Use Job infrastructure for Debug Replay (#23099)

* use ReplayState enum

* extract shared ffmpeg progress helper

* make start call non-blocking with worker thread

* expose replay state on status endpoint and return 202 from start

* cancel in-flight ffmpeg when stop is called during preparation

* add replay i18n strings for preparing and error states

* show status in replay UI

* navigate immediately on 202 from debug replay menus and dialog

* remove unused

* simplify to use Job infrastructure

* tests

* cleanup and tweaks

* fetch schema

* update api spec

* formatting

* fix e2e test

* mypy

* clean up

* formatting

* fix

* fix test

* don't try to show camera image until status reports ready

* simplify loading logic

* fix race in latest_frame on debug replay shutdown

* remove toast when successfully stopping

it gets hidden almost immediately

docs/static/frigate-api.yaml

@@ -5997,7 +5997,10 @@ paths:
       tags:
         - App
       summary: Start debug replay
-      description: Start a debug replay session from camera recordings.
+      description:
+        Start a debug replay session from camera recordings. Returns
+        immediately while clip generation runs as a background job; subscribe
+        to the 'debug_replay' job_state WS topic to track progress.
       operationId: start_debug_replay_debug_replay_start_post
       requestBody:
         required: true
@@ -6006,12 +6009,16 @@ paths:
             schema:
               $ref: "#/components/schemas/DebugReplayStartBody"
       responses:
-        "200":
+        "202":
           description: Successful Response
           content:
             application/json:
               schema:
                 $ref: "#/components/schemas/DebugReplayStartResponse"
+        "400":
+          description: Invalid camera, time range, or no recordings
+        "409":
+          description: A replay session is already active
         "422":
           description: Validation Error
           content:
@@ -6272,10 +6279,14 @@ components:
         replay_camera:
           type: string
           title: Replay Camera
+        job_id:
+          type: string
+          title: Job Id
       type: object
       required:
         - success
         - replay_camera
+        - job_id
       title: DebugReplayStartResponse
       description: Response for starting a debug replay session.
     DebugReplayStatusResponse:

frigate/api/debug_replay.py

@@ -10,6 +10,7 @@ from pydantic import BaseModel, Field
 
 from frigate.api.auth import require_role
 from frigate.api.defs.tags import Tags
+from frigate.jobs.debug_replay import start_debug_replay_job
 
 logger = logging.getLogger(__name__)
 
@@ -29,10 +30,17 @@ class DebugReplayStartResponse(BaseModel):
 
     success: bool
     replay_camera: str
+    job_id: str
 
 
 class DebugReplayStatusResponse(BaseModel):
-    """Response for debug replay status."""
+    """Response for debug replay status.
+
+    Returns only session-presence fields. Startup progress and error
+    details flow through the job_state WebSocket topic via the
+    debug_replay job (see frigate.jobs.debug_replay); the
+    Replay page subscribes there with useJobStatus("debug_replay").
+    """
 
     active: bool
     replay_camera: str | None = None
@@ -51,15 +59,32 @@ class DebugReplayStopResponse(BaseModel):
 @router.post(
     "/debug_replay/start",
     response_model=DebugReplayStartResponse,
+    status_code=202,
+    responses={
+        400: {"description": "Invalid camera, time range, or no recordings"},
+        409: {"description": "A replay session is already active"},
+    },
     dependencies=[Depends(require_role(["admin"]))],
     summary="Start debug replay",
-    description="Start a debug replay session from camera recordings.",
+    description="Start a debug replay session from camera recordings. Returns "
+    "immediately while clip generation runs as a background job; subscribe "
+    "to the 'debug_replay' job_state WS topic to track progress.",
 )
 async def start_debug_replay(request: Request, body: DebugReplayStartBody):
-    """Start a debug replay session."""
+    """Start a debug replay session asynchronously."""
     replay_manager = request.app.replay_manager
 
-    if replay_manager.active:
+    try:
+        job_id = await asyncio.to_thread(
+            start_debug_replay_job,
+            source_camera=body.camera,
+            start_ts=body.start_time,
+            end_ts=body.end_time,
+            frigate_config=request.app.frigate_config,
+            config_publisher=request.app.config_publisher,
+            replay_manager=replay_manager,
+        )
+    except RuntimeError:
         return JSONResponse(
             content={
                 "success": False,
@@ -67,38 +92,23 @@ async def start_debug_replay(request: Request, body: DebugReplayStartBody):
             },
             status_code=409,
         )
-
-    try:
-        replay_camera = await asyncio.to_thread(
-            replay_manager.start,
-            source_camera=body.camera,
-            start_ts=body.start_time,
-            end_ts=body.end_time,
-            frigate_config=request.app.frigate_config,
-            config_publisher=request.app.config_publisher,
-        )
     except ValueError:
-        logger.exception("Invalid parameters for debug replay start request")
+        logger.exception("Rejected debug replay start request")
         return JSONResponse(
             content={
                 "success": False,
-                "message": "Invalid debug replay request parameters",
+                "message": "Invalid debug replay parameters",
             },
             status_code=400,
         )
-    except RuntimeError:
-        logger.exception("Error while starting debug replay session")
-        return JSONResponse(
-            content={
-                "success": False,
-                "message": "An internal error occurred while starting debug replay",
-            },
-            status_code=500,
-        )
 
-    return DebugReplayStartResponse(
-        success=True,
-        replay_camera=replay_camera,
+    return JSONResponse(
+        content={
+            "success": True,
+            "replay_camera": replay_manager.replay_camera_name,
+            "job_id": job_id,
+        },
+        status_code=202,
     )
 
 
@@ -118,12 +128,16 @@ def get_debug_replay_status(request: Request):
 
     if replay_manager.active and replay_camera:
         frame_processor = request.app.detected_frames_processor
-        frame = frame_processor.get_current_frame(replay_camera)
+        frame = (
+            frame_processor.get_current_frame(replay_camera)
+            if frame_processor is not None
+            else None
+        )
 
         if frame is not None:
             frame_time = frame_processor.get_current_frame_time(replay_camera)
             camera_config = request.app.frigate_config.cameras.get(replay_camera)
-            retry_interval = 10
+            retry_interval = 10.0
 
             if camera_config is not None:
                 retry_interval = float(camera_config.ffmpeg.retry_interval or 10)

frigate/api/media.py

@@ -174,12 +174,10 @@ async def latest_frame(
     }
     quality_params = get_image_quality_params(extension.value, params.quality)
 
-    if camera_name in request.app.frigate_config.cameras:
+    camera_config = request.app.frigate_config.cameras.get(camera_name)
+    if camera_config is not None:
         frame = frame_processor.get_current_frame(camera_name, draw_options)
-        retry_interval = float(
-            request.app.frigate_config.cameras.get(camera_name).ffmpeg.retry_interval
-            or 10
-        )
+        retry_interval = float(camera_config.ffmpeg.retry_interval or 10)
 
         is_offline = False
         if frame is None or datetime.now().timestamp() > (

frigate/debug_replay.py

@@ -1,9 +1,13 @@
-"""Debug replay camera management for replaying recordings with detection overlays."""
+"""Debug replay camera management for replaying recordings with detection overlays.
+
+The startup work (ffmpeg concat + camera config publish) lives in
+frigate.jobs.debug_replay. This module owns only session presence
+(active), session metadata, and post-session cleanup.
+"""
 
 import logging
 import os
 import shutil
-import subprocess as sp
 import threading
 
 from ruamel.yaml import YAML
@@ -21,7 +25,7 @@ from frigate.const import (
     REPLAY_DIR,
     THUMB_DIR,
 )
-from frigate.models import Recordings
+from frigate.jobs.debug_replay import cancel_debug_replay_job, wait_for_runner
 from frigate.util.camera_cleanup import cleanup_camera_db, cleanup_camera_files
 from frigate.util.config import find_config_file
 
@@ -29,7 +33,14 @@ logger = logging.getLogger(__name__)
 
 
 class DebugReplayManager:
-    """Manages a single debug replay session."""
+    """Owns the lifecycle pointers for a single debug replay session.
+
+    A session exists from the moment mark_starting is called (synchronously,
+    inside the API handler) until clear_session runs (on success cleanup,
+    failure, or stop). The active property is the source of truth that the
+    status bar consumes — broader than the startup job, which only covers the
+    preparing_clip / starting_camera window.
+    """
 
     def __init__(self) -> None:
         self._lock = threading.Lock()
@@ -41,144 +52,66 @@ class DebugReplayManager:
 
     @property
     def active(self) -> bool:
-        """Whether a replay session is currently active."""
+        """True from mark_starting until clear_session."""
         return self.replay_camera_name is not None
 
-    def start(
+    def mark_starting(
         self,
         source_camera: str,
+        replay_camera_name: str,
         start_ts: float,
         end_ts: float,
-        frigate_config: FrigateConfig,
-        config_publisher: CameraConfigUpdatePublisher,
-    ) -> str:
-        """Start a debug replay session.
+    ) -> None:
+        """Synchronously claim the session before the job runner starts.
 
-        Args:
-            source_camera: Name of the source camera to replay
-            start_ts: Start timestamp
-            end_ts: End timestamp
-            frigate_config: Current Frigate configuration
-            config_publisher: Publisher for camera config updates
-
-        Returns:
-            The replay camera name
-
-        Raises:
-            ValueError: If a session is already active or parameters are invalid
-            RuntimeError: If clip generation fails
+        Called inside the API handler so the status bar sees active=True
+        immediately, before the worker thread does any ffmpeg work.
         """
         with self._lock:
-            return self._start_locked(
-                source_camera, start_ts, end_ts, frigate_config, config_publisher
-            )
+            self.replay_camera_name = replay_camera_name
+            self.source_camera = source_camera
+            self.start_ts = start_ts
+            self.end_ts = end_ts
+            self.clip_path = None
 
-    def _start_locked(
+    def mark_session_ready(self, clip_path: str) -> None:
+        """Record the on-disk clip path after the camera has been published."""
+        with self._lock:
+            self.clip_path = clip_path
+
+    def clear_session(self) -> None:
+        """Reset session pointers without publishing camera removal.
+
+        Used by the job runner on failure paths. stop() does the camera
+        teardown plus this clear in one step.
+        """
+        with self._lock:
+            self._clear_locked()
+
+    def _clear_locked(self) -> None:
+        self.replay_camera_name = None
+        self.source_camera = None
+        self.clip_path = None
+        self.start_ts = None
+        self.end_ts = None
+
+    def publish_camera(
         self,
         source_camera: str,
-        start_ts: float,
-        end_ts: float,
+        replay_name: str,
+        clip_path: str,
         frigate_config: FrigateConfig,
         config_publisher: CameraConfigUpdatePublisher,
-    ) -> str:
-        if self.active:
-            raise ValueError("A replay session is already active")
+    ) -> None:
+        """Build the in-memory replay camera config and publish the add event.
 
