From 949be8e5f1a75286b8b517dacda76ed27646e77b Mon Sep 17 00:00:00 2001
From: cai <cai@nbcai.cc>
Date: Tue, 11 Aug 2026 21:23:54 +0800
Subject: [PATCH] fix(helper): gate audio observer on fixture ack

---
 src/main.rs | 1030 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 986 insertions(+), 44 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index d357e4a..94b6589 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -59,6 +59,123 @@
 const STREAM_TIMING_FIRST_CHUNK: u64 = 1;
 const STREAM_TIMING_MAX_ELAPSED_MS: u64 = 5_000;
 const STREAM_TIMING_SOURCE: &str = "stream_anchor_monotonic";
+const CONTROLLED_FIXTURE_PROBE_TOPIC: &str = "controlled_fixture_attribute_probe";
+const CONTROLLED_FIXTURE_ACK_TOPIC: &str = "controlled_fixture_attribute_ack";
+const CONTROLLED_FIXTURE_PROTOCOL_VERSION: u64 = 1;
+const CONTROLLED_FIXTURE_GENERATION: u64 = 1;
+const CONTROLLED_FIXTURE_PROBE_RECHECKS: usize = 3;
+const CONTROLLED_FIXTURE_PROBE_RECHECK_DELAY: Duration = Duration::from_millis(25);
+const CONTROLLED_FIXTURE_PROBE_TTL: Duration = Duration::from_millis(250);
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct ControlledFixtureAttributeProbe {
+    #[serde(rename = "type")]
+    message_type: String,
+    protocol_version: u64,
+    call_id_hash: String,
+    call_trace_id_hash: String,
+    generation: u64,
+    client_fixture_sequence: String,
+}
+
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "camelCase")]
+struct ControlledFixtureAttributeAck {
+    #[serde(rename = "type")]
+    message_type: &'static str,
+    protocol_version: u64,
+    call_id_hash: String,
+    call_trace_id_hash: String,
+    generation: u64,
+    client_fixture_sequence: String,
+    result: &'static str,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    input_source_category: Option<&'static str>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    reject_reason: Option<&'static str>,
+}
+
+#[derive(Debug)]
+struct PendingControlledFixtureProbe {
+    sender: ParticipantIdentity,
+    sequence: String,
+    expires_at: Instant,
+}
+
+fn sha256_hex(value: &str) -> String {
+    let mut digest = Sha256::new();
+    digest.update(value.as_bytes());
+    digest
+        .finalize()
+        .iter()
+        .map(|byte| format!("{byte:02x}"))
+        .collect()
+}
+
+fn controlled_fixture_probe(
+    payload: &[u8],
+    call_id: &str,
+    trace_id: &str,
+    sender: &ParticipantIdentity,
+    expected_participant: Option<&str>,
+) -> Option<PendingControlledFixtureProbe> {
+    if !is_bound_user_participant(sender.as_str(), expected_participant) {
+        return None;
+    }
+    let probe: ControlledFixtureAttributeProbe = serde_json::from_slice(payload).ok()?;
+    if probe.message_type != CONTROLLED_FIXTURE_PROBE_TOPIC
+        || probe.protocol_version != CONTROLLED_FIXTURE_PROTOCOL_VERSION
+        || probe.generation != CONTROLLED_FIXTURE_GENERATION
+        || probe.call_id_hash != sha256_hex(call_id)
+        || probe.call_trace_id_hash != sha256_hex(trace_id)
+        || probe.client_fixture_sequence.trim().is_empty()
+    {
+        return None;
+    }
+    Some(PendingControlledFixtureProbe {
+        sender: sender.clone(),
+        sequence: probe.client_fixture_sequence,
+        expires_at: Instant::now() + CONTROLLED_FIXTURE_PROBE_TTL,
+    })
+}
+
+fn classify_controlled_fixture_attributes(
+    actual_participant: &str,
+    expected_participant: Option<&str>,
+    attributes: &std::collections::HashMap<String, String>,
+    requested_sequence: &str,
+) -> Result<(), &'static str> {
+    if !is_bound_user_participant(actual_participant, expected_participant) {
+        return Err("wrong_participant");
+    }
+    let source = attributes
+        .get("inputSourceCategory")
+        .map(String::as_str)
+        .unwrap_or("");
+    if source != "controlled_fixture" {
+        return Err(if source.is_empty() {
+            "missing_attributes"
+        } else {
+            "wrong_source"
+        });
+    }
+    let sequence = attributes
+        .get("clientFixtureSequence")
+        .map(String::as_str)
+        .unwrap_or("");
+    if sequence.trim().is_empty() {
+        return Err("missing_sequence");
+    }
+    if sequence != requested_sequence {
+        return Err("wrong_sequence");
+    }
+    Ok(())
+}
+
+fn controlled_fixture_observer_gate(pending_probe: bool, probe_result: Option<bool>) -> bool {
+    !pending_probe || probe_result == Some(true)
+}
 
 #[tokio::main(flavor = "multi_thread")]
 async fn main() -> Result<()> {
@@ -737,6 +854,10 @@
     })
 }
 
+fn is_bound_user_participant(identity: &str, expected: Option<&str>) -> bool {
+    expected.is_none_or(|value| identity == value)
+}
+
 async fn observe_user_audio_events(
     mut events: UnboundedReceiver<RoomEvent>,
     call_id: String,
@@ -764,6 +885,10 @@
         "runtime helper user_track_subscribe_requested"
     );
 
+    let mut current_user_participant: Option<RemoteParticipant> = None;
+    let mut pending_probe: Option<PendingControlledFixtureProbe> = None;
