diff --git a/packages/lit-query/src/__tests__/createQueryController.test-d.ts b/packages/lit-query/src/__tests__/createQueryController.test-d.ts
new file mode 100644
index 0000000000..676c763fd8
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+++ b/packages/lit-query/src/__tests__/createQueryController.test-d.ts
@@ -0,0 +1,376 @@
+import { QueryClient } from '@tanstack/query-core'
+import { queryKey } from '@tanstack/query-test-utils'
+import { LitElement } from 'lit'
+import { assertType, describe, expectTypeOf, it } from 'vitest'
+import { createQueryController } from '../createQueryController.js'
+import { queryOptions } from '../queryOptions.js'
+import type { OmitKeyof, QueryFunction } from '@tanstack/query-core'
+import type { CreateQueryOptions } from '../createQueryController.js'
+
+class Host extends LitElement {}
+
+describe('createQueryController', () => {
+  it('should default data to unknown when the query function is not specified', () => {
+    const query = createQueryController(
+      new Host(),
+      { queryKey: queryKey() },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<unknown>()
+    expectTypeOf(query().error).toEqualTypeOf<Error | null>()
+  })
+
+  it('should infer the result type from the query function', () => {
+    const query = createQueryController(
+      new Host(),
+      { queryKey: queryKey(), queryFn: () => 'test' },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<string | undefined>()
+    expectTypeOf(query().error).toEqualTypeOf<Error | null>()
+  })
+
+  it('should be possible to specify the result type', () => {
+    const query = createQueryController<string>(
+      new Host(),
+      { queryKey: queryKey(), queryFn: () => 'test' },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<string | undefined>()
+    expectTypeOf(query().error).toEqualTypeOf<Error | null>()
+  })
+
+  it('should be possible to specify the error type', () => {
+    const query = createQueryController<string, Error>(
+      new Host(),
+      { queryKey: queryKey(), queryFn: () => 'test' },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<string | undefined>()
+    expectTypeOf(query().error).toEqualTypeOf<Error | null>()
+  })
+
+  it('should be possible to specify a union type as result type', () => {
+    const unionTypeSync = createQueryController(
+      new Host(),
+      {
+        queryKey: queryKey(),
+        queryFn: () => (Math.random() > 0.5 ? ('a' as const) : ('b' as const)),
+      },
+      new QueryClient(),
+    )
+    expectTypeOf(unionTypeSync().data).toEqualTypeOf<'a' | 'b' | undefined>()
+
+    const unionTypeAsync = createQueryController<'a' | 'b'>(
+      new Host(),
+      {
+        queryKey: queryKey(),
+        queryFn: () => Promise.resolve(Math.random() > 0.5 ? 'a' : 'b'),
+      },
+      new QueryClient(),
+    )
+    expectTypeOf(unionTypeAsync().data).toEqualTypeOf<'a' | 'b' | undefined>()
+  })
+
+  it('should error when the query function result does not match with the specified type', () => {
+    assertType(
+      createQueryController<number>(
+        new Host(),
+        // @ts-expect-error
+        { queryKey: queryKey(), queryFn: () => 'test' },
+        new QueryClient(),
+      ),
+    )
+  })
+
+  it('should infer the result type from a generic query function', () => {
+    function queryFn<T = string>(): Promise<T> {
+      return Promise.resolve({} as T)
+    }
+
+    const query = createQueryController(
+      new Host(),
+      { queryKey: queryKey(), queryFn: () => queryFn() },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<string | undefined>()
+    expectTypeOf(query().error).toEqualTypeOf<Error | null>()
+  })
+
+  it('should infer the query key from a typed query function', () => {
+    const getMyDataStringKey: QueryFunction<number, ['1']> = (context) => {
+      expectTypeOf(context.queryKey).toEqualTypeOf<['1']>()
+      return Promise.resolve(Number(context.queryKey[0]) + 42)
+    }
+
