fix: add support for YouTube Shorts tab on channel pages

- Rewrite channel_ctoken_v5 with correct protobuf field numbers per tab
  (videos=15, shorts=10, streams=14) based on Invidious source
- Replace broken pbj=1 endpoint with youtubei browse API for shorts/streams
- Add shortsLockupViewModel parser to extract video data from new YT format
- Fix channel metadata not loading (get_metadata now uses browse API)
- Fix metadata caching: skip caching when channel_name is absent
- Show actual item count instead of UU playlist count for shorts/streams
- Format view counts with spaced suffixes (7.1 K, 1.2 M, 3 B)

2 files changed, 155 insertions, 84 deletions

diff --git a/youtube/channel.py b/youtube/channel.py
index 55c1124..3352ca2 100644
--- a/youtube/channel.py
+++ b/youtube/channel.py
@@ -36,64 +36,41 @@ generic_cookie = (('Cookie', 'VISITOR_INFO1_LIVE=ST1Ti53r4fU'),)
 # FIXED 2026: YouTube changed continuation token structure (from Invidious commit a9f8127)
 # Sort values for YouTube API (from Invidious): 2=popular, 4=newest, 5=oldest
 def channel_ctoken_v5(channel_id, page, sort, tab, view=1):
-    # Map sort values to YouTube API values (Invidious values)
-    # Input: sort=3 (newest), sort=4 (newest no shorts)
-    # YouTube expects: 4=newest
-    sort_mapping = {'1': 2, '2': 5, '3': 4, '4': 4}  # 4 is newest without shorts
-    new_sort = sort_mapping.get(sort, 4)
-
-    offset = 30*(int(page) - 1)
-
-    # Build continuation token using Invidious structure
-    # The structure is: base64(protobuf({
-    #   80226972: {
-    #     2: channel_id,
-    #     3: base64(protobuf({
-    #       110: {
-    #         3: {
-    #           tab: {
-    #             1: {
-    #               1: base64(protobuf({
-    #                 1: base64(protobuf({
-    #                   2: "ST:" + base64(offset_varint)
-    #                 }))
-    #               }))
-    #             },
-    #             2: base64(protobuf({1: UUID}))
-    #             4: sort_value
-    #             8: base64(protobuf({
-    #               1: UUID
-    #               3: sort_value
-    #             }))
-    #           }
-    #         }
-    #       }
-    #     }))
-    #   }
-    # }))
-
-    # UUID placeholder
-    uuid_proto = proto.string(1, "00000000-0000-0000-0000-000000000000")
-
-    # Offset encoding
-    offset_varint = proto.uint(1, offset)
-    offset_encoded = proto.string(2, proto.unpadded_b64encode(offset_varint))
-    offset_wrapper = proto.string(1, proto.unpadded_b64encode(offset_encoded))
-    offset_base = proto.string(1, proto.unpadded_b64encode(offset_wrapper))
-
-    # Sort value varint
-    sort_varint = proto.uint(4, new_sort)
-
-    # Embedded message with UUID and sort
-    embedded_inner = uuid_proto + proto.uint(3, new_sort)
-    embedded_encoded = proto.string(8, proto.unpadded_b64encode(embedded_inner))
-
-    # Combine: uuid_wrapper + sort_varint + embedded
-    tab_inner_content = offset_base + uuid_proto + sort_varint + embedded_encoded
-
-    tab_inner = proto.string(1, proto.unpadded_b64encode(tab_inner_content))
-    tab_wrapper = proto.string(tab, tab_inner)
+    # Tab-specific protobuf field numbers (from Invidious source)
+    # Each tab uses different field numbers in the protobuf structure:
+    #   videos:  110 -> 3 -> 15 -> { 2:{1:UUID}, 4:sort, 8:{1:UUID, 3:sort} }
+    #   shorts:  110 -> 3 -> 10 -> { 2:{1:UUID}, 4:sort, 7:{1:UUID, 3:sort} }
+    #   streams: 110 -> 3 -> 14 -> { 2:{1:UUID}, 5:sort, 8:{1:UUID, 3:sort} }
+    tab_config = {
+        'videos':  {'tab_field': 15, 'sort_field': 4, 'embedded_field': 8},
+        'shorts':  {'tab_field': 10, 'sort_field': 4, 'embedded_field': 7},
+        'streams': {'tab_field': 14, 'sort_field': 5, 'embedded_field': 8},
+    }
+    config = tab_config.get(tab, tab_config['videos'])
+    tab_field = config['tab_field']
+    sort_field = config['sort_field']
+    embedded_field = config['embedded_field']
+
+    # Map sort values to YouTube API values
+    if tab == 'streams':
+        sort_mapping = {'1': 14, '2': 13, '3': 12, '4': 12}
+    else:
+        sort_mapping = {'1': 2, '2': 5, '3': 4, '4': 4}
+    new_sort = sort_mapping.get(sort, sort_mapping['3'])
+
+    # UUID placeholder (field 1)
+    uuid_str = "00000000-0000-0000-0000-000000000000"
+
+    # Build the tab-level object matching Invidious structure exactly:
+    # { 2: embedded{1: UUID}, sort_field: sort_val, embedded_field: embedded{1: UUID, 3: sort_val} }
+    tab_content = (
+        proto.string(2, proto.string(1, uuid_str))
+        + proto.uint(sort_field, new_sort)
+        + proto.string(embedded_field,
+            proto.string(1, uuid_str) + proto.uint(3, new_sort))
+    )
 
