Add older content exploration: channel page + home feed Rediscover mode

Channel page:
- "Explore older videos" button fetches 100 videos at a time further back
  in the channel history using yt-dlp --playlist-start/--playlist-end
- "Fetch entire history" still available for full crawl
- Backend: /channels/{id}/explore?page=N endpoint + playlist offset support
  in fetch_channel_metadata(start_video=N)

Home feed:
- New "Rediscover" mode: older unwatched videos (90+ days old) from
  followed channels, randomly sampled then re-ranked by tag affinity

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/channels.py

@@ -758,6 +758,54 @@ def index_channel_full(
     return {"detail": "Full index started"}
 
 
+@router.post("/{channel_id}/explore", status_code=status.HTTP_202_ACCEPTED)
+def explore_channel_older(
+    channel_id: int,
+    page: int = 2,
+    background_tasks: BackgroundTasks = None,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """Fetch a page of older videos from this channel (page 1 = newest 30, page 2 = next 100, etc.)."""
+    _get_channel_or_404(db, channel_id)
+    start = 1 if page <= 1 else (30 + (page - 2) * 100 + 1)
+    background_tasks.add_task(_index_channel_explore_task, channel_id, current_user.id, start, 100)
+    return {"detail": f"Fetching older videos (page {page})", "start": start}
+
+
+def _index_channel_explore_task(channel_id: int, user_id: int, start_video: int, count: int):
+    from ..database import SessionLocal
+    db = SessionLocal()
+    try:
+        channel = db.query(Channel).filter_by(id=channel_id).first()
+        if not channel:
+            return
+        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=count, start_video=start_video)
+        if not result:
+            return
+        for vdata in result.get("videos", []):
+            yt_id = vdata.get("youtube_video_id")
+            if not yt_id or not vdata.get("published_at"):
+                continue
+            if not db.query(Video).filter_by(youtube_video_id=yt_id).first():
+                db.add(Video(
+                    youtube_video_id=yt_id,
+                    channel_id=channel.id,
+                    title=vdata.get("title", ""),
+                    description=vdata.get("description"),
+                    thumbnail_url=vdata.get("thumbnail_url"),
+                    duration_seconds=vdata.get("duration_seconds"),
+                    published_at=vdata.get("published_at"),
+                    tags=vdata.get("tags"),
+                    category=vdata.get("category"),
+                ))
+        db.commit()
+    except Exception:
+        db.rollback()
+    finally:
+        db.close()
+
+
 @router.post("/follow-bulk", status_code=200)
 def follow_bulk(
     body: dict,

backend/routers/videos.py

@@ -208,6 +208,58 @@ def home_feed(
             for r in rows
         ]
 
+    if mode == "rediscover":
+        # Older unwatched videos from followed channels, ranked by tag affinity
+        affinity_rows = db.execute(
+            text("SELECT tag, score FROM user_tag_affinity WHERE user_id = :user_id AND score > 0"),
+            {"user_id": current_user.id},
+        ).mappings().all()
+        affinity = {r["tag"]: r["score"] for r in affinity_rows}
+
+        rows = db.execute(
+            text(f"""
+                SELECT v.id, v.youtube_video_id, v.title, v.description, v.thumbnail_url,
+                       v.duration_seconds, v.published_at, v.tags, v.category,
+                       c.id AS channel_id, c.name AS channel_name,
+                       c.youtube_channel_id AS channel_youtube_id,
+                       c.thumbnail_url AS channel_thumbnail_url,
+                       COALESCE(uv.watched, 0)                AS watched,
+                       COALESCE(uv.watch_progress_seconds, 0) AS watch_progress_seconds,
+                       COALESCE(uv.downloaded, 0)             AS is_downloaded,
+                       COALESCE(uv.queued, 0)                 AS queued,
+                       NULL                                   AS file_path
+                FROM videos v
+                JOIN channels c ON v.channel_id = c.id
+                JOIN user_channels uc
+                    ON c.id = uc.channel_id AND uc.user_id = :user_id AND uc.status = 'followed'
+                LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
+                WHERE COALESCE(uv.watched, 0) = 0
+                  AND v.published_at < datetime('now', '-90 days')
+                  AND (uc.muted_until IS NULL OR datetime(uc.muted_until) < datetime('now'))
+                  {duration_clause}
+                ORDER BY RANDOM()
+                LIMIT :limit OFFSET :offset
+            """),
+            {"user_id": current_user.id, "limit": min(limit * 4, 200), "offset": offset},
+        ).mappings().all()
+
+        if affinity:
+            import json as _json
+            def _affinity_score(row):
+                try:
+                    tags = _json.loads(row["tags"] or "[]")
+                    return sum(affinity.get(t.lower().strip(), 0) for t in tags if isinstance(t, str))
+                except Exception:
+                    return 0
+            rows = sorted(rows, key=_affinity_score, reverse=True)
+
+        rows = rows[:limit]
+        return [
+            VideoDetail(**{k: v for k, v in dict(r).items() if k not in ("watched",)},
+                        is_watched=bool(r["watched"]))
+            for r in rows
+        ]
+
     if mode == "inbox":
         rows = db.execute(
             text(f"""

backend/services/ytdlp.py

@@ -287,7 +287,7 @@ def _rss_dates(uc_channel_id: str) -> dict[str, datetime]:
         return {}
 
 
-def fetch_channel_metadata(channel_id: str, max_videos: int = 30) -> dict | None:
+def fetch_channel_metadata(channel_id: str, max_videos: int = 30, start_video: int = 1) -> dict | None:
     """Fetch channel info + recent videos.
 
