Metrics (Prometheus)

GET /metrics returns Prometheus exposition format: default Node.js process metrics, bangasser_dev_build_info, bangasser_dev_http_requests_total{method,route}, and bangasser_dev_http_request_errors_total{route,status}. The 500 rate is a PromQL ratio:

rate(bangasser_dev_http_request_errors_total[5m])
  / rate(bangasser_dev_http_requests_total[5m])

Request counting uses a Node-runtime middleware.ts; error counting uses instrumentation.ts. Most useful on the long-running Docker deployment.