Sends an audio file as a native iMessage audio message (waveform balloon with a play button on the receiver) instead of a generic file pill.
Two-step flow: upload an audio file via POST /v1/files, then pass
the returned file ID as audio_message. Common formats are accepted
— m4a, mp3, wav, caf, aiff. Audio is transcoded server-side, so you
don’t need to pre-encode.
iMessage only — SMS lines are rejected. Some lines don’t support
audio messages; sending from one of those returns
400 advanced_features_required.
Like all writes, this is asynchronous: returns a delivery ID with
status: "pending". Track via GET /outbox or webhooks.
Use an API key as a bearer token: Authorization: Bearer sk_live_...
Sender line handle (phone number or Apple ID)
"+15551234567"
Recipient phone number, Apple ID, or chat ID (cht_...)
"+15559876543"
File ID (file_...) of the uploaded audio
"file_abc123"
Message ID (msg_...) or iMessage GUID to reply to
"msg_abc123"