From 85ba82cae5ad2f394125c075932967e59ae88cd4 Mon Sep 17 00:00:00 2001
From: Lazizbek Ergashev <lazerg2@gmail.com>
Date: Fri, 7 Aug 2026 04:45:15 +0500
Subject: [PATCH] fix(lit-query): add DataTag to the queryKey returned by
 infiniteQueryOptions

---
 .changeset/wise-doors-shout.md                |  5 +++++
 .../lit-query/src/infiniteQueryOptions.ts     | 14 ++++++++----
 .../src/tests/type-inference.test.ts          | 22 +++++++++++++++++++
 3 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/wise-doors-shout.md

diff --git a/.changeset/wise-doors-shout.md b/.changeset/wise-doors-shout.md
new file mode 100644
index 00000000000..8be502412a4
--- /dev/null
+++ b/.changeset/wise-doors-shout.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/lit-query': patch
+---
+
+Brand the `queryKey` returned by `infiniteQueryOptions` with `DataTag` so `getQueryData` and `setQueryData` infer `InfiniteData` instead of `unknown`.
diff --git a/packages/lit-query/src/infiniteQueryOptions.ts b/packages/lit-query/src/infiniteQueryOptions.ts
index f4bc8851ebe..c694e6aab5a 100644
--- a/packages/lit-query/src/infiniteQueryOptions.ts
+++ b/packages/lit-query/src/infiniteQueryOptions.ts
@@ -1,4 +1,5 @@
 import type {
+  DataTag,
   DefaultError,
   InfiniteData,
   InfiniteQueryObserverOptions,
@@ -6,10 +7,11 @@ import type {
 } from '@tanstack/query-core'
 
 /**
- * Preserves and types infinite query options for reuse across Lit Query APIs.
+ * Brands infinite query options so the `queryKey` carries the infinite query
+ * data and error types across TanStack Query APIs.
  *
- * @param options - Infinite query options to preserve.
- * @returns The same options object.
+ * @param options - Infinite query options to preserve and brand.
+ * @returns The same options object with a typed `queryKey`.
  *
  * @example
  * ```ts
@@ -43,6 +45,10 @@ export function infiniteQueryOptions<
   TData,
   TQueryKey,
   TPageParam
-> {
+> & {
+  queryKey: DataTag<TQueryKey, InfiniteData<TQueryFnData>, TError>
+}
+
+export function infiniteQueryOptions(options: unknown) {
   return options
 }
diff --git a/packages/lit-query/src/tests/type-inference.test.ts b/packages/lit-query/src/tests/type-inference.test.ts
index e8c6c3c525d..969935b5aa6 100644
--- a/packages/lit-query/src/tests/type-inference.test.ts
+++ b/packages/lit-query/src/tests/type-inference.test.ts
@@ -2,6 +2,7 @@ import {
   dataTagSymbol,
   QueryClient,
   type DefinedQueryObserverResult,
+  type InfiniteData,
   type QueryObserverResult,
 } from '@tanstack/query-core'
 import { describe, expectTypeOf, it } from 'vitest'
@@ -206,5 +207,26 @@ describe('type inference', () => {
     expectTypeOf(infinite().data?.pages).toEqualTypeOf<
       Array<{ page: number }> | undefined
     >()
+
+    const infiniteQueryOpts = infiniteQueryOptions({
+      queryKey: ['type-inference', 'infinite-query-options'] as const,
+      initialPageParam: 0,
+      queryFn: async () => ({ page: 3 }),
+      getNextPageParam: (lastPage) => lastPage.page + 1,
+    })
+    expectTypeOf(infiniteQueryOpts.queryKey[dataTagSymbol]).toEqualTypeOf<
+      InfiniteData<{ page: number }>
+    >()
+    const cachedPages = client.getQueryData(infiniteQueryOpts.queryKey)
+    expectTypeOf(cachedPages).toEqualTypeOf<
+      InfiniteData<{ page: number }> | undefined
+    >()
+    const updatedPages = client.setQueryData(infiniteQueryOpts.queryKey, {
+      pages: [{ page: 4 }],
+      pageParams: [0],
+    })
+    expectTypeOf(updatedPages).toEqualTypeOf<
+      InfiniteData<{ page: number }> | undefined
+    >()
   })
 })