Add Modal backend for audio mixdown

CHANGELOG.md

@@ -1,19 +1,5 @@
 # Changelog
 
-## [0.29.0](https://github.com/Monadical-SAS/reflector/compare/v0.28.1...v0.29.0) (2026-01-21)
-
-
-### Features
-
-* set hatchet as default for multitracks ([#822](https://github.com/Monadical-SAS/reflector/issues/822)) ([c723752](https://github.com/Monadical-SAS/reflector/commit/c723752b7e15aa48a41ad22856f147a5517d3f46))
-
-## [0.28.1](https://github.com/Monadical-SAS/reflector/compare/v0.28.0...v0.28.1) (2026-01-21)
-
-
-### Bug Fixes
-
-* ics non-sync bugfix ([#823](https://github.com/Monadical-SAS/reflector/issues/823)) ([23d2bc2](https://github.com/Monadical-SAS/reflector/commit/23d2bc283d4d02187b250d2055103e0374ee93d6))
-
 ## [0.28.0](https://github.com/Monadical-SAS/reflector/compare/v0.27.0...v0.28.0) (2026-01-20)
 
 

gpu/modal_deployments/deploy-all.sh

@@ -131,6 +131,15 @@ if [ -z "$DIARIZER_URL" ]; then
 fi
 echo "  -> $DIARIZER_URL"
 
+echo ""
+echo "Deploying mixdown (CPU audio processing)..."
+MIXDOWN_URL=$(modal deploy reflector_mixdown.py 2>&1 | grep -o 'https://[^ ]*web.modal.run' | head -1)
+if [ -z "$MIXDOWN_URL" ]; then
+    echo "Error: Failed to deploy mixdown. Check Modal dashboard for details."
+    exit 1
+fi
+echo "  -> $MIXDOWN_URL"
+
 # --- Output Configuration ---
 echo ""
 echo "=========================================="
@@ -147,4 +156,8 @@ echo ""
 echo "DIARIZATION_BACKEND=modal"
 echo "DIARIZATION_URL=$DIARIZER_URL"
 echo "DIARIZATION_MODAL_API_KEY=$API_KEY"
+echo ""
+echo "MIXDOWN_BACKEND=modal"
+echo "MIXDOWN_URL=$MIXDOWN_URL"
+echo "MIXDOWN_MODAL_API_KEY=$API_KEY"
 echo "# --- End Modal Configuration ---"

