perf: improve streaming generation pipeline

Add CUDA inference hot-path optimizations, safer attention fallback handling, and generation profiling hooks. Improve SSE streaming, browser buffering telemetry, and playback recovery while preserving default audio quality settings.

.gitattributes

@@ -0,0 +1,2 @@
+*.sh text eol=lf
+*.py text eol=lf

server/.python-version

@@ -0,0 +1 @@
+3.12

server/start.sh

@@ -7,6 +7,11 @@
 #   ./start.sh          — CUDA mode (default, uses PyTorch CUDA 12.4 wheel, venv: .venv)
 #   ./start.sh --cpu    — CPU-only mode (uses PyPI CPU torch wheel, venv: .venv-cpu)
 #
+# Optional CUDA acceleration:
+#   VIBEPOD_ENABLE_FLASH_ATTN=1 ./start.sh
+#   Installs a matching third-party Windows flash-attn wheel when the CUDA venv
+#   uses Python 3.12, torch 2.6.0, and CUDA 12.4.
+#
 # The two modes maintain completely separate virtual environments so their torch
 # installations never conflict. UV_PROJECT_ENVIRONMENT tells uv which venv to use;
 # --no-sources skips [tool.uv.sources] so the CPU run pulls the default PyPI torch wheel.
@@ -51,6 +56,19 @@ if ! command -v uv &>/dev/null; then
     exit 1
 fi
 
+validate_flash_attn() {
+    uv run python -c "import flash_attn; import triton; import transformers.modeling_utils" &>/dev/null
+}
+
+remove_broken_flash_attn() {
+    if uv run python -c "import importlib.util; raise SystemExit(0 if importlib.util.find_spec('flash_attn') else 1)" &>/dev/null; then
+        if ! validate_flash_attn; then
+            echo "    Installed flash-attn is not usable in this environment; removing it."
+            uv pip uninstall flash-attn
+        fi
+    fi
+}
+
 # ---------------------------------------------------------------------------
 # 2. Sync Python environment
 #    CPU mode:  use .venv-cpu and skip [tool.uv.sources] so uv pulls the
@@ -65,6 +83,36 @@ if $CPU_MODE; then
 else
     echo "--> Syncing CUDA Python environment (.venv)..."
     uv sync
+
+    remove_broken_flash_attn
+
+    if [[ "${VIBEPOD_ENABLE_FLASH_ATTN:-0}" == "1" ]]; then
+        echo ""
+        echo "--> Checking optional FlashAttention wheel..."
+
+        if validate_flash_attn; then
+            echo "    flash-attn already installed and importable."
+        else
+            PY_TAG="$(uv run python -c "import sys; print(f'cp{sys.version_info.major}{sys.version_info.minor}')")"
+            TORCH_TAG="$(uv run python -c "import torch; print(torch.__version__.split('+', 1)[0])")"
+            CUDA_TAG="$(uv run python -c "import torch; print('cu' + torch.version.cuda.replace('.', ''))")"
+
+            if [[ "$PY_TAG" == "cp312" && "$TORCH_TAG" == "2.6.0" && "$CUDA_TAG" == "cu124" ]]; then
+                FLASH_ATTN_WHEEL_URL="https://huggingface.co/lldacing/flash-attention-windows-wheel/resolve/main/flash_attn-2.7.4%2Bcu124torch2.6.0cxx11abiFALSE-cp312-cp312-win_amd64.whl"
+                echo "    Installing flash-attn for Python 3.12, torch 2.6.0, CUDA 12.4..."
+                uv pip install "$FLASH_ATTN_WHEEL_URL"
+                if validate_flash_attn; then
+                    echo "    flash-attn import check passed."
+                else
+                    echo "    flash-attn import check failed; removing it and continuing with SDPA."
+                    uv pip uninstall flash-attn
+                fi
+            else
+                echo "    No known wheel for Python tag $PY_TAG, torch $TORCH_TAG, CUDA $CUDA_TAG."
+                echo "    Continuing with PyTorch SDPA attention."
+            fi
+        fi
+    fi
 fi
 
