cmux-backend

SKILL.md

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: E2B_API_KEY, FREESTYLE_API_KEY, and the R2 upload vars web/scripts/build-cloud-vm-images.ts needs when creating Freestyle snapshots.