gpu/modal_deployments/reflector_mixdown.py

@@ -0,0 +1,379 @@
+"""
+Reflector GPU backend - audio mixdown
+======================================
+
+CPU-intensive audio mixdown service for combining multiple audio tracks.
+Uses PyAV filter graph (amix) for high-quality audio mixing.
+"""
+
+import os
+import tempfile
+import time
+from fractions import Fraction
+
+import modal
+
+MIXDOWN_TIMEOUT = 900  # 15 minutes
+SCALEDOWN_WINDOW = 60  # 1 minute idle before shutdown
+
+app = modal.App("reflector-mixdown")
+
+# CPU-based image (no GPU needed for audio processing)
+image = (
+    modal.Image.debian_slim(python_version="3.12")
+    .apt_install("ffmpeg")  # Required by PyAV
+    .pip_install(
+        "av==13.1.0",  # PyAV for audio processing
+        "requests==2.32.3",  # HTTP for presigned URL downloads/uploads
+        "fastapi==0.115.12",  # API framework
+    )
+)
+
+
+@app.function(
+    cpu=4.0,  # 4 CPU cores for audio processing
+    timeout=MIXDOWN_TIMEOUT,
+    scaledown_window=SCALEDOWN_WINDOW,
+    secrets=[modal.Secret.from_name("reflector-gpu")],
+    image=image,
+)
+@modal.concurrent(max_inputs=10)
+@modal.asgi_app()
+def web():
+    import logging
+    import secrets
+    import shutil
+
+    import av
+    import requests
+    from av.audio.resampler import AudioResampler
+    from fastapi import Depends, FastAPI, HTTPException, status
+    from fastapi.security import OAuth2PasswordBearer
+    from pydantic import BaseModel
+
+    # Setup logging
+    logging.basicConfig(
+        level=logging.INFO, format="%(asctime)s - %(levelname)s - %(message)s"
+    )
+    logger = logging.getLogger(__name__)
+
+    app = FastAPI()
+    oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
+
+    # Validate API key exists at startup
+    API_KEY = os.environ.get("REFLECTOR_GPU_APIKEY")
+    if not API_KEY:
+        raise RuntimeError("REFLECTOR_GPU_APIKEY not configured in Modal secrets")
+
+    def apikey_auth(apikey: str = Depends(oauth2_scheme)):
+        # Use constant-time comparison to prevent timing attacks
+        if secrets.compare_digest(apikey, API_KEY):
+            return
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid API key",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
+    class MixdownRequest(BaseModel):
+        track_urls: list[str]
+        output_url: str
+        target_sample_rate: int = 48000
+        expected_duration_sec: float | None = None
+
+    class MixdownResponse(BaseModel):
+        duration_ms: float
+        tracks_mixed: int
+        audio_uploaded: bool
+
+    def download_track(url: str, temp_dir: str, index: int) -> str:
+        """Download track from presigned URL to temp file using streaming."""
+        logger.info(f"Downloading track {index + 1}")
+        response = requests.get(url, stream=True, timeout=300)
+
+        if response.status_code == 404:
+            raise HTTPException(status_code=404, detail=f"Track {index} not found")
+        if response.status_code == 403:
+            raise HTTPException(
+                status_code=403, detail=f"Track {index} presigned URL expired"
+            )
+
+        response.raise_for_status()
+
+        temp_path = os.path.join(temp_dir, f"track_{index}.webm")
+        total_bytes = 0
+        with open(temp_path, "wb") as f:
+            for chunk in response.iter_content(chunk_size=8192):
+                if chunk:
+                    f.write(chunk)
+                    total_bytes += len(chunk)
+
+        logger.info(f"Track {index + 1} downloaded: {total_bytes} bytes")
+        return temp_path
+
+    def mixdown_tracks_modal(
+        track_paths: list[str],
+        output_path: str,
+        target_sample_rate: int,
+        expected_duration_sec: float | None,
+        logger,
+    ) -> float:
+        """Mix multiple audio tracks using PyAV filter graph.
+
+        Args:
+            track_paths: List of local file paths to audio tracks
+            output_path: Local path for output MP3 file
+            target_sample_rate: Sample rate for output (Hz)
+            expected_duration_sec: Optional fallback duration if container metadata unavailable
+            logger: Logger instance for progress tracking
+
+        Returns:
+            Duration in milliseconds
+        """
+        logger.info(f"Starting mixdown of {len(track_paths)} tracks")
+
+        # Build PyAV filter graph: N abuffer -> amix -> aformat -> sink
+        graph = av.filter.Graph()
+        inputs = []
+
+        for idx in range(len(track_paths)):
+            args = (
+                f"time_base=1/{target_sample_rate}:"
+                f"sample_rate={target_sample_rate}:"
+                f"sample_fmt=s32:"
+                f"channel_layout=stereo"
+            )
+            in_ctx = graph.add("abuffer", args=args, name=f"in{idx}")
+            inputs.append(in_ctx)
+
+        mixer = graph.add("amix", args=f"inputs={len(inputs)}:normalize=0", name="mix")
+        fmt = graph.add(
+            "aformat",
+            args=f"sample_fmts=s32:channel_layouts=stereo:sample_rates={target_sample_rate}",
+            name="fmt",
+        )
+        sink = graph.add("abuffersink", name="out")
+
+        # Connect inputs to mixer (no delays for Modal implementation)
+        for idx, in_ctx in enumerate(inputs):
+            in_ctx.link_to(mixer, 0, idx)
+
+        mixer.link_to(fmt)
+        fmt.link_to(sink)
+        graph.configure()
+
+        # Open all containers
+        containers = []
+        try:
+            for i, path in enumerate(track_paths):
+                try:
+                    c = av.open(path)
+                    containers.append(c)
+                except Exception as e:
+                    logger.warning(
+                        f"Failed to open container {i}: {e}",
+                    )
+
+            if not containers:
+                raise ValueError("Could not open any track containers")
+
+            # Calculate total duration for progress reporting
+            max_duration_sec = 0.0
+            for c in containers:
+                if c.duration is not None:
+                    dur_sec = c.duration / av.time_base
+                    max_duration_sec = max(max_duration_sec, dur_sec)
+            if max_duration_sec == 0.0 and expected_duration_sec:
+                max_duration_sec = expected_duration_sec
+
+            # Setup output container
+            out_container = av.open(output_path, "w", format="mp3")
+            out_stream = out_container.add_stream("libmp3lame", rate=target_sample_rate)
+
+            decoders = [c.decode(audio=0) for c in containers]
+            active = [True] * len(decoders)
+            resamplers = [
+                AudioResampler(format="s32", layout="stereo", rate=target_sample_rate)
+                for _ in decoders
+            ]
+
+            current_max_time = 0.0
+            last_log_time = time.monotonic()
+            start_time = time.monotonic()
+
+            total_duration = 0
+
+            while any(active):
+                for i, (dec, is_active) in enumerate(zip(decoders, active)):
+                    if not is_active:
+                        continue
+                    try:
+                        frame = next(dec)
+                    except StopIteration:
+                        active[i] = False
+                        inputs[i].push(None)  # Signal end of stream
+                        continue
+
+                    if frame.sample_rate != target_sample_rate:
+                        continue
+
+                    # Progress logging (every 5 seconds)
+                    if frame.time is not None:
+                        current_max_time = max(current_max_time, frame.time)
+                        now = time.monotonic()
+                        if now - last_log_time >= 5.0:
+                            elapsed = now - start_time
+                            if max_duration_sec > 0:
+                                progress_pct = min(
+                                    100.0, (current_max_time / max_duration_sec) * 100
+                                )
+                                logger.info(
+                                    f"Mixdown progress: {progress_pct:.1f}% @ {current_max_time:.1f}s (elapsed: {elapsed:.1f}s)"
+                                )
+                            else:
+                                logger.info(
+                                    f"Mixdown progress: @ {current_max_time:.1f}s (elapsed: {elapsed:.1f}s)"
+                                )
+                            last_log_time = now
+
+                    out_frames = resamplers[i].resample(frame) or []
+                    for rf in out_frames:
+                        rf.sample_rate = target_sample_rate
+                        rf.time_base = Fraction(1, target_sample_rate)
+                        inputs[i].push(rf)
+
+                    # Pull mixed frames from sink and encode
+                    while True:
+                        try:
+                            mixed = sink.pull()
+                        except Exception:
+                            break
+                        mixed.sample_rate = target_sample_rate
+                        mixed.time_base = Fraction(1, target_sample_rate)
+
+                        # Encode and mux
+                        for packet in out_stream.encode(mixed):
+                            out_container.mux(packet)
+                            total_duration += packet.duration
+
+            # Flush remaining frames from filter graph
+            while True:
+                try:
+                    mixed = sink.pull()
+                except Exception:
+                    break
+                mixed.sample_rate = target_sample_rate
+                mixed.time_base = Fraction(1, target_sample_rate)
+
+                for packet in out_stream.encode(mixed):
+                    out_container.mux(packet)
+                    total_duration += packet.duration
+
+            # Flush encoder
+            for packet in out_stream.encode():
+                out_container.mux(packet)
+                total_duration += packet.duration
+
+            # Calculate duration in milliseconds
+            if total_duration > 0:
+                # Use the same calculation as AudioFileWriterProcessor
+                duration_ms = round(
+                    float(total_duration * out_stream.time_base * 1000), 2
+                )
+            else:
+                duration_ms = 0.0
+
+            out_container.close()
+            logger.info(f"Mixdown complete: duration={duration_ms}ms")
+
+        finally:
+            # Cleanup all containers
+            for c in containers:
+                if c is not None:
+                    try:
+                        c.close()
+                    except Exception:
+                        pass
+
+        return duration_ms
+
+    @app.post("/v1/audio/mixdown", dependencies=[Depends(apikey_auth)])
+    def mixdown(request: MixdownRequest) -> MixdownResponse:
+        """Mix multiple audio tracks into a single MP3 file.
+
+        Tracks are downloaded from presigned S3 URLs, mixed using PyAV,
+        and uploaded to a presigned S3 PUT URL.
+        """
+        if not request.track_urls:
+            raise HTTPException(status_code=400, detail="No track URLs provided")
+
+        logger.info(f"Mixdown request: {len(request.track_urls)} tracks")
+
+        temp_dir = tempfile.mkdtemp()
+        temp_files = []
+        output_mp3_path = None
+
+        try:
+            # Download all tracks
+            for i, url in enumerate(request.track_urls):
+                temp_path = download_track(url, temp_dir, i)
+                temp_files.append(temp_path)
+
+            # Mix tracks
+            output_mp3_path = os.path.join(temp_dir, "mixed.mp3")
+            duration_ms = mixdown_tracks_modal(
+                temp_files,
+                output_mp3_path,
+                request.target_sample_rate,
+                request.expected_duration_sec,
+                logger,
+            )
+
+            # Upload result to S3
+            logger.info("Uploading result to S3")
+            file_size = os.path.getsize(output_mp3_path)
+            with open(output_mp3_path, "rb") as f:
+                upload_response = requests.put(
+                    request.output_url, data=f, timeout=300
+                )
+
+            if upload_response.status_code == 403:
+                raise HTTPException(
+                    status_code=403, detail="Output presigned URL expired"
+                )
+
+            upload_response.raise_for_status()
+            logger.info(f"Upload complete: {file_size} bytes")
+
+            return MixdownResponse(
+                duration_ms=duration_ms,
+                tracks_mixed=len(request.track_urls),
+                audio_uploaded=True,
+            )
+
+        except HTTPException:
+            raise
+        except Exception as e:
+            logger.error(f"Mixdown failed: {e}", exc_info=True)
+            raise HTTPException(status_code=500, detail=f"Mixdown failed: {str(e)}")
+
+        finally:
+            # Cleanup temp files
+            for temp_path in temp_files:
+                try:
+                    os.unlink(temp_path)
+                except Exception as e:
+                    logger.warning(f"Failed to cleanup temp file {temp_path}: {e}")
+
+            if output_mp3_path and os.path.exists(output_mp3_path):
+                try:
+                    os.unlink(output_mp3_path)
+                except Exception as e:
+                    logger.warning(f"Failed to cleanup output file {output_mp3_path}: {e}")
+
+            try:
+                shutil.rmtree(temp_dir)
+            except Exception as e:
+                logger.warning(f"Failed to cleanup temp directory {temp_dir}: {e}")
+
+    return app