 # ---------------------------------------------------------------------------

server/vibevoice_server.py

@@ -22,11 +22,13 @@ import asyncio
 import base64
 import copy
 import functools
+import importlib.util
 import json
 import logging
 import os
 import threading
 import time
+import types
 import urllib.request
 from contextlib import asynccontextmanager
 from pathlib import Path
@@ -211,8 +213,39 @@ def _init_processor():
 
 def _init_model(device: str):
     logger.info("Loading model on %s...", device)
-    load_dtype = torch.bfloat16 if device == "cuda" else torch.float32
+    if device == "cuda":
-    attn_impl = "flash_attention_2" if device == "cuda" else "sdpa"
+        torch.set_float32_matmul_precision("high")
+        torch.backends.cuda.matmul.allow_tf32 = True
+        torch.backends.cudnn.allow_tf32 = True
+        torch.backends.cudnn.benchmark = True
+        torch.backends.cuda.enable_flash_sdp(True)
+        torch.backends.cuda.enable_mem_efficient_sdp(True)
+        torch.backends.cuda.enable_math_sdp(True)
+        torch.backends.cuda.allow_fp16_bf16_reduction_math_sdp(True)
+        logger.info(
+            "PyTorch SDPA backends: flash=%s, mem_efficient=%s, math=%s",
+            torch.backends.cuda.flash_sdp_enabled(),
+            torch.backends.cuda.mem_efficient_sdp_enabled(),
+            torch.backends.cuda.math_sdp_enabled(),
+        )
+
+    cuda_dtype = os.environ.get("VIBEPOD_CUDA_DTYPE", "bf16").lower()
+    if device == "cuda" and cuda_dtype == "fp16":
+        load_dtype = torch.float16
+    else:
+        load_dtype = torch.bfloat16 if device == "cuda" else torch.float32
+    logger.info("Loading model weights with dtype %s", load_dtype)
+    requested_attn_impl = os.environ.get("VIBEPOD_ATTN_IMPL", "auto").lower()
+    has_flash_attn = importlib.util.find_spec("flash_attn") is not None
+    if requested_attn_impl in {"eager", "sdpa"}:
+        attn_impl = requested_attn_impl
+    elif requested_attn_impl == "flash_attention_2":
+        attn_impl = "flash_attention_2" if has_flash_attn else "sdpa"
+    else:
+        attn_impl = "flash_attention_2" if device == "cuda" and has_flash_attn else "sdpa"
+    logger.info("Using Transformers attention implementation: %s", attn_impl)
+    if device == "cuda" and not has_flash_attn:
+        logger.info("flash_attn is not installed; using PyTorch SDPA attention.")
 
     from vibevoice.modular.modeling_vibevoice_streaming_inference import (
         VibeVoiceStreamingForConditionalGenerationInference,
@@ -225,9 +258,13 @@ def _init_model(device: str):
             device_map=device,
             attn_implementation=attn_impl,
         )
-    except Exception:
+    except Exception as exc:
+        if attn_impl == "sdpa":
+            raise
         logger.warning(
-            "Model load with %s failed; falling back to sdpa", attn_impl, exc_info=True
+            "Model load with %s failed (%s); falling back to sdpa",
+            attn_impl,
+            exc,
         )
         model = VibeVoiceStreamingForConditionalGenerationInference.from_pretrained(
             MODEL_ID,
@@ -238,9 +275,164 @@ def _init_model(device: str):
 
     model.eval()
     model.set_ddpm_inference_steps(num_steps=_config["default_inference_steps"])
+    _install_generation_optimizations(model)
     return model
 
