From 2776a3104f076b1dbf33452ad88cb60036c39702 Mon Sep 17 00:00:00 2001
From: cai <cai@nbcai.cc>
Date: Fri, 10 Jul 2026 18:29:06 +0800
Subject: [PATCH] fix: decouple livekit audio drain from turn processing

---
 src/main.rs |  595 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 577 insertions(+), 18 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index cf7cb4f..02f9fdb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,9 @@
+mod asr_realtime;
 mod audio;
 mod service;
 
 use std::{
+    borrow::Cow,
     env, fs,
     path::{Path, PathBuf},
     sync::{
@@ -12,6 +14,7 @@
 };
 
 use anyhow::{Context, Result, anyhow};
+use asr_realtime::{RealtimeAsrConfig, RealtimeAsrOutcome, RealtimeAsrUpload};
 use audio::{AudioDiagnostics, load_pre_recorded_frames};
 use base64::{Engine as _, engine::general_purpose};
 use futures_util::StreamExt;
@@ -30,12 +33,18 @@
 use reqwest::Client;
 use serde::{Deserialize, Serialize};
 use serde_json::json;
-use tokio::time::{sleep, sleep_until};
-use tokio::{sync::mpsc::UnboundedReceiver, task::JoinHandle};
+use tokio::time::{sleep, sleep_until, timeout};
+use tokio::{
+    sync::{mpsc, mpsc::UnboundedReceiver, watch},
+    task::JoinHandle,
+};
 use tracing::{info, warn};
 
 const USER_AUDIO_SAMPLE_RATE_HZ: u32 = 48_000;
 const USER_AUDIO_NUM_CHANNELS: u16 = 1;
+const INBOUND_AUDIO_QUEUE_CAPACITY: usize = 100;
+const INBOUND_AUDIO_DROP_LOG_INTERVAL: u64 = 100;
+const AUDIO_DRAIN_STOP_GRACE: Duration = Duration::from_secs(2);
 const DEFAULT_BOT_AUDIO_PROFILE: &str = "pcm-16k";
 const LIVEKIT_48K_SAMPLE_RATE_HZ: u32 = 48_000;
 const PCM_16K_SAMPLE_RATE_HZ: u32 = 16_000;
@@ -270,6 +279,11 @@
     runtime_turn_bridge_url: Option<String>,
     runtime_turn_bridge_token: Option<String>,
     runtime_turn_bridge_mode: String,
+    runtime_asr_stream_enabled: bool,
+    runtime_asr_stream_url: Option<String>,
+    runtime_asr_realtime_enabled: bool,
+    runtime_asr_realtime_url: Option<String>,
+    runtime_asr_realtime_chunk_duration_ms: u64,
     runtime_turn_artifact_dir: Option<String>,
     runtime_session_nonce: Option<String>,
     user_audio_observer_enabled: bool,
@@ -332,6 +346,11 @@
     bridge_url: Option<String>,
     bridge_token: Option<String>,
     bridge_mode: String,
+    asr_stream_enabled: bool,
+    asr_stream_url: Option<String>,
+    asr_realtime_enabled: bool,
+    asr_realtime_url: Option<String>,
+    asr_realtime_chunk_duration_ms: u64,
     artifact_dir: Option<String>,
     runtime_session_nonce: Option<String>,
     audio_debug_dump_dir: Option<String>,
@@ -343,6 +362,11 @@
             bridge_url: config.runtime_turn_bridge_url.clone(),
             bridge_token: config.runtime_turn_bridge_token.clone(),
             bridge_mode: config.runtime_turn_bridge_mode.clone(),
+            asr_stream_enabled: config.runtime_asr_stream_enabled,
+            asr_stream_url: config.runtime_asr_stream_url.clone(),
+            asr_realtime_enabled: config.runtime_asr_realtime_enabled,
+            asr_realtime_url: config.runtime_asr_realtime_url.clone(),
+            asr_realtime_chunk_duration_ms: config.runtime_asr_realtime_chunk_duration_ms,
             artifact_dir: config.runtime_turn_artifact_dir.clone(),
             runtime_session_nonce: config.runtime_session_nonce.clone(),
             audio_debug_dump_dir: config.audio_debug_dump_dir.clone(),
@@ -374,6 +398,32 @@
                 .as_deref()
                 .is_some_and(|value| value.trim_end_matches('/').ends_with("/stream"))
     }
+
+    fn is_asr_stream_ready(&self) -> bool {
+        self.asr_stream_enabled
+            && self
+                .asr_stream_url
+                .as_ref()
+                .is_some_and(|value| !value.is_empty())
+            && self
+                .bridge_token
+                .as_ref()