+    const query = createQueryController(
+      new Host(),
+      { queryKey: ['1'], queryFn: getMyDataStringKey },
+      new QueryClient(),
+    )
+
+    expectTypeOf(query().data).toEqualTypeOf<number | undefined>()
+  })
+
+  it('should handle wrapped queries with a custom fetcher passed as an inline query function', () => {
+    const createWrappedQuery = <
+      TQueryKey extends [string, Record<string, unknown>?],
+      TQueryFnData,
+      TError,
+      TData = TQueryFnData,
+    >(
+      qk: TQueryKey,
+      fetcher: (
+        obj: TQueryKey[1],
+        token: string,
+        // return type must be wrapped with TQueryFnReturn
+      ) => Promise<TQueryFnData>,
+      options?: OmitKeyof<
+        CreateQueryOptions<
+          TQueryFnData,
+          TError,
+          TData,
+          TQueryFnData,
+          TQueryKey
+        >,
+        'queryKey' | 'queryFn' | 'initialData'
+      >,
+    ) =>
+      createQueryController(
+        new Host(),
+        {
+          queryKey: qk,
+          queryFn: () => fetcher(qk[1], 'token'),
+          ...options,
+        },
+        new QueryClient(),
+      )
+
+    const query = createWrappedQuery([''], () => Promise.resolve('1'))
+
+    expectTypeOf(query().data).toEqualTypeOf<string | undefined>()
+  })
+
+  it('should handle wrapped queries with a custom fetcher passed directly to createQueryController', () => {
+    const createWrappedFuncStyleQuery = <
+      TQueryKey extends [string, Record<string, unknown>?],
+      TQueryFnData,
+      TError,
+      TData = TQueryFnData,
+    >(
+      qk: TQueryKey,
+      fetcher: () => Promise<TQueryFnData>,
+      options?: OmitKeyof<
+        CreateQueryOptions<
+          TQueryFnData,
+          TError,
+          TData,
+          TQueryFnData,
+          TQueryKey
+        >,
+        'queryKey' | 'queryFn' | 'initialData'
+      >,
+    ) =>
+      createQueryController(
+        new Host(),
+        { queryKey: qk, queryFn: fetcher, ...options },
+        new QueryClient(),
+      )
+
+    const query = createWrappedFuncStyleQuery([''], () => Promise.resolve(true))
+
+    expectTypeOf(query().data).toEqualTypeOf<boolean | undefined>()
+  })
+
+  it('should return the correct states for a successful query', () => {
+    const query = createQueryController<string, Error>(
+      new Host(),
+      { queryKey: queryKey(), queryFn: () => Promise.resolve('test') },
+      new QueryClient(),
+    )
+    const state = query()
+
+    if (state.isPending) {
+      expectTypeOf(state.data).toEqualTypeOf<undefined>()
+      expectTypeOf(state.error).toEqualTypeOf<null>()
+      return
+    }
+
+    if (state.isLoadingError) {
+      expectTypeOf(state.data).toEqualTypeOf<undefined>()
+      expectTypeOf(state.error).toEqualTypeOf<Error>()
+      return
+    }
+
+    expectTypeOf(state.data).toEqualTypeOf<string>()
+    expectTypeOf(state.error).toEqualTypeOf<Error | null>()
+  })
+
+  describe('initialData', () => {
+    it('should be possible to define a different TData than TQueryFnData using select with queryOptions spread into createQueryController', () => {
+      const options = queryOptions({
+        queryKey: queryKey(),
+        queryFn: () => Promise.resolve(1),
+      })
+      const query = createQueryController(
+        new Host(),
+        { ...options, select: (data) => data > 1 },
+        new QueryClient(),
+      )
+
+      expectTypeOf(query().data).toEqualTypeOf<boolean | undefined>()
+    })
+
+    it('TData should have undefined in the union when initialData is NOT provided', () => {
+      const query = createQueryController(
+        new Host(),
+        { queryKey: queryKey(), queryFn: () => ({ wow: true }) },
+        new QueryClient(),
+      )
+
+      expectTypeOf(query().data).toEqualTypeOf<{ wow: boolean } | undefined>()
+    })
+
+    it('TData should have undefined in the union when initialData is provided as a function which can return undefined', () => {