+    let mut acknowledged_probe_sequences = HashSet::new();
+
     while let Some(event) = events.recv().await {
         match event {
             RoomEvent::TrackSubscribed {
@@ -771,10 +896,10 @@
                 publication: _,
                 participant,
             } => {
-                if user_participant_identity
-                    .as_deref()
-                    .is_some_and(|expected| participant.identity().to_string() != expected)
-                {
+                if !is_bound_user_participant(
+                    &participant.identity().to_string(),
+                    user_participant_identity.as_deref(),
+                ) {
                     warn!(call_id = %call_id, trace_id = %trace_id,
                         metadata_status = "wrong_participant",
                         "runtime helper ignored non-user audio participant");
@@ -793,6 +918,26 @@
                     track_source = %track_source,
                     "runtime helper user_track_subscribed"
                 );
+                let pending_sequence = pending_probe.as_ref().map(|probe| probe.sequence.clone());
+                let participant_for_probe = participant.clone();
+                let probe_result = process_controlled_fixture_probe(
+                    &mut pending_probe,
+                    &mut acknowledged_probe_sequences,
+                    Some(&participant_for_probe),
+                    &sink,
+                    &call_id,
+                    &trace_id,
+                    user_participant_identity.as_deref(),
+                )
+                .await;
+                if !controlled_fixture_observer_gate(pending_sequence.is_some(), probe_result) {
+                    warn!(
+                        call_id = %call_id,
+                        trace_id = %trace_id,
+                        "runtime helper withheld audio observer until controlled fixture ACK"
+                    );
+                    continue;
+                }
                 spawn_user_audio_frame_observer(
                     track,
                     call_id.clone(),
@@ -805,8 +950,41 @@
                     turn_bridge_config.clone(),
                     http.clone(),
                     sink.clone(),
+                    user_participant_identity.clone(),
                     participant,
                 );
+                current_user_participant = Some(participant_for_probe);
+            }
+            RoomEvent::DataReceived {
+                payload,
+                topic: Some(topic),
+                participant: Some(sender),
+                ..
+            } if topic == CONTROLLED_FIXTURE_PROBE_TOPIC => {
+                if let Ok(probe) =
+                    serde_json::from_slice::<ControlledFixtureAttributeProbe>(&payload)
+                {
+                    if acknowledged_probe_sequences.contains(&probe.client_fixture_sequence) {
+                        continue;
+                    }
+                }
+                pending_probe = controlled_fixture_probe(
+                    &payload,
+                    &call_id,
+                    &trace_id,
+                    &sender.identity(),
+                    user_participant_identity.as_deref(),
+                );
+                process_controlled_fixture_probe(
+                    &mut pending_probe,
+                    &mut acknowledged_probe_sequences,
+                    current_user_participant.as_ref(),
+                    &sink,
+                    &call_id,
+                    &trace_id,
+                    user_participant_identity.as_deref(),
+                )
+                .await;
             }
             RoomEvent::TrackSubscribed {
                 track: RemoteTrack::Video(track),
@@ -847,6 +1025,79 @@
             _ => {}
         }
     }
+}
+
+async fn process_controlled_fixture_probe(
+    pending_probe: &mut Option<PendingControlledFixtureProbe>,
+    acknowledged_probe_sequences: &mut HashSet<String>,
+    participant: Option<&RemoteParticipant>,
+    sink: &BotAudioOutputSink,
+    call_id: &str,
+    trace_id: &str,
+    expected_participant: Option<&str>,
+) -> Option<bool> {
+    let Some(probe) = pending_probe.take() else {
+        return None;
+    };
+    if acknowledged_probe_sequences.contains(&probe.sequence) || Instant::now() > probe.expires_at {
+        return Some(false);
+    }
+    let Some(participant) = participant else {
+        *pending_probe = Some(probe);
+        return None;
+    };
+    if participant.identity() != probe.sender {
+        return Some(false);
+    }
+    let mut decision = Err("timeout");
+    for attempt in 0..CONTROLLED_FIXTURE_PROBE_RECHECKS {
+        if Instant::now() > probe.expires_at {
+            break;
+        }
+        let attributes = participant.attributes();
+        decision = classify_controlled_fixture_attributes(
+            &participant.identity().to_string(),
+            expected_participant,
+            &attributes,
