Configuration

Curb reads everything below from the environment or the project’s .env. How an agent behaves is set in code, on <Agent> and in defineAgent.

Provider keys

The environment holds only the keys of the providers the agent uses. A missing one fails with an error naming it.

Provider	Variable
`kugelaudio.llm()`, `kugelaudio.stt()`, `kugelaudio.tts()`	`KUGELAUDIO_API_KEY`. With `npx curb login`, a project on this machine needs none
`anthropic()`	`ANTHROPIC_API_KEY`
`openai()`, `openai.stt()`, `openai.tts()`	`OPENAI_API_KEY`
`openaiCompatible()`	`AGENT_LLM_API_KEY`, else `OPENAI_API_KEY`; optional
`azure.stt()`	`AZURE_SPEECH_KEY`; `AZURE_SPEECH_REGION` (default `eastus`)
`deepgram.stt()`	`DEEPGRAM_API_KEY`
`elevenlabs.stt()`, `elevenlabs.tts()`	`ELEVEN_API_KEY`, or `ELEVENLABS_API_KEY`
`cartesia.tts()`	`CARTESIA_API_KEY`

KUGELAUDIO_API_BASE points the KugelAudio providers at another endpoint.

Voice

Variable	Default	What it does
`VOICE_ENDPOINTING_MIN_MS`	`300`	The shortest pause that can end a turn
`VOICE_ENDPOINTING_MAX_MS`	`3000`	The longest wait before a turn ends
`VOICE_SILENCE_FOLLOWUP_MS`	`6000`	Silence before the agent checks in

LiveKit

Variable	What it does
`LIVEKIT_URL`, `LIVEKIT_API_KEY`, `LIVEKIT_API_SECRET`	Your LiveKit server or Cloud project. All three, or `curb dev` names what is missing
`CURB_REALTIME_SESSION_URL`	Asks this URL for each call’s room and tokens, in place of the three above
`CURB_AGENT_NAME`	The name a worker registers under. Default: the `name` in `package.json`
`LIVEKIT_AGENTS_LOG_LEVEL`	Log level of the LiveKit agent runtime. Default `warn`

Running

Variable	Default	What it does
`PORT`, `WS_PORT`	`4000`	The port. `WS_PORT` wins. An explicit port is used exactly; otherwise `curb dev` takes the next free one
`WS_HOST`	`127.0.0.1`	The address to listen on
`AGENT_DEFAULT`	the first by name	The agent a project with several starts with
`AGENT_LLM_TIMEOUT_MS`	`60000`	How long a model may take to answer
`KUGEL_CONVERSATIONS_DB`	a local file	Where conversations are recorded. `off` turns it off (The preview)
`CURB_NO_OPEN`		`1` keeps `curb dev` from opening the browser
`CURB_CDN`	`https://cdn.kugelaudio.com/curb`	Where `curb upgrade` looks. Set it to a mirror
`MCP_SERVERS_FILE`	`mcp.servers.json`	The servers added in the preview
`MCP_AUTH_DIR`	`.mcp-auth`	Where MCP sign-ins are stored
`MCP_<ID>_TOKEN`		A bearer token for the MCP server with that id

Runner

These apply to a built artifact, and to curb dev and curb start with a management port (Self-hosting).

Variable	What it does
`CURB_MANAGEMENT_ADDR`	`host:port` for host protocol v1. Absent means not managed
`CURB_MANAGEMENT_TOKEN`	The bearer token, one per runner. Required with the address
`CURB_MAX_SESSIONS`	Concurrent calls. Default `1`
`CURB_DEPLOYMENT_ID`	Optional: which deployment this runner is
`CURB_CONFIGURATION_VERSION`	Optional: a positive integer
`CURB_REALTIME_URL`, `CURB_REALTIME_TOKEN`	Join this one room directly and serve one call
`CURB_SESSION_ID`	The call’s id on a direct join. Default: the room name
`CURB_READINESS_PROBE`	`1` loads the bundle, builds the agent and exits

`package.json`

{
  "curb": {
    "requiredRuntimeSecrets": ["KUGELAUDIO_API_KEY"]
  }
}

curb build writes these names into curb.bundle.json. A deployment or call then fails before a runner starts when one cannot be resolved (Self-hosting).

Next steps

CLI: every command.
Self-hosting: the ways to run an agent.