Backend TypeScript and Cloud VM development rules for cmux. Use when editing web/app/api, web/services, backend scripts, Cloud VM lifecycle, provider integrations, Postgres, Stack Auth pricing gates, migrations, or provider image build scripts.

cmux Backend Core rules Default backend TypeScript to Effect under web/app/api/ , web/services/ , 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 Postgres. Do not reintroduce Rivet or a raw actor protocol unless a later architecture doc explicitly changes the control plane. Postgres is the source of truth for VM lifecycle, active VM limits, idempotency, and usage events. Production and staging Cloud VM Postgres use the Vercel Marketplace AWS Aurora PostgreSQL OIDC/RDS IAM path, with runtime env CMUX DB DRIVER=aws rds iam , AWS ROLE ARN , AWS REGION , PGHOST , PGPORT , PGUSER , PGDATABASE . Run production/staging migrations with bun db:migrate:aws rds iam ; never from Vercel build or route startup. Local dev keeps the CMUX PORT derived Docker Postgres path from bun dev . Cloud VM create pricing gates use Stack Auth team payment items when enabled. Secrets Cloud VM build, test, and local dev scripts read provider secrets from ~/.secrets/cmux.env : FREESTYLE API KEY and the R2 upload vars web/scripts/build cloud vm images.ts needs when creating Freestyle snapshots. ~/.secrets/cmuxterm dev.env holds local Stack/web env and not the provider build keys. bun dev sources ~/.secrets/cmux.env first when present, then ~/.secrets/cmuxterm dev.env , so cmuxterm specific Stack settings override broader cmux secrets. The web dev loader still accepts the legacy ~/.secret/cmuxterm.env and ~/.secrets/cmuxterm.env paths while machines migrate. Detailed references [references/effect boundaries.md](references/effect boundaries.md): route handlers, services, typed errors, retries, dependency injection. [references/cloud vm control plane.md](references/cloud vm control plane.md): VM lifecycle, migrations, Postgres, provider idempotency, pricing gates.

cmux-backend