+                .is_some_and(|value| !value.is_empty())
+            && self
+                .runtime_session_nonce
+                .as_ref()
+                .is_some_and(|value| !value.is_empty())
+    }
+
+    fn realtime_asr_config(&self) -> RealtimeAsrConfig {
+        RealtimeAsrConfig {
+            enabled: self.asr_realtime_enabled,
+            url: self.asr_realtime_url.clone(),
+            runtime_token: self.bridge_token.clone(),
+            runtime_session_nonce: self.runtime_session_nonce.clone(),
+            chunk_duration_ms: self.asr_realtime_chunk_duration_ms,
+        }
+    }
 }
 
 impl Config {
@@ -395,6 +445,14 @@
             runtime_turn_bridge_token: optional_env("CV_RUNTIME_TURN_BRIDGE_TOKEN"),
             runtime_turn_bridge_mode: env::var("CV_RUNTIME_TURN_BRIDGE_MODE")
                 .unwrap_or_else(|_| "json".to_string()),
+            runtime_asr_stream_enabled: bool_env("CV_RUNTIME_ASR_STREAM_ENABLED", false),
+            runtime_asr_stream_url: optional_env("CV_RUNTIME_ASR_STREAM_URL"),
+            runtime_asr_realtime_enabled: bool_env("CV_RUNTIME_ASR_REALTIME_ENABLED", false),
+            runtime_asr_realtime_url: optional_env("CV_RUNTIME_ASR_REALTIME_URL"),
+            runtime_asr_realtime_chunk_duration_ms: u64_env(
+                "CV_RUNTIME_ASR_REALTIME_CHUNK_DURATION_MS",
+                200,
+            ),
             runtime_turn_artifact_dir: optional_env("CV_RUNTIME_TURN_ARTIFACT_DIR"),
             runtime_session_nonce: optional_env("CV_RUNTIME_SESSION_NONCE"),
             user_audio_observer_enabled: bool_env("CV_ENABLE_USER_AUDIO_OBSERVER", true),
@@ -596,6 +654,7 @@
         "traceId": trace_id,
         "turnId": turn_id,
         "eventName": event_name,
+        "eventWallTimeMs": current_time_millis(),
         "result": result,
         "reasonCode": reason_code,
         "retryable": retryable,
@@ -750,6 +809,7 @@
     call_id: &str,
     trace_id: &str,
     turn: FinishedSpeechTurn,
+    realtime_asr_result_ref: Option<String>,
 ) {
     let turn_pipeline_started_at = Instant::now();
     if !bridge_config.is_ready() {
@@ -806,9 +866,13 @@
                     "turnArtifactBytes": byte_size,
                     "frameCount": turn.frame_count,
                     "sampleCount": turn.sample_count,
-                    "endReason": turn.end_reason,
+                    "endReason": turn.end_reason.as_str(),
                 }),
             );
+            let asr_result_ref = match realtime_asr_result_ref {
+                Some(value) => Some(value),
+                None => request_asr_result_ref(http, bridge_config, call_id, trace_id, &turn).await,
+            };
             if bridge_config.is_stream_mode() {
                 match request_turn_bridge_stream(
                     http,
@@ -819,6 +883,7 @@
                     &turn,
                     &path_ref,
                     byte_size,
+                    asr_result_ref.as_deref(),
                     turn_pipeline_started_at,
                 )
                 .await
@@ -882,6 +947,7 @@
                 &turn,
                 &path_ref,
                 byte_size,
+                asr_result_ref.as_deref(),
                 turn_pipeline_started_at,
             )
             .await
@@ -1003,6 +1069,251 @@
     Ok((path_ref, byte_size))
 }
 
+async fn request_asr_result_ref(
+    http: &Client,
+    bridge_config: &TurnBridgeConfig,
+    call_id: &str,
+    trace_id: &str,
+    turn: &FinishedSpeechTurn,
+) -> Option<String> {
+    if !bridge_config.is_asr_stream_ready() {
+        return None;
+    }
+    match request_asr_stream(http, bridge_config, call_id, trace_id, turn).await {
+        Ok(Some(asr_result_ref)) => {
+            emit_activity(
+                call_id,
+                trace_id,