 
+def _install_generation_optimizations(model: object) -> None:
+    """Patch VibeVoice hot paths without changing model quality settings."""
+
+    def profile_enabled() -> bool:
+        return os.environ.get("VIBEPOD_PROFILE_GENERATION", "0") == "1"
+
+    def profile_sync() -> None:
+        if torch.cuda.is_available():
+            torch.cuda.synchronize()
+
+    def profile_record(self, key: str, elapsed: float) -> None:
+        stats = getattr(self, "_vibepod_profile", None)
+        if stats is None:
+            stats = {}
+            self._vibepod_profile = stats
+        bucket = stats.setdefault(key, {"count": 0, "seconds": 0.0})
+        bucket["count"] += 1
+        bucket["seconds"] += elapsed
+
+    def timed_method(self, key: str, fn, *args, **kwargs):
+        if not profile_enabled():
+            return fn(*args, **kwargs)
+        profile_sync()
+        started = time.perf_counter()
+        result = fn(*args, **kwargs)
+        profile_sync()
+        profile_record(self, key, time.perf_counter() - started)
+        return result
+
+    def prepare_noise_scheduler(self):
+        scheduler = self.model.noise_scheduler
+        cache_key = self.ddpm_inference_steps
+        cache = getattr(self, "_vibepod_scheduler_cache", {})
+        cached = cache.get(cache_key)
+
+        if cached is None:
+            scheduler.set_timesteps(self.ddpm_inference_steps)
+            cached = {
+                "num_inference_steps": scheduler.num_inference_steps,
+                "timesteps": scheduler.timesteps,
+                "sigmas": scheduler.sigmas,
+            }
+            cache[cache_key] = cached
+            self._vibepod_scheduler_cache = cache
+        else:
+            scheduler.num_inference_steps = cached["num_inference_steps"]
+            scheduler.timesteps = cached["timesteps"]
+            scheduler.sigmas = cached["sigmas"]
+            scheduler.model_outputs = [None] * scheduler.config.solver_order
+            scheduler.lower_order_nums = 0
+            scheduler._step_index = None
+            scheduler._begin_index = None
+
+        return scheduler
+
+    def sample_speech_tokens_optimized(self, condition, neg_condition, cfg_scale=3.0):
+        scheduler = prepare_noise_scheduler(self)
+
+        condition = torch.cat([condition, neg_condition], dim=0).to(
+            self.model.prediction_head.device
+        )
+        batch_size = condition.shape[0] // 2
+        speech = torch.randn(batch_size, self.config.acoustic_vae_dim).to(condition)
+        t_batch_cache_key = (
+            self.ddpm_inference_steps,
+            condition.device.type,
+            condition.device.index,
+            condition.dtype,
+            batch_size,
+        )
+        t_batch_cache = getattr(self, "_vibepod_t_batch_cache", {})
+        t_batches = t_batch_cache.get(t_batch_cache_key)
+        if t_batches is None or len(t_batches) != len(scheduler.timesteps):
+            t_batches = [
+                t.repeat(condition.shape[0]).to(
+                    device=condition.device, dtype=condition.dtype
+                )
+                for t in scheduler.timesteps
+            ]
+            t_batch_cache[t_batch_cache_key] = t_batches
+            self._vibepod_t_batch_cache = t_batch_cache
+
+        for t, t_batch in zip(scheduler.timesteps, t_batches):
+            if batch_size == 1:
+                combined = speech.expand(condition.shape[0], -1)
+            else:
+                combined = torch.cat([speech, speech], dim=0)
+            if profile_enabled():
+                profile_sync()
+                started = time.perf_counter()
+            eps = self.model.prediction_head(combined, t_batch, condition=condition)
+            if profile_enabled():