+      const query = createQueryController(
+        new Host(),
+        {
+          queryKey: queryKey(),
+          queryFn: () => ({ wow: true }),
+          initialData: () => undefined as { wow: boolean } | undefined,
+        },
+        new QueryClient(),
+      )
+
+      expectTypeOf(query().data).toEqualTypeOf<{ wow: boolean } | undefined>()
+    })
+
+    it('TData should be narrowed after an isSuccess check when initialData is provided as a function which can return undefined', () => {
+      const query = createQueryController(
+        new Host(),
+        {
+          queryKey: queryKey(),
+          queryFn: () => ({ wow: true }),
+          initialData: () => undefined as { wow: boolean } | undefined,
+        },
+        new QueryClient(),
+      )
+      const { data, isSuccess } = query()
+
+      if (isSuccess) {
+        expectTypeOf(data).toEqualTypeOf<{ wow: boolean }>()
+      }
+    })
+
+    it('should preserve discriminated-union narrowing', () => {
+      type Result =
+        { type: 'first'; first: string } | { type: 'second'; second: string }
+
+      const query = createQueryController(
+        new Host(),
+        {
+          queryKey: queryKey(),
+          queryFn: (): Result => ({ type: 'first', first: 'a' }),
+        },
+        new QueryClient(),
+      )
+      const data = query().data
+
+      const second = data?.type === 'first' ? undefined : data
+
+      expectTypeOf(second).toEqualTypeOf<
+        { type: 'second'; second: string } | undefined
+      >()
+    })
+  })
+
+  describe('custom controller', () => {
+    it('should allow custom controllers using CreateQueryOptions', () => {
+      type Data = string
+
+      const createCustomQuery = (
+        options?: OmitKeyof<CreateQueryOptions<Data>, 'queryKey' | 'queryFn'>,
+      ) =>
+        createQueryController(
+          new Host(),
+          {
+            ...options,
+            queryKey: queryKey(),
+            queryFn: () => Promise.resolve('data'),
+          },
+          new QueryClient(),
+        )
+
+      const query = createCustomQuery()
+
+      expectTypeOf(query().data).toEqualTypeOf<Data | undefined>()
+    })
+  })
+
+  describe('structuralSharing', () => {
+    it('should be able to use structuralSharing with unknown types', () => {
+      createQueryController(
+        new Host(),
+        {
+          queryKey: queryKey(),
+          queryFn: () => 5,
+          structuralSharing: (oldData, newData) => {
+            expectTypeOf(oldData).toBeUnknown()
+            expectTypeOf(newData).toBeUnknown()
+            return newData
+          },
+        },
+        new QueryClient(),
+      )
+    })
+  })
+
+  describe('generic indexed access TData', () => {
+    it('should be assignable back to its source indexed type when passed to a generic function parameter', () => {
+      enum DataType {
+        Account = 'account',
+        Product = 'product',
+      }
+
+      interface Account {
+        name: string
+      }
+      interface Product {
+        code: string
+      }
+
+      type DataTypeToEntity = {
+        [DataType.Account]: Account
+        [DataType.Product]: Product
+      }
+
+      const getData = <TDataType extends DataType>(
+        _dataType: TDataType,
+      ): Promise<DataTypeToEntity[TDataType]> =>
+        Promise.resolve({} as DataTypeToEntity[TDataType])
+
+      const getLabel = <TDataType extends DataType>(
+        _dataType: TDataType,
+        _data: DataTypeToEntity[TDataType],
+      ) => 'test'
+
+      const readLabel = <TDataType extends DataType>(dataType: TDataType) => {
+        const query = createQueryController(
+          new Host(),
+          { queryKey: ['test'], queryFn: () => getData(dataType) },
+          new QueryClient(),
+        )
+        const data = query().data
+
+        return data ? getLabel(dataType, data) : null
+      }
+
+      expectTypeOf(readLabel).toBeFunction()
+    })
+  })
+})