Vapi

Channels

• /{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 contro
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/assistant-request
  Vapi requests dynamic assistant configuration for an inbound call. Customer endpoint must respond within 7.5 seconds end-to-end with `{ assistantId }`, `{ assistant }`, `{ destination }`, or `{ error
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/assistant-speech-started
  Real-time word-level timing for assistant speech, opt-in via `serverMessages`. Variants: ElevenLabs word-alignment, Minimax word-progress, or text-only (other providers).
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/call-endpointing-request
  Smart endpointing decision delegated to a customer server configured via `assistant.startSpeakingPlan.smartEndpointingPlan.server.url`. Customer endpoint responds with `{ timeoutSeconds }`.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/chat-created
  A new chat was created.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/chat-deleted
  A chat was deleted.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/conversation-update
  Emitted when the conversation history is committed.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/end-of-call-report
  Final summary delivered after the call ends, with recording, transcript, and messages.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/hang
  The assistant has failed to reply within the hang threshold.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/knowledge-base-request
  Vapi asks a custom knowledge base provider for relevant documents. Customer endpoint replies with a `documents` array.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/language-change-detected
  Transcriber switched its detected language.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/model-output
  Streamed LLM tokens or tool-call outputs, correlated by `turnId`.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/phone-call-control
  Delegate hangup or forwarding to the customer server. Opt-in via `serverMessages`. `request` is either `forward` (with `destination`) or `hang-up`.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/session-created
  A new session was created.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/session-deleted
  A session was deleted.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/session-updated
  A session was updated.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/speech-update
  Speech-status change (started/stopped) for assistant or user.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/status-update
  Call state changes — scheduled, queued, ringing, in-progress, forwarding, ended.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/tool-calls
  Function/tool invocation triggered by the assistant. Customer endpoint replies with a `results` array correlating each `toolCallId` to a result string.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/transcript
  Streaming partial and final transcripts from the configured transcriber. Filtered by `transcriptType` (`partial` or `final`).
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/transfer-destination-request
  Vapi asks for a transfer destination when the assistant did not pre-specify one. Customer endpoint replies with a `destination` and optional spoken `message`.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/transfer-update
  Confirmation that a transfer executed, with the final destination.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/user-interrupted
  User interrupted the assistant — use `turnId` to discard the interrupted turn's tokens.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/voice-input
  Custom voice provider receives the user's transcribed input.
  Vapi Realtime API (WebSocket Transport + Server URL Events)
• server-url/voice-request
  TTS audio request sent to a custom voice server configured via `assistant.voice.server.url`. The customer endpoint must respond with raw 1-channel 16-bit PCM audio at the requested `sampleRate` (binar
  Vapi Realtime API (WebSocket Transport + Server URL Events)