]
+  release: [stable]
+
+mobile:
+  navigation:
+    assistant:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile assistant destination
+      ui_surface: mobile_shell
+    tasks:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile tasks destination
+      ui_surface: mobile_shell
+    workspace:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace hub destination
+      ui_surface: mobile_shell
+    secrets:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile secrets destination
+      ui_surface: mobile_shell
+    settings:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings destination
+      ui_surface: mobile_shell
+  workspace:
+    skills:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace skills launcher
+      ui_surface: mobile_workspace_hub
+    nodes:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace nodes launcher
+      ui_surface: mobile_workspace_hub
+    agents:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace agents launcher
+      ui_surface: mobile_workspace_hub
+    mcp_server:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace MCP launcher
+      ui_surface: mobile_workspace_hub
+    claw_hub:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile workspace ClawHub launcher
+      ui_surface: mobile_workspace_hub
+    connectors:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile workspace connectors launcher
+      ui_surface: mobile_workspace_hub
+    ai_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace LLM API launcher
+      ui_surface: mobile_workspace_hub
+    account:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile workspace account launcher
+      ui_surface: mobile_workspace_hub
+  assistant:
+    direct_ai:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Mobile does not expose direct AI assistant mode
+      ui_surface: assistant_page
+    local_gateway:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Mobile does not expose local gateway assistant mode
+      ui_surface: assistant_page
+    relay_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile relay gateway assistant mode
+      ui_surface: assistant_page
+    file_attachments:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile file attachment action in assistant composer
+      ui_surface: assistant_page
+    multi_agent:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile multi-agent toggle in assistant composer
+      ui_surface: assistant_page
+    local_runtime:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Mobile does not expose desktop runtime controls
+      ui_surface: assistant_page
+  settings:
+    general:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings general tab
+      ui_surface: settings_page
+    workspace:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings workspace tab
+      ui_surface: settings_page
+    gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings gateway tab
+      ui_surface: settings_page
+    account_access:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile account access section
+      ui_surface: settings_page
+    vault_server:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile Vault server integration section
+      ui_surface: settings_page
+    gateway_setup_code:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile gateway setup code editor
+      ui_surface: settings_page
+    agents:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile settings multi-agent tab
+      ui_surface: settings_page
+    appearance:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings appearance tab
+      ui_surface: settings_page
+    diagnostics:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings diagnostics tab
+      ui_surface: settings_page
+    experimental:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile settings experimental tab
+      ui_surface: settings_page
+    about:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Mobile settings about tab
+      ui_surface: settings_page
+    experimental_canvas:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile experimental canvas host toggle
+      ui_surface: settings_page
+    experimental_bridge:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile experimental bridge toggle
+      ui_surface: settings_page
+    experimental_debug:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Mobile experimental debug runtime toggle
+      ui_surface: settings_page
+
+desktop:
+  navigation:
+    assistant:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop assistant destination
+      ui_surface: sidebar_navigation
+    tasks:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop tasks destination
+      ui_surface: sidebar_navigation
+    skills:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop skills destination
+      ui_surface: sidebar_navigation
+    nodes:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop nodes destination
+      ui_surface: sidebar_navigation
+    agents:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop agents destination
+      ui_surface: sidebar_navigation
+    mcp_server:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop MCP Hub destination
+      ui_surface: sidebar_navigation
+    claw_hub:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop ClawHub destination
+      ui_surface: sidebar_navigation
+    secrets:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop secrets destination
+      ui_surface: sidebar_navigation
+    ai_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop LLM API destination
+      ui_surface: sidebar_navigation
+    settings:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings destination
+      ui_surface: sidebar_navigation
+    account:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop account destination
+      ui_surface: sidebar_navigation
+  workspace:
+    claw_hub:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop workspace ClawHub tab
+      ui_surface: modules_page
+    connectors:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop workspace connectors tab
+      ui_surface: modules_page
+  assistant:
+    direct_ai:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop direct AI assistant mode
+      ui_surface: assistant_page
+    local_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop local gateway assistant mode
