From f35335ce4545d73785da126fb955252908bda65d Mon Sep 17 00:00:00 2001
From: Will Drach <drach@splits.org>
Date: Thu, 9 Oct 2025 19:25:11 -0600
Subject: [PATCH 1/3] fix isFetchedAfterMount

---
 .../query-core/src/__tests__/query.test.tsx   | 43 +++++++++++++++++++
 packages/query-core/src/query.ts              |  4 +-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/packages/query-core/src/__tests__/query.test.tsx b/packages/query-core/src/__tests__/query.test.tsx
index f11bf173d3..a33bf75cfc 100644
--- a/packages/query-core/src/__tests__/query.test.tsx
+++ b/packages/query-core/src/__tests__/query.test.tsx
@@ -1304,4 +1304,47 @@ describe('query', () => {
       data: 'data1',
     })
   })
+
+  test('should not increment dataUpdateCount when setting initialData on prefetched query', async () => {
+    const key = queryKey()
+    const queryFn = vi.fn().mockImplementation(() => 'fetched-data')
+
+    // First prefetch the query (creates query without data)
+    queryClient.prefetchQuery({
+      queryKey: key,
+      queryFn,
+    })
+
+    const query = queryCache.find({ queryKey: key })!
+    expect(query.state.data).toBeUndefined()
+    expect(query.state.dataUpdateCount).toBe(0)
+
+    // Now create an observer with initialData
+    const observer = new QueryObserver(queryClient, {
+      queryKey: key,
+      queryFn,
+      initialData: 'initial-data',
+    })
+
+    // The query should now have the initial data but dataUpdateCount should still be 0
+    // since this was not fetched data but initial data
+    expect(query.state.data).toBe('initial-data')
+    expect(query.state.dataUpdateCount).toBe(0)
+
+    // Get the initial state as captured by the observer
+    const result = observer.getCurrentResult()
+    expect(result.data).toBe('initial-data')
+    expect(result.isFetchedAfterMount).toBe(false) // This should be false since no actual fetch occurred
+
+    // Now trigger a refetch through the observer to simulate real-world usage
+    await observer.refetch()
+
+    // After actual fetch, dataUpdateCount should increment
+    expect(query.state.dataUpdateCount).toBe(1)
+    expect(query.state.data).toBe('fetched-data')
+
+    // And isFetchedAfterMount should now be true
+    const updatedResult = observer.getCurrentResult()
+    expect(updatedResult.isFetchedAfterMount).toBe(true)
+  })
 })
diff --git a/packages/query-core/src/query.ts b/packages/query-core/src/query.ts
index a34c8630dc..8e85a75d38 100644
--- a/packages/query-core/src/query.ts
+++ b/packages/query-core/src/query.ts
@@ -636,7 +636,9 @@ export class Query<
           const newState = {
             ...state,
             data: action.data,
-            dataUpdateCount: state.dataUpdateCount + 1,
+            dataUpdateCount: action.manual && state.data === undefined
+              ? state.dataUpdateCount  // Don't increment for initial data
+              : state.dataUpdateCount + 1,
             dataUpdatedAt: action.dataUpdatedAt ?? Date.now(),
             error: null,
             isInvalidated: false,

From ad5d0ba5b6172ab78ebdebedfe8bfeeedd8fa9ab Mon Sep 17 00:00:00 2001
From: Will Drach <drach@splits.org>
Date: Thu, 9 Oct 2025 19:28:54 -0600
Subject: [PATCH 2/3] changeset

---
 .changeset/yummy-rooms-read.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/yummy-rooms-read.md

diff --git a/.changeset/yummy-rooms-read.md b/.changeset/yummy-rooms-read.md
new file mode 100644
index 0000000000..2c2648ebbe
--- /dev/null
+++ b/.changeset/yummy-rooms-read.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/react-query': patch
+---
+
+Fixed isFetchedAfterMount in cases where initialData is applied

From 478f5d08e31ee1419a51205e3e767b5e4f102b0e Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Sun, 12 Oct 2025 15:48:57 +0000
Subject: [PATCH 3/3] ci: apply automated fixes

---
 packages/query-core/src/query.ts | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/packages/query-core/src/query.ts b/packages/query-core/src/query.ts
index 8e85a75d38..bd188219d9 100644
--- a/packages/query-core/src/query.ts
+++ b/packages/query-core/src/query.ts
@@ -636,9 +636,10 @@ export class Query<
           const newState = {
             ...state,
             data: action.data,
-            dataUpdateCount: action.manual && state.data === undefined
-              ? state.dataUpdateCount  // Don't increment for initial data
-              : state.dataUpdateCount + 1,
+            dataUpdateCount:
+              action.manual && state.data === undefined
+                ? state.dataUpdateCount // Don't increment for initial data
+                : state.dataUpdateCount + 1,
             dataUpdatedAt: action.dataUpdatedAt ?? Date.now(),
             error: null,
             isInvalidated: false,