diff --git a/scripts/dispatcher.py b/scripts/dispatcher.py
index c38363c..f3b0b4f 100644
--- a/scripts/dispatcher.py
+++ b/scripts/dispatcher.py
@@ -432,19 +432,67 @@ def _extract_on_remote_host(job_id: int, worker: dict, src_host: str, src_path:
     new_idx = count_frames(worker, frames_dir)
     return new_idx, dur
 
+
+def _marker_path(frames_dir: str, vid_num: int) -> str:
+    return f"{frames_dir}/.video_{vid_num}.done"
+
+
+def _read_marker(worker: dict, frames_dir: str, vid_num: int) -> int | None:
+    """Return frame count stored in the done-marker, or None if not present."""
+    mp = _marker_path(frames_dir, vid_num)
+    rc, out, _ = ssh(worker["ssh_alias"], f"cat {shlex.quote(mp)} 2>/dev/null", timeout=10)
+    if rc == 0 and out.strip().isdigit():
+        return int(out.strip())
+    return None
+
+
+def _write_marker(worker: dict, frames_dir: str, vid_num: int, frame_count: int) -> None:
+    mp = _marker_path(frames_dir, vid_num)
+    ssh(worker["ssh_alias"],
+        f"echo {frame_count} > {shlex.quote(mp)}", timeout=10)
+
+
+def _drop_partial_frames(worker: dict, frames_dir: str, from_idx: int) -> None:
+    """Delete frame_*.jpg with sequence number >= from_idx (leftover from crashed extraction)."""
+    cmd = (
+        f"ls {shlex.quote(frames_dir)}/frame_*.jpg 2>/dev/null "
+        f"| awk -F'frame_' '{{n=int($2); if (n >= {from_idx}) print}}' "
+        f"| xargs -r rm -f"
+    )
+    ssh(worker["ssh_alias"], cmd, timeout=60)
+
 def do_extract(job: sqlite3.Row, worker: dict) -> str:
     videos = json.loads(job["video_paths"])
     frames_dir = f"{worker['frames_dir']}/job_{job['id']}"
-    # Clean any frame_*.jpg from a prior run so count_frames reflects this extraction only
-    # (retries/restarts otherwise inflate frame_count with duplicates).
-    ssh(worker["ssh_alias"], f"mkdir -p {shlex.quote(frames_dir)} && rm -f {shlex.quote(frames_dir)}/frame_*.jpg")
+    # Preserve existing frames — resume from last completed video on retry.
+    ssh(worker["ssh_alias"], f"mkdir -p {shlex.quote(frames_dir)}")
     idx = 0
-    total_frames_est = 0  # will be computed after each scp
+    total_frames_est = 0
     total_duration_s = 0.0
     n_videos = len(videos)
     for vid_num, v in enumerate(videos, start=1):
         vf = f"fps={FPS},scale={IMG_W}:{IMG_H}"
         pattern = f"{frames_dir}/frame_%06d.jpg"
+        # Resume: skip videos already fully extracted in a previous run.
+        done_frames = _read_marker(worker, frames_dir, vid_num)
+        if done_frames is not None:
+            print(f"  resume: video {vid_num}/{n_videos} already done ({done_frames} frames), skipping")
+            idx += done_frames
+            # Still need duration for total_duration_s / total_frames_est
+            _vpath = v.split(':', 1)[1] if ':' in v and not v.startswith('/') else v
+            _vhost = v.split(':', 1)[0] if ':' in v and not v.startswith('/') else worker['ssh_alias']
+            _dur_alias = _vhost if _vhost in (worker['ssh_alias'], worker['host']) else _vhost
+            _, _dur_str, _ = ssh(_dur_alias,
+                f"ffprobe -v error -show_entries format=duration -of csv=p=0 "
+                f"{shlex.quote(_vpath)} 2>/dev/null || echo 0", timeout=30)
+            _dur = float(_dur_str.strip()) if _dur_str.strip() else 0.0
+            total_duration_s += _dur
+            total_frames_est += max(1, int(_dur * FPS))
+            set_status(job["id"], frame_count=idx,
+                       progress=min(99, idx * 100 // max(1, total_frames_est)))
+            continue
+        # Drop any partial frames left by a previous crashed extraction of this video.
+        _drop_partial_frames(worker, frames_dir, idx)
         # Detect third-host sources (e.g. z620:) — extract frames remotely, pull only JPEGs
         _src_is_third_host = False
         if ":" in v and not v.startswith("/"):
@@ -453,15 +501,18 @@ def do_extract(job: sqlite3.Row, worker: dict) -> str:
                 _src_is_third_host = True
 
         if _src_is_third_host:
+            _frames_before = idx
             idx, dur = _extract_on_remote_host(
                 job["id"], worker, _src_host_v, _src_path_v,
                 frames_dir, vid_num, n_videos, idx, vf,
             )
             total_duration_s += dur
             total_frames_est += max(1, int(dur * FPS))
+            _write_marker(worker, frames_dir, vid_num, idx - _frames_before)
             set_status(job["id"], frame_count=idx,
                        progress=min(99, idx * 100 // max(1, total_frames_est)))
         else:
+            _frames_before_local = idx
             worker_src, is_ephemeral = resolve_worker_video_source(worker, v, frames_dir)
             ensure_worker_video_source(v, worker, worker_src, is_ephemeral, job["id"])
             dur = video_duration_s(worker, worker_src)
@@ -498,6 +549,7 @@ def do_extract(job: sqlite3.Row, worker: dict) -> str:
                 _, err, _ = ssh(worker["ssh_alias"], f"cat /tmp/cosma-ffmpeg-{job['id']}.log 2>/dev/null | tail -5 || echo ''")
                 raise RuntimeError(f"ffmpeg failed on {v}: {err[:200]}")
             idx = count_frames(worker, frames_dir)
+            _write_marker(worker, frames_dir, vid_num, idx - _frames_before_local)
             if is_ephemeral:
                 ssh(worker["ssh_alias"], f"rm -f {shlex.quote(worker_src)}")
             set_status(job["id"], frame_count=idx, progress=min(99, idx * 100 // total_frames_est))