diff --git a/eslint.config.js b/eslint.config.js
index d8a5458377..f156cd2e9c 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -45,10 +45,7 @@ export default [
   {
     files: ['**/*.spec.ts*', '**/*.test.ts*', '**/*.test-d.ts*'],
     plugins: { vitest },
-    rules: {
-      ...vitest.configs.recommended.rules,
-      'vitest/expect-expect': 'warn',
-    },
+    rules: vitest.configs.recommended.rules,
     settings: { vitest: { typecheck: true } },
   },
 ]
diff --git a/packages/angular-query-experimental/eslint.config.js b/packages/angular-query-experimental/eslint.config.js
index 84b0029c8e..a86775ff27 100644
--- a/packages/angular-query-experimental/eslint.config.js
+++ b/packages/angular-query-experimental/eslint.config.js
@@ -1,6 +1,7 @@
 // @ts-check
 
 import pluginJsdoc from 'eslint-plugin-jsdoc'
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
 export default [
@@ -28,4 +29,13 @@ export default [
       ],
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      'vitest/expect-expect': [
+        'error',
+        { assertFunctionNames: ['expect', 'expectSignals'] },
+      ],
+    },
+  },
 ]
diff --git a/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts b/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
index a49ca421cf..406789dc42 100644
--- a/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
+++ b/packages/angular-query-experimental/src/__tests__/inject-query.test-d.ts
@@ -108,11 +108,14 @@ describe('initialData', () => {
   })
 
   describe('structuralSharing', () => {
-    it('should restrict to same types', () => {
+    it('should be able to use structuralSharing with unknown types', () => {
+      // https://github.com/TanStack/query/issues/6525#issuecomment-1938411343
       injectQuery(() => ({
         queryKey: ['key'],
         queryFn: () => 5,
-        structuralSharing: (_oldData, newData) => {
+        structuralSharing: (oldData, newData) => {
+          expectTypeOf(oldData).toBeUnknown()
+          expectTypeOf(newData).toBeUnknown()
           return newData
         },
       }))
diff --git a/packages/angular-query-experimental/src/__tests__/mutation-options.test-d.ts b/packages/angular-query-experimental/src/__tests__/mutation-options.test-d.ts
index 0aea5556a8..97f4b0d946 100644
--- a/packages/angular-query-experimental/src/__tests__/mutation-options.test-d.ts
+++ b/packages/angular-query-experimental/src/__tests__/mutation-options.test-d.ts
@@ -2,12 +2,7 @@ import { mutationOptions } from '../mutation-options'
 
 describe('mutationOptions', () => {
   test('should not allow excess properties', () => {
-    return mutationOptions({
-      mutationFn: () => Promise.resolve(5),
-      mutationKey: ['key'],
-      // @ts-expect-error this is a good error, because onMutates does not exist!
-      onMutates: 1000,
-    })
+    expectTypeOf(mutationOptions).parameter(0).not.toHaveProperty('onMutates')
   })
 
   test('should infer types for callbacks', () => {
diff --git a/packages/angular-query-experimental/src/__tests__/query-options.test-d.ts b/packages/angular-query-experimental/src/__tests__/query-options.test-d.ts
index 0d49180b4a..18cd986adf 100644
--- a/packages/angular-query-experimental/src/__tests__/query-options.test-d.ts
+++ b/packages/angular-query-experimental/src/__tests__/query-options.test-d.ts
@@ -4,16 +4,11 @@ import type { Signal } from '@angular/core'
 
 describe('queryOptions', () => {
   test('should not allow excess properties', () => {
-    return queryOptions({
-      queryKey: ['key'],
-      queryFn: () => Promise.resolve(5),
-      // @ts-expect-error this is a good error, because stallTime does not exist!
-      stallTime: 1000,
-    })
+    expectTypeOf(queryOptions).parameter(0).not.toHaveProperty('stallTime')
   })
 
   test('should infer types for callbacks', () => {
-    return queryOptions({
+    queryOptions({
       queryKey: ['key'],
       queryFn: () => Promise.resolve(5),
       staleTime: 1000,
@@ -24,7 +19,7 @@ describe('queryOptions', () => {
   })
 
   test('should allow undefined response in initialData', () => {
-    return (id: string | null) =>
+    const options = (id: string | null) =>
       queryOptions({
         queryKey: ['todo', id],
         queryFn: () =>
@@ -40,6 +35,10 @@ describe('queryOptions', () => {
                 title: 'Initial Data',
               },
       })
+
+    expectTypeOf(options(null).initialData).returns.toEqualTypeOf<
+      { id: string; title: string } | undefined
+    >()
   })
 })
 
