diff --git a/frontend/sync-client/src/sync-operations/cursor-tracker.test.ts b/frontend/sync-client/src/sync-operations/cursor-tracker.test.ts
index 18acb14a..57ac5a1b 100644
--- a/frontend/sync-client/src/sync-operations/cursor-tracker.test.ts
+++ b/frontend/sync-client/src/sync-operations/cursor-tracker.test.ts
@@ -88,69 +88,89 @@ it("keeps the last usable cursor while retaining only the latest future update",
     assert.deepEqual(received, []);
 });
 
-it("refreshes unchanged cursors on reconnect and heartbeat, and follows the document through renames", async (context) => {
-    context.mock.timers.enable({ apis: ["setInterval"] });
-    const content = new TextEncoder().encode("hello");
-    let path = "note.md";
-    const database = createDatabase(await hash(content));
-    const sent: {
-        documentsWithCursors: {
-            relative_path: RelativePath;
-            vault_update_id: VaultUpdateId | null;
-        }[];
-    }[] = [];
-    const websocket = {
-        onWebSocketStatusChanged: new EventListeners<
-            (connected: boolean) => unknown
-        >(),
-        onRemoteCursorsUpdateReceived: new EventListeners(),
-        updateLocalCursors: (value: (typeof sent)[number]) => {
-            sent.push(value);
+it(
+    "refreshes unchanged cursors on reconnect and heartbeat, and follows the document through renames",
+    { timeout: 5_000 },
+    async (context) => {
+        context.mock.timers.enable({ apis: ["setInterval"] });
+        const content = new TextEncoder().encode("hello");
+        let path = "note.md";
+        const database = createDatabase(await hash(content));
+        const sent: {
+            documentsWithCursors: {
+                relative_path: RelativePath;
+                vault_update_id: VaultUpdateId | null;
+            }[];
+        }[] = [];
+        let published = Promise.withResolvers<undefined>();
+        const websocket = {
+            onWebSocketStatusChanged: new EventListeners<
+                (connected: boolean) => unknown
+            >(),
+            onRemoteCursorsUpdateReceived: new EventListeners(),
+            updateLocalCursors: (value: (typeof sent)[number]) => {
+                sent.push(value);
+                published.resolve(undefined);
+            }
+        } as unknown as WebSocketManager;
+        const notifier = new EventListeners<(path: RelativePath) => unknown>();
+        const read = context.mock.fn(async () => ({ content }));
+        const tracker = new CursorTracker(
+            database,
+            websocket,
+            { read } as unknown as FileSystemOperations,
+            notifier
+        );
+        const waitForSend = async (trigger: () => void): Promise<void> => {
+            published = Promise.withResolvers<undefined>();
+            trigger();
+            // Hashing finishes outside the event loop; a fixed number of turns
+            // cannot guarantee that the cursor snapshot has been published.
+            await published.promise;
+        };
+        try {
+            await tracker.sendLocalCursorsToServer({
+                "note.md": [{ start: 1, end: 2 }]
+            });
+            assert.equal(sent.length, 1);
+            await tracker.sendLocalCursorsToServer({
+                "note.md": [{ start: 1, end: 2 }]
+            });
+            assert.equal(sent.length, 1);
+            await waitForSend(() => {
+                websocket.onWebSocketStatusChanged.trigger(true);
+            });
+            assert.equal(sent.length, 2);
+            await waitForSend(() => {
+                context.mock.timers.tick(15_000);
+            });
+            assert.equal(sent.length, 3);
+            path = "renamed.md";
+            database.state.local.document = path;
+            await notifier.triggerAsync(path);
+            assert.equal(
+                sent.at(-1)!.documentsWithCursors[0].relative_path,
+                path
+            );
+            websocket.onWebSocketStatusChanged.trigger(false);
+            const count = sent.length;
+            const readCount = read.mock.callCount();
+            context.mock.timers.tick(30_000);
+            // A surviving heartbeat would start a snapshot read in the send lock's
+            // next microtask, even if hashing that snapshot has not finished yet.
+            await Promise.resolve();
+            assert.equal(read.mock.callCount(), readCount);
+            assert.equal(sent.length, count);
+            await waitForSend(() => {
+                websocket.onWebSocketStatusChanged.trigger(true);
+            });
+            assert.equal(sent.length, count + 1);
+        } finally {
+            tracker.reset();
+            context.mock.timers.reset();
         }
-    } as unknown as WebSocketManager;
-    const notifier = new EventListeners<(path: RelativePath) => unknown>();
-    const tracker = new CursorTracker(
-        database,
-        websocket,
-        { read: async () => ({ content }) } as unknown as FileSystemOperations,
-        notifier
-    );
-    const drain = async () => {
-        for (let i = 0; i < 20; i++)
-            await new Promise((resolve) => setImmediate(resolve));
-    };
-    try {
-        await tracker.sendLocalCursorsToServer({
-            "note.md": [{ start: 1, end: 2 }]
-        });
-        assert.equal(sent.length, 1);
-        await tracker.sendLocalCursorsToServer({
-            "note.md": [{ start: 1, end: 2 }]
-        });
-        assert.equal(sent.length, 1);
-        websocket.onWebSocketStatusChanged.trigger(true);
-        await drain();
-        assert.equal(sent.length, 2);
-        context.mock.timers.tick(15_000);
-        await drain();
-        assert.equal(sent.length, 3);
-        path = "renamed.md";
-        database.state.local.document = path;
-        await notifier.triggerAsync(path);
-        assert.equal(sent.at(-1)!.documentsWithCursors[0].relative_path, path);
-        websocket.onWebSocketStatusChanged.trigger(false);
-        const count = sent.length;
-        context.mock.timers.tick(30_000);
-        await drain();
-        assert.equal(sent.length, count);
-        websocket.onWebSocketStatusChanged.trigger(true);
-        await drain();
-        assert.equal(sent.length, count + 1);
-    } finally {
-        tracker.reset();
-        context.mock.timers.reset();
     }
-});
+);
 
 for (const interruption of ["disconnect", "reset"] as const) {
     it(`an in-flight cursor read cannot resurrect presence after ${interruption}`, async () => {