+                Some(&turn.turn_id),
+                "asr_stream_ref_ready",
+                "ok",
+                None,
+                None,
+                json!({
+                    "asrResultRefPresent": true,
+                    "format": "pcm_s16le",
+                    "sampleRate": 16000,
+                    "channels": 1,
+                }),
+            );
+            Some(asr_result_ref)
+        }
+        Ok(None) => None,
+        Err(error) => {
+            warn!(
+                call_id = %call_id,
+                trace_id = %trace_id,
+                turn_id = %turn.turn_id,
+                error = %safe_error(&error.to_string()),
+                "runtime helper asr_stream_failed_fallback"
+            );
+            emit_activity(
+                call_id,
+                trace_id,
+                Some(&turn.turn_id),
+                "asr_stream_fallback",
+                "skipped",
+                Some("ASR_STREAM_INTERRUPTED"),
+                Some(true),
+                json!({
+                    "fallbackReason": "asr_stream_request_failed",
+                    "fallbackStage": "asr_stream",
+                }),
+            );
+            None
+        }
+    }
+}
+
+async fn request_asr_stream(
+    http: &Client,
+    bridge_config: &TurnBridgeConfig,
+    call_id: &str,
+    trace_id: &str,
+    turn: &FinishedSpeechTurn,
+) -> Result<Option<String>> {
+    let started_at = Instant::now();
+    let ndjson = build_asr_stream_ndjson(call_id, trace_id, turn, bridge_config)?;
+    let response = http
+        .post(bridge_config.asr_stream_url.as_deref().unwrap_or_default())
+        .header("Content-Type", "application/x-ndjson")
+        .header(
+            "X-CV-Runtime-Token",
+            bridge_config.bridge_token.as_deref().unwrap_or_default(),
+        )
+        .header("X-CV-Call-Id", call_id)
+        .header("X-CV-Trace-Id", trace_id)
+        .header(
+            "X-CV-Runtime-Session-Nonce",
+            bridge_config
+                .runtime_session_nonce
+                .as_deref()
+                .unwrap_or_default(),
+        )
+        .body(ndjson)
+        .send()
+        .await
+        .context("failed to post asr stream")?;
+    let status = response.status();
+    if !status.is_success() {
+        let body_len = response.text().await.map(|body| body.len()).unwrap_or(0);
+        warn!(
+            call_id = %call_id,
+            trace_id = %trace_id,
+            turn_id = %turn.turn_id,
+            http_status = status.as_u16(),
+            body_len,
+            "runtime helper asr_stream_http_failed"
+        );
+        return Ok(None);
+    }
+    let body: RuntimeTurnCommonResult<RuntimeAsrStreamResp> = response
+        .json()
+        .await
+        .context("failed to decode asr stream response")?;
+    if body.code != 0 {
+        warn!(
+            call_id = %call_id,
+            trace_id = %trace_id,
+            turn_id = %turn.turn_id,
+            code = body.code,
+            msg_len = body.msg.as_deref().unwrap_or_default().len(),
+            "runtime helper asr_stream_common_result_failed"
+        );
+        return Ok(None);
+    }
+    let Some(data) = body.data else {
+        return Ok(None);
+    };
+    if data.status.as_deref() == Some("final") {
+        info!(
+            call_id = %call_id,
+            trace_id = %trace_id,
+            turn_id = %turn.turn_id,
+            chunk_count = data.chunk_count.unwrap_or_default(),
+            audio_bytes = data.audio_bytes.unwrap_or_default(),
+            asr_duration_ms = data.asr_duration_ms.unwrap_or_default(),
+            wall_ms = started_at.elapsed().as_millis() as u64,
+            provider = %data.provider_alias.as_deref().unwrap_or("unknown"),
