# `ytsubs` — implementation handover

**Target machine:** `susan`
**Audience:** a Claude Code agent implementing this from scratch
**Status:** design agreed, not started

---

## 1. What we're building

A self-hosted pipeline that keeps a rolling 14-day window of recent YouTube uploads from a
handful of subscribed channels, laid out on disk so Jellyfin presents each channel as a TV
show and each video as an episode. A small web UI lets a non-operator (the requester's
brother) subscribe, unsubscribe, and tweak settings.

The mental model is **a DVR for YouTube subscriptions**, not an archiver. Videos are
disposable. If a video ages out or a channel is unsubscribed, it goes away permanently.

### Explicitly in scope

- Poll subscribed channels for new uploads
- Download at ≤720p, h264/AAC, into a Jellyfin-friendly layout
- Generate Kodi-style `.nfo` metadata + artwork (no Jellyfin plugin)
- Delete videos older than the retention window
- Web admin: add/remove channels, edit settings
- Cron-driven, idempotent, monitored via Healthchecks

### Explicitly out of scope — do not build these

- **Cookie handling of any kind.** No browser extension, no cookie-receiving API, no
  `cookies.txt`. See §3.
- Members-only, age-restricted, or private content (follows from the above)
- Migration from the existing TubeArchivist install
- Multi-user support, authentication beyond a single shared credential
- Transcoding of any kind (see §6 — this matters on this hardware)

---

## 2. Environment facts you need

- **susan**: Linux rack server, dual Xeon X58, 12 threads, **no AVX**. Old and slow.
  Software video transcoding is effectively off the table.
- Already running on susan: Jellyfin, Docker, nginx (Let's Encrypt), Netdata,
  Healthchecks (`hc.jihakuz.xyz`), `runitor` for cron wrapping.
- susan is on a **residential IP**. This matters — YouTube flags datacenter IPs far more
  aggressively. Do not move any part of this to `victoria` (the Linode VPS).
- Tailnet: Headscale at `headscale.jihakuz.xyz`. The admin UI should bind to the tailnet
  interface rather than being published publicly (see §9).
- `/disks/Plex/YouTube` is **already in use by TubeArchivist**. Do not touch it. Use a
  fresh root (§5).
- Existing conventions to match: state under `/var/lib/<service>/`, deployed executables
  under `/usr/local/bin/`, bare git repos under `/disks/git-repos/`.

### Proposed paths

| Purpose | Path |
|---|---|
| Source (bare repo) | `/disks/git-repos/youtube-automate.git` |
| Checkout | `/opt/youtube-automate` |
| Entry point | `/usr/local/bin/youtube-automate` |
| State DB | `/var/lib/youtube-automate/subs.db` |
| Lock file | `/var/lib/youtube-automate/run.lock` |
| Media root | `/disks/Plex/YouTube/` |
| Scratch/work dir | `/disks/Plex/YouTube/.ingest/` |

The work dir **must** be on the same filesystem as the media root so finished downloads
move into place with an atomic `rename()` rather than a copy. Jellyfin should be
configured to ignore `.ingest` (it's dot-prefixed, which Jellyfin skips by default —
verify).

---

## 3. YouTube access: PO tokens, not cookies

This was the main open question in design and the answer is that it collapses.

yt-dlp's current recommended setup for reliable downloads is the **mweb client plus a PO
Token Provider plugin** supplying tokens for GVS (Google Video Server) requests. No
account, no cookies, no browser. Cookies only unlock age-restricted / members-only /
private content, which is out of scope, and carry a real risk of the Google account being
banned.

### Setup

1. Run the provider as a Docker sidecar:
!! tom: needs a way of starting up when system reboots

   ```
   docker run --name bgutil-provider -d --restart unless-stopped --init \
     -p 127.0.0.1:4416:4416 brainicism/bgutil-ytdlp-pot-provider
   ```

2. Install the matching plugin into the same Python environment as yt-dlp:
!! tom: do this in uv venv

   ```
   pip install bgutil-ytdlp-pot-provider
   ```

   The plugin and server versions should match.

