fix(annotations): address code review findings (1-8, 10)

1. toggleVote wrapped in transaction (race condition fix)
2. FeedbackPanel fetch calls now surface errors via onError/toast
3. Extracted resolveBoard/hasCollectionRole to shared board-access.js
4. AnnotationStore uses monotonic version counter for snapshots
5. PinOverlay uses object pool instead of destroy/recreate on refresh
6. canvasObjects prop memoized with useMemo
7. PinOverlay store subscription cleaned up on unmount
8. Comment content capped at 5000 chars (backend validation)
10. anchor_type validated to 'object' or 'point'

backend/db.js

@@ -534,7 +534,7 @@ function getVotesByBoard(boardId) {
   return db.prepare('SELECT * FROM object_votes WHERE board_id = ?').all(boardId);
 }
 
-function toggleVote(boardId, objectId, userId) {
+const _toggleVoteTx = db.transaction((boardId, objectId, userId) => {
   const existing = db.prepare(
     'SELECT 1 FROM object_votes WHERE board_id = ? AND object_id = ? AND user_id = ?'
   ).get(boardId, objectId, userId);
@@ -548,6 +548,10 @@ function toggleVote(boardId, objectId, userId) {
       .run(boardId, objectId, userId);
     return true; // vote added
   }
+});
+
+function toggleVote(boardId, objectId, userId) {
+  return _toggleVoteTx(boardId, objectId, userId);
 }
 
 // ---------------------

backend/routes/board-access.js

@@ -0,0 +1,27 @@
+const { getBoard, getCollection, getCollectionMember } = require('../db');
+
+function hasCollectionRole(member, minRole) {
+  if (!member) return false;
+  const hierarchy = { owner: 3, editor: 2, viewer: 1 };
+  return (hierarchy[member.role] || 0) >= (hierarchy[minRole] || 0);
+}
+
+function resolveBoard(req, res, minRole = 'viewer') {
+  const board = getBoard(req.params.boardId);
+  if (!board) { res.status(404).json({ error: 'Board not found' }); return null; }
+
+  const collection = getCollection(board.collection_id);
+  if (!collection) { res.status(404).json({ error: 'Collection not found' }); return null; }
+
+  const member = getCollectionMember(board.collection_id, req.user.id);
+  if (minRole === 'viewer' && collection.is_public) {
+    return { board, collection, member: member || { role: 'viewer' } };
+  }
+  if (!hasCollectionRole(member, minRole)) {
+    res.status(403).json({ error: `${minRole} access required` });
+    return null;
+  }
+  return { board, collection, member };
+}
+
+module.exports = { hasCollectionRole, resolveBoard };

backend/routes/threads.js

@@ -2,9 +2,6 @@ const { Router } = require('express');
 const { v4: uuidv4 } = require('uuid');
 const { authMiddleware } = require('../auth');
 const {
-  getBoard,
-  getCollection,
-  getCollectionMember,
   getThreadsByBoard,
   getThread,
   createThread,
@@ -18,34 +15,13 @@ const {
   incrementThreadCommentCount,
   decrementThreadCommentCount,
 } = require('../db');
+const { hasCollectionRole, resolveBoard } = require('./board-access');
 
 const router = Router();
 
 router.use(authMiddleware);
 
-function hasCollectionRole(member, minRole) {
+const MAX_COMMENT_LENGTH = 5000;
-  if (!member) return false;
-  const hierarchy = { owner: 3, editor: 2, viewer: 1 };
-  return (hierarchy[member.role] || 0) >= (hierarchy[minRole] || 0);
-}
-
-function resolveBoard(req, res, minRole = 'viewer') {
-  const board = getBoard(req.params.boardId);
-  if (!board) { res.status(404).json({ error: 'Board not found' }); return null; }
-
-  const collection = getCollection(board.collection_id);
-  if (!collection) { res.status(404).json({ error: 'Collection not found' }); return null; }
-
-  const member = getCollectionMember(board.collection_id, req.user.id);
-  if (minRole === 'viewer' && collection.is_public) {
-    return { board, collection, member: member || { role: 'viewer' } };
-  }
-  if (!hasCollectionRole(member, minRole)) {
-    res.status(403).json({ error: `${minRole} access required` });
-    return null;
-  }
-  return { board, collection, member };
-}
 