-        if source_camera not in frigate_config.cameras:
-            raise ValueError(f"Camera '{source_camera}' not found")
-
-        if end_ts <= start_ts:
-            raise ValueError("End time must be after start time")
-
-        # Query recordings for the source camera in the time range
-        recordings = (
-            Recordings.select(
-                Recordings.path,
-                Recordings.start_time,
-                Recordings.end_time,
-            )
-            .where(
-                Recordings.start_time.between(start_ts, end_ts)
-                | Recordings.end_time.between(start_ts, end_ts)
-                | ((start_ts > Recordings.start_time) & (end_ts < Recordings.end_time))
-            )
-            .where(Recordings.camera == source_camera)
-            .order_by(Recordings.start_time.asc())
-        )
-
-        if not recordings.count():
-            raise ValueError(
-                f"No recordings found for camera '{source_camera}' in the specified time range"
-            )
-
-        # Create replay directory
-        os.makedirs(REPLAY_DIR, exist_ok=True)
-
-        # Generate replay camera name
-        replay_name = f"{REPLAY_CAMERA_PREFIX}{source_camera}"
-
-        # Build concat file for ffmpeg
-        concat_file = os.path.join(REPLAY_DIR, f"{replay_name}_concat.txt")
-        clip_path = os.path.join(REPLAY_DIR, f"{replay_name}.mp4")
-
-        with open(concat_file, "w") as f:
-            for recording in recordings:
-                f.write(f"file '{recording.path}'\n")
-
-        # Concatenate recordings into a single clip with -c copy (fast)
-        ffmpeg_cmd = [
-            frigate_config.ffmpeg.ffmpeg_path,
-            "-hide_banner",
-            "-y",
-            "-f",
-            "concat",
-            "-safe",
-            "0",
-            "-i",
-            concat_file,
-            "-c",
-            "copy",
-            "-movflags",
-            "+faststart",
-            clip_path,
-        ]
-
-        logger.info(
-            "Generating replay clip for %s (%.1f - %.1f)",
-            source_camera,
-            start_ts,
-            end_ts,
-        )
-
-        try:
-            result = sp.run(
-                ffmpeg_cmd,
-                capture_output=True,
-                text=True,
-                timeout=120,
-            )
-            if result.returncode != 0:
-                logger.error("FFmpeg error: %s", result.stderr)
-                raise RuntimeError(
-                    f"Failed to generate replay clip: {result.stderr[-500:]}"
-                )
-        except sp.TimeoutExpired:
-            raise RuntimeError("Clip generation timed out")
-        finally:
-            # Clean up concat file
-            if os.path.exists(concat_file):
-                os.remove(concat_file)
-
-        if not os.path.exists(clip_path):
-            raise RuntimeError("Clip file was not created")
-
-        # Build camera config dict for the replay camera
+        Called by the job runner during the starting_camera phase.
+        """
         source_config = frigate_config.cameras[source_camera]
         camera_dict = self._build_camera_config_dict(
             source_config, replay_name, clip_path
         )
 
-        # Build an in-memory config with the replay camera added
         config_file = find_config_file()
         yaml_parser = YAML()
         with open(config_file, "r") as f:
@@ -191,75 +124,48 @@ class DebugReplayManager:
         try:
             new_config = FrigateConfig.parse_object(config_data)
         except Exception as e:
-            raise RuntimeError(f"Failed to validate replay camera config: {e}")
-
-        # Update the running config
+            raise RuntimeError(f"Failed to validate replay camera config: {e}") from e
         frigate_config.cameras[replay_name] = new_config.cameras[replay_name]
 
-        # Publish the add event
         config_publisher.publish_update(
             CameraConfigUpdateTopic(CameraConfigUpdateEnum.add, replay_name),
             new_config.cameras[replay_name],
         )
 
-        # Store session state
-        self.replay_camera_name = replay_name
-        self.source_camera = source_camera
-        self.clip_path = clip_path
-        self.start_ts = start_ts
-        self.end_ts = end_ts
-
-        logger.info("Debug replay started: %s -> %s", source_camera, replay_name)
-        return replay_name
-
     def stop(
         self,
         frigate_config: FrigateConfig,
         config_publisher: CameraConfigUpdatePublisher,
     ) -> None:
-        """Stop the active replay session and clean up all artifacts.
+        """Cancel any in-flight startup job and tear down the active session.
 
-        Args:
-            frigate_config: Current Frigate configuration
-            config_publisher: Publisher for camera config updates
+        Safe to call when no session is active (no-op with a warning).
         """
+        cancel_debug_replay_job()
+        wait_for_runner(timeout=2.0)
+
         with self._lock:
-            self._stop_locked(frigate_config, config_publisher)
+            if not self.active:
+                logger.warning("No active replay session to stop")
+                return
 
-    def _stop_locked(
-        self,
-        frigate_config: FrigateConfig,
-        config_publisher: CameraConfigUpdatePublisher,
-    ) -> None:
-        if not self.active:
-            logger.warning("No active replay session to stop")
-            return
+            replay_name = self.replay_camera_name
 
-        replay_name = self.replay_camera_name
+            # Only publish remove if the camera was actually added to the live
+            # config (i.e. the runner reached the starting_camera phase).
+            if replay_name is not None and replay_name in frigate_config.cameras:
+                config_publisher.publish_update(
+                    CameraConfigUpdateTopic(CameraConfigUpdateEnum.remove, replay_name),
+                    frigate_config.cameras[replay_name],
+                )
 
-        # Publish remove event so subscribers stop and remove from their config
-        if replay_name in frigate_config.cameras:
-            config_publisher.publish_update(
-                CameraConfigUpdateTopic(CameraConfigUpdateEnum.remove, replay_name),
-                frigate_config.cameras[replay_name],
-            )
-            # Do NOT pop here — let subscribers handle removal from the shared
-            # config dict when they process the ZMQ message to avoid race conditions
+            if replay_name is not None:
+                self._cleanup_db(replay_name)
+                self._cleanup_files(replay_name)
 
-        # Defensive DB cleanup
-        self._cleanup_db(replay_name)
+            self._clear_locked()
 
-        # Remove filesystem artifacts
-        self._cleanup_files(replay_name)
-
-        # Reset state
-        self.replay_camera_name = None
-        self.source_camera = None
-        self.clip_path = None
-        self.start_ts = None
-        self.end_ts = None
-
-        logger.info("Debug replay stopped and cleaned up: %s", replay_name)
+            logger.info("Debug replay stopped and cleaned up: %s", replay_name)
 
     def _build_camera_config_dict(
         self,
@@ -267,16 +173,7 @@ class DebugReplayManager:
         replay_name: str,
         clip_path: str,
     ) -> dict:
-        """Build a camera config dictionary for the replay camera.
-
-        Args:
-            source_config: Source camera's CameraConfig
-            replay_name: Name for the replay camera
-            clip_path: Path to the replay clip file
-
-        Returns:
-            Camera config as a dictionary
-        """
+        """Build a camera config dictionary for the replay camera."""
         # Extract detect config (exclude computed fields)
         detect_dict = source_config.detect.model_dump(
             exclude={"min_initialized", "max_disappeared", "enabled_in_config"}
@@ -311,7 +208,6 @@ class DebugReplayManager:
             zone_dump = zone_config.model_dump(
                 exclude={"contour", "color"}, exclude_defaults=True
             )
-            # Always include required fields
             zone_dump.setdefault("coordinates", zone_config.coordinates)
             zones_dict[zone_name] = zone_dump
 