3. Verify before writing any other code:

   ```
   yt-dlp -v 'https://www.youtube.com/watch?v=<some_id>' -F
   ```

   You must see a line like
   `[debug] [youtube] [pot] PO Token Providers: bgutil:http-1.x.x (external), ...`
   If you don't, stop and fix this first — everything downstream depends on it.

4. `ytsubs` should health-check the provider before each download batch (a plain HTTP
   GET against `http://127.0.0.1:4416/ping`) and fail loudly if it's down, rather than
   silently accumulating 403s.

### Caveats to be aware of

- The bgutil README carries a warning that PO tokens no longer bypass the "Sign in to
  confirm you're not a bot" interstitial in most cases. That is a **different failure
  mode** (IP reputation) from the 403s on format URLs that this solves. Residential IP +
  low request volume + sleep intervals should keep us clear of it. If it does start
  firing, that's the point at which cookies get reconsidered — not before.
- **yt-dlp's YouTube handling churns every few weeks.** Client recommendations,
  extractor-arg names, and which clients need tokens all move. Before implementing, read
  the current `PO Token Guide` and `Extractors` pages on the yt-dlp wiki and adjust the
  flags in §6 accordingly. Do not treat the flags in this document as authoritative —
  treat them as the shape of the answer.
- Keep yt-dlp itself updated (weekly `pip install -U yt-dlp` under the same runitor
  wrapper). A stale yt-dlp is the single most likely cause of "everything broke".

---

## 4. Discovery: RSS feeds

YouTube publishes an unauthenticated Atom feed per channel. Use the **undocumented
`UULF` playlist variant**, which returns long-form videos only — no Shorts, no
livestreams:

```
https://www.youtube.com/feeds/videos.xml?playlist_id=UULF<channel_id without the UC prefix>
```

So `UCabc123...` → `https://www.youtube.com/feeds/videos.xml?playlist_id=UULFabc123...`

This does most of the Shorts/livestream filtering for free, at the cheapest possible
point in the pipeline.

Related prefixes, for reference: `UU` all uploads, `UUSH` shorts, `UULV` livestreams,
`UUMF`/`UUMO` members-only.

### Robustness

These prefixes are undocumented and there have been reports through 2026 of intermittent
failures and missing entries in YouTube's native feeds. So:

- If the `UULF` feed 404s or returns zero entries, **fall back** to
  `?channel_id=UC...` and record `discovery_source = 'uc_feed'` on the resulting rows.
- Rows discovered via the fallback path get the duration/live filter applied at download
  time (§6). Rows from `UULF` don't need it.
- Track consecutive poll failures per channel and surface the count in the admin UI. Two
  channels quietly failing for a month is the realistic failure mode here.

### Parsing

`xml.etree.ElementTree`, no dependencies. Namespaces:

```python
NS = {
    "atom":  "http://www.w3.org/2005/Atom",
    "yt":    "http://www.youtube.com/xml/schemas/2015",
    "media": "http://search.yahoo.com/mrss/",
}
```

Per `atom:entry`: `yt:videoId`, `atom:title`, `atom:published`,
`media:group/media:description`. The feed does **not** carry duration.

### Backfill on subscribe

New subscriptions pull the last **7 days**. The RSS feed only returns ~15 items, which
can be under 7 days for a prolific channel. For the initial backfill only, use:

```
yt-dlp --flat-playlist --playlist-end 50 -J \
  'https://www.youtube.com/playlist?list=UULF<...>'
```

and date-filter the entries client-side. Steady-state polling uses the RSS feed.

### Getting the subscription list in

There is no need for a Google account or a subscriptions RSS feed. Either the brother
pastes channel URLs into the admin page one at a time, or he does a one-off Google
Takeout export (`subscriptions.csv`) and we bulk-insert. With single-digit channels,
manual entry is fine — do not build a CSV importer unless asked.

