# DETECT_PORT_FIXED

**What it means.** The start command forces a fixed port, so the app would never answer on the port the platform gives it.

**What to do.** Remove the fixed port from the "start" script in package.json. For Next.js, `next start` on its own reads PORT; for other servers, listen on process.env.PORT. Keep a fixed port in the "dev" script if you like. Then re-run deploy.

- HTTP status: 422
- Retryable after applying the fix: yes

Every failure from the CLI or an MCP tool has this shape:

```json
{
  "ok": false,
  "code": "DETECT_PORT_FIXED",
  "message": "The start command forces a fixed port, so the app would never answer on the port the platform gives it.",
  "fix": "Remove the fixed port from the \"start\" script in package.json. For Next.js, `next start` on its own reads PORT; for other servers, listen on process.env.PORT. Keep a fixed port in the \"dev\" script if you like. Then re-run deploy.",
  "file": "<where to edit, when known>",
  "retryable": true,
  "docs": "https://docs.uarpie.app/errors/DETECT_PORT_FIXED"
}
```

Apply `fix` (edit `file` when it is given), then run the same command again.