frigate/jobs/debug_replay.py

@@ -0,0 +1,386 @@
+"""Debug replay startup job: ffmpeg concat + camera config publish.
+
+The runner orchestrates the async portion of starting a debug replay
+session. The DebugReplayManager (in frigate.debug_replay) owns session
+presence so the status bar can keep reading a single `active` flag from
+/debug_replay/status for the entire session window — which is broader
+than this job's lifetime.
+"""
+
+import logging
+import os
+import subprocess as sp
+import threading
+import time
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any, Optional, cast
+
+from peewee import ModelSelect
+
+from frigate.config import FrigateConfig
+from frigate.config.camera.updater import CameraConfigUpdatePublisher
+from frigate.const import REPLAY_CAMERA_PREFIX, REPLAY_DIR
+from frigate.jobs.export import JobStatePublisher
+from frigate.jobs.job import Job
+from frigate.jobs.manager import job_is_running, set_current_job
+from frigate.models import Recordings
+from frigate.types import JobStatusTypesEnum
+from frigate.util.ffmpeg import run_ffmpeg_with_progress
+
+if TYPE_CHECKING:
+    from frigate.debug_replay import DebugReplayManager
+
+logger = logging.getLogger(__name__)
+
+# Coalesce frequent ffmpeg progress callbacks so the WS isn't flooded.
+PROGRESS_BROADCAST_MIN_INTERVAL = 1.0
+
+JOB_TYPE = "debug_replay"
+
+STEP_PREPARING_CLIP = "preparing_clip"
+STEP_STARTING_CAMERA = "starting_camera"
+
+
+_active_runner: Optional["DebugReplayJobRunner"] = None
+_runner_lock = threading.Lock()
+
+
+def _set_active_runner(runner: Optional["DebugReplayJobRunner"]) -> None:
+    global _active_runner
+    with _runner_lock:
+        _active_runner = runner
+
+
+def get_active_runner() -> Optional["DebugReplayJobRunner"]:
+    with _runner_lock:
+        return _active_runner
+
+
+@dataclass
+class DebugReplayJob(Job):
+    """Job state for a debug replay startup."""
+
+    job_type: str = JOB_TYPE
+    source_camera: str = ""
+    replay_camera_name: str = ""
+    start_ts: float = 0.0
+    end_ts: float = 0.0
+    current_step: Optional[str] = None
+    progress_percent: float = 0.0
+
+    def to_dict(self) -> dict[str, Any]:
+        """Whitelisted payload for the job_state WS topic.
+
+        Replay-specific fields land in results so the frontend's
+        generic Job<TResults> type can be parameterised cleanly.
+        """
+        return {
+            "id": self.id,
+            "job_type": self.job_type,
+            "status": self.status,
+            "start_time": self.start_time,
+            "end_time": self.end_time,
+            "error_message": self.error_message,
+            "results": {
+                "current_step": self.current_step,
+                "progress_percent": self.progress_percent,
+                "source_camera": self.source_camera,
+                "replay_camera_name": self.replay_camera_name,
+                "start_ts": self.start_ts,
+                "end_ts": self.end_ts,
+            },
+        }
+
+
+def query_recordings(source_camera: str, start_ts: float, end_ts: float) -> ModelSelect:
+    """Return the Recordings query for the time range.
+
+    Module-level so tests can patch it without instantiating a runner.
+    """
+    query = (
+        Recordings.select(
+            Recordings.path,
+            Recordings.start_time,
+            Recordings.end_time,
+        )
+        .where(
+            Recordings.start_time.between(start_ts, end_ts)
+            | Recordings.end_time.between(start_ts, end_ts)
+            | ((start_ts > Recordings.start_time) & (end_ts < Recordings.end_time))
+        )
+        .where(Recordings.camera == source_camera)
+        .order_by(Recordings.start_time.asc())
+    )
+    return cast(ModelSelect, query)
+
+
+class DebugReplayJobRunner(threading.Thread):
+    """Worker thread that drives the startup job to completion.
+
+    Owns the live ffmpeg Popen reference for cancellation. Cancellation
+    is two-step (threading.Event + proc.terminate()) so the runner
+    both knows it should stop and is unblocked from its blocking subprocess
+    wait.
+    """
+
+    def __init__(
+        self,
+        job: DebugReplayJob,
+        frigate_config: FrigateConfig,
+        config_publisher: CameraConfigUpdatePublisher,
+        replay_manager: "DebugReplayManager",
+        publisher: Optional[JobStatePublisher] = None,
+    ) -> None:
+        super().__init__(daemon=True, name=f"debug_replay_{job.id}")
+        self.job = job
+        self.frigate_config = frigate_config
+        self.config_publisher = config_publisher
+        self.replay_manager = replay_manager
+        self.publisher = publisher if publisher is not None else JobStatePublisher()
+        self._cancel_event = threading.Event()
+        self._active_process: sp.Popen | None = None
+        self._proc_lock = threading.Lock()
+        self._last_broadcast_monotonic: float = 0.0
+
+    def cancel(self) -> None:
+        """Request cancellation. Idempotent."""
+        self._cancel_event.set()
+        with self._proc_lock:
+            proc = self._active_process
+        if proc is not None:
+            try:
+                proc.terminate()
+            except Exception as exc:
+                logger.warning("Failed to terminate ffmpeg subprocess: %s", exc)
+
+    def is_cancelled(self) -> bool:
+        return self._cancel_event.is_set()
+
+    def _record_proc(self, proc: sp.Popen) -> None:
+        with self._proc_lock:
+            self._active_process = proc
+        # Race: cancel arrived between Popen and _record_proc.
+        if self._cancel_event.is_set():
+            try:
+                proc.terminate()
+            except Exception:
+                pass
+
+    def _broadcast(self, force: bool = False) -> None:
+        now = time.monotonic()
+        if (
+            not force
+            and now - self._last_broadcast_monotonic < PROGRESS_BROADCAST_MIN_INTERVAL
+        ):
+            return
+        self._last_broadcast_monotonic = now
+
+        try:
+            self.publisher.publish(self.job.to_dict())
+        except Exception as err:
+            logger.warning("Publisher raised during job state broadcast: %s", err)
+
+    def run(self) -> None:
+        replay_name = self.job.replay_camera_name
+        os.makedirs(REPLAY_DIR, exist_ok=True)
+        concat_file = os.path.join(REPLAY_DIR, f"{replay_name}_concat.txt")
+        clip_path = os.path.join(REPLAY_DIR, f"{replay_name}.mp4")
+
+        self.job.status = JobStatusTypesEnum.running
+        self.job.start_time = time.time()
+        self.job.current_step = STEP_PREPARING_CLIP
+        self._broadcast(force=True)
+
+        try:
+            recordings = query_recordings(
+                self.job.source_camera, self.job.start_ts, self.job.end_ts
+            )
+            with open(concat_file, "w") as f:
+                for recording in recordings:
+                    f.write(f"file '{recording.path}'\n")
+
+            ffmpeg_cmd = [
+                self.frigate_config.ffmpeg.ffmpeg_path,
+                "-hide_banner",
+                "-y",
+                "-f",
+                "concat",
+                "-safe",
+                "0",
+                "-i",
+                concat_file,
+                "-c",
+                "copy",
+                "-movflags",
+                "+faststart",
+                clip_path,
+            ]
+
+            logger.info(
+                "Generating replay clip for %s (%.1f - %.1f)",
+                self.job.source_camera,
+                self.job.start_ts,
+                self.job.end_ts,
+            )
+
+            def _on_progress(percent: float) -> None:
+                self.job.progress_percent = percent
+                self._broadcast()
+
+            try:
+                returncode, stderr = run_ffmpeg_with_progress(
+                    ffmpeg_cmd,
+                    expected_duration_seconds=max(
+                        0.0, self.job.end_ts - self.job.start_ts
+                    ),
+                    on_progress=_on_progress,
+                    process_started=self._record_proc,
+                    use_low_priority=True,
+                )
+            finally:
+                with self._proc_lock:
+                    self._active_process = None
+
+            if self._cancel_event.is_set():
+                self._finalize_cancelled(clip_path)
+                return
+
+            if returncode != 0:
+                raise RuntimeError(f"FFmpeg failed: {stderr[-500:]}")
+
+            if not os.path.exists(clip_path):
+                raise RuntimeError("Clip file was not created")
+
+            self.job.current_step = STEP_STARTING_CAMERA
+            self.job.progress_percent = 100.0
+            self._broadcast(force=True)
+
+            if self._cancel_event.is_set():
+                self._finalize_cancelled(clip_path)
+                return
+
+            self.replay_manager.publish_camera(
+                source_camera=self.job.source_camera,
+                replay_name=replay_name,
+                clip_path=clip_path,
+                frigate_config=self.frigate_config,
+                config_publisher=self.config_publisher,
+            )
+            self.replay_manager.mark_session_ready(clip_path)
+
+            self.job.status = JobStatusTypesEnum.success
+            self.job.end_time = time.time()
+            self._broadcast(force=True)
+            logger.info(
+                "Debug replay started: %s -> %s",
+                self.job.source_camera,
+                replay_name,
+            )
+        except Exception as exc:
+            logger.exception("Debug replay startup failed")
+            self.job.status = JobStatusTypesEnum.failed
+            self.job.error_message = str(exc)
+            self.job.end_time = time.time()
+            self._broadcast(force=True)
+            self.replay_manager.clear_session()
+            _remove_silent(clip_path)
+        finally:
+            _remove_silent(concat_file)
+            _set_active_runner(None)
+
+    def _finalize_cancelled(self, clip_path: str) -> None:
+        logger.info("Debug replay startup cancelled")
+        self.job.status = JobStatusTypesEnum.cancelled
+        self.job.end_time = time.time()
+        self._broadcast(force=True)
+        # The caller of cancel_debug_replay_job (DebugReplayManager.stop) owns
+        # session cleanup — db rows, filesystem artifacts, clear_session. We
+        # only clean up the partial concat output we created.
+        _remove_silent(clip_path)
+
+
+def _remove_silent(path: str) -> None:
+    try:
+        if os.path.exists(path):
+            os.remove(path)
+    except OSError:
+        pass
+
+
+def start_debug_replay_job(
+    *,
+    source_camera: str,
+    start_ts: float,
+    end_ts: float,
+    frigate_config: FrigateConfig,
+    config_publisher: CameraConfigUpdatePublisher,
+    replay_manager: "DebugReplayManager",
+) -> str:
+    """Validate, create job, start runner. Returns the job id.
+
+    Raises ValueError for bad params (camera missing, time range
+    invalid, no recordings) and RuntimeError if a session is already
+    active.
+    """
+    if job_is_running(JOB_TYPE) or replay_manager.active:
+        raise RuntimeError("A replay session is already active")
+
+    if source_camera not in frigate_config.cameras:
+        raise ValueError(f"Camera '{source_camera}' not found")
+
+    if end_ts <= start_ts:
+        raise ValueError("End time must be after start time")
+
+    recordings = query_recordings(source_camera, start_ts, end_ts)
+    if not recordings.count():
+        raise ValueError(
+            f"No recordings found for camera '{source_camera}' in the specified time range"
+        )
+
+    replay_name = f"{REPLAY_CAMERA_PREFIX}{source_camera}"
+    replay_manager.mark_starting(
+        source_camera=source_camera,
+        replay_camera_name=replay_name,
+        start_ts=start_ts,
+        end_ts=end_ts,
+    )
+
+    job = DebugReplayJob(
+        source_camera=source_camera,
+        replay_camera_name=replay_name,
+        start_ts=start_ts,
+        end_ts=end_ts,
+    )
+    set_current_job(job)
+
+    runner = DebugReplayJobRunner(
+        job=job,
+        frigate_config=frigate_config,
+        config_publisher=config_publisher,
+        replay_manager=replay_manager,
+    )
+    _set_active_runner(runner)
+    runner.start()
+
+    return job.id
+
+
+def cancel_debug_replay_job() -> bool:
+    """Signal the active runner to cancel.
+
+    Returns True if a runner was signalled, False if no job was active.
+    """
+    runner = get_active_runner()
+    if runner is None:
+        return False
+    runner.cancel()
+    return True
+
+
+def wait_for_runner(timeout: float = 2.0) -> bool:
+    """Join the active runner. Returns True if the runner ended in time."""
+    runner = get_active_runner()
+    if runner is None:
+        return True
+    runner.join(timeout=timeout)
+    return not runner.is_alive()

frigate/record/export.py

@@ -23,13 +23,13 @@ from frigate.const import (
     EXPORT_DIR,
     MAX_PLAYLIST_SECONDS,
     PREVIEW_FRAME_TYPE,
-    PROCESS_PRIORITY_LOW,
 )
 from frigate.ffmpeg_presets import (
     EncodeTypeEnum,
     parse_preset_hardware_acceleration_encode,
 )
 from frigate.models import Export, Previews, Recordings, ReviewSegment
+from frigate.util.ffmpeg import run_ffmpeg_with_progress
 from frigate.util.time import is_current_hour
 
 logger = logging.getLogger(__name__)
@@ -243,107 +243,29 @@ class RecordingExporter(threading.Thread):
 
         return total
 
-    def _inject_progress_flags(self, ffmpeg_cmd: list[str]) -> list[str]:
-        """Insert FFmpeg progress reporting flags before the output path.
-
-        ``-progress pipe:2`` writes structured key=value lines to stderr,
-        ``-nostats`` suppresses the noisy default stats output.
-        """
-        if not ffmpeg_cmd:
-            return ffmpeg_cmd
-        return ffmpeg_cmd[:-1] + ["-progress", "pipe:2", "-nostats", ffmpeg_cmd[-1]]
-
     def _run_ffmpeg_with_progress(
         self,
         ffmpeg_cmd: list[str],
         playlist_lines: str | list[str],
         step: str = "encoding",
     ) -> tuple[int, str]:
-        """Run an FFmpeg export command, parsing progress events from stderr.
+        """Delegate to the shared helper, mapping percent → (step, percent).
 
-        Returns ``(returncode, captured_stderr)``. Stdout is left attached to
-        the parent process so we don't have to drain it (and risk a deadlock
-        if the buffer fills). Progress percent is computed against the
-        expected output duration; values are clamped to [0, 100] inside
-        :py:meth:`_emit_progress`.
+        Returns ``(returncode, captured_stderr)``.
         """
-        cmd = ["nice", "-n", str(PROCESS_PRIORITY_LOW)] + self._inject_progress_flags(
-            ffmpeg_cmd
-        )
-
         if isinstance(playlist_lines, list):
             stdin_payload = "\n".join(playlist_lines)
         else:
             stdin_payload = playlist_lines
 
-        expected_duration = self._expected_output_duration_seconds()
-
-        self._emit_progress(step, 0.0)
-
-        proc = sp.Popen(
-            cmd,
-            stdin=sp.PIPE,
-            stderr=sp.PIPE,
-            text=True,
-            encoding="ascii",
-            errors="replace",
+        return run_ffmpeg_with_progress(
+            ffmpeg_cmd,
+            expected_duration_seconds=self._expected_output_duration_seconds(),
+            on_progress=lambda percent: self._emit_progress(step, percent),
+            stdin_payload=stdin_payload,
+            use_low_priority=True,
         )
 