---

## 5. On-disk layout

Media root: `/disks/Plex/YouTubeSubs/`

```
/disks/Plex/YouTubeSubs/
├── .work/                                   # scratch, ignored by Jellyfin
└── Some Channel/
    ├── tvshow.nfo
    ├── poster.jpg
    ├── fanart.jpg
    └── Season 2026/
        ├── Some Channel - S2026E08110 - Video Title [dQw4w9WgXcQ].mp4
        ├── Some Channel - S2026E08110 - Video Title [dQw4w9WgXcQ].nfo
        ├── Some Channel - S2026E08110 - Video Title [dQw4w9WgXcQ]-thumb.jpg
        ├── Some Channel - S2026E08110 - Video Title [dQw4w9WgXcQ].en.srt
        └── Some Channel - S2026E08110 - Video Title [dQw4w9WgXcQ].info.json
```

### Season / episode numbering

- **Season** = upload year (`2026`)
- **Episode** = `MMDD * 10 + ordinal_within_day`

So the first video uploaded on 11 August is `8110`, the second that day is `8111`, and
the first on 12 August is `8120`. This scheme sorts correctly across the whole year
(unlike appending a suffix to a bare `MMDD`) and tolerates up to 10 uploads per channel
per day. Clamp the ordinal at 9 and log a warning if exceeded.

The ordinal must be computed against **what's already in the DB for that channel+date**,
not against the current batch, so it's stable across runs.

### Filename sanitisation

Strip `/ \ : * ? " < > |`, collapse runs of whitespace, strip leading/trailing dots and
spaces, truncate the title component to 120 chars on a word boundary. The `[videoid]`
suffix guarantees uniqueness regardless.

Store the channel directory name in the DB (`channel.dir_name`) at subscribe time and
never recompute it — channels rename themselves and we don't want orphaned directories.

---

## 6. Download

### Format selection — read this bit carefully

susan has no AVX and cannot realistically transcode. YouTube serves 720p as VP9 or AV1 by
default. If a client can't direct-play those, Jellyfin will try to transcode and it will
be miserable. So we force h264 + AAC in mp4 at download time:

```
-f "bv*[height<=720]+ba/b[height<=720]"
-S "vcodec:h264,acodec:aac,res:720"
--merge-output-format mp4
```

If a video genuinely has no h264 rendition at ≤720p, `-S` will fall back to VP9 rather
than fail. Log those cases; they should be rare.

Do **not** use `--sponsorblock-remove` — it requires cutting and re-encoding. Use
`--sponsorblock-mark all` with `--embed-chapters`, which writes chapter markers only and
is free.

### Full invocation

```
yt-dlp \
  --extractor-args "youtube:player_client=default,mweb" \
  --extractor-args "youtubepot-bgutilhttp:base_url=http://127.0.0.1:4416" \
  -f "bv*[height<=720]+ba/b[height<=720]" \
  -S "vcodec:h264,acodec:aac,res:720" \
  --merge-output-format mp4 \
  --no-playlist \
  --write-info-json \
  --write-thumbnail --convert-thumbnails jpg \
  --write-auto-subs --sub-langs "en.*" --convert-subs srt \
  --sponsorblock-mark all --embed-chapters \
  --retries 3 --fragment-retries 10 \
  --sleep-requests 2 --sleep-interval 5 --max-sleep-interval 15 \
  -P "/disks/Plex/YouTubeSubs/.work" \
  -o "%(id)s.%(ext)s" \
  "https://www.youtube.com/watch?v=<VIDEO_ID>"
```

Verify the `youtubepot-bgutilhttp:base_url` arg name against the current plugin README —
this is the kind of thing that gets renamed.