server/migrations/versions/80beb1ea3269_replace_use_hatchet_with_use_celery.py

@@ -1,44 +0,0 @@
-"""replace_use_hatchet_with_use_celery
-
-Revision ID: 80beb1ea3269
-Revises: bd3a729bb379
-Create Date: 2026-01-20 16:26:25.555869
-
-"""
-
-from typing import Sequence, Union
-
-import sqlalchemy as sa
-from alembic import op
-
-# revision identifiers, used by Alembic.
-revision: str = "80beb1ea3269"
-down_revision: Union[str, None] = "bd3a729bb379"
-branch_labels: Union[str, Sequence[str], None] = None
-depends_on: Union[str, Sequence[str], None] = None
-
-
-def upgrade() -> None:
-    with op.batch_alter_table("room", schema=None) as batch_op:
-        batch_op.add_column(
-            sa.Column(
-                "use_celery",
-                sa.Boolean(),
-                server_default=sa.text("false"),
-                nullable=False,
-            )
-        )
-        batch_op.drop_column("use_hatchet")
-
-
-def downgrade() -> None:
-    with op.batch_alter_table("room", schema=None) as batch_op:
-        batch_op.add_column(
-            sa.Column(
-                "use_hatchet",
-                sa.Boolean(),
-                server_default=sa.text("false"),
-                nullable=False,
-            )
-        )
-        batch_op.drop_column("use_celery")