+                profile_sync()
+                profile_record(self, "diffusion_prediction_head", time.perf_counter() - started)
+            cond_eps, uncond_eps = torch.split(eps, batch_size, dim=0)
+            guided_eps = uncond_eps + cfg_scale * (cond_eps - uncond_eps)
+            if profile_enabled():
+                started = time.perf_counter()
+            speech = scheduler.step(guided_eps, t, speech).prev_sample
+            if profile_enabled():
+                profile_record(self, "diffusion_scheduler_step", time.perf_counter() - started)
+
+        return speech
+
+    forward_lm = model.forward_lm
+    forward_tts_lm = model.forward_tts_lm
+    acoustic_decode = model.model.acoustic_tokenizer.decode
+
+    def forward_lm_profiled(*args, **kwargs):
+        return timed_method(model, "forward_lm", forward_lm, *args, **kwargs)
+
+    def forward_tts_lm_profiled(*args, **kwargs):
+        return timed_method(model, "forward_tts_lm", forward_tts_lm, *args, **kwargs)
+
+    def acoustic_decode_profiled(*args, **kwargs):
+        return timed_method(model, "acoustic_decode", acoustic_decode, *args, **kwargs)
+
+    model.forward_lm = forward_lm_profiled
+    model.forward_tts_lm = forward_tts_lm_profiled
+    model.model.acoustic_tokenizer.decode = acoustic_decode_profiled
+    model.sample_speech_tokens = types.MethodType(sample_speech_tokens_optimized, model)
+    logger.info("Installed VibeVoice generation hot-path optimizations.")
+
+
+def _model_float_dtype() -> torch.dtype:
+    try:
+        return next(_model.parameters()).dtype
+    except StopIteration:
+        return torch.float32
+
+
+def _move_cached_prompt(value: object, device: str, dtype: torch.dtype) -> object:
+    if torch.is_tensor(value):
+        if torch.is_floating_point(value):
+            return value.to(device=device, dtype=dtype)
+        return value.to(device=device)
+    if isinstance(value, dict):
+        for k in list(value.keys()):
+            value[k] = _move_cached_prompt(value[k], device, dtype)
+        return value
+    if isinstance(value, list):
+        return [_move_cached_prompt(v, device, dtype) for v in value]
+    if isinstance(value, tuple):
+        return tuple(_move_cached_prompt(v, device, dtype) for v in value)
+    if hasattr(value, "key_cache") and hasattr(value, "value_cache"):
+        value.key_cache = [
+            _move_cached_prompt(t, device, dtype) for t in value.key_cache
+        ]
+        value.value_cache = [
+            _move_cached_prompt(t, device, dtype) for t in value.value_cache
+        ]
+    return value
+
+
 def _load_voice_presets(device: str) -> dict[str, object]:
     presets = {}
     for name, filename in EN_VOICES.items():
@@ -273,9 +465,9 @@ def _load_model_sync() -> None:
             is_cpu = _device == "cpu"
             _config["device"] = _device
             _config["chunk_accum"] = _env_int("VIBEPOD_CHUNK_ACCUM", 4 if is_cpu else 1)
-            _config["prebuffer_secs"] = _env_float("VIBEPOD_PREBUFFER_SECS", 5.0 if is_cpu else 2.0)
+            _config["prebuffer_secs"] = _env_float("VIBEPOD_PREBUFFER_SECS", 6.0 if is_cpu else 5.0)
-            _config["rebuffer_threshold_secs"] = _env_float("VIBEPOD_REBUFFER_THRESHOLD_SECS", 1.0 if is_cpu else 0.4)
+            _config["rebuffer_threshold_secs"] = _env_float("VIBEPOD_REBUFFER_THRESHOLD_SECS", 1.5 if is_cpu else 1.0)
-            _config["resume_threshold_secs"] = _env_float("VIBEPOD_RESUME_THRESHOLD_SECS", 2.5 if is_cpu else 1.5)
+            _config["resume_threshold_secs"] = _env_float("VIBEPOD_RESUME_THRESHOLD_SECS", 4.0 if is_cpu else 3.0)
             _config["default_inference_steps"] = _env_int("VIBEPOD_DEFAULT_INFERENCE_STEPS", 8 if is_cpu else 10)
 
