start-core/execution-model

Isomorphic execution in TanStack Start allows code to run across both server and client environments. It uses execution control APIs like createIsomorphicFn to route logic to the appropriate environment and manage SSR tasks alongside client-side state.

Use createServerFn when you need to govern server-bound operations and SSR tasks, and use createClientOnlyFn for browser utilities and client-side state management to strictly enforce environment boundaries in your application.

Create isomorphic route loaders in TanStack Start by utilizing the execution control APIs to define logic that executes on both environments. This ensures your data fetching runs on the server during SSR and on the client during navigation.

Yes, enforcing isomorphic runtime rules for server and client code in TanStack Start complies with frontmatter metadata requirements, specifically requiring name and description fields to properly identify execution boundaries.