Neekoras · Sep 23, 2026
diff --git a/.changeset/svelte-query-effect-root-cleanup.md b/.changeset/svelte-query-effect-root-cleanup.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/svelte-query': patch
+---
+
+fix(svelte-query): unsubscribe the observer when an `$effect.root` holding a query is disposed
diff --git a/packages/svelte-query/src/createBaseQuery.svelte.ts b/packages/svelte-query/src/createBaseQuery.svelte.ts
@@ -92,6 +92,11 @@ export function createBaseQuery<
       return unsubscribe
     },
   )
+  // ...and because the above only returns a cleanup from its second run onwards, tear the initial
+  // subscription down with an effect of its own, so disposing an `$effect.root` unsubscribes it.
+  try {
+    $effect.pre(() => () => unsubscribe())
+  } catch (e) {}
   // ...and finally also cleanup via onDestroy because that one runs on the server whereas $effect.pre does not.
   // (in a try-catch because it theoretically can be called in a non-component context - that should not happen
   // but it would be a breaking change technically to error out here. SSR-safe because this wouldn't be called during SSR if it was not in a component)

diff --git a/packages/svelte-query/tests/createQuery/observer-cleanup.svelte.test.ts b/packages/svelte-query/tests/createQuery/observer-cleanup.svelte.test.ts
@@ -0,0 +1,186 @@
+import { render } from '@testing-library/svelte'
+import { flushSync } from 'svelte'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import {
+  QueryClient,
+  createInfiniteQuery,
+  createQuery,
+} from '../../src/index.js'
+import Base from './Base.svelte'
+
+describe('effect root query cleanup', () => {
+  let client: QueryClient
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    client = new QueryClient({ defaultOptions: { queries: { retry: false } } })
+  })
+
+  afterEach(() => {
+    client.clear()
+    vi.useRealTimers()
+  })
+
+  describe.each(['query', 'infinite query'] as const)('%s', (kind) => {
+    it.each(['success', 'error', 'disabled'] as const)(
+      'removes the observer after disposing a %s query root',
+      async (state) => {
+        const key = ['root-cleanup', kind, state]
+        const queryFn = vi.fn(() => {
+          if (state === 'error')
+            return Promise.reject(new Error('expected failure'))
+          return Promise.resolve('data')
+        })
+        const options = () => ({
+          queryKey: key,
+          queryFn,
+          enabled: state !== 'disabled',
+          gcTime: 10,
+          initialPageParam: 0,
+          getNextPageParam: () => undefined,
+        })
+        const dispose = $effect.root(() => {
+          if (kind === 'query') createQuery(options, () => client)
+          else createInfiniteQuery(options, () => client)
+        })
+
+        try {
+          flushSync()
+          await vi.advanceTimersByTimeAsync(0)
+          const query = client.getQueryCache().find({ queryKey: key })!
+          expect(query.getObserversCount()).toBe(1)
+          expect(query.state.status).toBe(
+            state === 'disabled' ? 'pending' : state,
+          )
+
+          dispose()
+
+          expect.soft(query.getObserversCount()).toBe(0)
+          await vi.advanceTimersByTimeAsync(20)
+          expect(client.getQueryCache().find({ queryKey: key })).toBeUndefined()
+        } finally {
+          dispose()
+        }
+      },
+    )
+
+    it('does not retain an observer when disposed before effects run', () => {
+      const key = ['early-root-cleanup', kind]
+      const options = () => ({
+        queryKey: key,
+        enabled: false,
+        initialPageParam: 0,
+        getNextPageParam: () => undefined,
+      })
+      const dispose = $effect.root(() => {
+        if (kind === 'query') createQuery(options, () => client)
+        else createInfiniteQuery(options, () => client)
+      })
+
+      try {
+        dispose()
+        flushSync()
+        expect(
+          client.getQueryCache().find({ queryKey: key })!.getObserversCount(),
+        ).toBe(0)
+      } finally {
+        dispose()
+      }
+    })
+  })
+
+  it('aborts a signal-consuming request when its root is disposed', () => {
+    let signal: AbortSignal | undefined
+    const dispose = $effect.root(() => {
+      createQuery(
+        () => ({
+          queryKey: ['pending-root'],
+          queryFn: (context) => {
+            signal = context.signal
+            return new Promise<string>(() => {})
+          },
+        }),
+        () => client,
+      )
+    })
+
+    try {
+      flushSync()
+      expect(signal?.aborted).toBe(false)
+      dispose()
+      expect(signal?.aborted).toBe(true)
+    } finally {
+      dispose()
+    }
+  })
+
+  it('stops interval refetches when its root is disposed', async () => {
+    const queryFn = vi.fn(() => Promise.resolve('data'))
+    const dispose = $effect.root(() => {
+      createQuery(
+        () => ({
+          queryKey: ['polling-root'],
+          queryFn,
+          refetchInterval: 10,
+          refetchIntervalInBackground: true,
+        }),
+        () => client,
+      )
+    })
+
+    try {
+      flushSync()
+      await vi.advanceTimersByTimeAsync(0)
+      expect(queryFn).toHaveBeenCalledTimes(1)
+      dispose()
+      await vi.advanceTimersByTimeAsync(30)
+      expect(queryFn).toHaveBeenCalledTimes(1)
+    } finally {
+      dispose()
+    }
+  })
+
+  it('cleans up a normal component subscription on unmount', async () => {
+    const key = ['component-control']
+    const view = render(Base, {
+      queryClient: client,
+      options: () => ({
+        queryKey: key,
+        queryFn: () => Promise.resolve('data'),
+      }),
+    })
+    await vi.advanceTimersByTimeAsync(0)
+    const query = client.getQueryCache().find({ queryKey: key })!
+    expect(query.getObserversCount()).toBe(1)
+    await view.unmount()
+    expect(query.getObserversCount()).toBe(0)
+  })
+
+  it('cleans up after the subscription has changed clients', () => {
+    const replacement = new QueryClient()
+    let selected = $state(client)
+    const key = ['changed-client-control']
+    const dispose = $effect.root(() => {
+      createQuery(
+        () => ({ queryKey: key, enabled: false }),
+        () => selected,
+      )
+    })
+
+    try {
+      flushSync()
+      const original = client.getQueryCache().find({ queryKey: key })!
+      expect(original.getObserversCount()).toBe(1)
+      selected = replacement
+      flushSync()
+      expect(original.getObserversCount()).toBe(0)
+      const next = replacement.getQueryCache().find({ queryKey: key })!
+      expect(next.getObserversCount()).toBe(1)
+      dispose()
+      expect(next.getObserversCount()).toBe(0)
+    } finally {
+      dispose()
+      replacement.clear()
+    }
+  })
+})