perf: reduce idle desktop load by gating plan-mode checks

- Add startup feature flag for plan mode from OPENCODE_EXPERIMENTAL* env vars.
- Stop recurring app health polling and keep a one-time startup check.
- Skip plan-mode synthetic parsing and plan tab/file work when flag is off.

packages/ui/src/components/chat/ChatMessage.tsx

@@ -5,6 +5,7 @@ import { useShallow } from 'zustand/react/shallow';
 import { defaultCodeDark, defaultCodeLight } from '@/lib/codeTheme';
 import { MessageFreshnessDetector } from '@/lib/messageFreshness';
 import { useConfigStore } from '@/stores/useConfigStore';
+import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 import { useUIStore } from '@/stores/useUIStore';
 import { useContextStore } from '@/stores/contextStore';
 import { useStreamingStore } from '@/sync/streaming';
@@ -214,6 +215,7 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
     const showStickyInlineHoverRow = isUser && !isMobile && stickyUserHeader && !useExternalUserActionsRow;
 
     const sessionId = message.info.sessionID;
+    const planModeEnabled = useFeatureFlagsStore((state) => state.planModeEnabled);
 
     // Keep non-active-turn rows detached from context-store churn.
     const { currentContextAgent, savedSessionAgentSelection } = useContextStore(
@@ -228,8 +230,8 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
             return message.parts;
         }
 
-        return normalizeUserDisplayParts(message.parts);
-    }, [isUser, message.parts]);
+        return normalizeUserDisplayParts(message.parts, { planModeEnabled });
+    }, [isUser, message.parts, planModeEnabled]);
 
     const previousUserMetadata = React.useMemo(() => {
         if (isUser || !previousMessage) {
@@ -269,6 +271,7 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
     }, [isUser, previousMessage]);
 
     const previousIsModeSwitchMessage = React.useMemo(() => {
+        if (!planModeEnabled) return false;
         if (isUser || !previousMessage) return false;
         const parts = Array.isArray(previousMessage.parts) ? previousMessage.parts : [];
         for (let i = 0; i < parts.length; i++) {
@@ -281,7 +284,7 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
             }
         }
         return false;
-    }, [isUser, previousMessage]);
+    }, [isUser, planModeEnabled, previousMessage]);
 
     const agentName = React.useMemo(() => {
         if (isUser) return undefined;

packages/ui/src/components/chat/message/normalizeUserDisplayParts.ts

@@ -81,15 +81,16 @@ const buildGitHubAttachmentPart = (text: string): Part | null => {
     return null;
 };
 
-const shouldKeepSyntheticUserText = (text: string): boolean => {
+const shouldKeepSyntheticUserText = (text: string, planModeEnabled: boolean): boolean => {
     const trimmed = text.trim();
-    if (trimmed.startsWith('User has requested to enter plan mode')) return true;
-    if (trimmed.startsWith('The plan at ')) return true;
+    if (planModeEnabled && trimmed.startsWith('User has requested to enter plan mode')) return true;
+    if (planModeEnabled && trimmed.startsWith('The plan at ')) return true;
     if (trimmed.startsWith('The following tool was executed by the user')) return true;
     return false;
 };
 
-export const normalizeUserDisplayParts = (parts: Part[]): Part[] => {
+export const normalizeUserDisplayParts = (parts: Part[], options?: { planModeEnabled?: boolean }): Part[] => {
+    const planModeEnabled = options?.planModeEnabled === true;
     return parts
         .filter((part) => {
             const synthetic = (part as { synthetic?: boolean }).synthetic === true;
@@ -101,7 +102,7 @@ export const normalizeUserDisplayParts = (parts: Part[]): Part[] => {
             }
 
             const normalizedText = text.trimStart();
-            return shouldKeepSyntheticUserText(text)
+            return shouldKeepSyntheticUserText(text, planModeEnabled)
                 || normalizedText.startsWith(GITHUB_ISSUE_CONTEXT_PREFIX)
                 || normalizedText.startsWith(GITHUB_PR_CONTEXT_PREFIX);
         })

packages/ui/src/components/layout/Header.tsx

@@ -30,6 +30,7 @@ import { useFilesViewTabsStore } from '@/stores/useFilesViewTabsStore';
 import { useGitStore } from '@/stores/useGitStore';
 import { useGitHubPrStatusStore } from '@/stores/useGitHubPrStatusStore';
 import { useGlobalSessionsStore } from '@/stores/useGlobalSessionsStore';
+import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 
 import { useGitHubAuthStore } from '@/stores/useGitHubAuthStore';
 import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
@@ -807,7 +808,8 @@ export const Header: React.FC<HeaderProps> = ({
 
 
   const [planTabAvailable, setPlanTabAvailable] = React.useState(false);
-  const showPlanTab = planTabAvailable;
+  const planModeEnabled = useFeatureFlagsStore((state) => state.planModeEnabled);
+  const showPlanTab = planModeEnabled && planTabAvailable;
   const lastPlanSessionKeyRef = React.useRef<string>('');
 
   const handleGitHubAccountSwitch = React.useCallback(async (accountId: string) => {
@@ -843,6 +845,14 @@ export const Header: React.FC<HeaderProps> = ({
   }, [isSwitchingGitHubAccount, runtimeApis.github, setGitHubAuthStatus]);
 
   React.useEffect(() => {
+    if (!planModeEnabled) {
+      setPlanTabAvailable(false);
+      if (useUIStore.getState().activeMainTab === 'plan') {
+        useUIStore.getState().setActiveMainTab('chat');
+      }
+      return;
+    }
+
     let cancelled = false;
 
     const checkExists = async (directory: string, fileName: string): Promise<boolean> => {
@@ -903,6 +913,7 @@ export const Header: React.FC<HeaderProps> = ({
       window.clearInterval(interval);
     };
   }, [
+    planModeEnabled,
     sessionDirectory,
     currentSession?.slug,
     currentSession?.time?.created,

packages/ui/src/components/views/PlanView.tsx

@@ -18,6 +18,7 @@ import { RiCheckLine, RiClipboardLine, RiFileCopy2Line } from '@remixicon/react'
 import { useSessionUIStore } from '@/sync/session-ui-store';
 import { useSessions } from '@/sync/sync-context';
 import { useDirectoryStore } from '@/stores/useDirectoryStore';
+import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
 import { EditorView } from '@codemirror/view';
 import { copyTextToClipboard } from '@/lib/clipboard';
@@ -84,6 +85,7 @@ export const PlanView: React.FC = () => {
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
   const sessions = useSessions();
   const homeDirectory = useDirectoryStore((state) => state.homeDirectory);
+  const planModeEnabled = useFeatureFlagsStore((state) => state.planModeEnabled);
   const runtimeApis = useRuntimeAPIs();
   useUIStore();
   const { isMobile } = useDeviceInfo();
@@ -256,6 +258,13 @@ export const PlanView: React.FC = () => {
   }, [currentTheme, resolvedPath]);
 
   React.useEffect(() => {
+    if (!planModeEnabled) {
+      setResolvedPath(null);
+      setContent('');
+      setLoading(false);
+      return;
+    }
+
     let cancelled = false;
 
     const readText = async (path: string): Promise<string> => {
@@ -339,7 +348,7 @@ export const PlanView: React.FC = () => {
       cancelled = true;
       window.clearInterval(interval);
     };
-  }, [sessionDirectory, session?.slug, session?.time?.created, homeDirectory, runtimeApis.files]);
+  }, [planModeEnabled, sessionDirectory, session?.slug, session?.time?.created, homeDirectory, runtimeApis.files]);
 
   React.useEffect(() => {
     return () => {