+    tab_wrapper = proto.string(tab_field, tab_content)
     inner_container = proto.string(3, tab_wrapper)
     outer_container = proto.string(110, inner_container)
 
@@ -346,11 +323,10 @@ def get_channel_id(base_url):
 metadata_cache = cachetools.LRUCache(128)
 @cachetools.cached(metadata_cache)
 def get_metadata(channel_id):
-    base_url = 'https://www.youtube.com/channel/' + channel_id
-    polymer_json = util.fetch_url(base_url + '/about?pbj=1',
-                                  headers_desktop,
-                                  debug_name='gen_channel_about',
-                                  report_text='Retrieved channel metadata')
+    # Use youtubei browse API to get channel metadata
+    polymer_json = util.call_youtube_api('web', 'browse', {
+        'browseId': channel_id,
+    })
     info = yt_data_extract.extract_channel_info(json.loads(polymer_json),
                                                 'about',
                                                 continuation=False)
@@ -508,28 +484,35 @@ def get_channel_page_general_url(base_url, tab, request, channel_id=None):
 
     # Use the regular channel API
     if tab in ('shorts', 'streams') or (tab=='videos' and try_channel_api):
-        if channel_id:
-            num_videos_call = (get_number_of_videos_channel, channel_id)
-        else:
-            num_videos_call = (get_number_of_videos_general, base_url)
+        if not channel_id:
+            channel_id = get_channel_id(base_url)
 
-        # For page 1, use the first-page method which won't break
-        # Pass sort parameter directly (2=oldest, 3=newest, etc.)
-        if page_number == 1:
-            # Always use first-page method for page 1 with sort parameter
-            page_call = (get_channel_first_page, base_url, tab, None, sort)
-        else:
-            # For page 2+, we can't paginate without continuation tokens
-            # This is a YouTube limitation, not our bug
-            flask.abort(404, 'Pagination not available for this sort option. YouTube removed this feature.')
+        # Use youtubei browse API with continuation token for all pages
+        page_call = (get_channel_tab, channel_id, str(page_number), sort,
+                     tab, int(view))
+        continuation = True
 
-        tasks = (
-            gevent.spawn(*num_videos_call),
-            gevent.spawn(*page_call),
-        )
-        gevent.joinall(tasks)
-        util.check_gevent_exceptions(*tasks)
-        number_of_videos, polymer_json = tasks[0].value, tasks[1].value
+        if tab == 'videos':
+            # Only need video count for the videos tab
+            if channel_id:
+                num_videos_call = (get_number_of_videos_channel, channel_id)
+            else:
+                num_videos_call = (get_number_of_videos_general, base_url)
+            tasks = (
+                gevent.spawn(*num_videos_call),
+                gevent.spawn(*page_call),
+            )
+            gevent.joinall(tasks)
+            util.check_gevent_exceptions(*tasks)
+            number_of_videos, polymer_json = tasks[0].value, tasks[1].value
+        else:
+            # For shorts/streams, item count is used instead
+            polymer_json = gevent.spawn(*page_call)
+            polymer_json.join()
+            if polymer_json.exception:
+                raise polymer_json.exception
+            polymer_json = polymer_json.value
+            number_of_videos = 0  # will be replaced by actual item count later
 
     elif tab == 'about':
         # polymer_json = util.fetch_url(base_url + '/about?pbj=1', headers_desktop, debug_name='gen_channel_about')
@@ -577,7 +560,8 @@ def get_channel_page_general_url(base_url, tab, request, channel_id=None):
         channel_id = info['channel_id']
 
     # Will have microformat present, cache metadata while we have it
-    if channel_id and default_params and tab not in ('videos', 'about'):
+    if (channel_id and default_params and tab not in ('videos', 'about')
+            and info.get('channel_name') is not None):
         metadata = extract_metadata_for_caching(info)
         set_cached_metadata(channel_id, metadata)
     # Otherwise, populate with our (hopefully cached) metadata
@@ -595,8 +579,12 @@ def get_channel_page_general_url(base_url, tab, request, channel_id=None):
             item.update(additional_info)
 
     if tab in ('videos', 'shorts', 'streams'):
+        if tab in ('shorts', 'streams'):
+            # For shorts/streams, use the actual item count since
+            # get_number_of_videos_channel counts regular uploads only
+            number_of_videos = len(info.get('items', []))
         info['number_of_videos'] = number_of_videos
-        info['number_of_pages'] = math.ceil(number_of_videos/page_size)
+        info['number_of_pages'] = math.ceil(number_of_videos/page_size) if number_of_videos else 1
         info['header_playlist_names'] = local_playlist.get_playlist_names()
     if tab in ('videos', 'shorts', 'streams', 'playlists'):
         info['current_sort'] = sort
diff --git a/youtube/yt_data_extract/common.py b/youtube/yt_data_extract/common.py
index 9a940ea..dce1d30 100644
--- a/youtube/yt_data_extract/common.py
+++ b/youtube/yt_data_extract/common.py
@@ -332,6 +332,84 @@ def extract_lockup_view_model_info(item, additional_info={}):
     return info
 
