fix(voice): full E2EE bidirectional audio pipeline working
- bot.py: track active callers per room; only stop session when last caller leaves (fixes premature cancellation when Playwright browser hangs up while real app is still in call) - voice.py: pre-compute 8 HMAC-ratcheted keys from EC's base key so decryption works immediately without waiting ~30s for Matrix to deliver EC's key-rotation event (root cause of user→bot silence) - voice.py: fix set_key() argument order (identity, key, index) at all call sites — was (identity, index, key) causing TypeError - voice.py: add audio frame monitor (AUDIO_FLOW) and mute/unmute event handlers for diagnostics - voice.py: update livekit-agents 1.4.2 event names: user_state_changed, user_input_transcribed, conversation_item_added Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Christian Gick
119
voice.py
119
voice.py
@@ -96,6 +96,22 @@ def _hkdf_derive(ikm: bytes) -> bytes:
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return t1[:16]
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def _ratchet_keys(base_raw: bytes, count: int = 6) -> dict[int, bytes]:
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"""Pre-compute ratcheted keys 0..count-1 matching livekit-client-sdk-js ratchet().
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EC JS ratchet: new_raw = HMAC(key=current_raw, data="LKFrameEncryptionKey")[:16]
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Returns {index: raw_key} for all indices 0..count-1.
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Set these via set_key(identity, raw, index) with KDF_HKDF=1 so Rust applies HKDF.
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"""
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import hmac as _hmac
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keys = {}
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raw = base_raw
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for i in range(count):
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keys[i] = raw
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raw = _hmac.new(raw, b"LKFrameEncryptionKey", hashlib.sha256).digest()[:16]
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return keys
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def _build_e2ee_options() -> rtc.E2EEOptions:
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"""Build E2EE options — let Rust FFI apply HKDF internally (KDF_HKDF=1).
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@@ -141,9 +157,18 @@ class VoiceSession:
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if not self._caller_key:
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self._caller_key = key
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self._caller_identity = f"{sender}:{device_id}"
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self._caller_all_keys[index] = key
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logger.info("E2EE key received from %s:%s (index=%d, %d bytes)",
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sender, device_id, index, len(key))
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# Pre-compute ratcheted keys from this base key to cover EC's key rotation.
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# EC rotates (via HMAC ratchet) when new participants join — the rotated key
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# arrives via Matrix sync with ~30s delay. Setting ratcheted indices 0..N
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# proactively means decryption works immediately without waiting for Matrix.
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ratcheted = _ratchet_keys(key, count=8)
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for ridx, rkey in ratcheted.items():
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actual_idx = index + ridx
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if actual_idx not in self._caller_all_keys: # don't overwrite real received keys
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self._caller_all_keys[actual_idx] = rkey
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self._caller_all_keys[index] = key # always store the real key at its index
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logger.info("E2EE key received from %s:%s (index=%d, %d bytes) — pre-computed ratchets [%d..%d]",
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sender, device_id, index, len(key), index, index + 7)
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# Live-update key on rotation — use set_key() which applies HKDF via Rust FFI.
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# At this point the track is usually already subscribed so frame cryptor exists.
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if self.lk_room and self._caller_identity:
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@@ -152,7 +177,7 @@ class VoiceSession:
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if p.identity == caller_lk_id:
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try:
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kp = self.lk_room.e2ee_manager.key_provider
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ok = kp.set_key(p.identity, index, key)
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ok = kp.set_key(p.identity, key, index)
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logger.info("Live-updated set_key[%d] for %s (ok=%s, %d bytes)",
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index, p.identity, ok, len(key))
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except Exception as e:
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@@ -286,26 +311,63 @@ class VoiceSession:
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def on_tp(pub, p):
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logger.info("Track pub: %s %s kind=%s", p.identity, pub.sid, pub.kind)
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@self.lk_room.on("track_muted")
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def on_mute(pub, p):
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logger.info("Track MUTED: %s %s kind=%s", p.identity, pub.sid, pub.kind)
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@self.lk_room.on("track_unmuted")
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def on_unmute(pub, p):
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logger.info("Track UNMUTED: %s %s kind=%s", p.identity, pub.sid, pub.kind)
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@self.lk_room.on("track_subscribed")
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def on_ts(t, pub, p):
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logger.info("Track sub: %s %s kind=%s", p.identity, pub.sid, t.kind)
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logger.info("Track sub: %s %s kind=%s muted=%s", p.identity, pub.sid, t.kind, pub.muted)
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# Start audio frame counter for this track to confirm data flows
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if int(t.kind) == 1:
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async def _count_frames(track=t, pid=p.identity):
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try:
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audio_stream = rtc.AudioStream(track)
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count = 0
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async for _ in audio_stream:
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count += 1
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if count == 1:
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logger.info("AUDIO_FLOW: first frame from %s (E2EE OK)", pid)
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elif count % 1000 == 0:
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logger.info("AUDIO_FLOW: %d frames from %s", count, pid)
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except Exception as exc:
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logger.warning("AUDIO_FLOW monitor error: %s", exc)
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asyncio.ensure_future(_count_frames())
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# *** KEY FIX: set_key() with KDF_HKDF only applies HKDF when the frame cryptor
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# for this participant already exists. The frame cryptor is created at track
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# subscription time. Calling set_key() BEFORE track subscription (at connect)
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# skips HKDF derivation → raw key stored → DEC_FAILED.