server/reflector/db/rooms.py

@@ -58,7 +58,7 @@ rooms = sqlalchemy.Table(
         nullable=False,
     ),
     sqlalchemy.Column(
-        "use_celery",
+        "use_hatchet",
         sqlalchemy.Boolean,
         nullable=False,
         server_default=false(),
@@ -97,7 +97,7 @@ class Room(BaseModel):
     ics_last_sync: datetime | None = None
     ics_last_etag: str | None = None
     platform: Platform = Field(default_factory=lambda: settings.DEFAULT_VIDEO_PLATFORM)
-    use_celery: bool = False
+    use_hatchet: bool = False
     skip_consent: bool = False
 
 

server/reflector/hatchet/run_workers_cpu.py

@@ -12,9 +12,14 @@ from reflector.hatchet.workflows.daily_multitrack_pipeline import (
     daily_multitrack_pipeline,
 )
 from reflector.logger import logger
+from reflector.settings import settings
 
 
 def main():
+    if not settings.HATCHET_ENABLED:
+        logger.error("HATCHET_ENABLED is False, not starting CPU workers")
+        return
+
     hatchet = HatchetClientManager.get_client()
 
     logger.info(

server/reflector/hatchet/run_workers_llm.py

@@ -11,6 +11,7 @@ from reflector.hatchet.workflows.subject_processing import subject_workflow
 from reflector.hatchet.workflows.topic_chunk_processing import topic_chunk_workflow
 from reflector.hatchet.workflows.track_processing import track_workflow
 from reflector.logger import logger
+from reflector.settings import settings
 
 SLOTS = 10
 WORKER_NAME = "llm-worker-pool"
@@ -18,6 +19,10 @@ POOL = "llm-io"
 
 
 def main():
+    if not settings.HATCHET_ENABLED:
+        logger.error("HATCHET_ENABLED is False, not starting LLM workers")
+        return
+
     hatchet = HatchetClientManager.get_client()
 
     logger.info(

server/reflector/hatchet/workflows/daily_multitrack_pipeline.py

@@ -489,7 +489,7 @@ async def process_tracks(input: PipelineInput, ctx: Context) -> ProcessTracksRes
 )
 @with_error_handling(TaskName.MIXDOWN_TRACKS)
 async def mixdown_tracks(input: PipelineInput, ctx: Context) -> MixdownResult:
-    """Mix all padded tracks into single audio file using PyAV (same as Celery)."""
+    """Mix all padded tracks into single audio file using PyAV or Modal backend."""
     ctx.log("mixdown_tracks: mixing padded tracks into single audio file")
 
     track_result = ctx.task_output(process_tracks)
@@ -513,7 +513,7 @@ async def mixdown_tracks(input: PipelineInput, ctx: Context) -> MixdownResult:
 
     storage = _spawn_storage()
 
-    # Presign URLs on demand (avoids stale URLs on workflow replay)
+    # Presign URLs for padded tracks (same expiration for both backends)
     padded_urls = []
     for track_info in padded_tracks:
         if track_info.key:
@@ -534,13 +534,79 @@ async def mixdown_tracks(input: PipelineInput, ctx: Context) -> MixdownResult:
         logger.error("Mixdown failed - no decodable audio frames found")
         raise ValueError("No decodable audio frames in any track")
 
+    output_key = f"{input.transcript_id}/audio.mp3"
+
+    # Conditional: Modal or local backend
+    if settings.MIXDOWN_BACKEND == "modal":
+        ctx.log("mixdown_tracks: using Modal backend")
+
+        # Presign PUT URL for output (Modal will upload directly)
+        output_url = await storage.get_file_url(
+            output_key,
+            operation="put_object",
+            expires_in=PRESIGNED_URL_EXPIRATION_SECONDS,
+        )
+
+        from reflector.processors.audio_mixdown_modal import (  # noqa: PLC0415
+            AudioMixdownModalProcessor,
+        )
+
+        try:
+            processor = AudioMixdownModalProcessor()
+            result = await processor.mixdown(
+                track_urls=valid_urls,
+                output_url=output_url,
+                target_sample_rate=target_sample_rate,
+                expected_duration_sec=recording_duration
+                if recording_duration > 0
+                else None,
+            )
+            duration_ms = result.duration_ms
+            tracks_mixed = result.tracks_mixed
+
+            ctx.log(
+                f"mixdown_tracks: Modal returned duration={duration_ms}ms, tracks={tracks_mixed}"
+            )
+        except httpx.HTTPStatusError as e:
+            error_detail = e.response.text if hasattr(e.response, "text") else str(e)
+            logger.error(
+                "[Hatchet] Modal mixdown HTTP error",
+                transcript_id=input.transcript_id,
+                status_code=e.response.status_code if hasattr(e, "response") else None,
+                error=error_detail,
+            )
+            raise RuntimeError(
+                f"Modal mixdown failed with HTTP {e.response.status_code}: {error_detail}"
+            )
+        except httpx.TimeoutException:
+            logger.error(
+                "[Hatchet] Modal mixdown timeout",
+                transcript_id=input.transcript_id,
+                timeout=settings.MIXDOWN_TIMEOUT,
+            )
+            raise RuntimeError(
+                f"Modal mixdown timeout after {settings.MIXDOWN_TIMEOUT}s"
+            )
+        except ValueError as e:
+            logger.error(
+                "[Hatchet] Modal mixdown validation error",
+                transcript_id=input.transcript_id,
+                error=str(e),
+            )
+            raise
+    else:
+        ctx.log("mixdown_tracks: using local backend")
+
+        # Existing local implementation
         output_path = tempfile.mktemp(suffix=".mp3")
         duration_ms_callback_capture_container = [0.0]
 
