Troubleshooting

401 on the upgrade

The HMAC handshake failed. Causes:

• Secret mismatch - WORKER_SHARED_SECRET does not equal the value StandIn holds from pairing. They must match exactly.
• Clock skew - the timestamp is outside the freshness window (HMAC_FRESHNESS_MS, default 60 s). Sync the clocks (NTP).
• Replayed handshake - the same (callId, ts, sig) tuple was already used. This is the single-use guard doing its job; a genuine retry uses a fresh timestamp.
• Secret unset - the bridge fails closed if WORKER_SHARED_SECRET is empty; every upgrade is rejected.

409 Conflict

A live session already owns that call id (a retry or rollout reconnect). The bridge rejects the duplicate so it does not open a second billed agent stream for one call. It clears when the first session tears down (a silent dead peer clears after the 90 s idle window).

503 Service Unavailable

A connection cap was hit: MAX_CONNECTIONS (default 64) or MAX_CONNECTIONS_PER_IP (default = the total cap). Raise them for a busier deployment, or check for a client that is not closing sockets.

Call connects, then agent-unavailable

The bridge could not open (or configure) the Line stream. The log line carries the underlying error. Common causes:

• CARTESIA_API_KEY is invalid (the access-token mint fails with an HTTP status).
• CARTESIA_AGENT_ID does not exist or is not deployed (the socket rejects or closes before open).
• No ack within 10 s - the server accepted the socket but never confirmed the start. Check the agent’s deployment status in your Cartesia dashboard.

First call sounds wrong (garbled or silent)

Look for this log line right after the ack:

INFO  [call:...] first agent audio frame: 640 bytes (20ms if pcm_16000)

This is the output-format tripwire. The bridge pins the stream to pcm_16000 and Cartesia’s docs imply agent audio returns in the same format, but they stop short of stating it. If the first frame warns about an odd byte length, or the frame sizes do not look like clean 16 kHz frame durations, the agent is emitting a different format - check your Line agent’s audio configuration and raise it with Cartesia support.

Governor fires but the caller hears silence before the drop

MAX_CALL_MINUTES (or a StandIn cutoff) triggered, but no deterministic goodbye is configured. Without CARTESIA_TTS_MODEL + a voice id, the bridge can only send a goodbye_request custom event, which your Line agent code must handle to produce speech. The startup log warns about exactly this combination. Set CARTESIA_TTS_MODEL and CARTESIA_TTS_VOICE_ID for a spoken goodbye, or handle the event in agent code.

Call ends with goodbye-timeout

A goodbye was spoken (StandIn-side assistant.say) but nobody tore the call down within the grace window plus the hard cap. This is the bridge’s backstop doing its job; check the StandIn connection if it recurs.

Governor never fires

MAX_CALL_MINUTES must be a number. A non-numeric or negative value stops startup with a clear error (numeric env vars fail loud), so if the process started, the value parsed. Confirm it is greater than 0 (0 disables the governor).

Startup error about the Cartesia host

CARTESIA_API_HOST is restricted to *.cartesia.ai so the API key can only be sent to Cartesia. Use the default; set CARTESIA_HOST_ALLOW_ANY=true only for a proxy you control.

The agent never reacts to DTMF / context events

DTMF and call_context / goodbye_request events are delivered to your agent code on Cartesia’s platform (custom events arrive as UserCustomSent). If the agent does not react, the handling belongs in your Line agent - see Your Line Agent for the shapes.

Port already in use

The CLI prints a friendly hint on EADDRINUSE. Set PORT to a free port.

Where the logs are

The bridge logs one line per event to stdout/stderr, scoped by call id. Set LOG_LEVEL=debug for the verbose relay detail (an invalid value falls back to info).