 // GET /api/boards/:boardId/threads — all threads + comments for board
 router.get('/:boardId/threads', (req, res) => {
@@ -85,6 +61,12 @@ router.post('/:boardId/threads', (req, res) => {
     if (!object_id || !content || !content.trim()) {
       return res.status(400).json({ error: 'object_id and content are required' });
     }
+    if (content.length > MAX_COMMENT_LENGTH) {
+      return res.status(400).json({ error: `Content too long (max ${MAX_COMMENT_LENGTH} chars)` });
+    }
+    if (anchor_type && !['object', 'point'].includes(anchor_type)) {
+      return res.status(400).json({ error: 'anchor_type must be "object" or "point"' });
+    }
 
     const threadId = uuidv4();
     const commentId = uuidv4();
@@ -200,6 +182,9 @@ router.post('/:boardId/threads/:threadId/comments', (req, res) => {
     if (!content || !content.trim()) {
       return res.status(400).json({ error: 'content is required' });
     }
+    if (content.length > MAX_COMMENT_LENGTH) {
+      return res.status(400).json({ error: `Content too long (max ${MAX_COMMENT_LENGTH} chars)` });
+    }
 
     const thread = getThread(req.params.threadId);
     if (!thread || thread.board_id !== req.params.boardId) {
@@ -246,6 +231,9 @@ router.put('/:boardId/threads/:threadId/comments/:commentId', (req, res) => {
     if (!content || !content.trim()) {
       return res.status(400).json({ error: 'content is required' });
     }
+    if (content.length > MAX_COMMENT_LENGTH) {
+      return res.status(400).json({ error: `Content too long (max ${MAX_COMMENT_LENGTH} chars)` });
+    }
 
     const comment = getComment(req.params.commentId);
     if (!comment || comment.thread_id !== req.params.threadId) {

backend/routes/votes.js

@@ -1,41 +1,12 @@
 const { Router } = require('express');
 const { authMiddleware } = require('../auth');
-const {
+const { getVotesByBoard, toggleVote } = require('../db');
-  getBoard,
+const { resolveBoard } = require('./board-access');
-  getCollection,
-  getCollectionMember,
-  getVotesByBoard,
-  toggleVote,
-} = require('../db');
 
 const router = Router();
 
 router.use(authMiddleware);
 
-function hasCollectionRole(member, minRole) {
-  if (!member) return false;
-  const hierarchy = { owner: 3, editor: 2, viewer: 1 };
-  return (hierarchy[member.role] || 0) >= (hierarchy[minRole] || 0);
-}
-
-function resolveBoard(req, res, minRole = 'viewer') {
-  const board = getBoard(req.params.boardId);
-  if (!board) { res.status(404).json({ error: 'Board not found' }); return null; }
-
-  const collection = getCollection(board.collection_id);
-  if (!collection) { res.status(404).json({ error: 'Collection not found' }); return null; }
-
-  const member = getCollectionMember(board.collection_id, req.user.id);
-  if (minRole === 'viewer' && collection.is_public) {
-    return { board, collection, member: member || { role: 'viewer' } };
-  }
-  if (!hasCollectionRole(member, minRole)) {
-    res.status(403).json({ error: `${minRole} access required` });
-    return null;
-  }
-  return { board, collection, member };
-}
-
 // GET /api/boards/:boardId/votes — all votes for board
 router.get('/:boardId/votes', (req, res) => {
   try {

frontend/src/canvas/PinOverlay.ts

@@ -9,7 +9,8 @@ const PIN_COLOR_RESOLVED = 0x666666;
 
 export class PinOverlay extends Container {
   private _pins = new Map<string, Graphics>();
-  private _voteBadges: Graphics[] = [];
+  private _voteBadges = new Map<string, Graphics>();
+  private _pool: Graphics[] = [];
   private _viewport: Viewport;
   private _scene: SceneManager;
   private _store: AnnotationStore;
@@ -21,16 +22,30 @@ export class PinOverlay extends Container {
     this._store = store;
   }
 
