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Subscribe to live call events (SSE)

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Real-time streaming of user speech (STT) and agent speech (TTS) events for an active call via Server-Sent Events. The connection is real-time — events stream directly from the call runtime as they are produced. The SSE connection auto-closes when the call ends (`sse_close` event). Only active calls can be subscribed to; completed calls return a 400 error. **Transcript event types:** - `user_interim_transcription` — Partial, in-progress transcription as the user speaks. Use for live preview only; will be superseded by `user_transcription`. - `user_transcription` — Final transcription for a completed user speech turn. - `tts_completed` — Fired when the agent finishes speaking a TTS segment. Includes the spoken text and optionally TTS latency. **Lifecycle events:** - `sse_init` — Sent immediately when the SSE connection is established. - `sse_close` — Sent when the call ends, right before the server closes the connection. Other event types (e.g. `tool_call_start`, `pre_call_api`, `agent_log`, metrics) are also sent on this stream. - `call_start` - `call_end` - `turn_latency` - `metrics` - `agent_node_state` - `hopping` - `knowledgebase` - `variable_extraction` - `pre_call_api` - `post_call_api` - `agent_error` - `agent_log` - `tool_call_start` - `tool_call_end` - `tool_call_error` - `call_cancelled` - `call_recording`

Authentication

AuthorizationBearer

API key from the console ApiKey collection, sent as Bearer token. Also accepts session cookies for browser-based auth.

Headers

X-Organization-IdstringOptional

Required when using session-cookie auth. API-token auth may infer the organization from the token.

Query parameters

callIdstringRequired
The call ID to subscribe events for. Missing or invalid values return 400.

Response

SSE event stream established successfully
event_typeenumOptional
The type of event
event_idstringOptional
Unique identifier for the event
timestampdatetimeOptional
ISO 8601 timestamp of the event
call_idstringOptional
The call ID this event belongs to
event_timedatetimeOptional

Timestamp used by sse_init and sse_close

telephony_idstringOptional

Telephony ID for call_start

metadatamap from strings to anyOptional

Metadata for call_end, agent_error, or agent_log

turn_latencydoubleOptional

Turn latency value for turn_latency

stt_api_msdoubleOptional

STT API latency in milliseconds for turn_latency

stt_to_llm_msdoubleOptional

STT-to-LLM latency in milliseconds for turn_latency

smart_turn_msdoubleOptional

Smart-turn latency in milliseconds for turn_latency

llm_api_msdoubleOptional

LLM API latency in milliseconds for turn_latency

llm_to_tts_msdoubleOptional

LLM-to-TTS latency in milliseconds for turn_latency

tts_api_msdoubleOptional

TTS API latency in milliseconds for turn_latency

tts_to_audio_msdoubleOptional

TTS-to-audio latency in milliseconds for turn_latency

total_turn_msdoubleOptional

Total turn latency in milliseconds for turn_latency

turn_indexintegerOptional

Turn index for turn_latency

interruptedbooleanOptional

Whether the turn was interrupted for turn_latency

smart_turn_enabledbooleanOptional

Whether smart turn was enabled for turn_latency

interim_transcription_textstringOptional

Partial transcription text (only for user_interim_transcription)

user_transcription_textstringOptional

Final transcription text (only for user_transcription)

tts_textstringOptional

Text spoken by the agent (only for tts_completed)

tts_latencyintegerOptional

TTS latency in milliseconds (only for tts_completed)

metricslist of objectsOptional

Per-turn metrics payload for metrics events. Server emits an array of {processor, model, value} entries (one per pipeline stage), not a single object. The SDK previously dropped every metrics SSE event with a pydantic ValidationError when this was typed as an object (122 events on a 40s call); typing it as an array of objects fixes the decode.

node_idstringOptional

Node ID for agent_node_state

node_namestringOptional

Node name for agent_node_state

node_typestringOptional

Node type for agent_node_state

contextmap from strings to anyOptional

Context payload for agent-node and tool-call events

from_node_idstringOptional

Source node ID for hopping

to_node_idstringOptional

Destination node ID for hopping

knowledge_base_idstringOptional

Knowledge base ID for knowledgebase

user_transcriptstringOptional

User transcript for knowledgebase

responseany or nullOptional

Response payload for knowledgebase, API, or tool-call events

latencydoubleOptional

Latency for knowledgebase or variable_extraction

errorany or nullOptional
Error payload for knowledgebase, variable extraction, API, tool, or agent error events
variablesmap from strings to anyOptional

Variables extracted by variable_extraction

variable_extraction_promptstringOptional

Prompt used for variable_extraction

methodstringOptional

HTTP method for pre_call_api or post_call_api

headersmap from strings to anyOptional

Headers for pre_call_api or post_call_api

bodyany or nullOptional

Body for pre_call_api or post_call_api

timeoutdoubleOptional

Timeout for pre_call_api or post_call_api

extracted_variablesmap from strings to anyOptional

Extracted variables for pre_call_api or post_call_api

next_node_idstringOptional

Next node ID for pre_call_api or post_call_api

successbooleanOptional

Success status for API and tool-call events

turn_idstringOptional

Turn ID for tool-call events

tool_call_idstringOptional

Tool call ID for tool-call events

function_namestringOptional

Function name for tool-call events

latency_msdoubleOptional

Latency in milliseconds for tool_call_end

recording_urlstringOptional

Recording URL for call_recording

statusstringOptional

Recording status for call_recording

Errors

400
Bad Request Error
401
Unauthorized Error
403
Forbidden Error
404
Not Found Error
500
Internal Server Error