+            &probe.sequence,
+        );
+        if decision.is_ok() || !matches!(decision, Err("missing_attributes")) {
+            break;
+        }
+        if attempt + 1 < CONTROLLED_FIXTURE_PROBE_RECHECKS {
+            sleep(CONTROLLED_FIXTURE_PROBE_RECHECK_DELAY).await;
+        }
+    }
+    let (result, input_source_category, reject_reason) = match decision {
+        Ok(()) => ("observed", Some("controlled_fixture"), None),
+        Err(reason) => ("rejected", None, Some(reason)),
+    };
+    let ack = ControlledFixtureAttributeAck {
+        message_type: CONTROLLED_FIXTURE_ACK_TOPIC,
+        protocol_version: CONTROLLED_FIXTURE_PROTOCOL_VERSION,
+        call_id_hash: sha256_hex(call_id),
+        call_trace_id_hash: sha256_hex(trace_id),
+        generation: CONTROLLED_FIXTURE_GENERATION,
+        client_fixture_sequence: probe.sequence.clone(),
+        result,
+        input_source_category,
+        reject_reason,
+    };
+    let payload = match serde_json::to_vec(&ack) {
+        Ok(payload) => payload,
+        Err(_) => return Some(false),
+    };
+    let local_participant = sink.room.local_participant();
+    let publish = local_participant.publish_data(DataPacket {
+        payload,
+        topic: Some(CONTROLLED_FIXTURE_ACK_TOPIC.to_string()),
+        reliable: true,
+        destination_identities: vec![probe.sender],
+    });
+    if publish.await.is_ok() {
+        acknowledged_probe_sequences.insert(probe.sequence);
+    }
+    Some(result == "observed")
 }
 
 async fn handle_finished_turn(
@@ -2917,6 +3168,7 @@
     turn_bridge_config: TurnBridgeConfig,
     http: Client,
     sink: Arc<BotAudioOutputSink>,
+    expected_participant_identity: Option<String>,
     participant: RemoteParticipant,
 ) -> JoinHandle<()> {
     tokio::spawn(async move {
@@ -2996,6 +3248,7 @@
             None
         };
         let mut realtime_asr_upload: Option<RealtimeAsrUpload> = None;
+        let mut last_fixture_sequence: Option<String> = None;
 
         while let Some(drained) = frame_rx.recv().await {
             let frame = drained.frame;
@@ -3029,8 +3282,11 @@
 
             if let Some(vad) = simple_vad.as_mut() {
                 if vad_enabled_gate.load(Ordering::Acquire) {
-                    let was_in_speech = vad.in_speech;
-                    let turn = vad.observe_frame(
+                    let participant_identity = participant.identity().to_string();
+                    let (was_in_speech, is_in_speech, turn) = observe_bound_participant_frame(
+                        &participant_identity,
+                        expected_participant_identity.as_deref(),
+                        vad,
                         &call_id,
                         &trace_id,
                         &participant_alias,
@@ -3038,41 +3294,15 @@
                         frame_count,
                         elapsed_ms,
                         &frame,
+                        http.clone(),
+                        turn_bridge_config.realtime_asr_config(),
+                        || participant.attributes(),
+                        &mut realtime_asr_upload,
+                        &mut last_fixture_sequence,
+                        turn_bridge_config.asr_realtime_enabled,
                     );
-                    let is_in_speech = vad.in_speech;
 
-                    if !was_in_speech && is_in_speech {
-                        let turn_id = format!("turn-{:04}", vad.turn_index);
-                        match RealtimeAsrUpload::start_with_participant_attributes(
-                            http.clone(),
-                            turn_bridge_config.realtime_asr_config(),
-                            &call_id,
-                            &trace_id,
-                            &turn_id,
-                            &vad.speech_samples,
-                            || participant.attributes(),
-                        ) {
-                            Ok(upload) => {
-                                info!(
-                                    call_id = %call_id,
-                                    trace_id = %trace_id,
-                                    turn_id = %turn_id,
-                                    "runtime helper asr_realtime_session_started"
-                                );
-                                realtime_asr_upload = Some(upload);
-                            }
-                            Err(error) if turn_bridge_config.asr_realtime_enabled => {
-                                warn!(
-                                    call_id = %call_id,
-                                    trace_id = %trace_id,
-                                    turn_id = %turn_id,
-                                    error = %safe_error(&error.to_string()),
-                                    "runtime helper asr_realtime_start_failed_fallback"
-                                );
-                            }
-                            Err(_) => {}
-                        }
-                    } else if was_in_speech {