+            text_len = data.text_len.unwrap_or_default(),
+            "runtime helper asr_stream_final"
+        );
+        return Ok(data.asr_result_ref);
+    }
+    emit_activity(
+        call_id,
+        trace_id,
+        Some(&turn.turn_id),
+        "asr_stream_fallback",
+        "skipped",
+        None,
+        Some(true),
+        json!({
+            "fallbackReason": data.fallback_reason,
+            "fallbackStage": data.fallback_stage,
+            "status": data.status,
+        }),
+    );
+    Ok(None)
+}
+
+fn build_asr_stream_ndjson(
+    call_id: &str,
+    trace_id: &str,
+    turn: &FinishedSpeechTurn,
+    bridge_config: &TurnBridgeConfig,
+) -> Result<String> {
+    let chunks = asr_pcm_16k_chunks(turn)?;
+    let mut seq = 1u64;
+    let mut lines = Vec::with_capacity(chunks.len() + 3);
+    lines.push(serde_json::to_string(&json!({
+        "event": "asr_stream_started",
+        "seq": seq,
+        "callId": call_id,
+        "traceId": trace_id,
+        "turnId": turn.turn_id.as_str(),
+        "tsMs": current_time_millis(),
+        "payload": {
+            "format": "pcm_s16le",
+            "sampleRate": 16000,
+            "channels": 1,
+            "runtimeSessionNonce": bridge_config.runtime_session_nonce.as_deref().unwrap_or_default(),
+            "providerHint": "volcengine",
+        }
+    }))?);
+    for (index, samples) in chunks.iter().enumerate() {
+        seq += 1;
+        let bytes = pcm_i16_to_le_bytes(samples);
+        let duration_ms = ((samples.len() as u64) * 1000 / 16_000).max(1);
+        lines.push(serde_json::to_string(&json!({
+            "event": "asr_audio_chunk",
+            "seq": seq,
+            "callId": call_id,
+            "traceId": trace_id,
+            "turnId": turn.turn_id.as_str(),
+            "tsMs": current_time_millis(),
+            "payload": {
+                "chunkSeq": index + 1,
+                "format": "pcm_s16le",
+                "sampleRate": 16000,
+                "channels": 1,
+                "durationMs": duration_ms,
+                "payloadBase64": general_purpose::STANDARD.encode(bytes),
+            }
+        }))?);
+    }
+    seq += 1;
+    lines.push(serde_json::to_string(&json!({
+        "event": "vad_speech_end",
+        "seq": seq,
+        "callId": call_id,
+        "traceId": trace_id,
+        "turnId": turn.turn_id.as_str(),
+        "tsMs": current_time_millis(),
+        "payload": {
+            "endReason": turn.end_reason.as_str(),
+            "speechDurationMs": turn.duration_ms,
+        }
+    }))?);
+    seq += 1;
+    lines.push(serde_json::to_string(&json!({
+        "event": "asr_stream_finish",
+        "seq": seq,
+        "callId": call_id,
+        "traceId": trace_id,
+        "turnId": turn.turn_id.as_str(),
+        "tsMs": current_time_millis(),
+        "payload": {
+            "finalChunkSeq": chunks.len(),
+            "audioDurationMs": turn.duration_ms,
+        }
+    }))?);
+    Ok(lines.join("\n") + "\n")
+}
+
+fn asr_pcm_16k_chunks(turn: &FinishedSpeechTurn) -> Result<Vec<Vec<i16>>> {
+    if turn.samples.is_empty() {
+        return Err(anyhow!("empty turn samples"));
+    }
+    let samples_16k: Vec<i16> = turn.samples.iter().step_by(3).copied().collect();
+    if samples_16k.is_empty() {
+        return Err(anyhow!("empty 16k asr samples"));
+    }
+    let samples_per_chunk = 320usize;
+    Ok(samples_16k
+        .chunks(samples_per_chunk)
+        .map(|chunk| chunk.to_vec())
+        .collect())
+}
+
+fn pcm_i16_to_le_bytes(samples: &[i16]) -> Vec<u8> {
+    let mut bytes = Vec::with_capacity(samples.len() * 2);
+    for sample in samples {
+        bytes.extend_from_slice(&sample.to_le_bytes());
+    }
+    bytes
+}
+
 async fn request_turn_bridge_stream(
     http: &Client,
