cmux Backend Core rules - Default backend TypeScript to Effect under , , and backend scripts touching providers, databases, auth, rate limits, retries, timeouts, or telemetry. - Keep Next route handlers thin: parse the request, run one Effect program at the boundary, map typed errors to HTTP responses, treat unexpected defects separately. - Plain TypeScript is for trivial data shapes, constants, config files, frontend React, and small glue where Effect would add ceremony without improving failure handling. - Cloud VM backend logic stays in Vercel route handlers and Effect services backed by P…