fix(query-core): fix queriesObserver result and observer length mismatch

nrahnema · nrahnema · commit 13e69b0faa5a · 2025-12-16T03:24:49.000-05:00
In 1b54538, `setOptions` was changed to call `notifyListeners` which eventually leads to `QueriesObserver.setQueries` 1. Updating `#observerMatches` 2. Calling `setOptions` which leads to `#notify` being called 3. Updating `#result` This is an issue when `#notify` is called before the `#result` is updated, as `#trackResult` assumes these two are the same length, which may not be the case if the number of queries changed. When the length increases, `observerResult` becomes `undefined` and the function throws an exception. Fix by moving the `#observerMatches` assignment later in the function, next to the `#observers` and `#result` assignment.
diff --git a/.changeset/orange-flowers-post.md b/.changeset/orange-flowers-post.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/query-core': patch
+---
+
+fix useQueries race condition on queries length change (#9971)
diff --git a/packages/query-core/src/queriesObserver.ts b/packages/query-core/src/queriesObserver.ts
@@ -106,7 +106,6 @@ export class QueriesObserver<
       const prevObservers = this.#observers
 
       const newObserverMatches = this.#findMatchingObservers(this.#queries)
-      this.#observerMatches = newObserverMatches
 
       // set options for the new observers to notify of changes
       newObserverMatches.forEach((match) =>
@@ -134,6 +133,7 @@ export class QueriesObserver<
       if (!hasStructuralChange && !hasResultChange) return
 
       if (hasStructuralChange) {
+        this.#observerMatches = newObserverMatches
         this.#observers = newObservers
       }
 

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +'@tanstack/query-core': patch
 +---
++
 +fix useQueries race condition on queries length change (#9971)