Establishes the isomorphic/server-only boundary as an architectural concern: DB access, secrets, and filesystem work must sit behind createServerFn or createServerOnlyFn, never inside a bare loader.

Absolute rules include never hand-editing the generated src/routeTree.gen.ts, no module importing another feature module except cores/, no barrel exports, and no any types. Includes code templates for routes, server functions, interfaces, and hooks, and DRY guidance to grep for existing logic in src/modules/cores/ or src/lib/ before writing new code.

Do NOT use this skill for initial framework setup (use start-core), for the server/client execution-boundary deep dive itself (use start-execution-model), or for a generic React SPA that has no Start route tree (use solid-react).

SOLID TanStack Start

SOLID and clean architecture for TanStack Start v1.166.2 projects (Vite plugin tanstackStart(), file-based routes in src/routes/, server functions via createServerFn). Start code is isomorphic by default — architecture must make the server/client boundary explicit.

Codebase Analysis (MANDATORY)