Error patterns (compact)

Use this to quickly map log signatures to likely causes and fixes.

Log pattern	Likely cause	Quick fix
`KeyError`, `not defined`, `missing environment`	Missing env var	Add env var in render.yaml or via MCP, then redeploy
`EADDRINUSE`, `listen EADDRINUSE`	Port binding conflict	Bind to `0.0.0.0:$PORT`
`Cannot find module`, `ModuleNotFoundError`	Missing dependency	Add dependency to manifest and rebuild
`ECONNREFUSED`, `connection refused`	DB not reachable	Verify DATABASE_URL and DB status
`Health check timeout`	No healthy response	Add/verify health endpoint and port
`exit 137`, `out of memory`	OOM	Reduce memory use or upgrade plan
`Command failed`, `build failed`	Bad build command	Fix build command or dependencies