perf: match the bridge query by identity instead of re-hashing per cache entry

src/lib/queries/QueryClientProvider$.tsx

@@ -55,12 +55,14 @@ export class QueryClient$ {
     this.queryMap.set(queryHash, cacheEntry)
 
     const sub = sharedQuery$.subscribe({
+      /**
+       * Write on the closed-over entry directly: this subscription is torn
+       * down by `deleteQuery` before the map slot can ever point to another
+       * entry, so a per-emission `queryMap.get(queryHash)` lookup would
+       * always resolve to `cacheEntry` anyway.
+       */
       next: (data) => {
-        const entry = this.queryMap.get(queryHash)
-
-        if (entry) {
-          entry.lastData = { value: data }
-        }
+        cacheEntry.lastData = { value: data }
       },
       complete: () => {
         if (this.queryMap.get(queryHash) === cacheEntry) {
@@ -104,9 +106,14 @@ export class QueryClient$ {
      * final value — cancelling it would reject it prematurely.
      */
     if (cancelQuery && !entry.signal.aborted && entry.lastData !== undefined) {
+      /**
+       * Matched by identity for the same reason as the refetch path: the
+       * `{ queryKey, exact: true }` filter re-hashes the key for every
+       * query in the cache, while an identity predicate skips hashing and
+       * keeps all cancel semantics inside `cancelQueries`.
+       */
       this.queryClient?.cancelQueries({
-        queryKey: entry.queryKey,
-        exact: true,
+        predicate: (query) => query.queryKey === entry.queryKey,
       })
     }
   }

src/lib/queries/createObservableQueryFn.ts

@@ -65,9 +65,18 @@ export function createObservableQueryFn<
              */
             if (queryCacheEntry?.isCompleted) return
 
+            /**
+             * This runs once per emission of a live stream. The cost of
+             * the equivalent `{ queryKey, exact: true }` filter is not the
+             * iteration but the re-hashing: it JSON.stringifies the key
+             * again for every query in the cache. Matching the query by
+             * identity instead skips hashing entirely — `context.queryKey`
+             * is the very array the target query holds — while leaving all
+             * refetch semantics (batching, disabled/static skip,
+             * cancelRefetch, error swallowing) inside `refetchQueries`.
+             */
             queryClient?.refetchQueries({
-              queryKey: context.queryKey,
-              exact: true,
+              predicate: (query) => query.queryKey === context.queryKey,
             })
           })
         }

src/lib/queries/useQuery$.reactivity.test.tsx

@@ -91,6 +91,51 @@ describe("useQuery$ live-query reactivity", () => {
     )
   })
 
+  it("re-renders when the query uses a custom queryKeyHashFn", async () => {
+    const liveQuery$ = new BehaviorSubject(["a", "b"])
+    const db$ = new BehaviorSubject<object | undefined>({})
+    const queryClient = createQueryClient()
+
+    function Comp() {
+      const { data } = useQuery$({
+        ...liveQueryOptions,
+        queryKey: ["live", "custom-hash"],
+        /**
+         * TanStack stores the query under the hash produced here, which
+         * differs from the default `hashKey` output.
+         */
+        queryKeyHashFn: (queryKey) => `custom:${JSON.stringify(queryKey)}`,
+        queryFn: () =>
+          db$.pipe(
+            filter(isDefined),
+            switchMap(() => liveQuery$),
+            map((items) => [...items]),
+          ),
+      })
+
+      return <span data-testid="data">{JSON.stringify(data)}</span>
+    }
+
+    render(<Comp />, { wrapper: createWrapper(queryClient) })
+
+    await act(async () => {
+      await waitForTimeout(100)
+    })
+
+    expect(screen.getByTestId("data").textContent).toBe(
+      JSON.stringify(["a", "b"]),
+    )
+
+    await act(async () => {
+      liveQuery$.next(["a", "b", "c"])
+      await waitForTimeout(200)
+    })
+
+    expect(screen.getByTestId("data").textContent).toBe(
+      JSON.stringify(["a", "b", "c"]),
+    )
+  })
+
   it("re-renders with two observers on the same key", async () => {
     const liveQuery$ = new BehaviorSubject(["a", "b"])
     const db$ = new BehaviorSubject<object | undefined>({})