+                    if was_in_speech {
                         let push_failed = realtime_asr_upload
                             .as_mut()
                             .and_then(|upload| upload.push_48k_samples(frame.data.as_ref()).err());
@@ -3189,6 +3419,176 @@
             "runtime helper user_audio_stream_ended"
         );
     })
+}
+
+fn observe_frame_and_start_session<F>(
+    vad: &mut SimpleVad,
+    call_id: &str,
+    trace_id: &str,
+    participant_alias: &str,
+    track_sid_alias: &str,
+    frame_count: u64,
+    elapsed_ms: u64,
+    frame: &AudioFrame<'_>,
+    http: Client,
+    config: RealtimeAsrConfig,
+    read_attributes: F,
+    upload_slot: &mut Option<RealtimeAsrUpload>,
+    last_fixture_sequence: &mut Option<String>,
+    realtime_enabled: bool,
+) -> (bool, bool, Option<FinishedSpeechTurn>)
+where
+    F: FnOnce() -> std::collections::HashMap<String, String>,
+{
+    let was_in_speech = vad.in_speech;
+    let turn = vad.observe_frame(
+        call_id,
+        trace_id,
+        participant_alias,
+        track_sid_alias,
+        frame_count,
+        elapsed_ms,
+        frame,
+    );
+    let is_in_speech = vad.in_speech;
+    if !was_in_speech && is_in_speech {
+        start_realtime_session_for_new_speech(
+            http,
+            config,
+            call_id,
+            trace_id,
+            vad,
+            read_attributes,
+            upload_slot,
+            last_fixture_sequence,
+            realtime_enabled,
+        );
+    }
+    (was_in_speech, is_in_speech, turn)
+}
+
+fn observe_bound_participant_frame<F>(
+    participant_identity: &str,
+    expected_participant: Option<&str>,
+    vad: &mut SimpleVad,
+    call_id: &str,
+    trace_id: &str,
+    participant_alias: &str,
+    track_sid_alias: &str,
+    frame_count: u64,
+    elapsed_ms: u64,
+    frame: &AudioFrame<'_>,
+    http: Client,
+    config: RealtimeAsrConfig,
+    read_attributes: F,
+    upload_slot: &mut Option<RealtimeAsrUpload>,
+    last_fixture_sequence: &mut Option<String>,
+    realtime_enabled: bool,
+) -> (bool, bool, Option<FinishedSpeechTurn>)
+where
+    F: FnOnce() -> std::collections::HashMap<String, String>,
+{
+    if !is_bound_user_participant(participant_identity, expected_participant) {
+        warn!(
+            "audioIngressOriginStatus" = "wrong_participant_or_track",
+            "runtime helper rejected audio participant before VAD/session"
+        );
+        return (vad.in_speech, vad.in_speech, None);
+    }
+    observe_frame_and_start_session(
+        vad,
+        call_id,
+        trace_id,
+        participant_alias,
+        track_sid_alias,
+        frame_count,
+        elapsed_ms,
+        frame,
+        http,
+        config,
+        read_attributes,
+        upload_slot,
+        last_fixture_sequence,
+        realtime_enabled,
+    )
+}
+
+fn start_realtime_session_for_new_speech(
+    http: Client,
+    config: RealtimeAsrConfig,
+    call_id: &str,
+    trace_id: &str,
+    vad: &SimpleVad,
+    read_attributes: impl FnOnce() -> std::collections::HashMap<String, String>,
+    upload_slot: &mut Option<RealtimeAsrUpload>,
+    last_fixture_sequence: &mut Option<String>,
+    realtime_enabled: bool,
+) {
+    let turn_id = format!("turn-{:04}", vad.turn_index);
+    let attributes = read_attributes();
+    let origin_status = AudioIngressMetadata::origin_status(&attributes);
+    let metadata = match AudioIngressMetadata::from_participant(&attributes) {
+        Ok(metadata) => metadata,
+        Err(reason) => {
+            warn!(call_id = %call_id, trace_id = %trace_id, turn_id = %turn_id,
+                reason, audioIngressOriginStatus = %AudioIngressMetadata::rejected_origin_status(
+                    reason, &attributes
+                ),
+                "runtime helper asr_realtime_metadata_rejected");
+            return;
+        }
+    };
+    if let Some(metadata) = metadata.as_ref() {
+        if !fixture_sequence_is_new(
+            last_fixture_sequence.as_deref(),
+            &metadata.client_fixture_sequence,
+        ) {
+            warn!(call_id = %call_id, trace_id = %trace_id, turn_id = %turn_id,
+                audioIngressOriginStatus = "sequence_replayed_or_regressed",
+                "runtime helper asr_realtime_metadata_sequence_rejected");
+            return;
+        }
+    }
+    match RealtimeAsrUpload::start(
+        http,
+        config,
+        call_id,
+        trace_id,
+        &turn_id,
+        &vad.speech_samples,
+        metadata.as_ref(),
+    ) {
+        Ok(upload) => {
+            if let Some(metadata) = metadata {
+                *last_fixture_sequence = Some(metadata.client_fixture_sequence);
+            }
+            info!(call_id = %call_id, trace_id = %trace_id, turn_id = %turn_id,
+                origin_status, "runtime helper asr_realtime_session_started");
+            *upload_slot = Some(upload);
+        }
+        Err(error) if realtime_enabled => {