diff --git a/packages/eslint-plugin-query/eslint.config.js b/packages/eslint-plugin-query/eslint.config.js
index cb04452c99..b6464bd8c9 100644
--- a/packages/eslint-plugin-query/eslint.config.js
+++ b/packages/eslint-plugin-query/eslint.config.js
@@ -8,6 +8,7 @@ export default [
   {
     plugins: { vitest },
     rules: {
+      ...vitest.configs.recommended.rules,
       'vitest/expect-expect': [
         'warn',
         {
diff --git a/packages/query-async-storage-persister/eslint.config.js b/packages/query-async-storage-persister/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/query-async-storage-persister/eslint.config.js
+++ b/packages/query-async-storage-persister/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/query-broadcast-client-experimental/eslint.config.js b/packages/query-broadcast-client-experimental/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/query-broadcast-client-experimental/eslint.config.js
+++ b/packages/query-broadcast-client-experimental/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/query-codemods/eslint.config.js b/packages/query-codemods/eslint.config.js
index c3c009f41e..c48269cff1 100644
--- a/packages/query-codemods/eslint.config.js
+++ b/packages/query-codemods/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
 export default [
@@ -15,4 +16,11 @@ export default [
       'sort-imports': 'off',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/query-core/eslint.config.js b/packages/query-core/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/query-core/eslint.config.js
+++ b/packages/query-core/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/query-core/src/__tests__/query.test.tsx b/packages/query-core/src/__tests__/query.test.tsx
index 03a0222b7f..6d7485a6d7 100644
--- a/packages/query-core/src/__tests__/query.test.tsx
+++ b/packages/query-core/src/__tests__/query.test.tsx
@@ -1003,7 +1003,7 @@ describe('query', () => {
     const key = queryKey()
 
     const queryFn = vi
-      .fn()
+      .fn<() => Promise<string>>()
       .mockImplementation(() => sleep(10).then(() => 'data'))
 
     queryClient.prefetchQuery({
diff --git a/packages/query-persist-client-core/eslint.config.js b/packages/query-persist-client-core/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/query-persist-client-core/eslint.config.js
+++ b/packages/query-persist-client-core/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/query-sync-storage-persister/eslint.config.js b/packages/query-sync-storage-persister/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/query-sync-storage-persister/eslint.config.js
+++ b/packages/query-sync-storage-persister/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/react-query-devtools/eslint.config.js b/packages/react-query-devtools/eslint.config.js
index ec7943f019..9133d59894 100644
--- a/packages/react-query-devtools/eslint.config.js
+++ b/packages/react-query-devtools/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginReact from '@eslint-react/eslint-plugin'
 import pluginReactHooks from 'eslint-plugin-react-hooks'
 import rootConfig from './root.eslint.config.js'
@@ -19,4 +20,11 @@ export default [
       'react-hooks/rules-of-hooks': 'error',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/react-query-next-experimental/eslint.config.js b/packages/react-query-next-experimental/eslint.config.js
index 3554c211ee..45811bb8a1 100644
--- a/packages/react-query-next-experimental/eslint.config.js
+++ b/packages/react-query-next-experimental/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginReact from '@eslint-react/eslint-plugin'
 import pluginReactHooks from 'eslint-plugin-react-hooks'
 import rootConfig from './root.eslint.config.js'
@@ -20,4 +21,11 @@ export default [
       'react-hooks/rules-of-hooks': 'error',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/react-query-persist-client/eslint.config.js b/packages/react-query-persist-client/eslint.config.js
index ec7943f019..9133d59894 100644
--- a/packages/react-query-persist-client/eslint.config.js
+++ b/packages/react-query-persist-client/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginReact from '@eslint-react/eslint-plugin'
 import pluginReactHooks from 'eslint-plugin-react-hooks'
 import rootConfig from './root.eslint.config.js'
@@ -19,4 +20,11 @@ export default [
       'react-hooks/rules-of-hooks': 'error',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/react-query/eslint.config.js b/packages/react-query/eslint.config.js
index aadb420b90..60faf155e0 100644
--- a/packages/react-query/eslint.config.js
+++ b/packages/react-query/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginReact from '@eslint-react/eslint-plugin'
 // @ts-expect-error
 import pluginReactCompiler from 'eslint-plugin-react-compiler'
@@ -31,4 +32,11 @@ export default [
       'react-compiler/react-compiler': 'off',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/react-query/src/__tests__/useQuery.test-d.tsx b/packages/react-query/src/__tests__/useQuery.test-d.tsx
index c7feaf3c86..5aa37fc376 100644
--- a/packages/react-query/src/__tests__/useQuery.test-d.tsx
+++ b/packages/react-query/src/__tests__/useQuery.test-d.tsx
@@ -308,11 +308,14 @@ describe('useQuery', () => {
     })
 