     bridge_config: &TurnBridgeConfig,
@@ -1012,6 +1323,7 @@
     turn: &FinishedSpeechTurn,
     path_ref: &str,
     byte_size: u64,
+    asr_result_ref: Option<&str>,
     turn_pipeline_started_at: Instant,
 ) -> Result<RuntimeTurnStreamOutcome> {
     let bridge_started_at = Instant::now();
@@ -1019,7 +1331,7 @@
         call_id: call_id.to_string(),
         trace_id: trace_id.to_string(),
         turn_id: turn.turn_id.clone(),
-        audio_artifact: RuntimeTurnAudioArtifact {
+        audio_artifact: Some(RuntimeTurnAudioArtifact {
             artifact_type: "local_file".to_string(),
             path_ref: path_ref.to_string(),
             format: "wav".to_string(),
@@ -1027,7 +1339,8 @@
             channels: u32::from(USER_AUDIO_NUM_CHANNELS),
             duration_ms: turn.duration_ms,
             byte_size,
-        },
+        }),
+        asr_result_ref: asr_result_ref.map(str::to_string),
     };
     let response = http
         .post(bridge_config.bridge_url.as_deref().unwrap_or_default())
@@ -1620,6 +1933,7 @@
     turn: &FinishedSpeechTurn,
     path_ref: &str,
     byte_size: u64,
+    asr_result_ref: Option<&str>,
     turn_pipeline_started_at: Instant,
 ) -> Result<RuntimeTurnBridgeOutcome> {
     let bridge_started_at = Instant::now();
@@ -1627,7 +1941,7 @@
         call_id: call_id.to_string(),
         trace_id: trace_id.to_string(),
         turn_id: turn.turn_id.clone(),
-        audio_artifact: RuntimeTurnAudioArtifact {
+        audio_artifact: Some(RuntimeTurnAudioArtifact {
             artifact_type: "local_file".to_string(),
             path_ref: path_ref.to_string(),
             format: "wav".to_string(),
@@ -1635,7 +1949,8 @@
             channels: u32::from(USER_AUDIO_NUM_CHANNELS),
             duration_ms: turn.duration_ms,
             byte_size,
-        },
+        }),
+        asr_result_ref: asr_result_ref.map(str::to_string),
     };
     let response = http
         .post(bridge_config.bridge_url.as_deref().unwrap_or_default())
@@ -1926,7 +2241,10 @@
     #[serde(rename = "turnId")]
     turn_id: String,
     #[serde(rename = "audioArtifact")]
-    audio_artifact: RuntimeTurnAudioArtifact,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    audio_artifact: Option<RuntimeTurnAudioArtifact>,
+    #[serde(rename = "asrResultRef", skip_serializing_if = "Option::is_none")]
+    asr_result_ref: Option<String>,
 }
 
 #[derive(Serialize)]
@@ -1952,6 +2270,20 @@
     data: Option<T>,
     stage: Option<String>,
     retryable: Option<bool>,
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RuntimeAsrStreamResp {
+    status: Option<String>,
+    asr_result_ref: Option<String>,
+    chunk_count: Option<u64>,
+    audio_bytes: Option<u64>,
+    asr_duration_ms: Option<u64>,
+    provider_alias: Option<String>,
+    text_len: Option<u64>,
+    fallback_reason: Option<String>,
+    fallback_stage: Option<String>,
 }
 
 #[derive(Default)]
@@ -2144,6 +2476,68 @@
             i32::from(USER_AUDIO_NUM_CHANNELS),
         );
         let started_at = Instant::now();
+        let (frame_tx, mut frame_rx) =
+            mpsc::channel::<DrainedUserAudioFrame>(INBOUND_AUDIO_QUEUE_CAPACITY);
+        let (drain_shutdown_tx, mut drain_shutdown_rx) = watch::channel(false);
+        let drain_call_id = call_id.clone();
+        let drain_trace_id = trace_id.clone();
+        let drain_task = tokio::spawn(async move {
+            let mut received_frame_count: u64 = 0;
+            let mut dropped_frame_count: u64 = 0;
+            loop {
+                tokio::select! {
+                    changed = drain_shutdown_rx.changed() => {
+                        match changed {
+                            Ok(()) if *drain_shutdown_rx.borrow() => break,
+                            Ok(()) => {}
+                            Err(_) => break,