+            warn!(call_id = %call_id, trace_id = %trace_id, turn_id = %turn_id,
+                error = %safe_error(&error.to_string()),
+                "runtime helper asr_realtime_start_failed_fallback");
+        }
+        Err(_) => {}
+    }
+}
+
+fn fixture_sequence_is_new(previous: Option<&str>, current: &str) -> bool {
+    let Some(previous) = previous else {
+        return true;
+    };
+    let current_number = current
+        .rsplit_once('-')
+        .and_then(|(_, value)| value.parse::<u64>().ok());
+    let previous_number = previous
+        .rsplit_once('-')
+        .and_then(|(_, value)| value.parse::<u64>().ok());
+    match (previous_number, current_number) {
+        (Some(previous), Some(current)) => current > previous,
+        _ => previous != current,
+    }
 }
 
 struct DrainedUserAudioFrame {
@@ -3943,12 +4343,408 @@
 
 #[cfg(test)]
 mod tests {
-    use super::{
-        ReplyChunkMarker, ReplyChunkMarkerState, RuntimeTurnDeviceOutput, RuntimeTurnStreamEvent,
-        RuntimeTurnStreamState, RuntimeTurnStreamTimingPhase, runtime_session_nonce_hash,
-        should_publish_device_output,
+    use super::*;
+    use std::{
+        collections::HashSet,
+        io::{Read, Write},
+        net::TcpListener,
+        sync::{
+            Arc,
+            atomic::{AtomicUsize, Ordering},
+            mpsc,
+        },
+        thread,
+        time::Duration,
     };
-    use std::collections::HashSet;
+
+    #[test]
+    fn production_vad_session_boundary_reads_updated_attributes() {
+        let config = SimpleVadConfig {
+            rms_threshold: 0.001,
+            peak_threshold: 0.01,
+            start_frames: 2,
+            end_silence_ms: 100,
+            min_speech_ms: 1,
+            max_turn_ms: 1_000,
+            initial_ignore_ms: 0,
+        };
+        let mut vad = SimpleVad::new(config);
+        let samples = vec![1_000i16; 160];
+        let frame = AudioFrame {
+            data: samples.as_slice().into(),
+            sample_rate: 16_000,
+            num_channels: 1,
+            samples_per_channel: 160,
+        };
+        let mut attributes = std::collections::HashMap::from([
+            (
+                "inputSourceCategory".to_string(),
+                "controlled_fixture".to_string(),
+            ),
+            (
+                "clientFixtureSequence".to_string(),
+                "fixture-01".to_string(),
+            ),
+        ]);
+        let mut starts = Vec::new();
+        for (session_index, sequence) in [(1, "fixture-01"), (2, "fixture-02")] {
+            let was_in_speech = vad.in_speech;
+            vad.observe_frame(
+                "call-001",
+                "trace-001",
+                "participant",
+                "track",
+                session_index * 2 - 1,
+                1_000 * session_index,
+                &frame,
+            );
+            vad.observe_frame(
+                "call-001",
+                "trace-001",
+                "participant",
+                "track",
+                session_index * 2,
+                1_000 * session_index + 10,
+                &frame,
+            );
+            let is_in_speech = vad.in_speech;
+            assert!(!was_in_speech && is_in_speech);
+            attributes.insert("clientFixtureSequence".to_string(), sequence.to_string());
+            let metadata = AudioIngressMetadata::from_participant(&attributes)
+                .expect("valid participant attributes")
+                .expect("controlled fixture metadata");
+            let session_line = asr_realtime::session_start_line(
+                "call-001",
+                "trace-001",
+                &format!("turn-{session_index:04}"),
+                "nonce-001",
+                Some(&metadata),
+            )
+            .expect("session start line");
+            let session_json: serde_json::Value =
+                serde_json::from_slice(&session_line).expect("session start json");
+            assert_eq!(sequence, session_json["clientFixtureSequence"]);
+            starts.push(metadata.client_fixture_sequence);
+            vad.reset_current_turn();
+        }
+        assert_eq!(vec!["fixture-01", "fixture-02"], starts);
+        attributes.insert("inputSourceCategory".to_string(), "other".to_string());
+        assert!(AudioIngressMetadata::from_participant(&attributes).is_err());
+        assert!(
+            AudioIngressMetadata::from_participant(&std::collections::HashMap::new())
+                .expect("missing attributes is absent")
+                .is_none()
+        );
+        attributes.insert(
+            "clientFixtureSequence".to_string(),
+            "fixture-01".to_string(),
+        );
+        assert!(AudioIngressMetadata::from_participant(&attributes).is_err());
+    }
+
+    #[test]
+    fn production_observer_rejects_wrong_participant_before_vad_session() {
+        assert!(!is_bound_user_participant(
+            "participant-other",
+            Some("participant-user")
+        ));
+        assert!(is_bound_user_participant(