-        assert proc.stdin is not None
-        assert proc.stderr is not None
-
-        try:
-            proc.stdin.write(stdin_payload)
-        except (BrokenPipeError, OSError):
-            # FFmpeg may have rejected the input early; still wait for it
-            # to terminate so the returncode is meaningful.
-            pass
-        finally:
-            try:
-                proc.stdin.close()
-            except (BrokenPipeError, OSError):
-                pass
-
-        captured: list[str] = []
-
-        try:
-            for raw_line in proc.stderr:
-                captured.append(raw_line)
-                line = raw_line.strip()
-
-                if not line:
-                    continue
-
-                if line.startswith("out_time_us="):
-                    if expected_duration <= 0:
-                        continue
-                    try:
-                        out_time_us = int(line.split("=", 1)[1])
-                    except (ValueError, IndexError):
-                        continue
-                    if out_time_us < 0:
-                        continue
-                    out_seconds = out_time_us / 1_000_000.0
-                    percent = (out_seconds / expected_duration) * 100.0
-                    self._emit_progress(step, percent)
-                elif line == "progress=end":
-                    self._emit_progress(step, 100.0)
-                    break
-        except Exception:
-            logger.exception("Failed reading FFmpeg progress for %s", self.export_id)
-
-        proc.wait()
-
-        # Drain any remaining stderr so callers can log it on failure.
-        try:
-            remaining = proc.stderr.read()
-            if remaining:
-                captured.append(remaining)
-        except Exception:
-            pass
-
-        return proc.returncode, "".join(captured)
-
     def get_datetime_from_timestamp(self, timestamp: int) -> str:
         # return in iso format using the configured ui.timezone when set,
         # so the auto-generated export name reflects local time rather

frigate/test/http_api/test_debug_replay_api.py

@@ -0,0 +1,123 @@
+"""Tests for /debug_replay API endpoints."""
+
+from unittest.mock import patch
+
+from frigate.models import Event, Recordings, ReviewSegment
+from frigate.test.http_api.base_http_test import AuthTestClient, BaseTestHttp
+
+
+class TestDebugReplayAPI(BaseTestHttp):
+    def setUp(self):
+        super().setUp([Event, Recordings, ReviewSegment])
+        self.app = self.create_app()
+
+    def test_start_returns_202_with_job_id(self):
+        # Stub the factory to skip validation/threading and just record the
+        # name on the manager the way the real factory's mark_starting would.
+        def fake_start(**kwargs):
+            kwargs["replay_manager"].mark_starting(
+                source_camera=kwargs["source_camera"],
+                replay_camera_name="_replay_front",
+                start_ts=kwargs["start_ts"],
+                end_ts=kwargs["end_ts"],
+            )
+            return "job-1234"
+
+        with patch(
+            "frigate.api.debug_replay.start_debug_replay_job",
+            side_effect=fake_start,
+        ):
+            with AuthTestClient(self.app) as client:
+                resp = client.post(
+                    "/debug_replay/start",
+                    json={
+                        "camera": "front",
+                        "start_time": 100,
+                        "end_time": 200,
+                    },
+                )
+
+        self.assertEqual(resp.status_code, 202)
+        body = resp.json()
+        self.assertTrue(body["success"])
+        self.assertEqual(body["job_id"], "job-1234")
+        self.assertEqual(body["replay_camera"], "_replay_front")
+
+    def test_start_returns_400_on_validation_error(self):
+        with patch(
+            "frigate.api.debug_replay.start_debug_replay_job",
+            side_effect=ValueError("Camera 'missing' not found"),
+        ):
+            with AuthTestClient(self.app) as client:
+                resp = client.post(
+                    "/debug_replay/start",
+                    json={
+                        "camera": "missing",
+                        "start_time": 100,
+                        "end_time": 200,
+                    },
+                )
+
+        self.assertEqual(resp.status_code, 400)
+        body = resp.json()
+        self.assertFalse(body["success"])
+        # Message is hard-coded so we don't echo exception text back to clients
+        # (CodeQL: information exposure through an exception).
+        self.assertEqual(body["message"], "Invalid debug replay parameters")
+
+    def test_start_returns_409_when_session_already_active(self):
+        with patch(
+            "frigate.api.debug_replay.start_debug_replay_job",
+            side_effect=RuntimeError("A replay session is already active"),
+        ):
+            with AuthTestClient(self.app) as client:
+                resp = client.post(
+                    "/debug_replay/start",
+                    json={
+                        "camera": "front",
+                        "start_time": 100,
+                        "end_time": 200,
+                    },
+                )
+
+        self.assertEqual(resp.status_code, 409)
+        body = resp.json()
+        self.assertFalse(body["success"])
+
+    def test_status_inactive_when_no_session(self):
+        with AuthTestClient(self.app) as client:
+            resp = client.get("/debug_replay/status")
+
+        self.assertEqual(resp.status_code, 200)
+        body = resp.json()
+        self.assertFalse(body["active"])
+        self.assertIsNone(body["replay_camera"])
+        self.assertIsNone(body["source_camera"])
+        self.assertIsNone(body["start_time"])
+        self.assertIsNone(body["end_time"])
+        self.assertFalse(body["live_ready"])
+        # Make sure deprecated fields are gone
+        self.assertNotIn("state", body)
+        self.assertNotIn("progress_percent", body)
+        self.assertNotIn("error_message", body)
+
+    def test_status_active_after_mark_starting(self):
+        manager = self.app.replay_manager
+        manager.mark_starting(
+            source_camera="front",
+            replay_camera_name="_replay_front",
+            start_ts=100.0,
+            end_ts=200.0,
+        )
+
+        with AuthTestClient(self.app) as client:
+            resp = client.get("/debug_replay/status")
+
+        self.assertEqual(resp.status_code, 200)
+        body = resp.json()
+        self.assertTrue(body["active"])
+        self.assertEqual(body["replay_camera"], "_replay_front")
+        self.assertEqual(body["source_camera"], "front")
+        self.assertEqual(body["start_time"], 100.0)
+        self.assertEqual(body["end_time"], 200.0)
+        self.assertFalse(body["live_ready"])

frigate/test/test_debug_replay.py

@@ -0,0 +1,242 @@
+"""Tests for the simplified DebugReplayManager.
+
+Startup orchestration lives in ``frigate.jobs.debug_replay`` (covered by
+``test_debug_replay_job``). The manager owns only session presence and
+cleanup.
+"""
+
+import unittest
+import unittest.mock
+from unittest.mock import MagicMock, patch
+
+
+class TestDebugReplayManagerSession(unittest.TestCase):
+    def test_inactive_by_default(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+
+        self.assertFalse(manager.active)
+        self.assertIsNone(manager.replay_camera_name)
+        self.assertIsNone(manager.source_camera)
+        self.assertIsNone(manager.clip_path)
+        self.assertIsNone(manager.start_ts)
+        self.assertIsNone(manager.end_ts)
+
+    def test_mark_starting_sets_session_pointers_and_active(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+
+        manager.mark_starting(
+            source_camera="front",
+            replay_camera_name="_replay_front",
+            start_ts=100.0,
+            end_ts=200.0,
+        )
+
+        self.assertTrue(manager.active)
+        self.assertEqual(manager.replay_camera_name, "_replay_front")
+        self.assertEqual(manager.source_camera, "front")
+        self.assertEqual(manager.start_ts, 100.0)
+        self.assertEqual(manager.end_ts, 200.0)
+        self.assertIsNone(manager.clip_path)
+
+    def test_mark_session_ready_sets_clip_path(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        manager.mark_starting("front", "_replay_front", 100.0, 200.0)
+
+        manager.mark_session_ready(clip_path="/tmp/replay/_replay_front.mp4")
+
+        self.assertEqual(manager.clip_path, "/tmp/replay/_replay_front.mp4")
+        self.assertTrue(manager.active)
+
+    def test_clear_session_resets_all_pointers(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        manager.mark_starting("front", "_replay_front", 100.0, 200.0)
+        manager.mark_session_ready("/tmp/replay/clip.mp4")
+
+        manager.clear_session()
+
+        self.assertFalse(manager.active)
+        self.assertIsNone(manager.replay_camera_name)
+        self.assertIsNone(manager.source_camera)
+        self.assertIsNone(manager.clip_path)
+        self.assertIsNone(manager.start_ts)
+        self.assertIsNone(manager.end_ts)
+
+
+class TestDebugReplayManagerStop(unittest.TestCase):
+    def test_stop_when_inactive_is_a_noop(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        frigate_config = MagicMock()
+        frigate_config.cameras = {}
+        publisher = MagicMock()
+
+        # Should not raise; should not publish any events.
+        manager.stop(frigate_config=frigate_config, config_publisher=publisher)
+
+        publisher.publish_update.assert_not_called()
+
+    def test_stop_publishes_remove_when_camera_was_published(self) -> None:
+        from frigate.config.camera.updater import CameraConfigUpdateEnum
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        manager.mark_starting("front", "_replay_front", 100.0, 200.0)
+        manager.mark_session_ready("/tmp/replay/_replay_front.mp4")
+
+        camera_config = MagicMock()
+        frigate_config = MagicMock()
+        frigate_config.cameras = {"_replay_front": camera_config}
+        publisher = MagicMock()
+
+        with (
+            patch.object(manager, "_cleanup_db"),
+            patch.object(manager, "_cleanup_files"),
+            patch("frigate.debug_replay.cancel_debug_replay_job", return_value=False),
+        ):
+            manager.stop(frigate_config=frigate_config, config_publisher=publisher)
+
+        # One publish_update call with a remove topic.
+        self.assertEqual(publisher.publish_update.call_count, 1)
+        topic_arg = publisher.publish_update.call_args.args[0]
+        self.assertEqual(topic_arg.update_type, CameraConfigUpdateEnum.remove)
+        self.assertFalse(manager.active)
+
+    def test_stop_skips_remove_publish_when_camera_not_in_config(self) -> None:
+        """Cancellation during preparing_clip: no camera was published yet."""
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        manager.mark_starting("front", "_replay_front", 100.0, 200.0)
+        # clip_path stays None because we cancelled before camera publish.
+
+        frigate_config = MagicMock()
+        frigate_config.cameras = {}  # _replay_front not present
+        publisher = MagicMock()
+
+        with (
+            patch.object(manager, "_cleanup_db"),
+            patch.object(manager, "_cleanup_files"),
+            patch("frigate.debug_replay.cancel_debug_replay_job", return_value=True),
+        ):
+            manager.stop(frigate_config=frigate_config, config_publisher=publisher)
+
+        publisher.publish_update.assert_not_called()
+        self.assertFalse(manager.active)
+
+    def test_stop_calls_cancel_debug_replay_job(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        manager.mark_starting("front", "_replay_front", 100.0, 200.0)
+
+        frigate_config = MagicMock()
+        frigate_config.cameras = {}
+        publisher = MagicMock()
+
+        with (
+            patch.object(manager, "_cleanup_db"),
+            patch.object(manager, "_cleanup_files"),
+            patch(
+                "frigate.debug_replay.cancel_debug_replay_job",
+                return_value=True,
+            ) as mock_cancel,
+        ):
+            manager.stop(frigate_config=frigate_config, config_publisher=publisher)
+
+        mock_cancel.assert_called_once()
+
+
+class TestDebugReplayManagerPublishCamera(unittest.TestCase):
+    def test_publish_camera_invokes_publisher_with_add_topic(self) -> None:
+        from frigate.config.camera.updater import CameraConfigUpdateEnum
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+
+        source_config = MagicMock()
+        new_camera_config = MagicMock()
+        frigate_config = MagicMock()
+        frigate_config.cameras = {"front": source_config}
+        publisher = MagicMock()
+
+        with (
+            patch.object(
+                manager,
+                "_build_camera_config_dict",
+                return_value={"enabled": True},
+            ),
+            patch("frigate.debug_replay.find_config_file", return_value="/cfg.yml"),
+            patch("frigate.debug_replay.YAML") as yaml_cls,
+            patch("frigate.debug_replay.FrigateConfig.parse_object") as parse_object,
+            patch("builtins.open", unittest.mock.mock_open(read_data="cameras:\n")),
+        ):
+            yaml_instance = yaml_cls.return_value
+            yaml_instance.load.return_value = {"cameras": {}}
+            parsed = MagicMock()
+            parsed.cameras = {"_replay_front": new_camera_config}
+            parse_object.return_value = parsed
+
+            manager.publish_camera(
+                source_camera="front",
+                replay_name="_replay_front",
+                clip_path="/tmp/clip.mp4",
+                frigate_config=frigate_config,
+                config_publisher=publisher,
+            )
+
+        # Camera registered into the live config dict
+        self.assertIn("_replay_front", frigate_config.cameras)
+        # Publisher invoked with an add topic
+        self.assertEqual(publisher.publish_update.call_count, 1)
+        topic_arg = publisher.publish_update.call_args.args[0]
+        self.assertEqual(topic_arg.update_type, CameraConfigUpdateEnum.add)
+
+    def test_publish_camera_wraps_parse_failure_in_runtime_error(self) -> None:
+        from frigate.debug_replay import DebugReplayManager
+
+        manager = DebugReplayManager()
+        frigate_config = MagicMock()
+        frigate_config.cameras = {"front": MagicMock()}
+        publisher = MagicMock()
+
+        with (
+            patch.object(
+                manager,
+                "_build_camera_config_dict",
+                return_value={"enabled": True},
+            ),
+            patch("frigate.debug_replay.find_config_file", return_value="/cfg.yml"),
+            patch("frigate.debug_replay.YAML") as yaml_cls,
+            patch(
+                "frigate.debug_replay.FrigateConfig.parse_object",
+                side_effect=ValueError("zone foo has invalid coordinates"),
+            ),
+            patch("builtins.open", unittest.mock.mock_open(read_data="cameras:\n")),
+        ):
+            yaml_cls.return_value.load.return_value = {"cameras": {}}
+
+            with self.assertRaises(RuntimeError) as ctx:
+                manager.publish_camera(
+                    source_camera="front",
+                    replay_name="_replay_front",
+                    clip_path="/tmp/clip.mp4",
+                    frigate_config=frigate_config,
+                    config_publisher=publisher,
+                )
+
+        self.assertIn("replay camera config", str(ctx.exception))
+        self.assertIn("invalid coordinates", str(ctx.exception))
+        publisher.publish_update.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()