### Match filter (fallback-discovered videos only)

For rows with `discovery_source = 'uc_feed'`, append:

```
--match-filter "duration>?{min_duration_seconds} & live_status!=is_live & live_status!=is_upcoming & !was_live"
```

The `>?` form allows videos with unknown duration through rather than rejecting them.
`min_duration_seconds` defaults to 120 (Shorts can now run to 3 minutes, but so can
legitimate short videos — this is the tradeoff, and it's why `UULF` is the primary path).

A video rejected by the match filter should be recorded as `skipped_short` /
`skipped_live` and **never retried**.

### Concurrency and politeness

One download at a time. Single-digit channels over a 14-day window is a small workload;
there is no reason to be aggressive and every reason not to be.

### After a successful download

1. Read the `.info.json` from `.work/`
2. Compute season/episode/filename
3. Generate the episode `.nfo` (§7)
4. `os.rename()` all artefacts into the season directory
5. Update the DB row: `state='downloaded'`, `rel_path`, `downloaded_at`
6. After the whole batch, trigger a Jellyfin library refresh:
   `POST {jellyfin_url}/Library/Refresh` with header `X-Emby-Token: {api_key}`

If any step 1–4 fails, clean up `.work/` for that video ID and mark `failed` with
`attempts += 1`. Give up after 5 attempts and surface it in the UI.

---

## 7. Metadata — NFO files, no Jellyfin plugin

Jellyfin reads Kodi-style NFO sidecars natively. Configure the library as **Shows**,
disable all internet metadata providers, enable *Prefer local metadata* and *Save
artwork/metadata into media folders*. Do not write or install a metadata provider plugin.

### `tvshow.nfo` (per channel, written at subscribe time, refreshed on title change)

```xml
<?xml version="1.0" encoding="utf-8"?>
<tvshow>
  <title>Some Channel</title>
  <plot>Channel description from yt-dlp.</plot>
  <studio>YouTube</studio>
  <uniqueid type="youtube" default="true">UCabc123...</uniqueid>
</tvshow>
```

### Episode `.nfo` (one per video, filename matches the media file)

```xml
<?xml version="1.0" encoding="utf-8"?>
<episodedetails>
  <title>Video Title</title>
  <showtitle>Some Channel</showtitle>
  <season>2026</season>
  <episode>8110</episode>
  <plot>Video description.</plot>
  <aired>2026-08-11</aired>
  <runtime>12</runtime>
  <studio>YouTube</studio>
  <uniqueid type="youtube" default="true">dQw4w9WgXcQ</uniqueid>
</episodedetails>
```

`runtime` is in **minutes**. Escape all text content properly — video descriptions
contain everything.

### Artwork

At subscribe time, `yt-dlp --flat-playlist --playlist-items 0 -J <channel_url>` returns a
`thumbnails` array containing entries with `id` values like `avatar_uncropped` and
`banner_uncropped`. Download the avatar to `poster.jpg` and the banner to `fanart.jpg`.
Treat both as best-effort — if they're missing, carry on without them.

Per-episode thumbnails come from `--write-thumbnail`; rename to `<basename>-thumb.jpg`.