+            "participant-user",
+            Some("participant-user")
+        ));
+        assert!(is_bound_user_participant("participant-any", None));
+    }
+
+    #[tokio::test]
+    async fn production_observer_vad_to_session_entry_reads_each_updated_attribute() {
+        let listener = TcpListener::bind("127.0.0.1:0").expect("bind local ASR fixture");
+        let address = listener.local_addr().expect("fixture address");
+        let (request_tx, request_rx) = mpsc::channel::<String>();
+        let captured_count = Arc::new(AtomicUsize::new(0));
+        let captured_count_for_server = Arc::clone(&captured_count);
+        let server = thread::spawn(move || {
+            for _ in 0..2 {
+                let (mut stream, _) = listener.accept().expect("accept ASR session");
+                stream
+                    .set_read_timeout(Some(Duration::from_secs(2)))
+                    .expect("set fixture timeout");
+                let mut bytes = Vec::new();
+                let mut buffer = [0_u8; 4096];
+                loop {
+                    match stream.read(&mut buffer) {
+                        Ok(0) => break,
+                        Ok(size) => {
+                            bytes.extend_from_slice(&buffer[..size]);
+                            if bytes.windows(7).any(|window| window == b"0\r\n\r\n") {
+                                break;
+                            }
+                        }
+                        Err(_) => break,
+                    }
+                }
+                request_tx
+                    .send(String::from_utf8_lossy(&bytes).into_owned())
+                    .expect("capture ASR request");
+                captured_count_for_server.fetch_add(1, Ordering::SeqCst);
+                stream
+                    .write_all(b"HTTP/1.1 200 OK\r\ncontent-type: application/json\r\ncontent-length: 39\r\nconnection: close\r\n\r\n{\"code\":0,\"data\":{\"status\":\"ok\"}}")
+                    .expect("write fixture response");
+            }
+        });
+        let mut vad = SimpleVad::new(SimpleVadConfig {
+            rms_threshold: 0.001,
+            peak_threshold: 0.01,
+            start_frames: 1,
+            end_silence_ms: 100,
+            min_speech_ms: 1,
+            max_turn_ms: 1_000,
+            initial_ignore_ms: 0,
+        });
+        let frame_data = vec![1_000i16; 160];
+        let frame = AudioFrame {
+            data: frame_data.as_slice().into(),
+            sample_rate: 16_000,
+            num_channels: 1,
+            samples_per_channel: 160,
+        };
+        let mut attrs = std::collections::HashMap::from([
+            (
+                "inputSourceCategory".to_string(),
+                "controlled_fixture".to_string(),
+            ),
+            (
+                "clientFixtureSequence".to_string(),
+                "fixture-01".to_string(),
+            ),
+        ]);
+        let mut upload = None;
+        let mut last_fixture_sequence = None;
+        let config = RealtimeAsrConfig {
+            enabled: true,
+            url: Some(format!("http://{address}/runtime/asr/realtime")),
+            runtime_token: Some("test".to_string()),
+            runtime_session_nonce: Some("test".to_string()),
+            chunk_duration_ms: 200,
+        };
+        let (was, is, turn) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            1,
+            1_000,
+            &frame,
+            Client::new(),
+            config.clone(),
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(!was && is && turn.is_none());
+        assert!(upload.is_some());
+        upload.take().unwrap().cancel("test").await;
+        vad.reset_current_turn();
+        attrs.insert(
+            "clientFixtureSequence".to_string(),
+            "fixture-02".to_string(),
+        );
+        let (was, is, turn) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            2,
+            2_000,
+            &frame,
+            Client::new(),
+            config,
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(!was && is && turn.is_none());
+        assert!(upload.is_some());
+        upload.take().unwrap().cancel("test").await;
+
+        let first_request = request_rx
+            .recv_timeout(Duration::from_secs(2))
+            .expect("first session request");
+        let second_request = request_rx
+            .recv_timeout(Duration::from_secs(2))
+            .expect("second session request");
+        assert!(first_request.contains("\"clientFixtureSequence\":\"fixture-01\""));
+        assert!(second_request.contains("\"clientFixtureSequence\":\"fixture-02\""));
+        assert!(
+            first_request.contains("\"audioIngressOriginStatus\":\"controlled_fixture_bound\"")
+        );
+        assert!(
+            second_request.contains("\"audioIngressOriginStatus\":\"controlled_fixture_bound\"")
+        );
+        // The same production boundary rejects a wrong participant before VAD/session creation.