         async def capture_duration(d):
             duration_ms_callback_capture_container[0] = d
 
-    writer = AudioFileWriterProcessor(path=output_path, on_duration=capture_duration)
+        writer = AudioFileWriterProcessor(
+            path=output_path, on_duration=capture_duration
+        )
 
         await mixdown_tracks_pyav(
             valid_urls,
@@ -549,18 +615,23 @@ async def mixdown_tracks(input: PipelineInput, ctx: Context) -> MixdownResult:
             offsets_seconds=None,
             logger=logger,
             progress_callback=make_audio_progress_logger(ctx, TaskName.MIXDOWN_TRACKS),
-        expected_duration_sec=recording_duration if recording_duration > 0 else None,
+            expected_duration_sec=recording_duration
+            if recording_duration > 0
+            else None,
         )
         await writer.flush()
 
         file_size = Path(output_path).stat().st_size
-    storage_path = f"{input.transcript_id}/audio.mp3"
-
         with open(output_path, "rb") as mixed_file:
-        await storage.put_file(storage_path, mixed_file)
+            await storage.put_file(output_key, mixed_file)
 
         Path(output_path).unlink(missing_ok=True)
+        duration_ms = duration_ms_callback_capture_container[0]
+        tracks_mixed = len(valid_urls)
 
+        ctx.log(f"mixdown_tracks: local mixdown uploaded {file_size} bytes")
+
+    # Update DB (same for both backends)
     async with fresh_db_connection():
         from reflector.db.transcripts import transcripts_controller  # noqa: PLC0415
 
@@ -570,12 +641,12 @@ async def mixdown_tracks(input: PipelineInput, ctx: Context) -> MixdownResult:
                 transcript, {"audio_location": "storage"}
             )
 
-    ctx.log(f"mixdown_tracks complete: uploaded {file_size} bytes to {storage_path}")
+    ctx.log(f"mixdown_tracks complete: uploaded to {output_key}")
 
     return MixdownResult(
-        audio_key=storage_path,
-        duration=duration_ms_callback_capture_container[0],
-        tracks_mixed=len(valid_urls),
+        audio_key=output_key,
+        duration=duration_ms,
+        tracks_mixed=tracks_mixed,
     )
 
 

server/reflector/processors/audio_mixdown_modal.py

@@ -0,0 +1,89 @@
+"""
+Modal.com backend for audio mixdown.
+
+Uses Modal's CPU containers to offload audio mixing from Hatchet workers.
+Communicates via presigned S3 URLs for both input and output.
+"""
+
+import httpx
+from pydantic import BaseModel
+
+from reflector.settings import settings
+
+
+class MixdownResponse(BaseModel):
+    """Response from Modal mixdown endpoint."""
+
+    duration_ms: float
+    tracks_mixed: int
+    audio_uploaded: bool
+
+
+class AudioMixdownModalProcessor:
+    """Audio mixdown processor using Modal.com CPU backend.
+
+    Sends track URLs (presigned GET) and output URL (presigned PUT) to Modal.
+    Modal handles download, mixdown via PyAV, and upload.
+    """
+
+    def __init__(self, modal_api_key: str | None = None):
+        if not settings.MIXDOWN_URL:
+            raise ValueError("MIXDOWN_URL required to use AudioMixdownModalProcessor")
+
+        self.mixdown_url = settings.MIXDOWN_URL + "/v1"
+        self.timeout = settings.MIXDOWN_TIMEOUT
+        self.modal_api_key = modal_api_key or settings.MIXDOWN_MODAL_API_KEY
+
+        if not self.modal_api_key:
+            raise ValueError(
+                "MIXDOWN_MODAL_API_KEY required to use AudioMixdownModalProcessor"
+            )
+
+    async def mixdown(
+        self,
+        track_urls: list[str],
+        output_url: str,
+        target_sample_rate: int,
+        expected_duration_sec: float | None = None,
+    ) -> MixdownResponse:
+        """Mix multiple audio tracks via Modal backend.
+
+        Args:
+            track_urls: List of presigned GET URLs for audio tracks (non-empty)
+            output_url: Presigned PUT URL for output MP3
+            target_sample_rate: Sample rate for output (Hz, must be positive)
+            expected_duration_sec: Optional fallback duration if container metadata unavailable
+
+        Returns:
+            MixdownResponse with duration_ms, tracks_mixed, audio_uploaded
+
+        Raises:
+            ValueError: If track_urls is empty or target_sample_rate invalid
+            httpx.HTTPStatusError: On HTTP errors (404, 403, 500, etc.)
+            httpx.TimeoutException: On timeout
+        """
+        # Validate inputs
+        if not track_urls:
+            raise ValueError("track_urls cannot be empty")
+        if target_sample_rate <= 0:
+            raise ValueError(
+                f"target_sample_rate must be positive, got {target_sample_rate}"
+            )
+        if expected_duration_sec is not None and expected_duration_sec < 0:
+            raise ValueError(
+                f"expected_duration_sec cannot be negative, got {expected_duration_sec}"
+            )
+
+        async with httpx.AsyncClient(timeout=self.timeout) as client:
+            response = await client.post(
+                f"{self.mixdown_url}/audio/mixdown",
+                headers={"Authorization": f"Bearer {self.modal_api_key}"},
+                json={
+                    "track_urls": track_urls,
+                    "output_url": output_url,
+                    "target_sample_rate": target_sample_rate,
+                    "expected_duration_sec": expected_duration_sec,
+                },
+            )
+            response.raise_for_status()
+            return MixdownResponse(**response.json())

