fix(web): an unrelated tab settling no longer replays stale titles

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: juliusmarminge

apps/web/src/browserHistoryStore.test.ts

@@ -111,17 +111,17 @@ const threadRef = {
 
 let settledAt = 0;
 
-function settle(url: string, title: string, tabId = "tab_a"): void {
+function settle(url: string, title: string, tabId = "tab_a", ref = threadRef): void {
   settledAt += 1;
   const snapshot: PreviewSessionSnapshot = {
-    threadId: threadRef.threadId,
+    threadId: ref.threadId,
     tabId,
     navStatus: { _tag: "Success", url, title },
     canGoBack: false,
     canGoForward: false,
     updatedAt: new Date(settledAt).toISOString(),
   };
-  applyPreviewServerSnapshot(threadRef, snapshot);
+  applyPreviewServerSnapshot(ref, snapshot);
 }
 
 function resetStores(): () => void {
@@ -162,6 +162,22 @@ describe("useBrowserHistoryStore", () => {
     expect(useBrowserHistoryStore.getState().byProjectKey["proj-a"]?.[0]?.title).toBe("New");
   });
 
+  it("keeps another thread's newer title when an unrelated tab settles", () => {
+    const otherThreadRef = { ...threadRef, threadId: ThreadId.make("thread-2") };
+    const store = useBrowserHistoryStore.getState();
+    store.registerThreadProject(threadRef, "proj-a");
+    store.registerThreadProject(otherThreadRef, "proj-a");
+    recordVisitForThread(threadRef, "http://a.test/", 1);
+    settle("http://a.test/", "Old", "tab_a", threadRef);
+    settle("http://a.test/", "New", "tab_a", otherThreadRef);
+    settle("http://b.test/", "Unrelated", "tab_b", threadRef);
+    expect(
+      useBrowserHistoryStore
+        .getState()
+        .byProjectKey["proj-a"]?.find((e) => e.url === "http://a.test/")?.title,
+    ).toBe("New");
+  });
+
   it("sets a title against a settled url that differs from the stored one only by a trailing slash", () => {
     useBrowserHistoryStore.getState().registerThreadProject(threadRef, "proj-a");
     recordVisitForThread(threadRef, "http://a.test/community", 1);

apps/web/src/browserHistoryStore.ts

@@ -336,16 +336,22 @@ export function recordVisitForThread(ref: ScopedThreadRef, url: string, at?: num
  * Titles only update entries already in the thread's project history, so they
  * are applied both when a page settles and when its visit is recorded.
  */
-function recordPreviewTitles(ref: ScopedThreadRef, preview: ThreadPreviewState): void {
+function recordPreviewTitles(
+  ref: ScopedThreadRef,
+  preview: ThreadPreviewState,
+  previousSessions?: ThreadPreviewState["sessions"],
+): void {
   const state = useBrowserHistoryStore.getState();
   const projectKey = state.projectKeyByThreadKey[scopedThreadKey(ref)];
   if (!projectKey || !state.byProjectKey[projectKey]?.length) return;
   const connection = readPreparedConnection(ref.environmentId);
   const environmentHostname = connection ? new URL(connection.httpBaseUrl).hostname : null;
   // Tabs can share a URL; applying oldest first lets the newest settle win.
-  const sessions = Object.values(preview.sessions).toSorted((a, b) =>
-    a.updatedAt.localeCompare(b.updatedAt),
-  );
+  // Unchanged sessions are skipped so a stale title cannot overwrite a newer
+  // one another thread in the same project recorded since.
+  const sessions = Object.values(preview.sessions)
+    .filter((session) => previousSessions?.[session.tabId] !== session)
+    .toSorted((a, b) => a.updatedAt.localeCompare(b.updatedAt));
   for (const session of sessions) {
     const status = session.navStatus;
     if (status._tag !== "Success" || !status.title) continue;
@@ -365,8 +371,9 @@ export function startPreviewTitleRecording(): () => void {
         threadKey,
         appAtomRegistry.subscribe(atom, (next) => {
           if (next.sessions === previousSessions) return;
+          const changedSince = previousSessions;
           previousSessions = next.sessions;
-          recordPreviewTitles(threadRef, next);
+          recordPreviewTitles(threadRef, next, changedSince);
         }),
       );
     }