feat: first-class SponsorBlock toggle

A "Remove sponsor segments" switch next to "Split by chapters" queues
the download with the same postprocessor pair the CLI's
--sponsorblock-remove sponsor builds (SponsorBlock + ModifyChapters).
The flag persists as a cookie like the other form options, survives in
the queue records, and is carried into retries.

The pair is registered above the chapter-splitting block: yt-dlp runs
same-stage postprocessors in list order, so ModifyChapters has to
rewrite the chapter list before FFmpegSplitChapters cuts the file up,
matching what the CLI builds for --sponsorblock-remove sponsor
--split-chapters. With both toggles on the other way around the chapter
files keep the sponsor segments and the removal desyncs the remaining
chapter timings.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/main.py

@@ -725,6 +725,7 @@ def parse_download_options(post: dict) -> dict:
     playlist_item_limit = post.get('playlist_item_limit')
     auto_start = post.get('auto_start')
     split_by_chapters = post.get('split_by_chapters')
+    sponsorblock = bool(post.get('sponsorblock'))
     chapter_template = post.get('chapter_template')
     subtitle_language = post.get('subtitle_language')
     subtitle_mode = post.get('subtitle_mode')
@@ -845,6 +846,7 @@ def parse_download_options(post: dict) -> dict:
         'playlist_item_limit': playlist_item_limit,
         'auto_start': auto_start,
         'split_by_chapters': split_by_chapters,
+        'sponsorblock': sponsorblock,
         'chapter_template': chapter_template,
         'subtitle_language': subtitle_language,
         'subtitle_mode': subtitle_mode,
@@ -890,6 +892,7 @@ async def add(request):
         o['ytdl_options_overrides'],
         o['clip_start'],
         o['clip_end'],
+        sponsorblock=o['sponsorblock'],
     )
     return web.Response(text=serializer.encode(status))
 

app/tests/test_download_queue.py

@@ -476,6 +476,32 @@ async def test_retry_keeps_overrides_while_still_allowed(dq_env):
     assert dq.queue.get(url).info.ytdl_options_overrides == {"writesubtitles": True}
 
 
+@pytest.mark.asyncio
+async def test_retry_carries_the_sponsorblock_flag(dq_env):
+    notifier = AsyncMock()
+    dq = DownloadQueue(dq_env, notifier)
+    url = "https://example.com/watch?v=1"
+    dq.done.put(
+        Download(None, None, None, None, "best", "any", {}, _failed_playlist_item(url, sponsorblock=True))
+    )
+
+    def fake_extract(self, extracted_url, *_args, **_kwargs):
+        return {
+            "_type": "video",
+            "id": "vid1",
+            "title": "Test Video",
+            "url": extracted_url,
+            "webpage_url": extracted_url,
+        }
+
+    with patch.object(DownloadQueue, "_DownloadQueue__extract_info", fake_extract), \
+         patch.object(DownloadQueue, "_DownloadQueue__start_download", new=AsyncMock()):
+        result = await dq.retry(url)
+
+    assert result["status"] == "ok"
+    assert dq.queue.get(url).info.sponsorblock is True
+
+
 @pytest.mark.asyncio
 async def test_add_entry_duplicate_while_pending_is_skipped_not_clobbered(dq_env):
     notifier = AsyncMock()

app/tests/test_ytdl_utils.py

@@ -678,6 +678,69 @@ class DownloadResultTests(unittest.TestCase):
         )
 
 
+def _capture_ytdl_params(download: Download) -> dict:
+    """Run ``_download`` far enough to capture the params it builds."""
+    fake_ydl = MagicMock()
+    fake_ydl.download.return_value = 0
+    download.status_queue = types.SimpleNamespace(put=lambda _: None)
+
+    with patch('ytdl.install_socket_guard'), \
+            patch.object(Download, '_make_youtube_dl', return_value=fake_ydl) as make:
+        download._download()
+
+    params, = make.call_args.args
+    return params
+
+
+class SponsorBlockPostprocessorTests(unittest.TestCase):
+    def test_no_sponsorblock_postprocessors_when_disabled(self):
+        download = _make_test_download()
+
+        params = _capture_ytdl_params(download)
+
+        keys = [pp['key'] for pp in params.get('postprocessors', [])]
+        self.assertNotIn('SponsorBlock', keys)
+        self.assertNotIn('ModifyChapters', keys)
+
+    def test_sponsorblock_pair_matches_the_cli(self):
+        download = _make_test_download()
+        download.info.sponsorblock = True
+
+        params = _capture_ytdl_params(download)
+
+        self.assertEqual(
+            params['postprocessors'],
+            [
+                {
+                    'key': 'SponsorBlock',
+                    'categories': ['sponsor'],
+                    'when': 'after_filter',
+                },
+                {
+                    'key': 'ModifyChapters',
+                    'remove_sponsor_segments': ['sponsor'],
+                    'force_keyframes': False,
+                },
+            ],
+        )
+
+    def test_segment_removal_runs_before_the_chapter_split(self):
+        # yt-dlp runs same-stage postprocessors in list order, so ModifyChapters
+        # has to rewrite the chapter list before FFmpegSplitChapters cuts the
+        # file up -- the order the CLI builds for
+        # --sponsorblock-remove sponsor --split-chapters.
+        download = _make_test_download()
+        download.info.sponsorblock = True
+        download.info.split_by_chapters = True
+        download.info.chapter_template = '%(section_number)s.%(ext)s'
+
+        params = _capture_ytdl_params(download)
+
+        keys = [pp['key'] for pp in params['postprocessors']]
+        self.assertEqual(keys, ['SponsorBlock', 'ModifyChapters', 'FFmpegSplitChapters'])
+        self.assertEqual(params['outtmpl']['chapter'], '%(section_number)s.%(ext)s')
+
+
 class ProgressThrottleTests(unittest.TestCase):
     def test_downloading_ticks_are_throttled(self):
         dl = _make_test_download()