             _processor = _init_processor()
@@ -364,10 +556,15 @@ def _sync_generate(
         raise RuntimeError("Generation cancelled.")
 
     speaker = req.speaker if req.speaker in _voice_presets else DEFAULT_SPEAKER
-    voice_preset = copy.deepcopy(_voice_presets[speaker])
+    model_dtype = _model_float_dtype()
+    voice_preset = _move_cached_prompt(
+        copy.deepcopy(_voice_presets[speaker]), _device, model_dtype
+    )
 
     steps = req.inference_steps if req.inference_steps is not None else _config["default_inference_steps"]
     _model.set_ddpm_inference_steps(num_steps=steps)
+    if os.environ.get("VIBEPOD_PROFILE_GENERATION", "0") == "1":
+        _model._vibepod_profile = {}
 
     inputs = _processor.process_input_with_cached_prompt(
         text=req.text,
@@ -380,19 +577,20 @@ def _sync_generate(
         if torch.is_tensor(v):
             inputs[k] = v.to(_device)
 
-    outputs = _model.generate(
+    with torch.inference_mode():
-        **inputs,
+        _model.generate(
-        max_new_tokens=None,
+            **inputs,
-        cfg_scale=req.cfg_scale,
+            max_new_tokens=None,
-        tokenizer=_processor.tokenizer,
+            cfg_scale=req.cfg_scale,
-        generation_config={"do_sample": False},
+            tokenizer=_processor.tokenizer,
-        verbose=True,
+            generation_config={"do_sample": False},
-        all_prefilled_outputs=copy.deepcopy(voice_preset),
+            verbose=False,
-        audio_streamer=streamer,
+            show_progress_bar=False,
-    )
+            return_speech=False,
-
+            stop_check_fn=cancel_event.is_set if cancel_event else None,
-    if not outputs.speech_outputs or outputs.speech_outputs[0] is None:
+            all_prefilled_outputs=voice_preset,
-        raise ValueError("Model returned no audio output.")
+            audio_streamer=streamer,
+        )
 
     return speaker
 
@@ -401,6 +599,24 @@ def _sse(event: dict) -> str:
     return f"data: {json.dumps(event)}\n\n"
 
 
+def _generation_profile() -> Optional[dict[str, dict[str, float]]]:
+    if os.environ.get("VIBEPOD_PROFILE_GENERATION", "0") != "1":
+        return None
+    stats = getattr(_model, "_vibepod_profile", None)
+    if not stats:
+        return {}
+    return {
+        key: {
+            "count": value["count"],
+            "seconds": round(value["seconds"], 3),
+            "avg_ms": round(value["seconds"] * 1000 / value["count"], 3)
+            if value["count"]
+            else 0.0,
+        }
+        for key, value in sorted(stats.items())
+    }
+
+
 @app.post("/generate")
 async def generate(req: GenerateRequest, request: Request) -> StreamingResponse:
     if _model_status != "online":
@@ -417,20 +633,58 @@ async def generate(req: GenerateRequest, request: Request) -> StreamingResponse:
         )
 
     async def event_stream() -> AsyncGenerator[str, None]:
-        from vibevoice.modular.streamer import AsyncAudioStreamer
+        class NonBlockingAudioStreamer:
+            """Async streamer that keeps GPU->CPU copies out of the model thread."""
+
+            def __init__(self, batch_size: int, stop_signal: object = None) -> None:
+                self.batch_size = batch_size
+                self.stop_signal = stop_signal
+                self.audio_queues = [asyncio.Queue() for _ in range(batch_size)]
+                self.finished_flags = [False for _ in range(batch_size)]
+                self.loop = asyncio.get_running_loop()
+
+            def put(self, audio_chunks: torch.Tensor, sample_indices: torch.Tensor) -> None:
+                for i, sample_idx in enumerate(sample_indices):
+                    idx = sample_idx.item()
+                    if idx < self.batch_size and not self.finished_flags[idx]:
+                        self.loop.call_soon_threadsafe(
+                            self.audio_queues[idx].put_nowait,
+                            audio_chunks[i].detach(),
+                        )
+
+            def end(self, sample_indices: Optional[torch.Tensor] = None) -> None:
+                if sample_indices is None:
+                    indices_to_end = range(self.batch_size)
+                else:
+                    indices_to_end = [
+                        s.item() if torch.is_tensor(s) else s for s in sample_indices
+                    ]
+                for idx in indices_to_end:
+                    if idx < self.batch_size and not self.finished_flags[idx]:
+                        self.loop.call_soon_threadsafe(
+                            self.audio_queues[idx].put_nowait, self.stop_signal
+                        )
+                        self.finished_flags[idx] = True
 
         start = time.monotonic()
-        streamer = AsyncAudioStreamer(batch_size=1)
+        streamer = NonBlockingAudioStreamer(batch_size=1)
         cancel_event = threading.Event()
 
         accum_size = max(1, _config["chunk_accum"])
         accumulated_chunks = []
+        chunk_count = 0
+        audio_samples = 0
+        first_chunk_at: Optional[float] = None
+        last_chunk_at: Optional[float] = None
+        max_chunk_gap = 0.0
+        speaker = req.speaker if req.speaker in _voice_presets else DEFAULT_SPEAKER
 
         async with _generation_lock:
             loop = asyncio.get_event_loop()
             future = loop.run_in_executor(
                 None, functools.partial(_sync_generate, req, streamer, cancel_event)
             )
+            future.add_done_callback(lambda _: streamer.end())
 
