---name: cmux-backenddescription: 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 PlanetScale PostgreSQL database cmux-prod in organization cmux. The runtime reads DATABASE_URL with CMUX_DB_DRIVER=url; migration jobs use the protected DATABASE_URL secret. AWS credentials are not database credentials.
• Run production/staging migrations with bun run cloud-vm:migrate -- staging followed by -- production; 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.

set -a
source ~/.secrets/cmux.env
set +a

~/.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: route handlers, services, typed errors, retries, dependency injection.
• references/cloud-vm-control-plane.md: VM lifecycle, migrations, Postgres, provider idempotency, pricing gates.