     describe('structuralSharing', () => {
-      it('should restrict to same types', () => {
+      it('should be able to use structuralSharing with unknown types', () => {
+        // https://github.com/TanStack/query/issues/6525#issuecomment-1938411343
         useQuery({
           queryKey: ['key'],
           queryFn: () => 5,
-          structuralSharing: (_oldData, newData) => {
+          structuralSharing: (oldData, newData) => {
+            expectTypeOf(oldData).toBeUnknown()
+            expectTypeOf(newData).toBeUnknown()
             return newData
           },
         })
diff --git a/packages/solid-query-devtools/eslint.config.js b/packages/solid-query-devtools/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/solid-query-devtools/eslint.config.js
+++ b/packages/solid-query-devtools/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/solid-query-persist-client/eslint.config.js b/packages/solid-query-persist-client/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/solid-query-persist-client/eslint.config.js
+++ b/packages/solid-query-persist-client/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/solid-query/eslint.config.js b/packages/solid-query/eslint.config.js
index df75435c7e..7ccaf50177 100644
--- a/packages/solid-query/eslint.config.js
+++ b/packages/solid-query/eslint.config.js
@@ -1,5 +1,15 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig]
+export default [
+  ...rootConfig,
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/svelte-query-devtools/eslint.config.js b/packages/svelte-query-devtools/eslint.config.js
index f31c5e878b..b40d00982a 100644
--- a/packages/svelte-query-devtools/eslint.config.js
+++ b/packages/svelte-query-devtools/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginSvelte from 'eslint-plugin-svelte'
 import rootConfig from './root.eslint.config.js'
 
@@ -13,4 +14,11 @@ export default [
       'svelte/valid-compile': 'off',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/svelte-query-persist-client/eslint.config.js b/packages/svelte-query-persist-client/eslint.config.js
index f31c5e878b..b40d00982a 100644
--- a/packages/svelte-query-persist-client/eslint.config.js
+++ b/packages/svelte-query-persist-client/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginSvelte from 'eslint-plugin-svelte'
 import rootConfig from './root.eslint.config.js'
 
@@ -13,4 +14,11 @@ export default [
       'svelte/valid-compile': 'off',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/svelte-query/eslint.config.js b/packages/svelte-query/eslint.config.js
index f31c5e878b..b40d00982a 100644
--- a/packages/svelte-query/eslint.config.js
+++ b/packages/svelte-query/eslint.config.js
@@ -1,5 +1,6 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 import pluginSvelte from 'eslint-plugin-svelte'
 import rootConfig from './root.eslint.config.js'
 
@@ -13,4 +14,11 @@ export default [
       'svelte/valid-compile': 'off',
     },
   },
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
 ]
diff --git a/packages/vue-query-devtools/eslint.config.js b/packages/vue-query-devtools/eslint.config.js
index 6cd1d47ba7..0810a2d674 100644
--- a/packages/vue-query-devtools/eslint.config.js
+++ b/packages/vue-query-devtools/eslint.config.js
@@ -1,7 +1,18 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 // @ts-expect-error
 import pluginVue from 'eslint-plugin-vue'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig, ...pluginVue.configs['flat/base']]
+export default [
+  ...rootConfig,
+  ...pluginVue.configs['flat/base'],
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/vue-query/eslint.config.js b/packages/vue-query/eslint.config.js
index 6cd1d47ba7..0810a2d674 100644
--- a/packages/vue-query/eslint.config.js
+++ b/packages/vue-query/eslint.config.js
@@ -1,7 +1,18 @@
 // @ts-check
 
+import vitest from '@vitest/eslint-plugin'
 // @ts-expect-error
 import pluginVue from 'eslint-plugin-vue'
 import rootConfig from './root.eslint.config.js'
 
-export default [...rootConfig, ...pluginVue.configs['flat/base']]
+export default [
+  ...rootConfig,
+  ...pluginVue.configs['flat/base'],
+  {
+    plugins: { vitest },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/expect-expect': 'warn',
+    },
+  },
+]
diff --git a/packages/vue-query/src/__tests__/useQuery.test-d.ts b/packages/vue-query/src/__tests__/useQuery.test-d.ts
index 3185a88957..84437f8fc1 100644
--- a/packages/vue-query/src/__tests__/useQuery.test-d.ts
+++ b/packages/vue-query/src/__tests__/useQuery.test-d.ts
@@ -161,11 +161,14 @@ describe('useQuery', () => {
   })
 
   describe('structuralSharing', () => {
-    it('should restrict to same types', () => {
+    it('should be able to use structuralSharing with unknown types', () => {
+      // https://github.com/TanStack/query/issues/6525#issuecomment-1938411343
       useQuery({
         queryKey: ['key'],
         queryFn: () => 5,
-        structuralSharing: (_oldData, newData) => {
+        structuralSharing: (oldData, newData) => {
+          expectTypeOf(oldData).toBeUnknown()
+          expectTypeOf(newData).toBeUnknown()
           return newData
         },
       })