This page traces the lifecycle of an outbound call placed via POST /call. The same stages apply to inbound calls, starting from Step 3.
Full lifecycle
Your app → POST /call → Bolna API → Telephony provider → Recipient's phone
↓
Call answered (or not)
↓
Transcriber ← Audio stream
↓
LLM processes transcript
↓
Synthesizer → Audio stream → Caller
↓
Call ends (hangup or timeout)
↓
Post-call processing (transcript, cost, extraction)
↓
Execution record: status = completed
Step-by-step
1. Call request accepted
Your app calls POST /call with agent_id, recipient_phone_number, and optional call metadata. Bolna validates the request and returns:
{
"execution_id": "b7140255-af33-4608-8e97-04dd944b8e48",
"status": "queued"
}
queued state. No telephony has happened yet.
2. Telephony dialing
Bolna’s call scheduler picks up the queued execution and dials out via the configured telephony provider (Plivo, Twilio, Exotel, or your SIP trunk). The execution moves to initiated, then ringing as the call progresses through the network.
3. Call answered → pipeline starts
When the recipient answers, the status moves to in-progress. The real-time pipeline activates:
- Audio capture — the telephony provider streams caller audio to Bolna
- Transcription — the transcriber (e.g. Deepgram) converts audio to text in real-time
- LLM inference — the transcript is sent to the LLM with the agent’s system prompt; the LLM streams a response
- Synthesis — the synthesizer converts the LLM response to speech audio
- Audio playback — Bolna streams the synthesized audio back to the caller
This loop repeats for every conversational turn.
If the agent’s prompt triggers a tool call (function call, knowledge base lookup, call transfer), the LLM emits a tool-call intent. Bolna:
- Pauses synthesis
- Executes the tool (calls your API endpoint, queries the knowledge base, etc.)
- Feeds the tool result back to the LLM
- Resumes the conversation
Tool calls add 50–500ms of latency depending on the tool’s response time.
5. Call ends
The call ends when:
- The caller hangs up
- The agent’s hangup prompt fires (e.g. “Have a great day, goodbye!”)
call_terminate timeout is reached (configured in task_config)hangup_after_silence fires (no speech for N seconds)- The agent calls the hangup tool explicitly
The telephony provider signals the disconnect. The execution moves to call-disconnected.
6. Post-call processing
call-disconnected is NOT the final state. After the line drops, Bolna runs:
- Transcript assembly (merges partial chunks into the full conversation text)
- Cost calculation (platform fee + network + transcriber + LLM + synthesizer)
- Post-call extraction (if an extraction task is configured — runs the LLM over the transcript to pull structured data)
- Recording URL generation
When all processing completes, the execution moves to completed and all fields are populated.
Always wait for completed, not call-disconnected, before reading conversation_duration, total_cost, recording_url, or extracted_data. These are null or 0 at call-disconnected.
7. Webhook delivery
If webhook_url is set on the agent, Bolna POSTs the execution payload to your server at each status change. The final completed POST includes all populated fields.
Source IP: 13.203.39.153 — whitelist this on your server.
Execution status reference
| Status | Phase |
|---|
queued | Accepted, waiting to dial |
initiated | Dialing |
ringing | Recipient’s phone ringing |
in-progress | Call answered, pipeline active |
call-disconnected | Line dropped, post-processing |
completed | All fields finalized ✓ |
no-answer | Not picked up |
busy | Line busy |
failed | Telephony error |
canceled | Manually canceled before answer |
stopped | Stopped mid-execution |
error | Internal error during processing |
balance-low | Insufficient wallet balance |
