fix(pilot): persist Apply — stamp applied_at on click

Issue #2 from phase-8-review-issues.md. Apply was client-side-only via
a bannerApplied flag. Refresh / chat reselect / multi-tab would drop
Verifying state back to Proposed.

- New POST /ai-sessions/{sid}/suggested-fixes/{fid}/apply stamps
  applied_at without changing status (still 'proposed'). Idempotent
  if already stamped; 409 if fix is past proposed (a terminal outcome
  was already recorded).
- Bumps state_version so resolve/escalate preview bundles reflect that
  the fix has entered verifying.
- Frontend handleApplyFix calls the endpoint and uses the returned
  applied_at directly. bannerApplied client flag is removed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/api/sessionSuggestedFixes.ts

@@ -111,6 +111,19 @@ export const sessionSuggestedFixesApi = {
     return r.data
   },
 
+  /**
+   * Stamp applied_at when the engineer clicks Apply in the ProposalBanner.
+   * Does NOT change status (fix remains 'proposed'). Status flips only on
+   * a subsequent PATCH /outcome. Idempotent if applied_at is already set.
+   * Returns 409 if the fix is no longer in 'proposed' status.
+   */
+  async applyFix(sessionId: string, fixId: string): Promise<SessionSuggestedFix> {
+    const r = await apiClient.post<SessionSuggestedFix>(
+      `/ai-sessions/${sessionId}/suggested-fixes/${fixId}/apply`,
+    )
+    return r.data
+  },
+
   /**
    * Record the outcome of applying a suggested fix. Transition rules:
    * - from `proposed` or `applied_partial`: any outcome is valid (partial is

frontend/src/pages/AssistantChatPage.tsx

@@ -135,20 +135,19 @@ export default function AssistantChatPage() {
   const isNarrow = useMediaQuery('(max-width: 1199px)')
   // Phase 8: ProposalBanner + EscalateInterceptDialog state.
   const [bannerCollapsed, setBannerCollapsed] = useState(false)
-  const [bannerApplied, setBannerApplied] = useState(false)
   const [postApplyMsgCount, setPostApplyMsgCount] = useState(0)
   const [nudgeSilenced, setNudgeSilenced] = useState(false)
   const [escalateIntercept, setEscalateIntercept] = useState<{ fixId: string; fixTitle: string } | null>(null)
-  // Phase 8: compute the current banner mode from activeFix + client-side flags.
-  // bannerApplied is a client-side-only flag that flips on Apply click so we
-  // don't need a server round-trip just to stamp applied_at for mode computation.
+  // Phase 8: compute the current banner mode from activeFix.
+  // applied_at is now persisted on the server (stamped by POST /apply),
+  // so bannerMode is derived entirely from server state — no client-side flag.
   const bannerMode: BannerMode | null = (() => {
     if (!activeFix) return null
     if (activeFix.status === 'dismissed') return null
     if (activeFix.ai_outcome_proposal) return 'ai_confirming'
     if (activeFix.status === 'applied_partial') return 'partial'
     if (activeFix.status === 'applied_success' || activeFix.status === 'applied_failed') return null
-    if (bannerApplied || activeFix.applied_at) {
+    if (activeFix.applied_at) {
       if (postApplyMsgCount >= 3 && !nudgeSilenced) return 'nudge'
       return 'verifying'
     }
@@ -341,7 +340,6 @@ export default function AssistantChatPage() {
     setScriptPanelOpen(false)
     // Phase 8: banner state reset
     setBannerCollapsed(false)
-    setBannerApplied(false)
     setPostApplyMsgCount(0)
     setNudgeSilenced(false)
     setEscalateIntercept(null)
@@ -513,16 +511,23 @@ export default function AssistantChatPage() {
     refreshPreview(activeChatId, kind)
   }, [activeChatId, previewKind, refreshPreview])
 
