Yield bounded catch-up batches behind per-user readiness queues

src/habits/performance.test.ts

@@ -57,3 +57,29 @@ test('unchanged dashboard and calendar reads write no rows after synchronization
     expect((f.sqlite.query('SELECT total_changes() AS n').get() as {n:number}).n).toBe(before);
   } finally {f.close();}
 });
+
+test('catch-up yields to other users and serializes same-user edits until fully ready', async () => {
+  const f = fixture();
+  try {
+    const habit = await f.json('/habits', 'POST', {name:'Many tasks', method:'tasks', tasks:Array.from({length:50}, (_,i)=>({name:`Task ${i}`}))}, 201);
+    f.setTime('2027-09-04T12:00:00Z');
+    let complete = false;
+    const dashboard = f.json('/today').then(value => {complete=true; return value;});
+    await new Promise(resolve=>setTimeout(resolve,0));
+    expect(complete).toBe(false);
+    // Another user's request can complete while Alice is still catching up.
+    expect((await f.request('/today','GET',undefined,'b')).status).toBe(200);
+    expect(complete).toBe(false);
+    // The actual date can advance while catch-up yields; readiness revalidates it.
+    f.setTime('2027-09-05T12:00:00Z');
+    const edit = f.json(`/habits/${habit.id}`, 'PATCH', {name:'Renamed'});
+    const [today, changed] = await Promise.all([dashboard, edit]);
+    expect(today.date).toBe('2027-09-05');
+    expect(today.habits[0].tasks).toHaveLength(50);
+    expect(changed.name).toBe('Renamed');
+    const through = f.sqlite.query('SELECT materialized_through AS date FROM habits WHERE id=?').get(habit.id) as {date:string};
+    expect(through.date).toBe('2027-09-05');
+    const day = await f.json(`/habits/${habit.id}/days/2026-09-05`);
+    expect(day.tasks.every((task:any)=>task.expiredAt!==null && task.closedAt!==null)).toBe(true);
+  } finally {f.close();}
+});