frigate/test/test_debug_replay_job.py

@@ -0,0 +1,460 @@
+"""Tests for the debug replay job runner and factory."""
+
+import threading
+import time
+import unittest
+import unittest.mock
+from unittest.mock import MagicMock, patch
+
+from frigate.debug_replay import DebugReplayManager
+from frigate.jobs.debug_replay import (
+    DebugReplayJob,
+    cancel_debug_replay_job,
+    get_active_runner,
+    start_debug_replay_job,
+)
+from frigate.jobs.export import JobStatePublisher
+from frigate.jobs.manager import _completed_jobs, _current_jobs
+from frigate.types import JobStatusTypesEnum
+
+
+def _reset_job_manager() -> None:
+    """Clear the global job manager state between tests."""
+    _current_jobs.clear()
+    _completed_jobs.clear()
+
+
+def _patch_publisher(test_case: unittest.TestCase) -> None:
+    """Replace JobStatePublisher.publish with a no-op to avoid hanging on IPC."""
+    publisher_patch = patch.object(
+        JobStatePublisher, "publish", lambda self, payload: None
+    )
+    publisher_patch.start()
+    test_case.addCleanup(publisher_patch.stop)
+
+
+class TestDebugReplayJob(unittest.TestCase):
+    def test_default_fields(self) -> None:
+        job = DebugReplayJob()
+
+        self.assertEqual(job.job_type, "debug_replay")
+        self.assertEqual(job.status, JobStatusTypesEnum.queued)
+        self.assertIsNone(job.current_step)
+        self.assertEqual(job.progress_percent, 0.0)
+
+    def test_to_dict_whitelist(self) -> None:
+        job = DebugReplayJob(
+            source_camera="front",
+            replay_camera_name="_replay_front",
+            start_ts=100.0,
+            end_ts=200.0,
+        )
+        job.current_step = "preparing_clip"
+        job.progress_percent = 42.5
+
+        payload = job.to_dict()
+
+        # Top-level matches the standard Job<TResults> shape.
+        for key in (
+            "id",
+            "job_type",
+            "status",
+            "start_time",
+            "end_time",
+            "error_message",
+            "results",
+        ):
+            self.assertIn(key, payload, f"missing top-level field: {key}")
+
+        results = payload["results"]
+        self.assertEqual(results["source_camera"], "front")
+        self.assertEqual(results["replay_camera_name"], "_replay_front")
+        self.assertEqual(results["current_step"], "preparing_clip")
+        self.assertEqual(results["progress_percent"], 42.5)
+        self.assertEqual(results["start_ts"], 100.0)
+        self.assertEqual(results["end_ts"], 200.0)
+
+
+class TestStartDebugReplayJob(unittest.TestCase):
+    def setUp(self) -> None:
+        _reset_job_manager()
+        _patch_publisher(self)
+        self.manager = DebugReplayManager()
+        self.frigate_config = MagicMock()
+        self.frigate_config.cameras = {"front": MagicMock()}
+        self.frigate_config.ffmpeg.ffmpeg_path = "/bin/true"
+        self.publisher = MagicMock()
+
+        self.recordings_qs = MagicMock()
+        self.recordings_qs.count.return_value = 1
+        self.recordings_qs.__iter__.return_value = iter([MagicMock(path="/tmp/r1.mp4")])
+
+    def tearDown(self) -> None:
+        runner = get_active_runner()
+        if runner is not None:
+            runner.cancel()
+            runner.join(timeout=2.0)
+        _reset_job_manager()
+
+    def test_rejects_unknown_camera(self) -> None:
+        with self.assertRaises(ValueError):
+            start_debug_replay_job(
+                source_camera="missing",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+    def test_rejects_invalid_time_range(self) -> None:
+        with self.assertRaises(ValueError):
+            start_debug_replay_job(
+                source_camera="front",
+                start_ts=200.0,
+                end_ts=100.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+    def test_rejects_when_no_recordings(self) -> None:
+        empty_qs = MagicMock()
+        empty_qs.count.return_value = 0
+        with patch("frigate.jobs.debug_replay.query_recordings", return_value=empty_qs):
+            with self.assertRaises(ValueError):
+                start_debug_replay_job(
+                    source_camera="front",
+                    start_ts=100.0,
+                    end_ts=200.0,
+                    frigate_config=self.frigate_config,
+                    config_publisher=self.publisher,
+                    replay_manager=self.manager,
+                )
+
+    def test_returns_job_id_and_marks_session_starting(self) -> None:
+        block = threading.Event()
+
+        def slow_helper(cmd, **kwargs):
+            block.wait(timeout=5)
+            return 0, ""
+
+        with (
+            patch(
+                "frigate.jobs.debug_replay.query_recordings",
+                return_value=self.recordings_qs,
+            ),
+            patch(
+                "frigate.jobs.debug_replay.run_ffmpeg_with_progress",
+                side_effect=slow_helper,
+            ),
+            patch.object(self.manager, "publish_camera"),
+            patch("os.path.exists", return_value=True),
+            patch("os.makedirs"),
+            patch("builtins.open", unittest.mock.mock_open()),
+        ):
+            job_id = start_debug_replay_job(
+                source_camera="front",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+            self.assertIsInstance(job_id, str)
+            self.assertTrue(self.manager.active)
+            self.assertEqual(self.manager.replay_camera_name, "_replay_front")
+            self.assertEqual(self.manager.source_camera, "front")
+
+            block.set()
+
+    def test_rejects_concurrent_calls(self) -> None:
+        block = threading.Event()
+
+        def slow_helper(cmd, **kwargs):
+            block.wait(timeout=5)
+            return 0, ""
+
+        with (
+            patch(
+                "frigate.jobs.debug_replay.query_recordings",
+                return_value=self.recordings_qs,
+            ),
+            patch(
+                "frigate.jobs.debug_replay.run_ffmpeg_with_progress",
+                side_effect=slow_helper,
+            ),
+            patch.object(self.manager, "publish_camera"),
+            patch("os.path.exists", return_value=True),
+            patch("os.makedirs"),
+            patch("builtins.open", unittest.mock.mock_open()),
+        ):
+            start_debug_replay_job(
+                source_camera="front",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+            with self.assertRaises(RuntimeError):
+                start_debug_replay_job(
+                    source_camera="front",
+                    start_ts=100.0,
+                    end_ts=200.0,
+                    frigate_config=self.frigate_config,
+                    config_publisher=self.publisher,
+                    replay_manager=self.manager,
+                )
+
+            block.set()
+
+
+class TestRunnerHappyPath(unittest.TestCase):
+    def setUp(self) -> None:
+        _reset_job_manager()
+        _patch_publisher(self)
+        self.manager = DebugReplayManager()
+        self.frigate_config = MagicMock()
+        self.frigate_config.cameras = {"front": MagicMock()}
+        self.frigate_config.ffmpeg.ffmpeg_path = "/bin/true"
+        self.publisher = MagicMock()
+
+        self.recordings_qs = MagicMock()
+        self.recordings_qs.count.return_value = 1
+        self.recordings_qs.__iter__.return_value = iter([MagicMock(path="/tmp/r1.mp4")])
+
+    def tearDown(self) -> None:
+        runner = get_active_runner()
+        if runner is not None:
+            runner.cancel()
+            runner.join(timeout=2.0)
+        _reset_job_manager()
+
+    def _wait_for(self, predicate, timeout: float = 5.0) -> bool:
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            if predicate():
+                return True
+            time.sleep(0.02)
+        return False
+
+    def test_progress_callback_updates_job_percent(self) -> None:
+        captured: list[float] = []
+
+        def fake_helper(cmd, *, on_progress=None, **kwargs):
+            on_progress(0.0)
+            on_progress(50.0)
+            on_progress(100.0)
+            return 0, ""
+
+        with (
+            patch(
+                "frigate.jobs.debug_replay.query_recordings",
+                return_value=self.recordings_qs,
+            ),
+            patch(
+                "frigate.jobs.debug_replay.run_ffmpeg_with_progress",
+                side_effect=fake_helper,
+            ),
+            patch.object(
+                self.manager,
+                "publish_camera",
+                side_effect=lambda *a, **kw: captured.append("published"),
+            ),
+            patch("os.path.exists", return_value=True),
+            patch("os.makedirs"),
+            patch("builtins.open", unittest.mock.mock_open()),
+        ):
+            start_debug_replay_job(
+                source_camera="front",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+            self.assertTrue(
+                self._wait_for(lambda: get_active_runner() is None),
+                "runner did not finish",
+            )
+
+        from frigate.jobs.manager import get_current_job
+
+        job = get_current_job("debug_replay")
+        self.assertIsNotNone(job)
+        self.assertEqual(job.status, JobStatusTypesEnum.success)
+        self.assertEqual(job.progress_percent, 100.0)
+        self.assertEqual(captured, ["published"])
+        # Manager should have been told the session is ready with the clip path.
+        self.assertIsNotNone(self.manager.clip_path)
+
+
+class TestRunnerFailurePath(unittest.TestCase):
+    def setUp(self) -> None:
+        _reset_job_manager()
+        _patch_publisher(self)
+        self.manager = DebugReplayManager()
+        self.frigate_config = MagicMock()
+        self.frigate_config.cameras = {"front": MagicMock()}
+        self.frigate_config.ffmpeg.ffmpeg_path = "/bin/true"
+        self.publisher = MagicMock()
+        self.recordings_qs = MagicMock()
+        self.recordings_qs.count.return_value = 1
+        self.recordings_qs.__iter__.return_value = iter([MagicMock(path="/tmp/r1.mp4")])
+
+    def tearDown(self) -> None:
+        runner = get_active_runner()
+        if runner is not None:
+            runner.cancel()
+            runner.join(timeout=2.0)
+        _reset_job_manager()
+
+    def _wait_for(self, predicate, timeout: float = 5.0) -> bool:
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            if predicate():
+                return True
+            time.sleep(0.02)
+        return False
+
+    def test_ffmpeg_failure_marks_job_failed_and_clears_session(self) -> None:
+        def failing_helper(cmd, **kwargs):
+            return 1, "ffmpeg exploded"
+
+        with (
+            patch(
+                "frigate.jobs.debug_replay.query_recordings",
+                return_value=self.recordings_qs,
+            ),
+            patch(
+                "frigate.jobs.debug_replay.run_ffmpeg_with_progress",
+                side_effect=failing_helper,
+            ),
+            patch("os.path.exists", return_value=True),
+            patch("os.makedirs"),
+            patch("os.remove"),
+            patch("builtins.open", unittest.mock.mock_open()),
+        ):
+            start_debug_replay_job(
+                source_camera="front",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+            self.assertTrue(
+                self._wait_for(lambda: get_active_runner() is None),
+                "runner did not finish",
+            )
+
+        from frigate.jobs.manager import get_current_job
+
+        job = get_current_job("debug_replay")
+        self.assertIsNotNone(job)
+        self.assertEqual(job.status, JobStatusTypesEnum.failed)
+        self.assertIsNotNone(job.error_message)
+        self.assertIn("ffmpeg", job.error_message.lower())
+        # Session cleared so a new /start is allowed
+        self.assertFalse(self.manager.active)
+
+
+class TestRunnerCancellation(unittest.TestCase):
+    def setUp(self) -> None:
+        _reset_job_manager()
+        _patch_publisher(self)
+        self.manager = DebugReplayManager()
+        self.frigate_config = MagicMock()
+        self.frigate_config.cameras = {"front": MagicMock()}
+        self.frigate_config.ffmpeg.ffmpeg_path = "/bin/true"
+        self.publisher = MagicMock()
+        self.recordings_qs = MagicMock()
+        self.recordings_qs.count.return_value = 1
+        self.recordings_qs.__iter__.return_value = iter([MagicMock(path="/tmp/r1.mp4")])
+
+    def tearDown(self) -> None:
+        runner = get_active_runner()
+        if runner is not None:
+            runner.cancel()
+            runner.join(timeout=2.0)
+        _reset_job_manager()
+
+    def _wait_for(self, predicate, timeout: float = 5.0) -> bool:
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            if predicate():
+                return True
+            time.sleep(0.02)
+        return False
+
+    def test_cancel_terminates_ffmpeg_and_marks_cancelled(self) -> None:
+        terminated = threading.Event()
+        fake_proc = MagicMock()
+        fake_proc.terminate = MagicMock(side_effect=lambda: terminated.set())
+
+        def fake_helper(cmd, *, process_started=None, **kwargs):
+            if process_started is not None:
+                process_started(fake_proc)
+            terminated.wait(timeout=5)
+            return -15, "killed"
+
+        with (
+            patch(
+                "frigate.jobs.debug_replay.query_recordings",
+                return_value=self.recordings_qs,
+            ),
+            patch(
+                "frigate.jobs.debug_replay.run_ffmpeg_with_progress",
+                side_effect=fake_helper,
+            ),
+            patch("os.path.exists", return_value=True),
+            patch("os.makedirs"),
+            patch("os.remove"),
+            patch("builtins.open", unittest.mock.mock_open()),
+        ):
+            start_debug_replay_job(
+                source_camera="front",
+                start_ts=100.0,
+                end_ts=200.0,
+                frigate_config=self.frigate_config,
+                config_publisher=self.publisher,
+                replay_manager=self.manager,
+            )
+
+            # Wait for the runner to register the active process.
+            self.assertTrue(
+                self._wait_for(
+                    lambda: (
+                        get_active_runner() is not None
+                        and get_active_runner()._active_process is fake_proc
+                    )
+                )
+            )
+
+            cancelled = cancel_debug_replay_job()
+            self.assertTrue(cancelled)
+            self.assertTrue(fake_proc.terminate.called)
+
+            self.assertTrue(
+                self._wait_for(lambda: get_active_runner() is None),
+                "runner did not finish",
+            )
+
+        from frigate.jobs.manager import get_current_job
+
+        job = get_current_job("debug_replay")
+        self.assertEqual(job.status, JobStatusTypesEnum.cancelled)
+        # Runner must not clear the manager session on cancellation —
+        # that belongs to the caller of cancel_debug_replay_job (stop()).
+        # If the runner cleared it, stop() would log "no active session"
+        # and skip its cleanup_db / cleanup_files calls.
+        self.assertTrue(self.manager.active)
+
+
+if __name__ == "__main__":
+    unittest.main()