     Uses --dump-single-json --flat-playlist for speed, then enriches video dates
@@ -304,8 +304,11 @@ def fetch_channel_metadata(channel_id: str, max_videos: int = 30) -> dict | None
         "--quiet",
         *_cookie_args(),
     ]
+    if start_video > 1:
+        args += ["--playlist-start", str(start_video)]
     if max_videos > 0:
-        args += ["--playlist-end", str(max_videos)]
+        end = (start_video - 1 + max_videos) if start_video > 1 else max_videos
+        args += ["--playlist-end", str(end)]
 
     stdout, _, code = _run(args, timeout=60)
     if not stdout.strip():

frontend/src/api/index.js

@@ -48,6 +48,7 @@ export const followChannel = (id) => api.post(`/channels/${id}/follow`);
 export const unfollowChannel = (id) => api.delete(`/channels/${id}/follow`);
 export const indexChannel = (id) => api.post(`/channels/${id}/index`);
 export const indexChannelFull = (id) => api.post(`/channels/${id}/index-full`);
+export const exploreChannelOlder = (id, page) => api.post(`/channels/${id}/explore`, null, { params: { page } });
 export const followChannelByUrl = (data) => api.post("/channels/follow-by-url", data);
 export const setChannelAutoDownload = (id, value) => api.patch(`/channels/${id}/auto-download`, { auto_download: value });
 export const markChannelsSeen = () => api.post("/channels/mark-seen");

frontend/src/pages/Channel.jsx

@@ -3,7 +3,7 @@ import { useParams } from "react-router-dom";
 import { useQuery, useMutation, useQueryClient, useInfiniteQuery } from "@tanstack/react-query";
 import {
   getChannel, getChannelVideos, searchChannelYoutube,
-  followChannel, unfollowChannel, indexChannel, indexChannelFull, downloadChannel,
+  followChannel, unfollowChannel, indexChannel, indexChannelFull, exploreChannelOlder, downloadChannel,
 } from "../api";
 import VideoCard from "../components/VideoCard";
 
@@ -30,6 +30,7 @@ export default function ChannelPage() {
   const [search, setSearch] = useState("");
   const [activeQ, setActiveQ] = useState("");
   const [indexing, setIndexing] = useState(false);
+  const [explorePage, setExplorePage] = useState(2);
   const searchInputRef = useRef(null);
 
   const { data: channel, isLoading: loadingChannel } = useQuery({
@@ -94,6 +95,14 @@ export default function ChannelPage() {
     onSuccess: () => scheduleRefetch(45000),
   });
 
+  const exploreMut = useMutation({
+    mutationFn: () => exploreChannelOlder(id, explorePage),
+    onSuccess: () => {
+      setExplorePage(p => p + 1);
+      scheduleRefetch(20000);
+    },
+  });
+
   const deepSearchMut = useMutation({
     mutationFn: () => searchChannelYoutube(id, activeQ || search),
     onSuccess: () => scheduleRefetch(20000),
@@ -130,7 +139,7 @@ export default function ChannelPage() {
   if (!channel) return <p className="text-zinc-500">Channel not found.</p>;
 
   const isFollowed = channel.status === "followed";
-  const isPending = indexMut.isPending || fullIndexMut.isPending || deepSearchMut.isPending || indexing;
+  const isPending = indexMut.isPending || fullIndexMut.isPending || deepSearchMut.isPending || exploreMut.isPending || indexing;
 
   return (
     <div className="flex flex-col gap-5">
@@ -282,12 +291,19 @@ export default function ChannelPage() {
               {isFetchingNextPage ? "Loading…" : "Load more"}
             </button>
           ) : !activeQ && (
-            <div className="mt-4 flex flex-col items-center gap-2 py-4 border-t border-zinc-800/50">
-              <p className="text-xs text-zinc-600">All {videos.length} indexed videos shown</p>
-              <button onClick={() => fullIndexMut.mutate()} disabled={isPending}
-                className="text-xs text-zinc-500 hover:text-zinc-300 transition-colors disabled:opacity-40">
-                Fetch full history from YouTube
-              </button>
+            <div className="mt-4 flex flex-col items-center gap-3 py-4 border-t border-zinc-800/50">
+              <p className="text-xs text-zinc-600">{videos.length} videos indexed</p>
+              <div className="flex items-center gap-4">
+                <button onClick={() => exploreMut.mutate()} disabled={isPending}
+                  className="text-xs text-zinc-400 hover:text-zinc-100 font-medium transition-colors disabled:opacity-40">
+                  Explore older videos
+                </button>
+                <span className="text-zinc-800 text-xs">·</span>
+                <button onClick={() => fullIndexMut.mutate()} disabled={isPending}
+                  className="text-xs text-zinc-500 hover:text-zinc-300 transition-colors disabled:opacity-40">
+                  Fetch entire history
+                </button>
+              </div>
             </div>
           )}
         </div>

frontend/src/pages/Home.jsx

@@ -9,6 +9,7 @@ const PAGE_SIZE = 25;
 const FEED_MODES = [
   { value: "ranked",        label: "For you",      hint: "Ranked by your taste" },
   { value: "chronological", label: "New",           hint: "Everything in date order" },
+  { value: "rediscover",    label: "Rediscover",    hint: "Older unwatched videos ranked by your taste" },
   { value: "random",        label: "Explore",       hint: "Random from discovery pool" },
   { value: "inbox",         label: "Inbox",         hint: "New from followed channels since last visit" },
 ];