+        assert!(!is_bound_user_participant(
+            "participant-other",
+            Some("participant-user")
+        ));
+        assert_eq!(0, request_rx.try_iter().count());
+        vad.reset_current_turn();
+        attrs.insert(
+            "clientFixtureSequence".to_string(),
+            "fixture-03".to_string(),
+        );
+        let (_, is_wrong, wrong_turn) = observe_bound_participant_frame(
+            "participant-other",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            3,
+            3_000,
+            &frame,
+            Client::new(),
+            RealtimeAsrConfig {
+                enabled: true,
+                url: Some(format!("http://{address}/runtime/asr/realtime")),
+                runtime_token: Some("test".to_string()),
+                runtime_session_nonce: Some("test".to_string()),
+                chunk_duration_ms: 200,
+            },
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(!is_wrong && wrong_turn.is_none() && upload.is_none());
+        vad.reset_current_turn();
+        attrs.insert(
+            "clientFixtureSequence".to_string(),
+            "fixture-01".to_string(),
+        );
+        let (_, _, _) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            4,
+            4_000,
+            &frame,
+            Client::new(),
+            RealtimeAsrConfig {
+                enabled: true,
+                url: Some(format!("http://{address}/runtime/asr/realtime")),
+                runtime_token: Some("test".to_string()),
+                runtime_session_nonce: Some("test".to_string()),
+                chunk_duration_ms: 200,
+            },
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(upload.is_none());
+        vad.reset_current_turn();
+        let (_, _, _) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            5,
+            5_000,
+            &frame,
+            Client::new(),
+            RealtimeAsrConfig {
+                enabled: true,
+                url: Some(format!("http://{address}/runtime/asr/realtime")),
+                runtime_token: Some("test".to_string()),
+                runtime_session_nonce: Some("test".to_string()),
+                chunk_duration_ms: 200,
+            },
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(upload.is_none());
+        vad.reset_current_turn();
+        attrs.remove("clientFixtureSequence");
+        let (_, _, missing_sequence_turn) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-user",
+            "track-001",
+            6,
+            6_000,
+            &frame,
+            Client::new(),
+            RealtimeAsrConfig {
+                enabled: true,
+                url: Some(format!("http://{address}/runtime/asr/realtime")),
+                runtime_token: Some("test".to_string()),
+                runtime_session_nonce: Some("test".to_string()),
+                chunk_duration_ms: 200,
+            },
+            || attrs.clone(),
+            &mut upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(missing_sequence_turn.is_none() && upload.is_none());
+        assert_eq!(
+            "sequence_absent",
+            AudioIngressMetadata::rejected_origin_status("incomplete_metadata", &attrs)
+        );
+        assert_eq!(2, captured_count.load(Ordering::SeqCst));
+        vad.reset_current_turn();
+        attrs.insert("inputSourceCategory".to_string(), "other".to_string());
+        let mut invalid_upload = None;
+        let (_, _, invalid_turn) = observe_bound_participant_frame(
+            "participant-user",
+            Some("participant-user"),
+            &mut vad,
+            "call-001",
+            "trace-001",
+            "participant-other",
+            "track-001",
+            3,
+            3_000,
+            &frame,
+            Client::new(),
+            RealtimeAsrConfig {
+                enabled: true,
+                url: Some("http://127.0.0.1:9".to_string()),
+                runtime_token: Some("test".to_string()),
+                runtime_session_nonce: Some("test".to_string()),
+                chunk_duration_ms: 200,
+            },
+            || attrs,
+            &mut invalid_upload,
+            &mut last_fixture_sequence,
+            true,
+        );
+        assert!(invalid_turn.is_none());
+        assert!(invalid_upload.is_none());
+        assert_eq!(2, captured_count.load(Ordering::SeqCst));
+        assert_eq!(0, request_rx.try_iter().count());
+        server.join().expect("fixture server");
+    }
 
     #[test]
     fn reply_chunk_marker_state_emits_turn_first_once_and_later_segment_first_once() {
@@ -4078,4 +4874,150 @@
             assert!(published.is_empty());
         }
     }
+
+    #[test]
+    fn controlled_fixture_probe_requires_bound_hashes_and_protocol() {
+        let call_id = "call-ack-1";
+        let trace_id = "trace-ack-1";
+        let payload = serde_json::to_vec(&json!({
+            "type": CONTROLLED_FIXTURE_PROBE_TOPIC,