frigate/test/test_export_progress.py

@@ -14,6 +14,7 @@ from frigate.jobs.export import (
 )
 from frigate.record.export import PlaybackSourceEnum, RecordingExporter
 from frigate.types import JobStatusTypesEnum
+from frigate.util.ffmpeg import inject_progress_flags
 
 
 def _make_exporter(
@@ -118,10 +119,9 @@ class TestExpectedOutputDuration(unittest.TestCase):
 
 class TestProgressFlagInjection(unittest.TestCase):
     def test_inserts_before_output_path(self) -> None:
-        exporter = _make_exporter()
         cmd = ["ffmpeg", "-i", "input.m3u8", "-c", "copy", "/tmp/output.mp4"]
 
-        result = exporter._inject_progress_flags(cmd)
+        result = inject_progress_flags(cmd)
 
         assert result == [
             "ffmpeg",
@@ -136,8 +136,7 @@ class TestProgressFlagInjection(unittest.TestCase):
         ]
 
     def test_handles_empty_cmd(self) -> None:
-        exporter = _make_exporter()
-        assert exporter._inject_progress_flags([]) == []
+        assert inject_progress_flags([]) == []
 
 
 class TestFfmpegProgressParsing(unittest.TestCase):
@@ -167,7 +166,7 @@ class TestFfmpegProgressParsing(unittest.TestCase):
         fake_proc.returncode = 0
         fake_proc.wait = MagicMock(return_value=0)
 
-        with patch("frigate.record.export.sp.Popen", return_value=fake_proc):
+        with patch("frigate.util.ffmpeg.sp.Popen", return_value=fake_proc):
             returncode, _stderr = exporter._run_ffmpeg_with_progress(
                 ["ffmpeg", "-i", "x.m3u8", "/tmp/out.mp4"], "playlist", step="encoding"
             )

frigate/test/test_ffmpeg_progress.py

@@ -0,0 +1,111 @@
+"""Tests for the shared ffmpeg progress helper."""
+
+import unittest
+from unittest.mock import MagicMock, patch
+
+from frigate.util.ffmpeg import inject_progress_flags, run_ffmpeg_with_progress
+
+
+class TestInjectProgressFlags(unittest.TestCase):
+    def test_inserts_flags_before_output_path(self):
+        cmd = ["ffmpeg", "-i", "in.mp4", "-c", "copy", "out.mp4"]
+        result = inject_progress_flags(cmd)
+        self.assertEqual(
+            result,
+            [
+                "ffmpeg",
+                "-i",
+                "in.mp4",
+                "-c",
+                "copy",
+                "-progress",
+                "pipe:2",
+                "-nostats",
+                "out.mp4",
+            ],
+        )
+
+    def test_empty_cmd_returns_empty(self):
+        self.assertEqual(inject_progress_flags([]), [])
+
+
+class TestRunFfmpegWithProgress(unittest.TestCase):
+    def _make_fake_proc(self, stderr_lines, returncode=0):
+        proc = MagicMock()
+        proc.stderr = iter(stderr_lines)
+        proc.stdin = MagicMock()
+        proc.returncode = returncode
+        proc.wait = MagicMock()
+        return proc
+
+    def test_emits_percent_from_out_time_us_lines(self):
+        captured: list[float] = []
+
+        def on_progress(percent: float) -> None:
+            captured.append(percent)
+
+        stderr_lines = [
+            "out_time_us=1000000\n",
+            "out_time_us=5000000\n",
+            "progress=end\n",
+        ]
+        proc = self._make_fake_proc(stderr_lines)
+        proc.stderr = MagicMock()
+        proc.stderr.__iter__ = lambda self: iter(stderr_lines)
+        proc.stderr.read = MagicMock(return_value="")
+
+        with patch("subprocess.Popen", return_value=proc):
+            returncode, _stderr = run_ffmpeg_with_progress(
+                ["ffmpeg", "-i", "in", "out"],
+                expected_duration_seconds=10.0,
+                on_progress=on_progress,
+                use_low_priority=False,
+            )
+
+        self.assertEqual(returncode, 0)
+        self.assertEqual(len(captured), 4)  # initial 0.0 + two parsed + final 100.0
+        self.assertAlmostEqual(captured[0], 0.0)
+        self.assertAlmostEqual(captured[1], 10.0)
+        self.assertAlmostEqual(captured[2], 50.0)
+        self.assertAlmostEqual(captured[3], 100.0)
+
+    def test_passes_started_process_to_callback(self):
+        proc = self._make_fake_proc([])
+        proc.stderr = MagicMock()
+        proc.stderr.__iter__ = lambda self: iter([])
+        proc.stderr.read = MagicMock(return_value="")
+
+        seen: list = []
+
+        with patch("subprocess.Popen", return_value=proc):
+            run_ffmpeg_with_progress(
+                ["ffmpeg", "out"],
+                expected_duration_seconds=1.0,
+                process_started=lambda p: seen.append(p),
+                use_low_priority=False,
+            )
+
+        self.assertEqual(seen, [proc])
+
+    def test_clamps_percent_to_0_100(self):
+        captured: list[float] = []
+
+        def on_progress(percent: float) -> None:
+            captured.append(percent)
+
+        stderr_lines = ["out_time_us=999999999999\n"]
+        proc = self._make_fake_proc(stderr_lines)
+        proc.stderr = MagicMock()
+        proc.stderr.__iter__ = lambda self: iter(stderr_lines)
+        proc.stderr.read = MagicMock(return_value="")
+
+        with patch("subprocess.Popen", return_value=proc):
+            run_ffmpeg_with_progress(
+                ["ffmpeg", "out"],
+                expected_duration_seconds=10.0,
+                on_progress=on_progress,
+                use_low_priority=False,
+            )
+
+        # initial 0.0 then a clamped reading
+        self.assertEqual(captured[-1], 100.0)

frigate/util/ffmpeg.py

@@ -2,8 +2,9 @@
 
 import logging
 import subprocess as sp
-from typing import Any
+from typing import Any, Callable, Optional
 