server/reflector/services/ics_sync.py

@@ -319,6 +319,21 @@ class ICSSyncService:
             calendar = self.fetch_service.parse_ics(ics_content)
 
             content_hash = hashlib.md5(ics_content.encode()).hexdigest()
+            if room.ics_last_etag == content_hash:
+                logger.info("No changes in ICS for room", room_id=room.id)
+                room_url = f"{settings.UI_BASE_URL}/{room.name}"
+                events, total_events = self.fetch_service.extract_room_events(
+                    calendar, room.name, room_url
+                )
+                return {
+                    "status": SyncStatus.UNCHANGED,
+                    "hash": content_hash,
+                    "events_found": len(events),
+                    "total_events": total_events,
+                    "events_created": 0,
+                    "events_updated": 0,
+                    "events_deleted": 0,
+                }
 
             # Extract matching events
             room_url = f"{settings.UI_BASE_URL}/{room.name}"
@@ -356,44 +371,6 @@ class ICSSyncService:
         time_since_sync = datetime.now(timezone.utc) - room.ics_last_sync
         return time_since_sync.total_seconds() >= room.ics_fetch_interval
 
-    def _event_data_changed(self, existing: CalendarEvent, new_data: EventData) -> bool:
-        """Check if event data has changed by comparing relevant fields.
-
-        IMPORTANT: When adding fields to CalendarEvent/EventData, update this method
-        and the _COMPARED_FIELDS set below for runtime validation.
-        """
-        # Fields that come from ICS and should trigger updates when changed
-        _COMPARED_FIELDS = {
-            "title",
-            "description",
-            "start_time",
-            "end_time",
-            "location",
-            "attendees",
-            "ics_raw_data",
-        }
-
-        # Runtime exhaustiveness check: ensure we're comparing all EventData fields
-        event_data_fields = set(EventData.__annotations__.keys()) - {"ics_uid"}
-        if event_data_fields != _COMPARED_FIELDS:
-            missing = event_data_fields - _COMPARED_FIELDS
-            extra = _COMPARED_FIELDS - event_data_fields
-            raise RuntimeError(
-                f"_event_data_changed() field mismatch: "
-                f"missing={missing}, extra={extra}. "
-                f"Update the comparison logic when adding/removing fields."
-            )
-
-        return (
-            existing.title != new_data["title"]
-            or existing.description != new_data["description"]
-            or existing.start_time != new_data["start_time"]
-            or existing.end_time != new_data["end_time"]
-            or existing.location != new_data["location"]
-            or existing.attendees != new_data["attendees"]
-            or existing.ics_raw_data != new_data["ics_raw_data"]
-        )
-
     async def _sync_events_to_database(
         self, room_id: str, events: list[EventData]
     ) -> SyncStats:
@@ -409,14 +386,11 @@ class ICSSyncService:
             )
 
             if existing:
-                # Only count as updated if data actually changed
-                if self._event_data_changed(existing, event_data):
                 updated += 1
-                    await calendar_events_controller.upsert(calendar_event)
             else:
                 created += 1
-                await calendar_events_controller.upsert(calendar_event)
 
+            await calendar_events_controller.upsert(calendar_event)
             current_ics_uids.append(event_data["ics_uid"])
 
         # Soft delete events that are no longer in calendar

server/reflector/services/transcript_process.py

@@ -23,6 +23,7 @@ from reflector.pipelines.main_file_pipeline import task_pipeline_file_process
 from reflector.pipelines.main_multitrack_pipeline import (
     task_pipeline_multitrack_process,
 )
+from reflector.settings import settings
 from reflector.utils.string import NonEmptyString
 
 
@@ -101,8 +102,8 @@ async def validate_transcript_for_processing(
     if transcript.locked:
         return ValidationLocked(detail="Recording is locked")
 
-    # Check if recording is ready for processing
-    if transcript.status == "idle" and not transcript.workflow_run_id:
+    # hatchet is idempotent anyways + if it wasn't dispatched successfully
+    if transcript.status == "idle" and not settings.HATCHET_ENABLED:
         return ValidationNotReady(detail="Recording is not ready for processing")
 
     # Check Celery tasks
@@ -115,8 +116,7 @@ async def validate_transcript_for_processing(
     ):
         return ValidationAlreadyScheduled(detail="already running")
 
