Event types

The typed events a call emits, and what each one carries. This is the internal call vocabulary, used in two places: the call event stream (GET /calls/{call}/events) and the NATS subjects the two planes exchange. Defined as CallEventType in @callagent/contracts and mirrored in App\Enums\CallEventType, with a test that reads the PHP source and fails on drift.

These are not webhook event names

Outbound webhooks use a separate, deliberately versioned vocabulary of 28 names, and the two overlap enough to catch you out:

Here (call events)	There (webhooks)
call.created	call.started
call.connected	call.answered
tool.started	tool.called
user.speech.started	speech.started

Subscribe a webhook endpoint to a name from this page and it is rejected as unknown.

Every event shares the envelope; only data differs, and only that is described below.

Lifecycle

Event	data
call.created	direction, from, to, phoneNumberId, assistantId, squadId, campaignId, telephonyProvider, idempotencyKey
call.ringing	ringingAt, destination
call.connected	answeredAt, setupMs, sipCallId
call.ended	endedReason, durationMs, billableSeconds, endedBy (customer · assistant · operator · system · provider)
call.failed	endedReason, error
call.state.changed	from, to, reason
transport.connected	transport, remoteAddress, connectMs, codec, sampleRate
transport.disconnected	code, reason

Speech in stt

Event	data
user.speech.started	energyDb, duringAssistantSpeech
user.speech.ended	speechMs, silenceMs
transcript.partial	text, isFinal: false, confidence, speaker, language, words[]
transcript.final	as above with isFinal: true
endpoint.detected	strategy (provider · vad_timeout · punctuation · semantic · hybrid), silenceMs, minSpeechMs, maxWaitMs, confidence, transcript

words[] carries per-word startMs, endMs, confidence and speaker when the transcriber provides them.

Model llm

Event	data
llm.started	provider, model, temperature, maxTokens, messageCount
llm.first_token	as above plus ttftMs
llm.completed	plus tokens (prompt, completion, total, cachedPrompt, reasoning), durationMs, finishReason, toolCallCount, fallbackIndex
llm.failed	error (code, message, statusCode, retryable)
llm.aborted	abortReason: barge_in · timeout · handoff · call_ended · operator

finishReason is stop, length, tool_calls, content_filter, aborted or error.

Synthesis tts

Event	data
tts.started	voice (provider, voiceId, model), text, chunkIndex
tts.first_audio	plus ttfaMs
tts.completed	plus characters, durationMs, audioMs, fallbackIndex
tts.failed	error
tts.aborted	abortReason

Playback playback

Event	data
assistant.speech.started	text, messageId
assistant.speech.interrupted	spokenText, remainingText, spokenMs, detectionMs, stopAudioMs
assistant.speech.completed	text, audioMs, messageId

spokenText versus remainingText is the pair that matters: the transcript keeps only what the caller actually heard.

Speech to speech

s2s.started · s2s.first_audio (ttfaMs) · s2s.completed (durationMs, inputAudioMs, outputAudioMs, tokens) · s2s.failed.

Tools tool

Event	data
tool.started	toolId, toolCallId, name, toolType, args
tool.completed	plus result, durationMs, async
tool.failed	plus error
tool.rejected	plus rejectionReason, rejectionMessage

rejectionReason is one of the eleven on error codes.

MCP

mcp.started · mcp.completed · mcp.failed, each carrying serverId, serverName, transport (streamable_http · sse · stdio), toolName, args, and on completion result and durationMs.

Knowledge

Event	data
knowledge.queried	knowledgeBaseId, query, provider, matchCount, topScore, durationMs, documentIds
knowledge.insufficient	knowledgeBaseId, query, threshold, topScore, safetyMode

knowledge.insufficient is the honest-answer signal: retrieval came back below the threshold and the assistant said so rather than inventing one. See knowledge-only mode.

Routing

Event	data
handoff.started	fromAssistantId, toAssistantId, squadId, trigger (tool · intent · variable · dynamic · explicit · silent), contextMode, reason
handoff.completed	toAssistantId, durationMs, messagesCarried
transfer.started	mode (blind · warm · queue · sip_uri · assistant · dynamic), destination, destinationType
transfer.completed	plus legId, durationMs
transfer.failed	plus error

Contact centre

operator.queued · operator.ringing · operator.connected · operator.rejected · operator.missed · operator.wrap_up · queue.abandoned · queue.overflowed.

All carry operatorId, operatorName, queueId, queueName, extension, waitMs, ringMs, position and reason where they apply. operator.wrap_up adds dispositionId, disposition, notes and wrapUpMs; queue.abandoned adds abandonedAfterMs; queue.overflowed adds overflowTo and overflowType (queue · ring_group · voicemail · assistant · number).

DTMF, SIP and voicemail

Event	data
dtmf.received	digits, method (rfc2833 · rfc4733 · sip_info · inband · provider), buffer
dtmf.sent	digits, method, interDigitMs
sip.request.sent	method (INFO · MESSAGE · NOTIFY · REFER · OPTIONS · UPDATE), destination, headers, body
sip.response.received	statusCode, reason, method, headers
voicemail.detected	detector (provider_amd · classifier · beep · tool), confidence, beepDetected, policy (hangup · leave_message · continue · custom), detectionMs

Artifacts

Event	data
recording.consent_announced	mode, spokenText, audioUrl, region
recording.consent_recorded	plus acknowledged
recording.started	recordingId, channels (mono · stereo · dual), track (mixed · caller · assistant · operator), format
recording.paused	plus reason
recording.resumed	as recording.started
recording.ready	plus url, storagePath, bytes, durationMs
analysis.completed	summary, sentiment, success, successReason, topics, structuredOutputs, scorecardIds, durationMs

analysis.completed

The event type and its payload are defined, and the control plane stores the results if they arrive. The post-call analysis pipeline that would produce them is not currently dispatched by the control plane — see Implementation status and Analytics & cost.

Provider health

Event	data
provider.fallback	component, from, to, reason (timeout · error · rate_limit · auth · circuit_open · health_check), attempt
provider.error	component, provider, model, error, circuitOpened

component is model, transcriber, voice, speech_to_speech, telephony, and for provider.error also storage and observability.

Categorising them

The prefix before the first dot is the category, which is how a consumer can subscribe broadly without enumerating 60 names:

const category = (type: string) => type.split('.')[0];
// 'endpoint.detected' → 'endpoint'

const isError = (type: string) =>
  type.includes('failed') || type.includes('error') || type === 'tool.rejected';

Both helpers ship as eventCategory() and isErrorEvent() in @callagent/contracts.