Fix branch refresh.

web/src/App.tsx

@@ -205,6 +205,9 @@ export default function App() {
   const [toast, setToast] = useState<string | null>(null);
 
   const path = repo?.path ?? null;
+  // What the header currently says the work tree is on. The poll below compares
+  // against it to notice a branch switch made outside this pane.
+  const branch = repo?.branch ?? null;
 
   // ctxByRepo holds only the repos whose base ref you've actually changed;
   // anything else falls back to HEAD. Deriving rather than seeding state avoids a
@@ -338,6 +341,18 @@ export default function App() {
     if (path) loadDiff(ctx);
   }, [path, ctx, loadDiff]);
 
+  // What the refresh button and the stale banner do. Deliberately more than
+  // reloading the patch: the reason to press either is that the world moved, and
+  // everything the header shows — the branch, the ref list the base picker offers,
+  // the draft counts — is otherwise fetched once when the page loads and never
+  // again. The poll below catches a branch switch on its own, but it stops once
+  // the diff is known to be stale, and it can't see a ref that was merely
+  // created; pressing refresh is the answer to both.
+  const reload = useCallback(() => {
+    loadRepo();
+    loadDiff(ctx);
+  }, [loadRepo, loadDiff, ctx]);
+
   // Tell the server which diff is on screen, so an agent asked to review it lands
   // its comments on the lines you're actually looking at. Best-effort — nothing on
   // screen depends on it.
@@ -404,10 +419,18 @@ export default function App() {
       busy = true;
       const seq = reqRef.current;
       try {
-        const { revision: now } = await api.revision(ctx, { ignoreWhitespace: ignoreWs });
+        const { revision: now, branch: on } = await api.revision(ctx, {
+          ignoreWhitespace: ignoreWs,
+        });
         // A load that started while this was in flight has already answered the
         // question, with a revision this closure doesn't know about.
         if (canceled || seq !== reqRef.current) return;
+        // A branch switch is news about the repository rather than about the
+        // diff, and the two don't always arrive together — so it is acted on
+        // rather than announced. The header is describing the work tree, which
+        // really is on another branch now; the diff below it is still the one
+        // you were reading, and the banner is what offers to move that.
+        if (on && on !== branch) loadRepo();
         if (now && now !== revision) setStale(now);
       } catch {
         // A failed poll says nothing about the diff — the next one will.
@@ -428,7 +451,7 @@ export default function App() {
       document.removeEventListener('visibilitychange', onVisible);
       window.removeEventListener('focus', onVisible);
     };
-  }, [path, ctx, ignoreWs, revision, stale]);
+  }, [path, ctx, ignoreWs, revision, stale, branch, loadRepo]);
 
   // dismissStale keeps the diff you are reading and stops pointing at it, but
   // takes the newer state as the baseline — so the *next* change says so too,
@@ -723,7 +746,7 @@ export default function App() {
 
           <button
             className={`icon-btn${stale ? ' is-attention' : ''}`}
-            onClick={() => loadDiff(ctx)}
+            onClick={reload}
             title={stale ? 'Reload the diff — the work tree has moved on' : 'Refresh diff'}
             aria-label="Refresh diff"
           >
@@ -779,7 +802,7 @@ export default function App() {
           <span className="banner-text">
             This diff is out of date — the work tree has changed since it loaded.
           </span>
-          <button className="btn-ghost" onClick={() => loadDiff(ctx)}>
+          <button className="btn-ghost" onClick={reload}>
             <Icon name="sync" size={14} />
             Refresh
           </button>

web/src/api.ts

@@ -108,13 +108,19 @@ export const api = {
   // `revision` that came with the diff on screen. One hash, so it's cheap to ask
   // for repeatedly — which is what lets the page notice the diff is out of date
   // without pulling it out from under whoever is reading it.
+  //
+  // `branch` is the work tree's current branch, answered here because this is the
+  // one thing the page asks about on a timer. The header names the branch, and
+  // nothing else would tell the page it had changed: the digest covers HEAD's
+  // sha, so branching off the commit you're on doesn't move it (see
+  // Server.handleRevision), and repo info is otherwise fetched once at load.
   revision: (ctx: DiffContext, opts: { ignoreWhitespace?: boolean } = {}) =>
     fetch(
       `${apiBase}/diff/revision${q(
         ...ctxParams(ctx),
         ...(opts.ignoreWhitespace ? ['ignoreWhitespace=1'] : []),
       )}`,
-    ).then(json<{ revision: string }>),
+    ).then(json<{ revision: string; branch?: string }>),
 
   // Full contents of a file at a ref, for expanding collapsed context. Null when
   // the file doesn't exist at that ref (e.g. a newly added file).