react-doctor/tanstack-start-no-use-server-in-handler

TanStack Start handles server boundaries automatically via the Vite plugin — "use server" inside createServerFn causes compilation errors

• Category: TanStack Start
• Severity: error
• Source: oxlint-plugin-react-doctor
• Framework: tanstack-start
• Enabled when: framework=tanstack-start and capabilities=tanstack-start

Validation prompt

Use this to decide whether a fired diagnostic is real or a false positive.

Fires (error severity) when a .handler(() => { 'use server'; ... }) callback's first statement is a 'use server' directive — detected either via the parser's directive field or a top-level string-literal ExpressionStatement. False positive: essentially none in practice; a stray string-literal statement is the only realistic non-directive trigger.

Fix prompt

Use this once validation confirms the diagnostic is real.

Delete the 'use server' line entirely. TanStack Start's Vite plugin already extracts the handler body into a server-only module and replaces the client-side reference with an RPC stub; the React 'use server' directive duplicates that transform and breaks the build. See https://tanstack.com/start/latest/docs/framework/react/server-functions

Related rules

More TanStack Start rules from the rules reference:

• react-doctor/tanstack-start-no-useeffect-fetch: Fetch data in the route `loader` instead — the router coordinates loading before rendering to avoid waterfalls
• react-doctor/tanstack-start-redirect-in-try-catch: TanStack Router's `redirect()` and `notFound()` throw special errors caught by the router. Move them outside the try block or re-throw in the catch
• react-doctor/tanstack-start-route-property-order: Follow the order: params/validateSearch → loaderDeps → context → beforeLoad → loader → head. See https://tanstack.com/router/latest/docs/eslint/create-route-property-order
• react-doctor/tanstack-start-server-fn-method-order: Chain methods in order: .middleware() → .inputValidator() → .client() → .server() → .handler() — types depend on this sequence
• react-doctor/tanstack-start-server-fn-validate-input: Add `.inputValidator(schema)` before `.handler()` — data crosses a network boundary and must be validated at runtime