+                        }
+                    }
+                    maybe_frame = stream.next() => {
+                        let Some(frame) = maybe_frame else {
+                            break;
+                        };
+                        received_frame_count = received_frame_count.saturating_add(1);
+                        let drained = DrainedUserAudioFrame {
+                            frame_index: received_frame_count,
+                            captured_elapsed_ms: started_at.elapsed().as_millis() as u64,
+                            frame: AudioFrame {
+                                data: Cow::Owned(frame.data.as_ref().to_vec()),
+                                sample_rate: frame.sample_rate,
+                                num_channels: frame.num_channels,
+                                samples_per_channel: frame.samples_per_channel,
+                            },
+                        };
+                        match frame_tx.try_send(drained) {
+                            Ok(()) => {}
+                            Err(mpsc::error::TrySendError::Full(_)) => {
+                                dropped_frame_count = dropped_frame_count.saturating_add(1);
+                                if dropped_frame_count % INBOUND_AUDIO_DROP_LOG_INTERVAL == 1 {
+                                    warn!(
+                                        call_id = %drain_call_id,
+                                        trace_id = %drain_trace_id,
+                                        dropped_frame_count,
+                                        received_frame_count,
+                                        queue_capacity = INBOUND_AUDIO_QUEUE_CAPACITY,
+                                        "runtime helper inbound_audio_queue_full_dropping_newest"
+                                    );
+                                }
+                            }
+                            Err(mpsc::error::TrySendError::Closed(_)) => break,
+                        }
+                    }
+                }
+            }
+            stream.close();
+            info!(
+                call_id = %drain_call_id,
+                trace_id = %drain_trace_id,
+                received_frame_count,
+                dropped_frame_count,
+                queue_capacity = INBOUND_AUDIO_QUEUE_CAPACITY,
+                "runtime helper user_audio_drain_ended"
+            );
+        });
         let mut frame_count: u64 = 0;
         let mut sample_count: u64 = 0;
         let mut simple_vad = if simple_vad_enabled {
@@ -2151,11 +2545,13 @@
         } else {
             None
         };
+        let mut realtime_asr_upload: Option<RealtimeAsrUpload> = None;
 
-        while let Some(frame) = stream.next().await {
-            frame_count += 1;
+        while let Some(drained) = frame_rx.recv().await {
+            let frame = drained.frame;
+            frame_count = drained.frame_index;
             sample_count += u64::from(frame.samples_per_channel) * u64::from(frame.num_channels);
-            let elapsed_ms = started_at.elapsed().as_millis() as u64;
+            let elapsed_ms = drained.captured_elapsed_ms;
             if frame_count == 1 {
                 info!(
                     call_id = %call_id,
@@ -2183,7 +2579,8 @@
 
             if let Some(vad) = simple_vad.as_mut() {
                 if vad_enabled_gate.load(Ordering::Acquire) {
-                    if let Some(turn) = vad.observe_frame(
+                    let was_in_speech = vad.in_speech;
+                    let turn = vad.observe_frame(
                         &call_id,
                         &trace_id,
                         &participant_alias,
@@ -2191,7 +2588,65 @@
                         frame_count,
                         elapsed_ms,
