From 4d003d067ef10b9286292591e27dcb55a6b10693 Mon Sep 17 00:00:00 2001
From: alex-js-ltd <alex.js.ltd@gmail.com>
Date: Sat, 8 Aug 2026 10:53:34 +0100
Subject: [PATCH 1/3] test(svelte-query/useMutationState): add coverage for
 shrinking filtered results

---
 .../useMutationState.svelte.test.ts           | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts b/packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts
index 703c05df631..be9c8980b1c 100644
--- a/packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts
+++ b/packages/svelte-query/tests/useMutationState/useMutationState.svelte.test.ts
@@ -156,4 +156,40 @@ describe('useMutationState', () => {
     expect(errorMutationFn).toHaveBeenCalledTimes(1)
     expect(rendered.getByText('Data: ["success"]')).toBeInTheDocument()
   })
+
+  it('should remove mutations that no longer match the filter', async () => {
+    const firstKey = queryKey()
+    const secondKey = queryKey()
+    const mutationFn = vi.fn(() => sleep(10).then(() => 'data'))
+
+    const rendered = render(Base, {
+      props: {
+        queryClient,
+        successMutationOpts: () => ({
+          mutationKey: firstKey,
+          mutationFn,
+        }),
+        errorMutationOpts: () => ({
+          mutationKey: secondKey,
+          mutationFn,
+        }),
+        mutationStateOpts: {
+          filters: { status: 'pending' },
+        },
+      },
+    })
+
+    fireEvent.click(rendered.getByRole('button', { name: /Success/i }))
+    fireEvent.click(rendered.getByRole('button', { name: /Error/i }))
+
+    await vi.advanceTimersByTimeAsync(0)
+
+    expect(
+      rendered.getByText('Data: ["pending","pending"]'),
+    ).toBeInTheDocument()
+
+    await vi.advanceTimersByTimeAsync(10)
+
+    expect(rendered.getByText('Data: []')).toBeInTheDocument()
+  })
 })

From 85079bdd9bb60712b1c0244d48218611479ef113 Mon Sep 17 00:00:00 2001
From: alex-js-ltd <alex.js.ltd@gmail.com>
Date: Sat, 8 Aug 2026 11:02:07 +0100
Subject: [PATCH 2/3] fix(svelte-query): shrink useMutationState results

---
 packages/svelte-query/src/useMutationState.svelte.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/svelte-query/src/useMutationState.svelte.ts b/packages/svelte-query/src/useMutationState.svelte.ts
index c517e64b480..5316da7445a 100644
--- a/packages/svelte-query/src/useMutationState.svelte.ts
+++ b/packages/svelte-query/src/useMutationState.svelte.ts
@@ -33,7 +33,7 @@ export function useMutationState<TResult = MutationState>(
         getResult(mutationCache, options),
       )
       if (result !== nextResult) {
-        Object.assign(result, nextResult)
+        result.splice(0, result.length, ...nextResult)
       }
     })
 

From 9f71f4f69a79d61a160c642c7fe5ded6bb344702 Mon Sep 17 00:00:00 2001
From: alex-js-ltd <alex.js.ltd@gmail.com>
Date: Sat, 8 Aug 2026 11:06:59 +0100
Subject: [PATCH 3/3] chore: add changeset for useMutationState fix

---
 .changeset/svelte-query-usemutationstate-filter-shrink.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/svelte-query-usemutationstate-filter-shrink.md

diff --git a/.changeset/svelte-query-usemutationstate-filter-shrink.md b/.changeset/svelte-query-usemutationstate-filter-shrink.md
new file mode 100644
index 00000000000..668701557d6
--- /dev/null
+++ b/.changeset/svelte-query-usemutationstate-filter-shrink.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/svelte-query': patch
+---
+
+fix(svelte-query): remove mutations that no longer match the filter in `useMutationState`