AsyncAPI channel · Vapi · Vapi Realtime API (WebSocket Transport + Server URL Events)

/{callId}/transport

Per-call WebSocket transport. Carries: - Binary audio frames in both directions (PCM s16le or G.711 mu-law, format set when the call is created). - JSON text frames for client-to-server control messages (`hangup`, `end-call`).

Open source AsyncAPI → All Vapi channels Vapi provider profile
Provider: Vapi AsyncAPI: v2.6.0 Spec: Vapi Realtime API (WebSocket Transport + Server URL Events) Operations: 2 Messages: 4

Channel address

/{callId}/transport

Parameters

Operations

publish
publish /{callId}/transport
Frames the client sends to Vapi over the WebSocket transport.
subscribe /{callId}/transport
Frames Vapi sends to the client over the WebSocket transport.

Messages

ClientAudioFrame
Raw microphone audio chunk in the call's configured format.
Content-Type: application/octet-stream
ClientHangup
Terminate the call.
Content-Type:
ClientEndCall
End the WebSocket call.
Content-Type:
ServerAudioFrame
Raw assistant audio chunk in the call's configured format.
Content-Type: application/octet-stream

About AsyncAPI

The AsyncAPI specification describes event-driven APIs the way OpenAPI describes request/response APIs. A channel is the named pipe — a webhook URL, a Kafka topic, a WebSocket route, an MQTT subject — that producers and consumers publish or subscribe to. Each channel carries one or more messages with structured payloads, and an operation declares whether a given party sends or receives on that channel.

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