+  private _acquire(): Graphics {
+    const gfx = this._pool.pop() || new Graphics();
+    gfx.clear();
+    gfx.removeChildren();
+    gfx.visible = true;
+    gfx.eventMode = 'none';
+    gfx.cursor = 'default';
+    return gfx;
+  }
+
+  private _release(gfx: Graphics) {
+    gfx.visible = false;
+    this._pool.push(gfx);
+  }
+
   /** Call on every viewport moved/zoomed event and on store change */
   refresh(showResolved = false) {
-    const scale = 1 / this._viewport.scale.x; // scale-independent size
+    const scale = 1 / this._viewport.scale.x;
 
-    // Remove old pins + badges
+    // Return current pins and badges to pool
-    for (const gfx of this._pins.values()) gfx.destroy();
+    for (const gfx of this._pins.values()) this._release(gfx);
-    for (const gfx of this._voteBadges) gfx.destroy();
+    for (const gfx of this._voteBadges.values()) this._release(gfx);
     this._pins.clear();
-    this._voteBadges = [];
+    this._voteBadges.clear();
-    this.removeChildren();
 
     // ── Thread pins ──
     for (const thread of this._store.threads.values()) {
@@ -46,12 +61,11 @@ export class PinOverlay extends Container {
         wx = bounds.x + thread.pin_x * bounds.width;
         wy = bounds.y + thread.pin_y * bounds.height;
       } else {
-        // Object-level: top-right corner
         wx = bounds.x + bounds.width;
         wy = bounds.y;
       }
 
-      const gfx = new Graphics();
+      const gfx = this._acquire();
       const r = PIN_RADIUS * scale;
       const color = thread.status === 'open' ? PIN_COLOR_OPEN : PIN_COLOR_RESOLVED;
 
@@ -59,27 +73,21 @@ export class PinOverlay extends Container {
       gfx.fill({ color, alpha: 0.9 });
       gfx.stroke({ color: 0xffffff, width: 1.5 * scale, alpha: 0.8 });
       gfx.position.set(wx, wy);
+      gfx.eventMode = 'static';
+      gfx.cursor = 'pointer';
+      (gfx as any)._threadId = thread.id;
 
-      // Count label
       if (thread.comment_count > 1) {
         const label = new Text({
           text: String(thread.comment_count),
-          style: new TextStyle({
+          style: new TextStyle({ fontSize: 9 * scale, fill: '#ffffff', fontWeight: 'bold' }),
-            fontSize: 9 * scale,
-            fill: '#ffffff',
-            fontWeight: 'bold',
-          }),
         });
         label.anchor.set(0.5);
         gfx.addChild(label);
       }
 
-      gfx.eventMode = 'static';
+      if (!gfx.parent) this.addChild(gfx);
-      gfx.cursor = 'pointer';
-      (gfx as any)._threadId = thread.id;
-
       this._pins.set(thread.id, gfx);
-      this.addChild(gfx);
     }
 
     // ── Vote badges ──
@@ -92,7 +100,7 @@ export class PinOverlay extends Container {
       const wx = bounds.x + bounds.width;
       const wy = bounds.y + bounds.height;
 
-      const gfx = new Graphics();
+      const gfx = this._acquire();
       const pw = 24 * scale;
       const ph = 16 * scale;
       const pr = 4 * scale;
@@ -106,8 +114,9 @@ export class PinOverlay extends Container {
       });
       label.anchor.set(0.5);
       gfx.addChild(label);
-      this.addChild(gfx);
+
-      this._voteBadges.push(gfx);
+      if (!gfx.parent) this.addChild(gfx);
+      this._voteBadges.set(objectId, gfx);
     }
   }
 
