Kamal Proxy
Kamal Proxy is a minimal HTTP reverse proxy written in Go that powers the zero-downtime deploy switchover behind Kamal. It exposes a small `kamal-proxy` CLI with `run`, `deploy`, and `remove` commands; the Kamal CLI talks to it over SSH to register new container instances (`hostname:port`), runs health checks (default `GET /up` once per second returning `200`), drains traffic from old instances, and atomically switches new traffic to the healthy instance. The proxy supports host-based routing (multiple apps on one server), path-based routing with optional prefix stripping, custom health-check paths/ports/timeouts, automatic TLS via Let's Encrypt, and custom TLS certificate/key files (useful for Cloudflare origin certs or private CAs). It can also be run standalone outside of Kamal.