-    # Check Hatchet workflow status if workflow_run_id exists
-    if transcript.workflow_run_id:
+    if settings.HATCHET_ENABLED and transcript.workflow_run_id:
         try:
             status = await HatchetClientManager.get_workflow_run_status(
                 transcript.workflow_run_id
@@ -181,16 +181,19 @@ async def dispatch_transcript_processing(
     Returns AsyncResult for Celery tasks, None for Hatchet workflows.
     """
     if isinstance(config, MultitrackProcessingConfig):
-        use_celery = False
+        # Check if room has use_hatchet=True (overrides env vars)
+        room_forces_hatchet = False
         if config.room_id:
             room = await rooms_controller.get_by_id(config.room_id)
-            use_celery = room.use_celery if room else False
+            room_forces_hatchet = room.use_hatchet if room else False
 
-        use_hatchet = not use_celery
+        # Start durable workflow if enabled (Hatchet)
+        # and if room has use_hatchet=True
+        use_hatchet = settings.HATCHET_ENABLED and room_forces_hatchet
 
-        if use_celery:
+        if room_forces_hatchet:
             logger.info(
-                "Room uses legacy Celery processing",
+                "Room forces Hatchet workflow",
                 room_id=config.room_id,
                 transcript_id=config.transcript_id,
             )

server/reflector/settings.py

@@ -98,6 +98,17 @@ class Settings(BaseSettings):
     # Diarization: local pyannote.audio
     DIARIZATION_PYANNOTE_AUTH_TOKEN: str | None = None
 
+    # Audio Mixdown
+    # backends:
+    #   - local: in-process PyAV mixdown (runs in same process as Hatchet worker)
+    #   - modal: HTTP API client to Modal.com CPU container
+    MIXDOWN_BACKEND: str = "local"
+    MIXDOWN_URL: str | None = None
+    MIXDOWN_TIMEOUT: int = 900  # 15 minutes
+
+    # Mixdown: modal backend
+    MIXDOWN_MODAL_API_KEY: str | None = None
+
     # Sentry
     SENTRY_DSN: str | None = None
 
@@ -158,10 +169,19 @@ class Settings(BaseSettings):
     ZULIP_API_KEY: str | None = None
     ZULIP_BOT_EMAIL: str | None = None
 
-    # Hatchet workflow orchestration (always enabled for multitrack processing)
+    # Durable workflow orchestration
+    # Provider: "hatchet" (or "none" to disable)
+    DURABLE_WORKFLOW_PROVIDER: str = "none"
+
+    # Hatchet workflow orchestration
     HATCHET_CLIENT_TOKEN: str | None = None
     HATCHET_CLIENT_TLS_STRATEGY: str = "none"  # none, tls, mtls
     HATCHET_DEBUG: bool = False
 
+    @property
+    def HATCHET_ENABLED(self) -> bool:
+        """True if Hatchet is the active provider."""
+        return self.DURABLE_WORKFLOW_PROVIDER == "hatchet"
+
 
 settings = Settings()

server/reflector/worker/process.py

@@ -287,12 +287,11 @@ async def _process_multitrack_recording_inner(
             room_id=room.id,
         )
 
-    use_celery = room and room.use_celery
-    use_hatchet = not use_celery
+    use_hatchet = settings.HATCHET_ENABLED and room and room.use_hatchet
 
-    if use_celery:
+    if room and room.use_hatchet and not settings.HATCHET_ENABLED:
         logger.info(
-            "Room uses legacy Celery processing",
+            "Room forces Hatchet workflow",
             room_id=room.id,
             transcript_id=transcript.id,
         )
@@ -811,6 +810,7 @@ async def reprocess_failed_daily_recordings():
                 )
                 continue
 
+            # Fetch room to check use_hatchet flag
             room = None
             if meeting.room_id:
                 room = await rooms_controller.get_by_id(meeting.room_id)
@@ -834,10 +834,10 @@ async def reprocess_failed_daily_recordings():
                 )
                 continue
 
-            use_celery = room and room.use_celery
-            use_hatchet = not use_celery
+            use_hatchet = settings.HATCHET_ENABLED and room and room.use_hatchet
 
             if use_hatchet:
+                # Hatchet requires a transcript for workflow_run_id tracking
                 if not transcript:
                     logger.warning(
                         "No transcript for Hatchet reprocessing, skipping",

server/tests/test_hatchet_dispatch.py

@@ -2,9 +2,10 @@
 Tests for Hatchet workflow dispatch and routing logic.
 
 These tests verify:
-1. Hatchet workflow validation and replay logic
-2. Force flag to cancel and restart workflows
-3. Validation prevents concurrent workflows
+1. Routing to Hatchet when HATCHET_ENABLED=True
+2. Replay logic for failed workflows
+3. Force flag to cancel and restart
+4. Validation prevents concurrent workflows
 """
 
 from unittest.mock import AsyncMock, patch
@@ -33,6 +34,9 @@ async def test_hatchet_validation_blocks_running_workflow():
         workflow_run_id="running-workflow-123",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -68,6 +72,9 @@ async def test_hatchet_validation_blocks_queued_workflow():
         workflow_run_id="queued-workflow-123",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -103,6 +110,9 @@ async def test_hatchet_validation_allows_failed_workflow():
         recording_id="test-recording-id",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -139,6 +149,9 @@ async def test_hatchet_validation_allows_completed_workflow():
         recording_id="test-recording-id",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -174,6 +187,9 @@ async def test_hatchet_validation_allows_when_status_check_fails():
         recording_id="test-recording-id",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -211,6 +227,9 @@ async def test_hatchet_validation_skipped_when_no_workflow_id():
         recording_id="test-recording-id",
     )
 
