refer

Update a call in progress — cancel, complete, or redirect the SWML flow. State-transition rules: - `status: canceled` is only valid while the leg is `queued` or `ringing`. - `status: completed` is only valid while the leg is `answered` (or in-progress). - Supplying `url` or `swml` (redirect) is only valid while the leg is `answered`. - Calls in terminal states (`busy`, `failed`, `no-answer`, `canceled`, `completed`) cannot be updated.

Play media (audio files, text-to-speech, silence, or ringtones) on an active call. The HTTP response confirms the command was accepted. Playback lifecycle is delivered asynchronously via the `status_url` webhook, with payloads of the form `{control_id, call_id, node_id, state}` where `state` is one of `playing`, `paused`, `finished`, or `error`.

Starts recording an active call. The HTTP response returns the call leg — the recording URL is not included. Recording runs asynchronously; provide `status_url` to receive a webhook when the recording finishes (with the final URL), or query the call's events endpoint.

Collect user input (DTMF digits, speech, or both) on an active call. At least one of `digits` or `speech` must be provided; requests missing both return 400. Results are delivered asynchronously via the `status_url` webhook. Digit events have the shape `{control_id, call_id, node_id, result: {type:"digit", params: {digits, terminator}}}` and speech events `{..., result: {type:"speech", params: {text, confidence}}}`. When `start_input_timers` is `false`, the `initial_timeout` clock does not start until you send `calling.collect.start_input_timers` for the same `control_id`.

Start detection (answering machine, fax tone, or DTMF digits) on an active call. Detection runs asynchronously up to `timeout` seconds. Results are delivered via the `status_url` webhook.

Capture audio from an active call and stream it to an external destination. Audio is streamed via RTP (to a public IP/port) or WebSocket (to a `ws://`/`wss://` URI). Stop the tap with `calling.tap.stop` using the same `control_id`.

Stream call audio to an external WebSocket endpoint. Audio is sent to a `wss://` URL; `custom_parameters` pass through to the endpoint as connection metadata. Stream lifecycle webhooks are delivered to `status_url` (default method `POST`). Stop the stream with `calling.stream.stop` using the same `control_id`.

Enable noise reduction on an active call. Denoise is per-call (no `control_id`); a call has at most one active denoise filter. Use `calling.denoise.stop` to disable it.

Returned when the call is a standard PSTN, SIP, or WebRTC call.

Returned when the call is a Fabric subscriber device leg. The `status` field is always null for this type.