+            "protocolVersion": CONTROLLED_FIXTURE_PROTOCOL_VERSION,
+            "callIdHash": sha256_hex(call_id),
+            "callTraceIdHash": sha256_hex(trace_id),
+            "generation": CONTROLLED_FIXTURE_GENERATION,
+            "clientFixtureSequence": "fixture-01"
+        }))
+        .unwrap();
+        let sender = ParticipantIdentity("user-1".to_string());
+        let pending =
+            controlled_fixture_probe(&payload, call_id, trace_id, &sender, Some("user-1"))
+                .expect("valid probe");
+        assert_eq!(pending.sequence, "fixture-01");
+        assert!(
+            controlled_fixture_probe(&payload, call_id, "other-trace", &sender, Some("user-1"),)
+                .is_none()
+        );
+        assert!(
+            controlled_fixture_probe(
+                &payload,
+                call_id,
+                trace_id,
+                &ParticipantIdentity("other-user".to_string()),
+                Some("user-1"),
+            )
+            .is_none()
+        );
+    }
+
+    #[test]
+    fn controlled_fixture_attributes_ack_only_on_exact_current_sequence() {
+        let mut attributes = std::collections::HashMap::from([
+            (
+                "inputSourceCategory".to_string(),
+                "controlled_fixture".to_string(),
+            ),
+            (
+                "clientFixtureSequence".to_string(),
+                "fixture-01".to_string(),
+            ),
+        ]);
+        assert!(
+            classify_controlled_fixture_attributes(
+                "user-1",
+                Some("user-1"),
+                &attributes,
+                "fixture-01"
+            )
+            .is_ok()
+        );
+        attributes.insert(
+            "clientFixtureSequence".to_string(),
+            "fixture-02".to_string(),
+        );
+        assert_eq!(
+            classify_controlled_fixture_attributes(
+                "user-1",
+                Some("user-1"),
+                &attributes,
+                "fixture-01"
+            ),
+            Err("wrong_sequence")
+        );
+        attributes.remove("clientFixtureSequence");
+        assert_eq!(
+            classify_controlled_fixture_attributes(
+                "user-1",
+                Some("user-1"),
+                &attributes,
+                "fixture-01"
+            ),
+            Err("missing_sequence")
+        );
+        assert_eq!(
+            classify_controlled_fixture_attributes(
+                "other-user",
+                Some("user-1"),
+                &attributes,
+                "fixture-01"
+            ),
+            Err("wrong_participant")
+        );
+    }
+
+    #[test]
+    fn controlled_fixture_ack_payload_is_reliable_and_redacted() {
+        let ack = ControlledFixtureAttributeAck {
+            message_type: CONTROLLED_FIXTURE_ACK_TOPIC,
+            protocol_version: CONTROLLED_FIXTURE_PROTOCOL_VERSION,
+            call_id_hash: sha256_hex("call-1"),
+            call_trace_id_hash: sha256_hex("trace-1"),
+            generation: CONTROLLED_FIXTURE_GENERATION,
+            client_fixture_sequence: "fixture-01".to_string(),
+            result: "observed",
+            input_source_category: Some("controlled_fixture"),
+            reject_reason: None,
+        };
+        let encoded = serde_json::to_vec(&ack).unwrap();
+        let decoded: serde_json::Value = serde_json::from_slice(&encoded).unwrap();
+        assert_eq!(decoded["type"], CONTROLLED_FIXTURE_ACK_TOPIC);
+        assert_eq!(
+            decoded["protocolVersion"],
+            CONTROLLED_FIXTURE_PROTOCOL_VERSION
+        );
+        assert_eq!(decoded["result"], "observed");
+        assert!(decoded.get("callId").is_none());
+        assert!(decoded.get("traceId").is_none());
+        assert!(decoded.get("participantIdentity").is_none());
+        assert!(decoded.get("audio").is_none());
+    }
+
+    #[test]
+    fn controlled_fixture_probe_does_not_create_session_or_audio_side_effects() {
+        let attributes = std::collections::HashMap::new();
+        assert_eq!(
+            classify_controlled_fixture_attributes(
+                "user-1",
+                Some("user-1"),
+                &attributes,
+                "fixture-01"
+            ),
+            Err("missing_attributes")
+        );
+        assert_eq!(
+            CONTROLLED_FIXTURE_PROBE_TOPIC,
+            "controlled_fixture_attribute_probe"
+        );
+        assert_eq!(
+            CONTROLLED_FIXTURE_ACK_TOPIC,
+            "controlled_fixture_attribute_ack"
+        );
+    }
+
+    #[test]
+    fn controlled_fixture_probe_must_be_observed_before_audio_observer() {
+        assert!(controlled_fixture_observer_gate(false, None));
+        assert!(controlled_fixture_observer_gate(true, Some(true)));
+        assert!(!controlled_fixture_observer_gate(true, Some(false)));
+        assert!(!controlled_fixture_observer_gate(true, None));
+    }
 }

--
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