Type alias CallState

States a voice call can be in.

Transitions follow a monotonic order (initiated -> ringing -> answered -> active -> speaking/listening), except speaking <-> listening which can cycle during conversation turns. Terminal states can be reached from any non-terminal state.

Non-terminal states (forward-only progression)

• initiated -- Call record created, provider request sent.
• ringing -- Provider confirmed the destination phone is ringing.
• answered -- Callee picked up; media channel not yet established.
• active -- Bidirectional media stream is established.

Conversation cycling states (can alternate freely)

• speaking -- Agent TTS is playing audio to the caller.
• listening -- Agent STT is listening for caller speech.

Terminal states (once reached, no further transitions)

• completed -- Normal call completion (both parties done).
• hangup-user -- The remote caller hung up.
• hangup-bot -- The agent initiated the hangup.
• timeout -- Call exceeded maxDurationSeconds.
• error -- Unrecoverable error during the call.
• failed -- Provider could not place the call at all.
• no-answer -- Callee did not pick up within the ring timeout.
• busy -- Callee line is busy.
• voicemail -- Answering machine / voicemail detected.