             # Drain audio chunks as they arrive from the diffusion head.
             # stop_signal=None is the default sentinel that ends the queue.
@@ -454,17 +708,45 @@ async def generate(req: GenerateRequest, request: Request) -> StreamingResponse:
                 if chunk is None:  # stop signal
                     break
 
-                accumulated_chunks.append(chunk.detach().cpu().float())
+                accumulated_chunks.append(chunk.detach())
 
                 if len(accumulated_chunks) >= accum_size:
-                    combined = torch.cat(accumulated_chunks, dim=0)
+                    now = time.monotonic()
+                    if first_chunk_at is None:
+                        first_chunk_at = now
+                    if last_chunk_at is not None:
+                        max_chunk_gap = max(max_chunk_gap, now - last_chunk_at)
+                    last_chunk_at = now
+
+                    combined = (
+                        torch.cat(accumulated_chunks, dim=0)
+                        .detach()
+                        .to("cpu", dtype=torch.float32)
+                        .contiguous()
+                    )
+                    chunk_count += 1
+                    audio_samples += combined.numel()
                     pcm_b64 = base64.b64encode(combined.numpy().tobytes()).decode()
                     yield _sse({"type": "audio_chunk", "data": pcm_b64})
                     accumulated_chunks = []
 
             # Flush any remaining chunks
             if accumulated_chunks:
-                combined = torch.cat(accumulated_chunks, dim=0)
+                now = time.monotonic()
+                if first_chunk_at is None:
+                    first_chunk_at = now
+                if last_chunk_at is not None:
+                    max_chunk_gap = max(max_chunk_gap, now - last_chunk_at)
+                last_chunk_at = now
+
+                combined = (
+                    torch.cat(accumulated_chunks, dim=0)
+                    .detach()
+                    .to("cpu", dtype=torch.float32)
+                    .contiguous()
+                )
+                chunk_count += 1
+                audio_samples += combined.numel()
                 pcm_b64 = base64.b64encode(combined.numpy().tobytes()).decode()
                 yield _sse({"type": "audio_chunk", "data": pcm_b64})
 
@@ -479,17 +761,42 @@ async def generate(req: GenerateRequest, request: Request) -> StreamingResponse:
                 yield _sse(
                     {
                         "type": "error",
-                        "message": "Internal server error during generation.",
+                        "message": f"Generation failed: {exc}",
                     }
                 )
                 return
 
         elapsed = round(time.monotonic() - start, 1)
+        audio_secs = audio_samples / SAMPLE_RATE
+        realtime_factor = audio_secs / elapsed if elapsed > 0 else None
+        profile = _generation_profile()
+        if profile is not None:
+            logger.info("Generation profile: %s", profile)
         logger.info("Generation complete in %.1fs", elapsed)
-        yield _sse({"type": "complete", "elapsed": elapsed, "speaker": speaker})
+        complete_event = {
+            "type": "complete",
+            "elapsed": elapsed,
+            "speaker": speaker,
+            "audio_secs": round(audio_secs, 2),
+            "realtime_factor": round(realtime_factor, 3)
+            if realtime_factor is not None
+            else None,
+            "chunks": chunk_count,
+            "first_chunk_secs": round(first_chunk_at - start, 2)
+            if first_chunk_at is not None
+            else None,
+            "max_chunk_gap_secs": round(max_chunk_gap, 2),
+        }
+        if profile is not None:
+            complete_event["profile"] = profile
+        yield _sse(complete_event)
 
     return StreamingResponse(
         event_stream(),
         media_type="text/event-stream",
-        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
+        headers={
+            "Cache-Control": "no-cache, no-transform",
+            "X-Accel-Buffering": "no",
+            "X-Content-Type-Options": "nosniff",
+        },
     )

web/app/api/generate/route.ts

@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 
+export const dynamic = "force-dynamic";
+export const runtime = "nodejs";
+
 export async function POST(request: NextRequest) {
   const pythonServerUrl = process.env.VIBEVOICE_SERVER_URL ?? "http://localhost:8000";
 