---

## 8. Data model

SQLite at `/var/lib/ytsubs/subs.db`. **Enable WAL mode** — the cron job and the web
server both write.

```sql
PRAGMA journal_mode = WAL;
PRAGMA foreign_keys = ON;

CREATE TABLE channel (
  id                INTEGER PRIMARY KEY,
  channel_id        TEXT NOT NULL UNIQUE,      -- UC...
  handle            TEXT,                      -- @handle, informational
  title             TEXT NOT NULL,
  description       TEXT,
  dir_name          TEXT NOT NULL UNIQUE,      -- sanitised, immutable after creation
  added_at          TEXT NOT NULL,
  backfilled        INTEGER NOT NULL DEFAULT 0,
  last_polled_at    TEXT,
  last_poll_ok      INTEGER,
  consecutive_poll_failures INTEGER NOT NULL DEFAULT 0
);

CREATE TABLE video (
  id                INTEGER PRIMARY KEY,
  video_id          TEXT NOT NULL UNIQUE,
  channel_pk        INTEGER NOT NULL REFERENCES channel(id) ON DELETE CASCADE,
  title             TEXT,
  upload_date       TEXT,                      -- YYYY-MM-DD
  duration          INTEGER,
  season            INTEGER,
  episode           INTEGER,
  state             TEXT NOT NULL,
  discovery_source  TEXT NOT NULL,             -- 'uulf_feed' | 'uc_feed' | 'backfill'
  rel_path          TEXT,                      -- relative to media root, NULL unless downloaded
  size_bytes        INTEGER,
  attempts          INTEGER NOT NULL DEFAULT 0,
  last_error        TEXT,
  discovered_at     TEXT NOT NULL,
  downloaded_at     TEXT,
  deleted_at        TEXT
);

CREATE INDEX idx_video_state ON video(state);
CREATE INDEX idx_video_upload_date ON video(upload_date);

CREATE TABLE setting (
  key   TEXT PRIMARY KEY,
  value TEXT NOT NULL
);
```

### `video.state` values

| State | Meaning | Retried? |
|---|---|---|
| `pending` | discovered, queued | — |
| `downloading` | claimed by a worker | recovered on startup → `pending` |
| `downloaded` | on disk, `rel_path` set | — |
| `deleted` | aged out; tombstone prevents re-download | never |
| `skipped_short` | rejected by match filter | never |
| `skipped_live` | rejected by match filter | never |
| `skipped_old` | discovered but already outside the window | never |
| `failed` | download error | yes, up to 5 attempts |

The tombstone behaviour is the important part: a `deleted` row must never be
re-discovered and re-downloaded. This is why we keep our own state table rather than
using yt-dlp's `--download-archive`.

### Settings (all editable from the admin page)

Store as strings; provide typed accessors with defaults so a missing key never crashes.

| Key | Default | Notes |
|---|---|---|
| `retention_days` | `14` | delete videos with `upload_date` older than this |
| `backfill_days` | `7` | window pulled when a channel is added |
| `max_height` | `720` | |
| `min_duration_seconds` | `120` | fallback-path Shorts filter |
| `sponsorblock_mark` | `true` | |
| `write_subs` | `true` | |
| `sub_langs` | `en.*` | |
| `respect_jellyfin_watch_state` | `true` | §10 |
| `jellyfin_url` | `http://127.0.0.1:8096` | |
| `jellyfin_api_key` | *(empty)* | masked in the UI |
| `jellyfin_user_id` | *(empty)* | |
| `pot_provider_url` | `http://127.0.0.1:4416` | |
| `max_attempts` | `5` | |
| `disk_cap_gb` | `0` | `0` = disabled; if set, evict oldest downloaded videos |

Validate on save (integers parse, URLs well-formed) and re-render the form with an inline
error rather than 500-ing.

---

## 9. Entry point and scheduling

Single executable `ytsubs` with subcommands:

| Command | Purpose |
|---|---|
| `ytsubs run` | poll → download → reap. This is what cron calls. |
| `ytsubs poll [--channel ID]` | discovery only |
| `ytsubs download` | drain the pending queue |
| `ytsubs reap` | retention pass |
| `ytsubs serve` | admin HTTP server (systemd unit) |
| `ytsubs subscribe <url>` / `unsubscribe <id>` | CLI equivalents, useful for debugging |
| `ytsubs doctor` | check yt-dlp version, POT provider reachable, DB writable, media root writable, Jellyfin reachable |

`run` takes a **non-blocking `flock`** on `/var/lib/ytsubs/run.lock` and exits 0 silently
if already held. On startup, reset any `downloading` rows to `pending` (crash recovery).

### Cron

```
17 * * * * runitor -uuid <hc-uuid> -- /usr/local/bin/ytsubs run
```

Hourly is ample for single-digit channels. Register the check in Healthchecks with a
generous grace period.