app/ytdl.py

@@ -453,6 +453,7 @@ class DownloadInfo:
         clip_end=None,
         live_status=None,
         live_release_timestamp=None,
+        sponsorblock=False,
     ):
         self.id = id if len(custom_name_prefix) == 0 else f'{custom_name_prefix}.{id}'
         self.title = title if len(custom_name_prefix) == 0 else f'{custom_name_prefix}.{title}'
@@ -472,6 +473,7 @@ class DownloadInfo:
         self.entry = _sanitize_entry_for_pickle(entry) if entry is not None else None
         self.playlist_item_limit = playlist_item_limit
         self.split_by_chapters = split_by_chapters
+        self.sponsorblock = sponsorblock
         self.chapter_template = chapter_template
         self.subtitle_language = subtitle_language
         self.subtitle_mode = subtitle_mode
@@ -541,6 +543,8 @@ class DownloadInfo:
             self.playlist_item_limit = 0
         if not hasattr(self, "split_by_chapters"):
             self.split_by_chapters = False
+        if not hasattr(self, "sponsorblock"):
+            self.sponsorblock = False
         if not hasattr(self, "chapter_template"):
             self.chapter_template = ""
         if not hasattr(self, "subtitle_language"):
@@ -585,6 +589,7 @@ _PERSISTED_DOWNLOAD_FIELDS = (
     "custom_name_prefix",
     "playlist_item_limit",
     "split_by_chapters",
+    "sponsorblock",
     "chapter_template",
     "subtitle_language",
     "subtitle_mode",
@@ -822,6 +827,27 @@ class Download:
             # this logger, so a user-supplied one must not replace it.
             ytdl_params['logger'] = ytdl_logger
 
+            # SponsorBlock: mark sponsor segments and cut them out, the same
+            # postprocessor pair the CLI's --sponsorblock-remove sponsor builds.
+            # This has to stay above the chapter-splitting block: yt-dlp runs
+            # same-stage postprocessors in list order, and ModifyChapters must
+            # rewrite the chapter list before FFmpegSplitChapters cuts the file
+            # up, or the chapter files keep the sponsor segments and the
+            # removal desyncs the remaining chapter timings.
+            if getattr(self.info, 'sponsorblock', False):
+                if 'postprocessors' not in ytdl_params:
+                    ytdl_params['postprocessors'] = []
+                ytdl_params['postprocessors'].append({
+                    'key': 'SponsorBlock',
+                    'categories': ['sponsor'],
+                    'when': 'after_filter',
+                })
+                ytdl_params['postprocessors'].append({
+                    'key': 'ModifyChapters',
+                    'remove_sponsor_segments': ['sponsor'],
+                    'force_keyframes': False,
+                })
+
             # Add chapter splitting options if enabled
             if self.info.split_by_chapters:
                 ytdl_params['outtmpl']['chapter'] = self.info.chapter_template
@@ -1619,6 +1645,7 @@ class DownloadQueue:
         already,
         _add_gen=None,
         retry_entry=None,
+        sponsorblock=False,
     ):
         if not entry:
             return {'status': 'error', 'msg': "Invalid/empty data was given."}
@@ -1662,6 +1689,7 @@ class DownloadQueue:
                 already,
                 _add_gen,
                 retry_entry,
+                sponsorblock=sponsorblock,
             )
         elif etype == 'playlist' or etype == 'channel':
             if etype == 'playlist' and self.__is_channel_extraction(entry):
@@ -1729,6 +1757,7 @@ class DownloadQueue:
                         clip_end,
                         already,
                         _add_gen,
+                        sponsorblock=sponsorblock,
                     )
                 )
             if any(res['status'] == 'error' for res in results):
@@ -1769,6 +1798,7 @@ class DownloadQueue:
                 clip_end=clip_end,
                 live_status=entry.get('live_status'),
                 live_release_timestamp=entry.get('release_timestamp'),
+                sponsorblock=sponsorblock,
             )
             await self.__add_download(dl, auto_start)
             return {'status': 'ok'}
@@ -1849,13 +1879,14 @@ class DownloadQueue:
         already=None,
         _add_gen=None,
         retry_entry=None,
+        sponsorblock=False,
     ):
         if ytdl_options_presets is None:
             ytdl_options_presets = []
         log.info(
             f'adding {url}: {download_type=} {codec=} {format=} {quality=} {already=} {folder=} {custom_name_prefix=} '
             f'{playlist_item_limit=} {auto_start=} {split_by_chapters=} {chapter_template=} '
-            f'{subtitle_language=} {subtitle_mode=} {ytdl_options_presets=} {clip_start=} {clip_end=}'
+            f'{subtitle_language=} {subtitle_mode=} {ytdl_options_presets=} {clip_start=} {clip_end=} {sponsorblock=}'
         )
         if already is None:
             _add_gen = self._add_generation
@@ -1918,6 +1949,7 @@ class DownloadQueue:
             already,
             _add_gen,
             retry_entry,
+            sponsorblock=sponsorblock,
         )
 
     async def retry(self, id):
@@ -1954,6 +1986,7 @@ class DownloadQueue:
             info.clip_start,
             info.clip_end,
             retry_entry=info.entry,
+            sponsorblock=info.sponsorblock,
         )
 
     async def add_entry(