@@ -125,9 +134,11 @@ export class PinOverlay extends Container {
 
   override destroy(options?: any) {
     for (const gfx of this._pins.values()) gfx.destroy();
-    for (const gfx of this._voteBadges) gfx.destroy();
+    for (const gfx of this._voteBadges.values()) gfx.destroy();
+    for (const gfx of this._pool) gfx.destroy();
     this._pins.clear();
-    this._voteBadges = [];
+    this._voteBadges.clear();
+    this._pool = [];
     super.destroy(options);
   }
 }

frontend/src/components/FeedbackPanel.tsx

@@ -9,6 +9,7 @@ interface FeedbackPanelProps {
   token: string;
   canvasObjects: Map<string, { id: string; name?: string; type: string }>;
   onJumpToObject?: (objectId: string) => void;
+  onError?: (msg: string) => void;
 }
 
 export default function FeedbackPanel({
@@ -19,6 +20,7 @@ export default function FeedbackPanel({
   token,
   canvasObjects,
   onJumpToObject,
+  onError,
 }: FeedbackPanelProps) {
   const [collapsed, setCollapsed] = useState(false);
   const [expandedThreadId, setExpandedThreadId] = useState<string | null>(null);
@@ -30,7 +32,7 @@ export default function FeedbackPanel({
   // Subscribe to store changes
   const _version = useSyncExternalStore(
     (cb) => annotationStore.subscribe(cb),
-    () => annotationStore.threads.size + annotationStore.votes.size,
+    () => annotationStore.version,
   );
 
   const allThreads = Array.from(annotationStore.threads.values());
@@ -54,42 +56,65 @@ export default function FeedbackPanel({
 
   // ── API helpers ──
 
+  const apiFetch = useCallback(async (url: string, init?: RequestInit) => {
+    try {
+      const res = await fetch(url, init);
+      if (!res.ok) {
+        const body = await res.json().catch(() => ({}));
+        throw new Error(body.error || `Request failed (${res.status})`);
+      }
+      return res;
+    } catch (err: any) {
+      onError?.(err.message || 'Request failed');
+      throw err;
+    }
+  }, [onError]);
+
   const postReply = useCallback(async (threadId: string) => {
     if (!replyText.trim()) return;
-    await fetch(`/api/boards/${boardId}/threads/${threadId}/comments`, {
+    try {
+      await apiFetch(`/api/boards/${boardId}/threads/${threadId}/comments`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${token}` },
         body: JSON.stringify({ content: replyText.trim() }),
       });
       setReplyText('');
-  }, [boardId, token, replyText]);
+    } catch {}
+  }, [boardId, token, replyText, apiFetch]);
 
   const resolveThread = useCallback(async (threadId: string, status: string) => {
-    await fetch(`/api/boards/${boardId}/threads/${threadId}`, {
+    try {
+      await apiFetch(`/api/boards/${boardId}/threads/${threadId}`, {
         method: 'PATCH',
         headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${token}` },
         body: JSON.stringify({ status }),
       });
-  }, [boardId, token]);
+    } catch {}
+  }, [boardId, token, apiFetch]);
 
   const deleteComment = useCallback(async (threadId: string, commentId: string) => {
-    await fetch(`/api/boards/${boardId}/threads/${threadId}/comments/${commentId}`, {
+    try {
+      await apiFetch(`/api/boards/${boardId}/threads/${threadId}/comments/${commentId}`, {
         method: 'DELETE',
         headers: { Authorization: `Bearer ${token}` },
       });
-  }, [boardId, token]);
+    } catch {}
+  }, [boardId, token, apiFetch]);
 
   const toggleVote = useCallback(async (objectId: string) => {
-    await fetch(`/api/boards/${boardId}/votes`, {
+    try {
+      await apiFetch(`/api/boards/${boardId}/votes`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${token}` },
         body: JSON.stringify({ object_id: objectId }),
       });
-  }, [boardId, token]);
+    } catch {}
+  }, [boardId, token, apiFetch]);
 
   const createThread = useCallback(async () => {
     if (!newCommentText.trim() || !selectedObjectId) return;
-    await fetch(`/api/boards/${boardId}/threads`, {
+    try {
+      await apiFetch(`/api/boards/${boardId}/threads`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${token}` },
         body: JSON.stringify({
@@ -99,7 +124,8 @@ export default function FeedbackPanel({
         }),
       });
       setNewCommentText('');
-  }, [boardId, token, newCommentText, selectedObjectId]);
+    } catch {}
+  }, [boardId, token, newCommentText, selectedObjectId, apiFetch]);
 