+      ui_surface: assistant_page
+    relay_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop relay gateway assistant mode
+      ui_surface: assistant_page
+    file_attachments:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop file attachment action in assistant composer
+      ui_surface: assistant_page
+    multi_agent:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop multi-agent toggle in assistant composer
+      ui_surface: assistant_page
+    local_runtime:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop local runtime and gateway orchestration entry
+      ui_surface: assistant_page
+  settings:
+    general:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings general tab
+      ui_surface: settings_page
+    workspace:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings workspace tab
+      ui_surface: settings_page
+    gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings gateway tab
+      ui_surface: settings_page
+    account_access:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop account access section
+      ui_surface: settings_page
+    vault_server:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop Vault server integration section
+      ui_surface: settings_page
+    gateway_setup_code:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop gateway setup code editor
+      ui_surface: settings_page
+    agents:
+      enabled: false
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop settings multi-agent tab
+      ui_surface: settings_page
+    appearance:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings appearance tab
+      ui_surface: settings_page
+    diagnostics:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings diagnostics tab
+      ui_surface: settings_page
+    experimental:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop settings experimental tab
+      ui_surface: settings_page
+    about:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Desktop settings about tab
+      ui_surface: settings_page
+    experimental_canvas:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop experimental canvas host toggle
+      ui_surface: settings_page
+    experimental_bridge:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop experimental bridge toggle
+      ui_surface: settings_page
+    experimental_debug:
+      enabled: true
+      release_tier: experimental
+      build_modes: [debug, profile, release]
+      description: Desktop experimental debug runtime toggle
+      ui_surface: settings_page
+
+web:
+  navigation:
+    assistant:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web assistant destination
+      ui_surface: web_shell
+    tasks:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web tasks destination
+      ui_surface: web_shell
+    skills:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web skills destination
+      ui_surface: web_shell
+    nodes:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web nodes destination
+      ui_surface: web_shell
+    secrets:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web secrets destination
+      ui_surface: web_shell
+    ai_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web LLM API destination
+      ui_surface: web_shell
+    settings:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web settings destination
+      ui_surface: web_shell
+  assistant:
+    direct_ai:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web direct AI assistant mode
+      ui_surface: web_assistant_page
+    relay_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web relay gateway assistant mode
+      ui_surface: web_assistant_page
+    file_attachments:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web file attachment action in assistant composer
+      ui_surface: web_assistant_page
+    multi_agent:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web multi-agent toggle in assistant composer
+      ui_surface: web_assistant_page
+    local_gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web local gateway assistant mode
+      ui_surface: web_assistant_page
+    local_runtime:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Web does not expose desktop runtime controls
+      ui_surface: web_assistant_page
+  settings:
+    general:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web settings general tab
+      ui_surface: web_settings_page
+    gateway:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web settings gateway tab
+      ui_surface: web_settings_page
+    account_access:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Web does not expose account access section
+      ui_surface: web_settings_page
+    vault_server:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Web does not expose vault server integration
+      ui_surface: web_settings_page
+    gateway_setup_code:
+      enabled: false
+      release_tier: experimental
+      build_modes: []
+      description: Web does not expose gateway setup code editor
+      ui_surface: web_settings_page
+    appearance:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web settings appearance tab
+      ui_surface: web_settings_page
+    about:
+      enabled: true
+      release_tier: stable
+      build_modes: [debug, profile, release]
+      description: Web settings about tab
+      ui_surface: web_settings_page
+''';
diff --git a/test/app/ui_feature_manifest_test.dart b/test/app/ui_feature_manifest_test.dart
index afcfb9ea..3bce8c65 100644
--- a/test/app/ui_feature_manifest_test.dart
+++ b/test/app/ui_feature_manifest_test.dart
@@ -137,4 +137,28 @@ web: {}
       throwsFormatException,
     );
   });
+
+  test('copyWithFeature keeps build mode sets isolated', () {
+    final manifest = UiFeatureManifest.fallback();
+    final originalFlag = manifest.lookup(
+      UiFeaturePlatform.desktop,
+      'assistant',
+      'direct_ai',
+    )!;
+
+    final copied = manifest.copyWithFeature(
+      platform: UiFeaturePlatform.desktop,
+      module: 'assistant',
+      feature: 'direct_ai',
+      enabled: false,
+    );
+    final copiedFlag = copied.lookup(
+      UiFeaturePlatform.desktop,
+      'assistant',
+      'direct_ai',
+    )!;
+
+    expect(identical(copiedFlag.buildModes, originalFlag.buildModes), isFalse);
+    expect(copiedFlag.buildModes, equals(originalFlag.buildModes));
+  });
 }