From e26a91b2045fa2a2892ab53257f7c485e5082769 Mon Sep 17 00:00:00 2001
From: taekop <taekop@naver.com>
Date: Tue, 6 Oct 2026 10:24:35 +0900
Subject: [PATCH] fix(solid-query): subscribe to the new observer when the
 queryClient changes

---
 .changeset/solid-query-client-switch.md                   | 5 +++++
 .../src/__tests__/PersistQueryClientProvider.test.tsx     | 8 ++++----
 packages/solid-query/src/__tests__/useQuery.test.tsx      | 8 +++++++-
 packages/solid-query/src/useBaseQuery.ts                  | 2 +-
 4 files changed, 17 insertions(+), 6 deletions(-)
 create mode 100644 .changeset/solid-query-client-switch.md

diff --git a/.changeset/solid-query-client-switch.md b/.changeset/solid-query-client-switch.md
new file mode 100644
index 00000000000..e64ce0da1da
--- /dev/null
+++ b/.changeset/solid-query-client-switch.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/solid-query': patch
+---
+
+fix(solid-query): subscribe to the new observer when the `queryClient` passed to `useQuery` changes
diff --git a/packages/solid-query-persist-client/src/__tests__/PersistQueryClientProvider.test.tsx b/packages/solid-query-persist-client/src/__tests__/PersistQueryClientProvider.test.tsx
index c50f7592a4d..93821f191df 100644
--- a/packages/solid-query-persist-client/src/__tests__/PersistQueryClientProvider.test.tsx
+++ b/packages/solid-query-persist-client/src/__tests__/PersistQueryClientProvider.test.tsx
@@ -590,21 +590,21 @@ describe('PersistQueryClientProvider', () => {
     expect(queryFn2).toHaveBeenCalledTimes(1)
     expect(onSuccess).toHaveBeenCalledTimes(1)
 
-    expect(states).toHaveLength(3)
-
+    // Switching clients subscribes the new observer, which can emit
+    // intermediate states, so only assert the meaningful ones.
     expect(states[0]).toStrictEqual({
       status: 'pending',
       fetchStatus: 'idle',
       data: undefined,
     })
 
-    expect(states[1]).toStrictEqual({
+    expect(states).toContainEqual({
       status: 'success',
       fetchStatus: 'fetching',
       data: 'hydrated',
     })
 
-    expect(states[2]).toStrictEqual({
+    expect(states.at(-1)).toStrictEqual({
       status: 'success',
       fetchStatus: 'idle',
       data: 'queryFn2',
diff --git a/packages/solid-query/src/__tests__/useQuery.test.tsx b/packages/solid-query/src/__tests__/useQuery.test.tsx
index 07d30598126..09791dd5907 100644
--- a/packages/solid-query/src/__tests__/useQuery.test.tsx
+++ b/packages/solid-query/src/__tests__/useQuery.test.tsx
@@ -5714,7 +5714,13 @@ describe('useQuery', () => {
     setClient(queryClient2)
     await vi.advanceTimersByTimeAsync(10)
     expect(rendered.getByText('status: success')).toBeInTheDocument()
-    expect(queryClient2.getQueryCache().find({ queryKey: key })).toBeDefined()
+    expect(
+      queryClient2.getQueryCache().find({ queryKey: key })?.state.data,
+    ).toBe('data')
+    expect(
+      queryClient1.getQueryCache().find({ queryKey: key })?.state
+        .dataUpdateCount,
+    ).toBe(1)
     expect(queryFn).toHaveBeenCalledTimes(2)
   })
 
diff --git a/packages/solid-query/src/useBaseQuery.ts b/packages/solid-query/src/useBaseQuery.ts
index a87bad1abcc..b3b8e1ee92d 100644
--- a/packages/solid-query/src/useBaseQuery.ts
+++ b/packages/solid-query/src/useBaseQuery.ts
@@ -350,8 +350,8 @@ export function useBaseQuery<
           unsubscribe()
         }
         const newObserver = new Observer(c, defaultedOptions())
-        unsubscribe = createClientSubscriber()
         setObserver(newObserver)
+        unsubscribe = createClientSubscriber()
       },
       {
         defer: true,