fix(canvas): review cleanups — head-failure toolbar gate, derived pin state

Gate the view-mode toolbar on currentHeadBuildFailure too, matching the
fix already applied in CanvasBuildStatus, so a failed head build behind an
older ready build still surfaces. Fold the pin's refresh key into the
PinnedArtifact object instead of a third useState, track the eviction
count with a running counter, avoid a Set round-trip in setThreadMounted,
and share the post-publish re-read between the home-seed success and
409-retry paths.

Generated-By: PostHog Code
Task-Id: 50c0257c-3627-45cd-887c-f87101f06463

Author: k11kirky

packages/core/src/canvas/dashboardsService.ts

@@ -386,9 +386,8 @@ export class DashboardsService {
       // POST. On the 409 version conflict, re-read the head and retry once
       // against the fresh version id rather than failing the channel open.
       if (apiErrorStatus(error) !== 409) throw error;
-      const fresh = await this.get(record.id);
-      await publish(fresh?.currentVersionId ?? null);
-      return fresh ?? record;
+      const conflicted = await this.get(record.id);
+      await publish(conflicted?.currentVersionId ?? null);
     }
     const fresh = await this.get(record.id);
     return fresh ?? record;

packages/ui/src/features/canvas/freeform/FreeformCanvasView.tsx

@@ -9,6 +9,7 @@ import {
   WarningIcon,
 } from "@phosphor-icons/react";
 import {
+  currentHeadBuildFailure,
   hasActiveCanvasBuild,
   latestFinishedCanvasBuild,
   publishedCanvasBuild,
@@ -89,6 +90,10 @@ interface PinnedArtifact {
   url: string;
   /** Epoch ms the pinned URL was minted (the builds fetch that produced it). */
   mintedAt: number;
+  /** The refresh nonce the pin was adopted under, so a remount also re-stamps
+   * the pin's mint time (otherwise the expiry timer would keep firing on a URL
+   * that's already been recovered). */
+  refreshKey: number;
 }
 
 // A freeform (React-in-iframe) canvas. The rendered output is, in priority
@@ -258,22 +263,18 @@ export function FreeformCanvasView({
   // what guarantees a wedged iframe actually retries: the token endpoint is the
   // authority, and a new URL for the same bucket would be byte-identical.
   const [artifactRefreshKey, setArtifactRefreshKey] = useState(0);
-  // Track the refresh key the current pin was adopted under, so a remount also
-  // re-stamps the pin's mint time (otherwise the expiry timer would keep firing
-  // on a URL that's already been recovered).
-  const [pinnedForRefreshKey, setPinnedForRefreshKey] = useState(-1);
   if (publishedBuild?.artifactUrl) {
     const adoptFresh =
       !pinnedArtifact ||
       pinnedArtifact.buildId !== publishedBuild.id ||
-      pinnedForRefreshKey !== artifactRefreshKey;
+      pinnedArtifact.refreshKey !== artifactRefreshKey;
     if (adoptFresh) {
       setPinnedArtifact({
         buildId: publishedBuild.id,
         url: publishedBuild.artifactUrl,
         mintedAt: buildsUpdatedAt || Date.now(),
+        refreshKey: artifactRefreshKey,
       });
-      setPinnedForRefreshKey(artifactRefreshKey);
     }
   } else if (lifecycle && pinnedArtifact) {
     // The lifecycle says there's no published build anymore — drop the pin.
@@ -502,6 +503,7 @@ export function FreeformCanvasView({
     !!lifecycle &&
     lifecycle.builds.length > 0 &&
     (hasActiveCanvasBuild(lifecycle) ||
+      !!currentHeadBuildFailure(lifecycle) ||
       latestFinishedCanvasBuild(lifecycle)?.buildStatus === "failed");
   const showToolbar = interactive || hasBuildSignal;
 

packages/ui/src/features/canvas/stores/freeformChatStore.ts

@@ -65,18 +65,17 @@ export const useFreeformChatStore = create<FreeformChatStore>()((set) => {
         [threadId]: fn(s.threads[threadId] ?? EMPTY_FREEFORM_THREAD),
       };
       const mounted = new Set(s.mountedThreadIds);
+      let evictable = threadOrder.filter((id) => !mounted.has(id)).length;
       let index = 0;
-      while (
-        threadOrder.length - mountedCount(threadOrder, mounted) > MAX_THREADS &&
-        index < threadOrder.length
-      ) {
+      while (evictable > MAX_THREADS && index < threadOrder.length) {
         const candidate = threadOrder[index];
         if (mounted.has(candidate)) {
           index++;
           continue;
         }
         threadOrder.splice(index, 1);
         delete threads[candidate];
+        evictable--;
       }
       return { threads, threadOrder };
     });
@@ -98,17 +97,15 @@ export const useFreeformChatStore = create<FreeformChatStore>()((set) => {
     setThreadMounted: (threadId, mounted) => {
       set((s) => ({
         mountedThreadIds: mounted
-          ? [...new Set([...s.mountedThreadIds, threadId])]
+          ? s.mountedThreadIds.includes(threadId)
+            ? s.mountedThreadIds
+            : [...s.mountedThreadIds, threadId]
           : s.mountedThreadIds.filter((id) => id !== threadId),
       }));
     },
   };
 });
 
-function mountedCount(order: string[], mounted: ReadonlySet<string>): number {
-  return order.reduce((count, id) => (mounted.has(id) ? count + 1 : count), 0);
-}
-
 export function useFreeformThread(threadId: string): FreeformThreadState {
   return useFreeformChatStore(
     (s) => s.threads[threadId] ?? EMPTY_FREEFORM_THREAD,