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# Solution: set caller key HERE, after frame cryptor is initialized.
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if int(t.kind) == 1 and e2ee_opts is not None: # audio track only
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caller_id = p.identity
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try:
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kp_local = self.lk_room.e2ee_manager.key_provider
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if self._caller_all_keys:
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for idx, base_k in sorted(self._caller_all_keys.items()):
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ok = kp_local.set_key(p.identity, idx, base_k)
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ok = kp_local.set_key(caller_id, base_k, idx)
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logger.info("on_ts: set_key[%d] for %s (ok=%s, %d bytes)",
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idx, p.identity, ok, len(base_k))
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idx, caller_id, ok, len(base_k))
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else:
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logger.warning("on_ts: no caller keys available yet — will set on key receipt")
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logger.warning("on_ts: no caller keys available yet")
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except Exception as exc:
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logger.warning("on_ts: set_key failed: %s", exc)
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# Delayed retry — frame cryptor may not be ready at track_subscribed time
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async def _delayed_set_key(pid=caller_id):
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await asyncio.sleep(1.0)
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try:
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kp_d = self.lk_room.e2ee_manager.key_provider
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if self._caller_all_keys:
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for idx, base_k in sorted(self._caller_all_keys.items()):
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ok = kp_d.set_key(pid, base_k, idx)
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logger.info("on_ts_delayed: set_key[%d] for %s (ok=%s, %d bytes)",
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idx, pid, ok, len(base_k))
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except Exception as exc:
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logger.warning("on_ts_delayed: set_key failed: %s", exc)
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asyncio.ensure_future(_delayed_set_key())
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_e2ee_state_names = {0:"NEW",1:"OK",2:"ENC_FAILED",3:"DEC_FAILED",4:"MISSING_KEY",5:"RATCHETED",6:"INTERNAL_ERR"}
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@self.lk_room.on("e2ee_state_changed")
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@@ -313,6 +375,16 @@ class VoiceSession:
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state_name = _e2ee_state_names.get(int(state), f"UNKNOWN_{state}")
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p_id = participant.identity if participant else "local"
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logger.info("E2EE_STATE: participant=%s state=%s", p_id, state_name)
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# When remote participant frame cryptor is NEW or MISSING_KEY → set their key
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if participant and p_id != bot_identity and int(state) in (0, 4):
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if self._caller_all_keys:
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try:
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kp_e = self.lk_room.e2ee_manager.key_provider
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for idx, base_k in sorted(self._caller_all_keys.items()):
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ok = kp_e.set_key(p_id, base_k, idx)
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logger.info("e2ee_state set_key[%d] for %s (ok=%s)", idx, p_id, ok)
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except Exception as exc:
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logger.warning("e2ee_state set_key failed: %s", exc)
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await self.lk_room.connect(self.lk_url, jwt, options=room_opts)
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logger.info("Connected (E2EE=HKDF), remote=%d",
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@@ -322,7 +394,7 @@ class VoiceSession:
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# CALLER keys are set in on_track_subscribed (NOT here) because the caller's frame cryptor
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# is only created when their track arrives. Calling set_key() before that skips HKDF.
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kp = self.lk_room.e2ee_manager.key_provider
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ok = kp.set_key(bot_identity, 0, self._bot_key)
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ok = kp.set_key(bot_identity, self._bot_key, 0)
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logger.info("Set bot key for %s (ok=%s, %d bytes)", bot_identity, ok, len(self._bot_key))
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# Element Call rotates its encryption key when bot joins the LiveKit room.
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@@ -368,7 +440,7 @@ class VoiceSession:
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if self._caller_all_keys and remote_identity:
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try:
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for idx, base_k in sorted(self._caller_all_keys.items()):
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ok = kp.set_key(remote_identity, idx, base_k)
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ok = kp.set_key(remote_identity, base_k, idx)
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logger.info("Post-rotation set_key[%d] for %s (ok=%s)",
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idx, remote_identity, ok)
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except Exception as e:
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@@ -391,22 +463,21 @@ class VoiceSession:
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vad=_get_vad(),
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)
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# Debug: log speech pipeline events to pinpoint where audio is lost
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@self.session.on("user_started_speaking")
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def _on_speaking_start():
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logger.info("VAD: user_started_speaking")
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# Pipeline event logging (livekit-agents 1.4.2 event names)
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@self.session.on("user_state_changed")
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def _on_user_state(ev):
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logger.info("VAD: user_state=%s", ev.new_state)
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@self.session.on("user_stopped_speaking")
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def _on_speaking_stop():
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logger.info("VAD: user_stopped_speaking")
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@self.session.on("user_input_transcribed")
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def _on_user_speech(ev):
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logger.info("USER_SPEECH: %s", ev.transcript)
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@self.session.on("user_speech_committed")
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def _on_user_speech(msg):
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logger.info("USER_SPEECH: %s", msg.text_content)
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@self.session.on("agent_speech_committed")
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def _on_agent_speech(msg):
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logger.info("AGENT_SPEECH: %s", msg.text_content)
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@self.session.on("conversation_item_added")
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def _on_conversation_item(ev):
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role = getattr(ev.item, "role", "?")
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text = getattr(ev.item, "text_content", "") or ""
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if role == "assistant" and text:
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logger.info("AGENT_SPEECH: %s", text)
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agent = Agent(instructions=_build_voice_prompt())
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io_opts = room_io.RoomOptions(
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