@@ -24,6 +27,7 @@ export async function POST(request: NextRequest) {
         cfg_scale: body.cfg_scale ?? 1.5,
         inference_steps: body.inference_steps ?? 10,
       }),
+      signal: request.signal,
     });
 
     if (!upstream.ok) {
@@ -36,8 +40,9 @@ export async function POST(request: NextRequest) {
       status: 200,
       headers: {
         "Content-Type": "text/event-stream",
-        "Cache-Control": "no-cache",
+        "Cache-Control": "no-cache, no-transform",
         "Connection": "keep-alive",
+        "X-Content-Type-Options": "nosniff",
         "X-Accel-Buffering": "no",
       },
     });

web/app/api/health/route.ts

@@ -27,6 +27,7 @@ export async function GET() {
           message: data.message,
           progress: data.progress ?? null,
           voices: data.voices ?? [],
+          config: data.config ?? null,
         },
         COMMON_OPTIONS
       );

web/app/page.tsx

@@ -130,9 +130,9 @@ const initialState: AppState = {
   speaker: "carter",
   cfgScale: 1.5,
   inferenceSteps: 10,
-  prebufferSecs: 2.0,
+  prebufferSecs: 5.0,
-  rebufferThresholdSecs: 0.4,
+  rebufferThresholdSecs: 1.0,
-  resumeThresholdSecs: 1.5,
+  resumeThresholdSecs: 3.0,
   isGenerating: false,
   genElapsed: 0,
   genPct: null,

web/hooks/useStreamingGeneration.ts

@@ -3,9 +3,10 @@
 import { useCallback, useEffect, useRef, useState } from "react";
 
 const SAMPLE_RATE = 24_000;
-const DEFAULT_PREBUFFER_SECS = 2.0;
+const DEFAULT_PREBUFFER_SECS = 5.0;
-const DEFAULT_REBUFFER_THRESHOLD_SECS = 0.4;
+const DEFAULT_REBUFFER_THRESHOLD_SECS = 1.0;
-const DEFAULT_RESUME_THRESHOLD_SECS = 1.5;
+const DEFAULT_RESUME_THRESHOLD_SECS = 3.0;
+const MAX_ADAPTIVE_RESUME_SECS = 18.0;
 
 interface GenerateOptions {
   text: string;
@@ -104,6 +105,10 @@ export function useStreamingGeneration({
   const isAutoBufferingRef = useRef(false);
   const isUserPausedRef = useRef(false);
   const audioUrlRef = useRef<string | null>(null);
+  const firstChunkSeenRef = useRef(false);
+  const underrunCountRef = useRef(0);
+  const totalAudioSamplesRef = useRef(0);
+  const adaptiveResumeSecsRef = useRef(DEFAULT_RESUME_THRESHOLD_SECS);
 
   const revokeCurrentUrl = useCallback(() => {
     if (audioUrlRef.current) {
@@ -122,8 +127,12 @@ export function useStreamingGeneration({
     hasStartedPlaybackRef.current = false;
     isAutoBufferingRef.current = false;
     isUserPausedRef.current = false;
+    firstChunkSeenRef.current = false;
+    underrunCountRef.current = 0;
+    totalAudioSamplesRef.current = 0;
+    adaptiveResumeSecsRef.current = resumeThresholdSecs;
     setIsStreamPaused(false);
-  }, []);
+  }, [resumeThresholdSecs]);
 
   useEffect(() => {
     return () => {
@@ -158,10 +167,17 @@ export function useStreamingGeneration({
     if (!ctx) return;
 
     chunksRef.current.push(chunk);
+    totalAudioSamplesRef.current += chunk.length;
+
+    if (!firstChunkSeenRef.current) {
+      firstChunkSeenRef.current = true;
+      onLog("First audio chunk received");
+    }
 
     if (!hasStartedPlaybackRef.current) {
       const bufferedSecs = chunksRef.current.reduce((sum, c) => sum + c.length, 0) / SAMPLE_RATE;
       if (bufferedSecs >= prebufferSecs) {
+        onLog(`Playback started after ${bufferedSecs.toFixed(1)}s buffered`);
         flushBufferedAudio();
       }
       return;
@@ -171,18 +187,30 @@ export function useStreamingGeneration({
     if (isUserPausedRef.current) return;
 
