fix(desktop): stabilize workstream PR subscriptions

Signed-off-by: loganj <loganj@squareup.com>
Co-authored-by: Amp <amp@ampcode.com>

desktop/src/features/workstream-board/lib/workstreamPullRequestStatus.test.mjs

@@ -236,6 +236,51 @@ test("workstream status hook preserves a synchronous live callback", async () =>
   cleanup();
 });
 
+test("workstream status hook keeps subscriptions stable across equivalent rerenders", async () => {
+  const { act, cleanup, renderHook } = await import("@testing-library/react");
+  const { useWorkstreamPullRequestStatuses } = await import(
+    "./workstreamPullRequestStatus.ts"
+  );
+  const reference = parseWorkstreamPullRequestReference(
+    "https://github.com/block/buzz/pull/42",
+  );
+  let subscribes = 0;
+  let unsubscribes = 0;
+  const registry = {
+    subscribe: (_reference, listener) => {
+      subscribes += 1;
+      listener({ status: "loading" });
+      return () => {
+        unsubscribes += 1;
+      };
+    },
+  };
+  const { rerender, unmount } = renderHook(
+    ({ refs }) => useWorkstreamPullRequestStatuses(refs, registry),
+    { initialProps: { refs: [reference] } },
+  );
+
+  await act(async () => {
+    rerender({ refs: [{ ...reference }] });
+    rerender({ refs: [{ ...reference }] });
+  });
+  assert.equal(subscribes, 1);
+  assert.equal(unsubscribes, 0);
+
+  const replacement = parseWorkstreamPullRequestReference(
+    "https://github.com/block/buzz/pull/43",
+  );
+  await act(async () => {
+    rerender({ refs: [replacement] });
+  });
+  assert.equal(subscribes, 2);
+  assert.equal(unsubscribes, 1);
+
+  unmount();
+  assert.equal(unsubscribes, 2);
+  cleanup();
+});
+
 test("workstream status hook removes stale references and preserves unsupported state", async () => {
   const { act, cleanup, renderHook } = await import("@testing-library/react");
   const { useWorkstreamPullRequestStatuses } = await import(

desktop/src/features/workstream-board/lib/workstreamPullRequestStatus.ts

@@ -519,11 +519,26 @@ export function useWorkstreamPullRequestStatuses(
   const [states, setStates] = React.useState<
     ReadonlyMap<string, WorkstreamPullRequestDisplayState>
   >(() => new Map());
-  const referencesByIdentity = React.useMemo(() => {
+  // Cards rebuild parsed references on every render. Subscribe by their
+  // semantic identity instead of that transient array/object identity so a
+  // synchronous registry listener cannot cause an effect resubscribe loop.
+  const referenceIdentityKey = references
+    .map((reference) => reference.identity)
+    .sort()
+    .join("\u0000");
+  const referencesByIdentityRef = React.useRef<{
+    identityKey: string;
+    references: ReadonlyMap<string, WorkstreamPullRequestReference>;
+  } | null>(null);
+  if (referencesByIdentityRef.current?.identityKey !== referenceIdentityKey) {
     const next = new Map<string, WorkstreamPullRequestReference>();
     for (const reference of references) next.set(reference.identity, reference);
-    return next;
-  }, [references]);
+    referencesByIdentityRef.current = {
+      identityKey: referenceIdentityKey,
+      references: next,
+    };
+  }
+  const referencesByIdentity = referencesByIdentityRef.current.references;
 
   React.useEffect(() => {
     const initial = new Map<string, WorkstreamPullRequestDisplayState>();