 
+def extract_shorts_lockup_view_model_info(item, additional_info={}):
+    """Extract info from shortsLockupViewModel format (YouTube Shorts)"""
+    info = {'error': None, 'type': 'video'}
+
+    # Video ID from reelWatchEndpoint or entityId
+    info['id'] = deep_get(item,
+        'onTap', 'innertubeCommand', 'reelWatchEndpoint', 'videoId')
+    if not info['id']:
+        entity_id = item.get('entityId', '')
+        if entity_id.startswith('shorts-shelf-item-'):
+            info['id'] = entity_id[len('shorts-shelf-item-'):]
+
+    # Thumbnail
+    info['thumbnail'] = normalize_url(deep_get(item,
+        'onTap', 'innertubeCommand', 'reelWatchEndpoint',
+        'thumbnail', 'thumbnails', 0, 'url'))
+
+    # Parse title and views from accessibilityText
+    # Format: "Title, N views - play Short"
+    acc_text = item.get('accessibilityText', '')
+    info['title'] = ''
+    info['view_count'] = None
+    info['approx_view_count'] = None
+    if acc_text:
+        # Remove trailing " - play Short"
+        cleaned = re.sub(r'\s*-\s*play Short$', '', acc_text)
+        # Split on last comma+views pattern to separate title from view count
+        match = re.match(r'^(.*?),\s*([\d,.]+\s*(?:thousand|million|billion|)\s*views?)$',
+                         cleaned, re.IGNORECASE)
+        if match:
+            info['title'] = match.group(1).strip()
+            view_text = match.group(2)
+            info['view_count'] = extract_int(view_text)
+            # Convert "7.1 thousand" -> "7.1 K" for display
+            suffix_map = {'thousand': 'K', 'million': 'M', 'billion': 'B'}
+            suffix_match = re.search(r'([\d,.]+)\s*(thousand|million|billion)?', view_text, re.IGNORECASE)
+            if suffix_match:
+                num = suffix_match.group(1)
+                word = suffix_match.group(2)
+                if word:
+                    info['approx_view_count'] = num + ' ' + suffix_map[word.lower()]
+                else:
+                    info['approx_view_count'] = '{:,}'.format(int(num.replace(',', ''))) if num.isdigit() or num.replace(',','').isdigit() else num
+            else:
+                info['approx_view_count'] = extract_approx_int(view_text)
+        else:
+            # Fallback: try "N views" at end
+            match2 = re.match(r'^(.*?),\s*(.+views?)$', cleaned, re.IGNORECASE)
+            if match2:
+                info['title'] = match2.group(1).strip()
+                info['approx_view_count'] = extract_approx_int(match2.group(2))
+            else:
+                info['title'] = cleaned
+
+    # Overlay text (usually has the title too)
+    overlay_metadata = deep_get(item, 'overlayMetadata',
+        'secondaryText', 'content')
+    if overlay_metadata and not info['approx_view_count']:
+        info['approx_view_count'] = extract_approx_int(overlay_metadata)
+
+    primary_text = deep_get(item, 'overlayMetadata',
+        'primaryText', 'content')
+    if primary_text and not info['title']:
+        info['title'] = primary_text
+
+    info['duration'] = ''
+    info['time_published'] = None
+    info['description'] = None
+    info['badges'] = []
+    info['author'] = None
+    info['author_id'] = None
+    info['author_url'] = None
+    info['index'] = None
+
+    info.update(additional_info)
+    return info
+
+
 def extract_item_info(item, additional_info={}):
     if not item:
         return {'error': 'No item given'}
@@ -353,6 +431,10 @@ def extract_item_info(item, additional_info={}):
     if type == 'lockupViewModel':
         return extract_lockup_view_model_info(item, additional_info)
 
+    # Handle shortsLockupViewModel format (YouTube Shorts)
+    if type == 'shortsLockupViewModel':
+        return extract_shorts_lockup_view_model_info(item, additional_info)
+
     # type looks like e.g. 'compactVideoRenderer' or 'gridVideoRenderer'
     # camelCase split, https://stackoverflow.com/a/37697078
     type_parts = [s.lower() for s in re.sub(r'([A-Z][a-z]+)', r' \1', type).split()]
@@ -561,6 +643,7 @@ _item_types = {
 
     # New viewModel format (YouTube 2024+)
     'lockupViewModel',
+    'shortsLockupViewModel',
 }
 
 def _traverse_browse_renderer(renderer):