+from frigate.const import PROCESS_PRIORITY_LOW
 from frigate.log import LogPipe
 
 
@@ -46,3 +47,124 @@ def start_or_restart_ffmpeg(
             start_new_session=True,
         )
     return process
+
+
+logger = logging.getLogger(__name__)
+
+
+def inject_progress_flags(cmd: list[str]) -> list[str]:
+    """Insert `-progress pipe:2 -nostats` immediately before the output path.
+
+    `-progress pipe:2` writes structured key=value lines to stderr;
+    `-nostats` suppresses the noisy default stats output. The output path
+    is conventionally the last token in an FFmpeg argv.
+    """
+    if not cmd:
+        return cmd
+    return cmd[:-1] + ["-progress", "pipe:2", "-nostats", cmd[-1]]
+
+
+def run_ffmpeg_with_progress(
+    cmd: list[str],
+    *,
+    expected_duration_seconds: float,
+    on_progress: Optional[Callable[[float], None]] = None,
+    stdin_payload: Optional[str] = None,
+    process_started: Optional[Callable[[sp.Popen], None]] = None,
+    use_low_priority: bool = True,
+) -> tuple[int, str]:
+    """Run an ffmpeg command, streaming progress via `-progress pipe:2`.
+
+    Args:
+        cmd: ffmpeg argv. Output path must be the last token.
+        expected_duration_seconds: Duration of the expected output clip in
+            seconds. Used to convert ffmpeg's `out_time_us` into a percent.
+        on_progress: Optional callback invoked with a percent in [0, 100].
+            Called once with 0.0 at start, again on each `out_time_us=`
+            stderr line, and once with 100.0 on `progress=end`.
+        stdin_payload: Optional string written to ffmpeg stdin (used by
+            export for concat playlists).
+        process_started: Optional callback invoked with the live `Popen`
+            once spawned — lets callers store the ref for cancellation.
+        use_low_priority: When True, prepend `nice -n PROCESS_PRIORITY_LOW`
+            so concat doesn't starve detection.
+
+    Returns:
+        Tuple of `(returncode, captured_stderr)`. Stdout is left attached
+        to the parent process to avoid buffer-full deadlocks.
+    """
+    full_cmd = inject_progress_flags(cmd)
+    if use_low_priority:
+        full_cmd = ["nice", "-n", str(PROCESS_PRIORITY_LOW)] + full_cmd
+
+    def emit(percent: float) -> None:
+        if on_progress is None:
+            return
+        try:
+            on_progress(max(0.0, min(100.0, percent)))
+        except Exception:
+            logger.exception("FFmpeg progress callback failed")
+
+    emit(0.0)
+
+    proc = sp.Popen(
+        full_cmd,
+        stdin=sp.PIPE if stdin_payload is not None else None,
+        stderr=sp.PIPE,
+        text=True,
+        encoding="ascii",
+        errors="replace",
+    )
+    if process_started is not None:
+        try:
+            process_started(proc)
+        except Exception:
+            logger.exception("FFmpeg process_started callback failed")
+
+    if stdin_payload is not None and proc.stdin is not None:
+        try:
+            proc.stdin.write(stdin_payload)
+        except (BrokenPipeError, OSError):
+            pass
+        finally:
+            try:
+                proc.stdin.close()
+            except (BrokenPipeError, OSError):
+                pass
+
+    captured: list[str] = []
+    if proc.stderr is not None:
+        try:
+            for raw_line in proc.stderr:
+                captured.append(raw_line)
+                line = raw_line.strip()
+                if not line:
+                    continue
+                if line.startswith("out_time_us="):
+                    if expected_duration_seconds <= 0:
+                        continue
+                    try:
+                        out_time_us = int(line.split("=", 1)[1])
+                    except (ValueError, IndexError):
+                        continue
+                    if out_time_us < 0:
+                        continue
+                    out_seconds = out_time_us / 1_000_000.0
+                    emit((out_seconds / expected_duration_seconds) * 100.0)
+                elif line == "progress=end":
+                    emit(100.0)
+                    break
+        except Exception:
+            logger.exception("Failed reading FFmpeg progress stream")
+
+    proc.wait()
+
+    if proc.stderr is not None:
+        try:
+            remaining = proc.stderr.read()
+            if remaining:
+                captured.append(remaining)
+        except Exception:
+            pass
+
+    return proc.returncode or 0, "".join(captured)

web/e2e/specs/replay.spec.ts

@@ -31,7 +31,7 @@ test.describe("Replay — no active session @medium", () => {
     await expect(
       frigateApp.page.getByRole("heading", {
         level: 2,
-        name: /No Active Replay Session/i,
+        name: /No Active Debug Replay Session/i,
       }),
     ).toBeVisible({ timeout: 10_000 });
     const goButton = frigateApp.page.getByRole("button", {
@@ -48,7 +48,7 @@ test.describe("Replay — no active session @medium", () => {
     await expect(
       frigateApp.page.getByRole("heading", {
         level: 2,
-        name: /No Active Replay Session/i,
+        name: /No Active Debug Replay Session/i,
       }),
     ).toBeVisible({ timeout: 10_000 });
     await frigateApp.page
@@ -297,7 +297,7 @@ test.describe("Replay — mobile @medium @mobile", () => {
     await expect(
       frigateApp.page.getByRole("heading", {
         level: 2,
-        name: /No Active Replay Session/i,
+        name: /No Active Debug Replay Session/i,
       }),
     ).toBeVisible({ timeout: 10_000 });
   });

web/public/locales/en/views/replay.json

@@ -19,26 +19,31 @@
     "startLabel": "Start",
     "endLabel": "End",
     "toast": {
-      "success": "Debug replay started successfully",
       "error": "Failed to start debug replay: {{error}}",
       "alreadyActive": "A replay session is already active",
-      "stopped": "Debug replay stopped",
       "stopError": "Failed to stop debug replay: {{error}}",
       "goToReplay": "Go to Replay"
     }
   },
   "page": {
-    "noSession": "No Active Replay Session",
-    "noSessionDesc": "Start a debug replay from the History view by clicking the Debug Replay button in the toolbar.",
+    "noSession": "No Active Debug Replay Session",
+    "noSessionDesc": "Start a Debug Replay from History view by clicking the Actions button in the toolbar and choosing Debug Replay.",
     "goToRecordings": "Go to History",
+    "preparingClip": "Preparing clip…",
+    "preparingClipDesc": "Frigate is stitching together recordings for the selected time range. This can take a minute for longer ranges.",
+    "startingCamera": "Starting Debug Replay…",
+    "startError": {
+      "title": "Failed to start Debug Replay",
+      "back": "Back to History"
+    },
     "sourceCamera": "Source Camera",
     "replayCamera": "Replay Camera",
-    "initializingReplay": "Initializing replay...",
-    "stoppingReplay": "Stopping replay...",
+    "initializingReplay": "Initializing Debug Replay...",
+    "stoppingReplay": "Stopping Debug Replay...",
     "stopReplay": "Stop Replay",
     "confirmStop": {
       "title": "Stop Debug Replay?",
-      "description": "This will stop the replay session and clean up all temporary data. Are you sure?",
+      "description": "This will stop the session and clean up all temporary data. Are you sure?",
       "confirm": "Stop Replay",
       "cancel": "Cancel"
     },
@@ -49,6 +54,6 @@
     "activeTracking": "Active tracking",
     "noActiveTracking": "No active tracking",
     "configuration": "Configuration",
-    "configurationDesc": "Fine tune motion detection and object tracking settings for the debug replay camera. No changes are saved to your Frigate configuration file."
+    "configurationDesc": "Fine tune motion detection and object tracking settings for the Debug Replay camera. No changes are saved to your Frigate configuration file."
   }
 }

web/src/components/menu/SearchResultActions.tsx

@@ -90,10 +90,6 @@ export default function SearchResultActions({
   const handleDebugReplay = useCallback(
     (event: SearchResult) => {
       setIsStarting(true);
-      const toastId = toast.loading(
-        t("dialog.starting", { ns: "views/replay" }),
-        { position: "top-center" },
-      );
 
       axios
         .post("debug_replay/start", {
@@ -102,11 +98,7 @@ export default function SearchResultActions({
           end_time: event.end_time,
         })
         .then((response) => {
-          if (response.status === 200) {
-            toast.success(t("dialog.toast.success", { ns: "views/replay" }), {
-              id: toastId,
-              position: "top-center",
-            });
+          if (response.status === 202 || response.status === 200) {
             navigate("/replay");
           }
         })
@@ -120,7 +112,6 @@ export default function SearchResultActions({
             toast.error(
               t("dialog.toast.alreadyActive", { ns: "views/replay" }),
               {
-                id: toastId,
                 position: "top-center",
                 closeButton: true,
                 dismissible: false,
@@ -135,7 +126,6 @@ export default function SearchResultActions({
             );
           } else {
             toast.error(t("dialog.toast.error", { error: errorMessage }), {
-              id: toastId,
               position: "top-center",
             });
           }

web/src/components/overlay/DebugReplayDialog.tsx

@@ -209,10 +209,7 @@ export default function DebugReplayDialog({
         end_time: range.before,
       })
       .then((response) => {
-        if (response.status === 200) {
-          toast.success(t("dialog.toast.success"), {
-            position: "top-center",
-          });
+        if (response.status === 202 || response.status === 200) {
           setMode("none");
           setRange(undefined);
           navigate("/replay");

web/src/components/overlay/MobileReviewSettingsDrawer.tsx

@@ -262,10 +262,7 @@ export default function MobileReviewSettingsDrawer({
         end_time: debugReplayRange.before,
       });
 
-      if (response.status === 200) {
-        toast.success(t("dialog.toast.success", { ns: "views/replay" }), {
-          position: "top-center",
-        });
+      if (response.status === 202 || response.status === 200) {
         setDebugReplayMode("none");
         setDebugReplayRange(undefined);
         setDrawerMode("none");

web/src/components/timeline/EventMenu.tsx

@@ -53,10 +53,6 @@ export default function EventMenu({
   const handleDebugReplay = useCallback(
     (event: Event) => {
       setIsStarting(true);
-      const toastId = toast.loading(
-        t("dialog.starting", { ns: "views/replay" }),
-        { position: "top-center" },
-      );
 
       axios
         .post("debug_replay/start", {
@@ -65,11 +61,7 @@ export default function EventMenu({
           end_time: event.end_time,
         })
         .then((response) => {
-          if (response.status === 200) {
-            toast.success(t("dialog.toast.success", { ns: "views/replay" }), {
-              id: toastId,
-              position: "top-center",
-            });
+          if (response.status === 202 || response.status === 200) {
             navigate("/replay");
           }
         })
@@ -83,7 +75,6 @@ export default function EventMenu({
             toast.error(
               t("dialog.toast.alreadyActive", { ns: "views/replay" }),
               {
-                id: toastId,
                 position: "top-center",
                 closeButton: true,
                 dismissible: false,
@@ -98,7 +89,6 @@ export default function EventMenu({
             );
           } else {
             toast.error(t("dialog.toast.error", { error: errorMessage }), {
-              id: toastId,
               position: "top-center",
             });
           }

web/src/pages/Replay.tsx

@@ -42,7 +42,9 @@ import { CameraConfig, FrigateConfig } from "@/types/frigateConfig";
 import { getIconForLabel } from "@/utils/iconUtil";
 import { getTranslatedLabel } from "@/utils/i18n";
 import { Card } from "@/components/ui/card";
+import { Progress } from "@/components/ui/progress";
 import { ObjectType } from "@/types/ws";
+import { useJobStatus } from "@/api/ws";
 import WsMessageFeed from "@/components/ws/WsMessageFeed";
 import { ConfigSectionTemplate } from "@/components/config-form/sections/ConfigSectionTemplate";
 