                         &frame,
-                    ) {
+                    );
+                    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(
+                            http.clone(),
+                            turn_bridge_config.realtime_asr_config(),
+                            &call_id,
+                            &trace_id,
+                            &turn_id,
+                            &vad.speech_samples,
+                        ) {
+                            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 {
+                        let push_failed = realtime_asr_upload
+                            .as_mut()
+                            .and_then(|upload| upload.push_48k_samples(frame.data.as_ref()).err());
+                        if let Some(error) = push_failed {
+                            warn!(
+                                call_id = %call_id,
+                                trace_id = %trace_id,
+                                error = %safe_error(&error.to_string()),
+                                "runtime helper asr_realtime_upload_failed_fallback"
+                            );
+                            if let Some(upload) = realtime_asr_upload.take() {
+                                tokio::spawn(async move {
+                                    upload.cancel("upload_backpressure").await;
+                                });
+                            }
+                        }
+                    }
+
+                    if let Some(turn) = turn {
+                        let realtime_asr_result_ref = match realtime_asr_upload.take() {
+                            Some(upload) => {
+                                finish_realtime_asr_upload(upload, &call_id, &trace_id, &turn).await
+                            }
+                            None => None,
+                        };
                         handle_finished_turn(
                             &http,
                             &turn_bridge_config,
@@ -2199,10 +2654,22 @@
                             &call_id,
                             &trace_id,
                             turn,
+                            realtime_asr_result_ref,
                         )
                         .await;
+                    } else if was_in_speech && !is_in_speech {
+                        if let Some(upload) = realtime_asr_upload.take() {
+                            tokio::spawn(async move {
+                                upload.cancel("speech_too_short").await;
+                            });
+                        }
                     }
                 } else {
+                    if let Some(upload) = realtime_asr_upload.take() {
+                        tokio::spawn(async move {
+                            upload.cancel("vad_disabled").await;
+                        });
+                    }
                     vad.observe_disabled_frame(
                         &call_id,
                         &trace_id,
@@ -2223,9 +2690,41 @@
                 &track_sid_alias,
                 started_at.elapsed().as_millis() as u64,
             ) {
-                handle_finished_turn(&http, &turn_bridge_config, &sink, &call_id, &trace_id, turn)
-                    .await;
+                let realtime_asr_result_ref = match realtime_asr_upload.take() {
+                    Some(upload) => {
+                        finish_realtime_asr_upload(upload, &call_id, &trace_id, &turn).await
+                    }
+                    None => None,
+                };
+                handle_finished_turn(
+                    &http,
+                    &turn_bridge_config,
+                    &sink,
+                    &call_id,
+                    &trace_id,
+                    turn,
+                    realtime_asr_result_ref,