   // ── Collapsed state ──
 

frontend/src/hooks/useCanvasSetup.ts

@@ -355,13 +355,18 @@ export function useCanvasSetup(deps: CanvasSetupDeps) {
         pinOverlayRef.current = pinOverlay;
 
         // Refresh overlay on viewport move
-        viewport.on('moved', () => {
+        const onViewportMoved = () => {
           if (pinOverlay.visible) pinOverlay.refresh();
-        });
+        };
-        // Refresh on store change
+        viewport.on('moved', onViewportMoved);
-        annotationStoreRef.current!.subscribe(() => {
+        // Refresh on store change (save unsub for cleanup)
+        const unsubPinOverlay = annotationStoreRef.current!.subscribe(() => {
           if (pinOverlay.visible) pinOverlay.refresh();
         });
+        (pinOverlay as any)._cleanup = () => {
+          viewport.off('moved', onViewportMoved);
+          unsubPinOverlay();
+        };
       }
 
       // Setup drag/drop and paste
@@ -394,6 +399,7 @@ export function useCanvasSetup(deps: CanvasSetupDeps) {
       dropCleanupRef.current?.();
       pasteCleanupRef.current?.();
       if (pinOverlayRef.current) {
+        (pinOverlayRef.current as any)._cleanup?.();
         pinOverlayRef.current.destroy();
         pinOverlayRef.current = null;
       }

frontend/src/pages/Editor.tsx

@@ -162,6 +162,19 @@ export default function Editor({ isPublicView }: EditorProps) {
     uploadManager, onCanvasChange, showToast, setOnlineUsers, setSelectedLayerIds,
   });
 
+  // Build canvas objects map for FeedbackPanel (memoized on object count changes)
+  const canvasObjectMap = React.useMemo(() => {
+    const scene = canvasRef.current?.getScene();
+    const map = new Map<string, { id: string; name?: string; type: string }>();
+    if (scene) {
+      for (const item of scene.items.values()) {
+        map.set(item.id, { id: item.id, name: item.data.name, type: item.data.type });
+      }
+    }
+    return map;
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [objectCount]);
+
   // Toggle pin overlay visibility with review mode
   useEffect(() => {
     if (pinOverlay) {
@@ -663,16 +676,8 @@ export default function Editor({ isPublicView }: EditorProps) {
             userId={user.id}
             boardId={resolvedBoardId}
             token={localStorage.getItem('token') || ''}
-            canvasObjects={(() => {
+            canvasObjects={canvasObjectMap}
-              const scene = canvasRef.current?.getScene();
+            onError={(msg) => showToast(msg)}
-              const map = new Map<string, { id: string; name?: string; type: string }>();
-              if (scene) {
-                for (const item of scene.items.values()) {
-                  map.set(item.id, { id: item.id, name: item.data.name, type: item.data.type });
-                }
-              }
-              return map;
-            })()}
             onJumpToObject={(objectId) => {
               const scene = canvasRef.current?.getScene();
               const vp = canvasRef.current?.getViewport();

frontend/src/stores/annotationStore.ts

@@ -42,6 +42,10 @@ export class AnnotationStore {
   votes = new Map<string, Set<string>>();
 
   private _listeners = new Set<Listener>();
+  private _version = 0;
+
+  /** Monotonic version counter for useSyncExternalStore snapshots */
+  get version(): number { return this._version; }
 
   subscribe(fn: Listener): () => void {
     this._listeners.add(fn);
@@ -49,6 +53,7 @@ export class AnnotationStore {
   }
 
   private _notify() {
+    this._version++;
     for (const fn of this._listeners) fn();
   }