@@ -53,6 +55,7 @@ import { isDesktop, isMobile } from "react-device-detect";
 import Logo from "@/components/Logo";
 import { Separator } from "@/components/ui/separator";
 import { useDocDomain } from "@/hooks/use-doc-domain";
+import { useConfigSchema } from "@/hooks/use-config-schema";
 import DebugDrawingLayer from "@/components/overlay/DebugDrawingLayer";
 import { IoMdArrowRoundBack } from "react-icons/io";
 
@@ -65,6 +68,15 @@ type DebugReplayStatus = {
   live_ready: boolean;
 };
 
+type DebugReplayJobResults = {
+  current_step: "preparing_clip" | "starting_camera" | null;
+  progress_percent: number | null;
+  source_camera: string | null;
+  replay_camera_name: string | null;
+  start_ts: number | null;
+  end_ts: number | null;
+};
+
 type DebugOptions = {
   bbox: boolean;
   timestamp: boolean;
@@ -105,8 +117,6 @@ const DEBUG_OPTION_I18N_KEY: Record<keyof DebugOptions, string> = {
   paths: "paths",
 };
 
-const REPLAY_INIT_SKELETON_TIMEOUT_MS = 8000;
-
 export default function Replay() {
   const { t } = useTranslation(["views/replay", "views/settings", "common"]);
   const navigate = useNavigate();
@@ -119,6 +129,9 @@ export default function Replay() {
   } = useSWR<DebugReplayStatus>("debug_replay/status", {
     refreshInterval: 1000,
   });
+  const { payload: replayJob } =
+    useJobStatus<DebugReplayJobResults>("debug_replay");
+  const configSchema = useConfigSchema();
   const [isInitializing, setIsInitializing] = useState(true);
 
   // Refresh status immediately on mount to avoid showing "no session" briefly
@@ -130,12 +143,6 @@ export default function Replay() {
     initializeStatus();
   }, [refreshStatus]);
 
-  useEffect(() => {
-    if (status?.live_ready) {
-      setShowReplayInitSkeleton(false);
-    }
-  }, [status?.live_ready]);
-
   const [options, setOptions] = useState<DebugOptions>(DEFAULT_OPTIONS);
   const [isStopping, setIsStopping] = useState(false);
   const [configDialogOpen, setConfigDialogOpen] = useState(false);
@@ -160,11 +167,7 @@ export default function Replay() {
     axios
       .post("debug_replay/stop")
       .then(() => {
-        toast.success(t("dialog.toast.stopped"), {
-          position: "top-center",
-        });
         refreshStatus();
-        navigate("/review");
       })
       .catch((error) => {
         const errorMessage =
@@ -178,7 +181,7 @@ export default function Replay() {
       .finally(() => {
         setIsStopping(false);
       });
-  }, [navigate, refreshStatus, t]);
+  }, [refreshStatus, t]);
 
   // Camera activity for the replay camera
   const { data: config } = useSWR<FrigateConfig>("config", {
@@ -191,35 +194,10 @@ export default function Replay() {
 
   const { objects } = useCameraActivity(replayCameraConfig);
 
-  const [showReplayInitSkeleton, setShowReplayInitSkeleton] = useState(false);
-
   // debug draw
   const containerRef = useRef<HTMLDivElement>(null);
   const [debugDraw, setDebugDraw] = useState(false);
 
-  useEffect(() => {
-    if (!status?.active || !status.replay_camera) {
-      setShowReplayInitSkeleton(false);
-      return;
-    }
-
-    setShowReplayInitSkeleton(true);
-
-    const timeout = window.setTimeout(() => {
-      setShowReplayInitSkeleton(false);
-    }, REPLAY_INIT_SKELETON_TIMEOUT_MS);
-
-    return () => {
-      window.clearTimeout(timeout);
-    };
-  }, [status?.active, status?.replay_camera]);
-
-  useEffect(() => {
-    if (status?.live_ready) {
-      setShowReplayInitSkeleton(false);
-    }
-  }, [status?.live_ready]);
-
   // Format time range for display
   const timeRangeDisplay = useMemo(() => {
     if (!status?.start_time || !status?.end_time) return "";
@@ -237,8 +215,39 @@ export default function Replay() {
     );
   }
 
-  // No active session
-  if (!status?.active) {
+  // Startup error (job failed). Only show when status.active is also true so
+  // we don't surface stale failed jobs after a session ended cleanly.
+  if (replayJob?.status === "failed" && status?.active) {
+    return (
+      <div className="flex size-full flex-col items-center justify-center gap-4 p-8">
+        <Heading as="h2" className="text-center">
+          {t("page.startError.title")}
+        </Heading>
+        {replayJob.error_message && (
+          <p className="max-w-xl text-center text-sm text-muted-foreground">
+            {replayJob.error_message}
+          </p>
+        )}
+        <Button
+          variant="default"
+          onClick={() => {
+            axios
+              .post("debug_replay/stop")
+              .catch(() => {})
+              .finally(() => navigate("/review"));
+          }}
+        >
+          {t("page.startError.back")}
+        </Button>
+      </div>
+    );
+  }
+
+  // No active session. Also covers the brief window between the runner
+  // pushing job.status = "cancelled" via WS and the next SWR refresh
+  // flipping status.active to false — without this, render falls through
+  // to the full replay UI and you see a flash of it before stop completes.
+  if (!status?.active || replayJob?.status === "cancelled") {
     return (
       <div className="flex size-full flex-col items-center justify-center gap-4 p-8">
         <MdReplay className="size-12" />
@@ -255,6 +264,52 @@ export default function Replay() {
     );
   }
 
+  // Startup in progress (job is running). The session is active but the
+  // replay camera isn't ready yet; show progress / phase from the job.
+  const startupStep =
+    replayJob?.status === "running"
+      ? (replayJob.results?.current_step ?? null)
+      : null;
+  if (startupStep === "preparing_clip" || startupStep === "starting_camera") {
+    const phaseTitle =
+      startupStep === "preparing_clip"
+        ? t("page.preparingClip")
+        : t("page.startingCamera");
+    const progressPercent = replayJob?.results?.progress_percent ?? null;
+    const showProgressBar =
+      startupStep === "preparing_clip" && progressPercent != null;
+    return (
+      <div className="flex size-full flex-col items-center justify-center gap-4 p-8">
+        {showProgressBar ? (
+          <div className="flex w-64 flex-col items-center gap-2">
+            <Progress value={progressPercent ?? 0} />
+            <div className="text-xs text-muted-foreground">
+              {Math.round(progressPercent ?? 0)}%
+            </div>
+          </div>
+        ) : (
+          <ActivityIndicator className="size-8" />
+        )}
+        <Heading as="h3" className="text-center">
+          {phaseTitle}
+        </Heading>
+        {startupStep === "preparing_clip" && (
+          <p className="max-w-md text-center text-sm text-muted-foreground">
+            {t("page.preparingClipDesc")}
+          </p>
+        )}
+        <Button
+          variant="outline"
+          size="sm"
+          disabled={isStopping}
+          onClick={handleStop}
+        >
+          {t("button.cancel", { ns: "common" })}
+        </Button>
+      </div>
+    );
+  }
+
   return (
     <div className="flex size-full flex-col overflow-hidden">
       <Toaster position="top-center" closeButton={true} />
@@ -345,27 +400,30 @@ export default function Replay() {
           ) : (
             status.replay_camera && (
               <div className="relative size-full min-h-10" ref={containerRef}>
-                <AutoUpdatingCameraImage
-                  className="size-full"
-                  cameraClasses="relative w-full h-full flex flex-col justify-start"
-                  searchParams={searchParams}
-                  camera={status.replay_camera}
-                  showFps={false}
-                />
-                {debugDraw && (
-                  <DebugDrawingLayer
-                    containerRef={containerRef}
-                    cameraWidth={
-                      config?.cameras?.[status.source_camera ?? ""]?.detect
-                        .width ?? 1280
-                    }
-                    cameraHeight={
-                      config?.cameras?.[status.source_camera ?? ""]?.detect
-                        .height ?? 720
-                    }
-                  />
-                )}
-                {showReplayInitSkeleton && (
+                {status.live_ready ? (
+                  <>
+                    <AutoUpdatingCameraImage
+                      className="size-full"
+                      cameraClasses="relative w-full h-full flex flex-col justify-start"
+                      searchParams={searchParams}
+                      camera={status.replay_camera}
+                      showFps={false}
+                    />
+                    {debugDraw && (
+                      <DebugDrawingLayer
+                        containerRef={containerRef}
+                        cameraWidth={
+                          config?.cameras?.[status.source_camera ?? ""]?.detect
+                            .width ?? 1280
+                        }
+                        cameraHeight={
+                          config?.cameras?.[status.source_camera ?? ""]?.detect
+                            .height ?? 720
+                        }
+                      />
+                    )}
+                  </>
+                ) : (
                   <div className="pointer-events-none absolute inset-0 z-10 size-full rounded-lg bg-background">
                     <Skeleton className="size-full rounded-lg" />
                     <div className="absolute left-1/2 top-1/2 flex -translate-x-1/2 -translate-y-1/2 flex-col items-center justify-center gap-2">
@@ -595,32 +653,38 @@ export default function Replay() {
               {t("page.configurationDesc")}
             </DialogDescription>
           </DialogHeader>
-          <div className="space-y-6">
-            <ConfigSectionTemplate
-              sectionKey="motion"
-              level="replay"
-              cameraName={status.replay_camera ?? undefined}
-              skipSave
-              noStickyButtons
-              requiresRestart={false}
-              collapsible
-              defaultCollapsed={false}
-              showTitle
-              showOverrideIndicator={false}
-            />
-            <ConfigSectionTemplate
-              sectionKey="objects"
-              level="replay"
-              cameraName={status.replay_camera ?? undefined}
-              skipSave
-              noStickyButtons
-              requiresRestart={false}
-              collapsible
-              defaultCollapsed={false}
-              showTitle
-              showOverrideIndicator={false}
-            />
-          </div>
+          {configSchema == null ? (
+            <div className="flex h-40 items-center justify-center">
+              <ActivityIndicator />
+            </div>
+          ) : (
+            <div className="space-y-6">
+              <ConfigSectionTemplate
+                sectionKey="motion"
+                level="replay"
+                cameraName={status.replay_camera ?? undefined}
+                skipSave
+                noStickyButtons
+                requiresRestart={false}
+                collapsible
+                defaultCollapsed={false}
+                showTitle
+                showOverrideIndicator={false}
+              />
+              <ConfigSectionTemplate
+                sectionKey="objects"
+                level="replay"
+                cameraName={status.replay_camera ?? undefined}
+                skipSave
+                noStickyButtons
+                requiresRestart={false}
+                collapsible
+                defaultCollapsed={false}
+                showTitle
+                showOverrideIndicator={false}
+              />
+            </div>
+          )}
         </DialogContent>
       </Dialog>
     </div>