+                )
+                .await;
             }
+        }
+        if let Some(upload) = realtime_asr_upload.take() {
+            upload.cancel("stream_end").await;
+        }
+        let _ = drain_shutdown_tx.send(true);
+        let mut drain_task = drain_task;
+        if timeout(AUDIO_DRAIN_STOP_GRACE, &mut drain_task)
+            .await
+            .is_err()
+        {
+            drain_task.abort();
+            let _ = drain_task.await;
+            warn!(
+                call_id = %call_id,
+                trace_id = %trace_id,
+                stop_grace_ms = AUDIO_DRAIN_STOP_GRACE.as_millis() as u64,
+                "runtime helper user_audio_drain_stop_timeout"
+            );
         }
 
         info!(
@@ -2239,6 +2738,64 @@
             "runtime helper user_audio_stream_ended"
         );
     })
+}
+
+struct DrainedUserAudioFrame {
+    frame_index: u64,
+    captured_elapsed_ms: u64,
+    frame: AudioFrame<'static>,
+}
+
+async fn finish_realtime_asr_upload(
+    upload: RealtimeAsrUpload,
+    call_id: &str,
+    trace_id: &str,
+    turn: &FinishedSpeechTurn,
+) -> Option<String> {
+    match upload.finish(turn.duration_ms, &turn.end_reason).await {
+        Ok(RealtimeAsrOutcome {
+            status,
+            asr_result_ref,
+            provider_alias,
+            partial_count,
+            fallback_reason,
+            fallback_stage,
+            chunk_count,
+            audio_bytes,
+            wall_ms,
+        }) => {
+            info!(
+                call_id = %call_id,
+                trace_id = %trace_id,
+                turn_id = %turn.turn_id,
+                status = %status,
+                provider_alias = ?provider_alias,
+                partial_count,
+                chunk_count,
+                audio_bytes,
+                wall_ms,
+                asr_result_ref_present = asr_result_ref.is_some(),
+                fallback_reason = ?fallback_reason,
+                fallback_stage = ?fallback_stage,
+                "runtime helper asr_realtime_finished"
+            );
+            if status == "final" {
+                asr_result_ref
+            } else {
+                None
+            }
+        }
+        Err(error) => {
+            warn!(
+                call_id = %call_id,
+                trace_id = %trace_id,
+                turn_id = %turn.turn_id,
+                error = %safe_error(&error.to_string()),
+                "runtime helper asr_realtime_failed_fallback"
+            );
+            None
+        }
+    }
 }
 
 #[derive(Clone)]
@@ -2258,8 +2815,8 @@
             rms_threshold: f64_env("CV_VAD_RMS_THRESHOLD", 0.012),
             peak_threshold: f64_env("CV_VAD_PEAK_THRESHOLD", 0.08),
             start_frames: u32_env("CV_VAD_START_FRAMES", 5).max(1),
-            end_silence_ms: u64_env("CV_VAD_END_SILENCE_MS", 700).max(100),
-            min_speech_ms: u64_env("CV_VAD_MIN_SPEECH_MS", 300).max(1),
+            end_silence_ms: u64_env("CV_VAD_END_SILENCE_MS", 400).max(100),
+            min_speech_ms: u64_env("CV_VAD_MIN_SPEECH_MS", 250).max(1),
             max_turn_ms: u64_env("CV_VAD_MAX_TURN_MS", 10_000).max(1_000),
             initial_ignore_ms: u64_env("CV_VAD_INITIAL_IGNORE_MS", 500),
         }
@@ -2372,7 +2929,9 @@
             return None;
         }
 
-        let voiced = rms >= self.config.rms_threshold || peak >= self.config.peak_threshold;
+        // Align with cb-sdk's energy-based segmentation: peak is diagnostic only,
+        // otherwise isolated spikes can keep a turn open until max_turn_ms.
+        let voiced = rms >= self.config.rms_threshold;
         if !self.in_speech {
             self.remember_pre_speech_frame(frame);
         }

--
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