     const ahead = nextStartTimeRef.current - ctx.currentTime;
-    if (ctx.state === "running" && ahead < rebufferThresholdSecs) {
+    if (
-      ctx.suspend().catch(() => {});
+      ctx.state === "running" &&
-      isAutoBufferingRef.current = true;
+      !isAutoBufferingRef.current &&
-    } else if (
+      ahead < rebufferThresholdSecs
-      ctx.state === "suspended" &&
+    ) {
-      isAutoBufferingRef.current &&
+      isAutoBufferingRef.current = true;
-      ahead >= resumeThresholdSecs
+      underrunCountRef.current += 1;
+      adaptiveResumeSecsRef.current = Math.min(
+        MAX_ADAPTIVE_RESUME_SECS,
+        Math.max(resumeThresholdSecs, prebufferSecs + underrunCountRef.current * 2),
+      );
+      ctx.suspend().catch(() => {});
+      onLog(
+        `Buffer underrun ${underrunCountRef.current}; refilling to ${adaptiveResumeSecsRef.current.toFixed(1)}s`,
+      );
+    } else if (
+      isAutoBufferingRef.current &&
+      ahead >= adaptiveResumeSecsRef.current
     ) {
-      ctx.resume().catch(() => {});
       isAutoBufferingRef.current = false;
+      ctx.resume().catch(() => {});
+      onLog(`Buffer recovered with ${ahead.toFixed(1)}s queued`);
     }
-  }, [enqueue, flushBufferedAudio, prebufferSecs, rebufferThresholdSecs, resumeThresholdSecs]);
+  }, [enqueue, flushBufferedAudio, onLog, prebufferSecs, rebufferThresholdSecs, resumeThresholdSecs]);
 
   const generate = useCallback(async (options: GenerateOptions) => {
     if (!options.text.trim()) return;
@@ -239,6 +267,11 @@ export function useStreamingGeneration({
             type: "audio_chunk" | "complete" | "error" | "cancelled";
             data?: string;
             elapsed?: number;
+            audio_secs?: number;
+            realtime_factor?: number | null;
+            chunks?: number;
+            first_chunk_secs?: number | null;
+            max_chunk_gap_secs?: number;
             message?: string;
           };
 
@@ -247,12 +280,26 @@ export function useStreamingGeneration({
           } else if (event.type === "complete") {
             if (!hasStartedPlaybackRef.current) {
               flushBufferedAudio();
+            } else if (isAutoBufferingRef.current) {
+              isAutoBufferingRef.current = false;
+              audioCtxRef.current?.resume().catch(() => {});
             }
             const wavBlob = buildWav(mergeFloat32Arrays(chunksRef.current), SAMPLE_RATE);
             const audioUrl = URL.createObjectURL(wavBlob);
             audioUrlRef.current = audioUrl;
             const kb = (wavBlob.size / 1024).toFixed(0);
-            onLog(`Done in ${event.elapsed}s - ${kb} KB`);
+            const audioSecs = event.audio_secs ?? totalAudioSamplesRef.current / SAMPLE_RATE;
+            const realtimeFactor =
+              event.realtime_factor ??
+              (event.elapsed && event.elapsed > 0 ? audioSecs / event.elapsed : null);
+            const speedText =
+              realtimeFactor === null ? "" : ` - ${realtimeFactor.toFixed(2)}x realtime`;
+            onLog(`Done in ${event.elapsed}s - ${audioSecs.toFixed(1)}s audio${speedText} - ${kb} KB`);
+            if (event.chunks && event.first_chunk_secs !== undefined) {
+              onLog(
+                `Stream: first chunk ${event.first_chunk_secs}s, ${event.chunks} chunks, max gap ${event.max_chunk_gap_secs}s`,
+              );
+            }
             onSuccess(audioUrl);
           } else if (event.type === "cancelled") {
             throw new DOMException("Generation cancelled", "AbortError");

web/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "scripts": {
     "dev": "next dev --turbopack",
-    "build": "next build --turbopack",
+    "build": "next build",
     "start": "next start"
   },
   "dependencies": {