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = True
+
         with patch(
             "reflector.services.transcript_process.HatchetClientManager"
         ) as mock_hatchet:
@@ -229,6 +248,38 @@ async def test_hatchet_validation_skipped_when_no_workflow_id():
             assert isinstance(result, ValidationOk)
 
 
+@pytest.mark.usefixtures("setup_database")
+@pytest.mark.asyncio
+async def test_hatchet_validation_skipped_when_disabled():
+    """Test that Hatchet validation is skipped when HATCHET_ENABLED is False."""
+    from reflector.services.transcript_process import (
+        ValidationOk,
+        validate_transcript_for_processing,
+    )
+
+    mock_transcript = Transcript(
+        id="test-transcript-id",
+        name="Test",
+        status="uploaded",
+        source_kind="room",
+        workflow_run_id="some-workflow-123",
+        recording_id="test-recording-id",
+    )
+
+    with patch("reflector.services.transcript_process.settings") as mock_settings:
+        mock_settings.HATCHET_ENABLED = False  # Hatchet disabled
+
+        with patch(
+            "reflector.services.transcript_process.task_is_scheduled_or_active"
+        ) as mock_celery_check:
+            mock_celery_check.return_value = False
+
+            result = await validate_transcript_for_processing(mock_transcript)
+
+        # Should not check Hatchet at all
+        assert isinstance(result, ValidationOk)
+
+
 @pytest.mark.usefixtures("setup_database")
 @pytest.mark.asyncio
 async def test_validation_locked_transcript():

server/tests/test_ics_sync.py

@@ -189,17 +189,14 @@ async def test_ics_sync_service_sync_room_calendar():
         assert events[0].ics_uid == "sync-event-1"
         assert events[0].title == "Sync Test Meeting"
 
-        # Second sync with same content (calendar unchanged, but sync always runs)
+        # Second sync with same content (should be unchanged)
         # Refresh room to get updated etag and force sync by setting old sync time
         room = await rooms_controller.get_by_id(room.id)
         await rooms_controller.update(
             room, {"ics_last_sync": datetime.now(timezone.utc) - timedelta(minutes=10)}
         )
         result = await sync_service.sync_room_calendar(room)
-        assert result["status"] == "success"
-        assert result["events_created"] == 0
-        assert result["events_updated"] == 0
-        assert result["events_deleted"] == 0
+        assert result["status"] == "unchanged"
 
         # Third sync with updated event
         event["summary"] = "Updated Meeting Title"
@@ -291,43 +288,3 @@ async def test_ics_sync_service_error_handling():
         result = await sync_service.sync_room_calendar(room)
         assert result["status"] == "error"
         assert "Network error" in result["error"]
-
-
-@pytest.mark.asyncio
-async def test_event_data_changed_exhaustiveness():
-    """Test that _event_data_changed compares all EventData fields (except ics_uid).
-
-    This test ensures programmers don't forget to update the comparison logic
-    when adding new fields to EventData/CalendarEvent.
-    """
-    from reflector.services.ics_sync import EventData
-
-    sync_service = ICSSyncService()
-
-    from reflector.db.calendar_events import CalendarEvent
-
-    now = datetime.now(timezone.utc)
-    event_data: EventData = {
-        "ics_uid": "test-123",
-        "title": "Test",
-        "description": "Desc",
-        "location": "Loc",
-        "start_time": now,
-        "end_time": now + timedelta(hours=1),
-        "attendees": [],
-        "ics_raw_data": "raw",
-    }
-
-    existing = CalendarEvent(
-        room_id="room1",
-        **event_data,
-    )
-
-    # Will raise RuntimeError if fields are missing from comparison
-    result = sync_service._event_data_changed(existing, event_data)
-    assert result is False
-
-    modified_data = event_data.copy()
-    modified_data["title"] = "Changed Title"
-    result = sync_service._event_data_changed(existing, modified_data)
-    assert result is True

server/tests/test_transcripts_process.py

@@ -162,24 +162,9 @@ async def test_dailyco_recording_uses_multitrack_pipeline(client):
     from datetime import datetime, timezone
 
     from reflector.db.recordings import Recording, recordings_controller
-    from reflector.db.rooms import rooms_controller
     from reflector.db.transcripts import transcripts_controller
 
-    room = await rooms_controller.add(
-        name="test-room",
-        user_id="test-user",
-        zulip_auto_post=False,
-        zulip_stream="",
-        zulip_topic="",
-        is_locked=False,
-        room_mode="normal",
-        recording_type="cloud",
-        recording_trigger="automatic-2nd-participant",
-        is_shared=False,
-    )
-    # Force Celery backend for test
-    await rooms_controller.update(room, {"use_celery": True})
-
+    # Create transcript with Daily.co multitrack recording
     transcript = await transcripts_controller.add(
         "",
         source_kind="room",
@@ -187,7 +172,6 @@ async def test_dailyco_recording_uses_multitrack_pipeline(client):
         target_language="en",
         user_id="test-user",
         share_mode="public",
-        room_id=room.id,
     )
 
     track_keys = [