-  // Phase 8: handleApplyFix — opens the existing script panel (same as clicking
-  // the SuggestedFix card) and stamps the client-side bannerApplied flag so
-  // bannerMode transitions to 'verifying' without a server round-trip.
-  const handleApplyFix = useCallback(() => {
-    if (!activeFix) return
-    setBannerApplied(true)
+  // Phase 8: handleApplyFix — stamps applied_at on the server so Verifying state
+  // survives refresh/reselect/multi-tab, then opens the script panel.
+  const handleApplyFix = useCallback(async () => {
+    if (!activeFix || !activeChatId) return
     setPostApplyMsgCount(0)
     setNudgeSilenced(false)
+    try {
+      const updated = await sessionSuggestedFixesApi.applyFix(activeChatId, activeFix.id)
+      setActiveFix(updated)
+    } catch (err: unknown) {
+      // Non-fatal: the script panel still opens. The banner will stay in
+      // 'proposed' mode until the next refreshActiveFix succeeds, which is
+      // a cosmetic gap only — no data loss.
+      console.error('[AssistantChat] applyFix failed:', err)
+    }
     setScriptPanelOpen(true)
-  }, [activeFix])
+  }, [activeFix, activeChatId])
 
   // Phase 8: record a terminal outcome for the active fix. Updates local state
   // on success. For applied_success also opens the Resolve preview.
@@ -532,7 +537,6 @@ export default function AssistantChatPage() {
       const updated = await sessionSuggestedFixesApi.patchOutcome(activeChatId, activeFix.id, outcome, notes)
       setActiveFix(updated)
       // Reset apply tracking state since we now have a terminal outcome.
-      setBannerApplied(false)
       setPostApplyMsgCount(0)
       setNudgeSilenced(false)
       if (outcome === 'applied_success') {
@@ -586,7 +590,7 @@ export default function AssistantChatPage() {
   const handleEscalateClick = useCallback(() => {
     const inVerifyState =
       activeFix && (
-        ((bannerApplied || !!activeFix.applied_at) && activeFix.status === 'proposed') ||
+        (!!activeFix.applied_at && activeFix.status === 'proposed') ||
         activeFix.status === 'applied_partial'
       )
     if (inVerifyState && activeFix) {
@@ -594,7 +598,7 @@ export default function AssistantChatPage() {
       return
     }
     setShowConclude(true)
-  }, [activeFix, bannerApplied])
+  }, [activeFix])
 
   const handleInterceptChoice = useCallback(async (choice: InterceptChoice) => {
     const stored = escalateIntercept
@@ -614,7 +618,7 @@ export default function AssistantChatPage() {
   // Phase 8: Resolve click — auto-mark applied_success if in verifying state
   // before opening the resolution note preview.
   const handleResolveClick = useCallback(async () => {
-    if (activeFix && (bannerApplied || activeFix.applied_at) && activeFix.status === 'proposed' && activeChatId) {
+    if (activeFix && activeFix.applied_at && activeFix.status === 'proposed' && activeChatId) {
       try {
         const updated = await sessionSuggestedFixesApi.patchOutcome(activeChatId, activeFix.id, 'applied_success')
         setActiveFix(updated)
@@ -623,7 +627,7 @@ export default function AssistantChatPage() {
       }
     }
     setShowConclude(true)
-  }, [activeChatId, activeFix, bannerApplied])
+  }, [activeChatId, activeFix])
 
   const handleClosePreview = () => {
     setPreviewKind(null)
@@ -841,8 +845,7 @@ export default function AssistantChatPage() {
       // Only increments when fix is still in 'proposed' (verifying) state —
       // partial/dismissed/terminal states don't render the nudge, and a
       // partial→verifying transition could inherit an already-saturated counter.
-      if (activeFix && (bannerApplied || activeFix.applied_at) &&
-          activeFix.status === 'proposed') {
+      if (activeFix && activeFix.applied_at && activeFix.status === 'proposed') {
         setPostApplyMsgCount(c => c + 1)
       }
       // Refetch facts + active fix; preview refreshes if open.
@@ -917,8 +920,7 @@ export default function AssistantChatPage() {
       }
       // Phase 8: increment post-apply message counter for nudge logic (mirrors handleSend).
       // Only increments in 'proposed' (verifying) state — same rationale as handleSend.
-      if (activeFix && (bannerApplied || activeFix.applied_at) &&
-          activeFix.status === 'proposed') {
+      if (activeFix && activeFix.applied_at && activeFix.status === 'proposed') {
         setPostApplyMsgCount(c => c + 1)
       }
       // Refetch facts + active fix; answering tasks is the primary trigger.