### systemd unit for the admin server

Standard `simple` unit, `Restart=always`, running as the same unprivileged user that owns
the DB and media root. When the user subscribes to a channel via the web UI, the handler
should spawn `ytsubs run --channel <id>` detached so the backfill starts immediately
rather than waiting up to an hour.

### nginx

Bind the admin server to `127.0.0.1:8085`. Front it with nginx on the **tailnet
interface only** — `yt.jihakuz.xyz` resolving inside Headscale, HTTP basic auth on top.
Given the brother will be on the tailnet anyway, there's no reason to expose this
publicly, and it removes the need for a Let's Encrypt cert and any real CSRF story.
Confirm this before implementing; if it does need to be public, add proper CSRF tokens.

---

## 10. Retention and deletion

### Aging out (`ytsubs reap`)

Candidates: `state = 'downloaded'` and `upload_date < today - retention_days`.

Before deleting, if `respect_jellyfin_watch_state` is on:

1. `GET {jellyfin_url}/Items?userId={user_id}&recursive=true&includeItemTypes=Episode&fields=Path,UserData`
   with header `X-Emby-Token: {api_key}` — one call per reap, build a `path → UserData` map.
2. **Skip** any candidate where `UserData.PlaybackPositionTicks > 0 and not UserData.Played`
   (part-watched) or `UserData.IsFavorite` is true.
3. Apply a hard backstop: delete anyway once `upload_date` is older than
   `retention_days * 2`, so a half-watched video doesn't live forever.

Nothing wrecks "set and forget" like a video disappearing at the 20-minute mark. This
check is worth the complexity.

Deletion removes the media file plus its `.nfo`, `-thumb.jpg`, `.srt`, and `.info.json`
siblings, then prunes the season directory if empty. Set `state='deleted'`,
`deleted_at`, and `rel_path=NULL`. **Keep the row** — it's the tombstone.

If the Jellyfin API is unreachable, skip the whole reap for that run and log it. Do not
delete blindly.

### Unsubscribe

Hard delete, as agreed: `shutil.rmtree()` the channel directory, then `DELETE FROM
channel` (cascades to `video`). Re-subscribing later starts from scratch and re-downloads
the last 7 days. Put a confirmation step in the UI — this is destructive and irreversible.

### Disk cap (optional, `disk_cap_gb`)

If enabled, after each reap, sum `size_bytes` over `downloaded` rows and evict oldest-by-
`upload_date` until under the cap, honouring the same watch-state protection.

---

## 11. Admin UI

Stdlib only — `http.server.ThreadingHTTPServer` + `BaseHTTPRequestHandler`. No Flask, no
FastAPI, no npm. Server-rendered HTML with a single embedded `<style>` block. The only
JavaScript should be a `confirm()` on the unsubscribe button.

### Routes

| Method | Path | Behaviour |
|---|---|---|
| `GET` | `/` | Channel list + add form + settings form |
| `POST` | `/channels` | Resolve URL → insert → spawn backfill → redirect to `/` |
| `POST` | `/channels/<id>/delete` | Confirm-guarded hard delete → redirect |
| `POST` | `/settings` | Validate + persist → redirect |
| `GET` | `/health` | JSON: yt-dlp version, POT provider up, last run time, queue depth |

All POSTs redirect (303) so refresh doesn't resubmit.

### Channel list should show, per channel

Title, `@handle`, video count on disk, disk usage, most recent upload date, last poll
time, and a warning badge if `consecutive_poll_failures > 2`.

### Channel URL resolution

Accept: `https://www.youtube.com/@handle`, `/channel/UC...`, `/c/name`, `/user/name`,
a bare `@handle`, or a bare `UC...` ID.

```
yt-dlp --flat-playlist --playlist-items 0 -J <url>
```

`--playlist-items 0` fetches channel metadata **without enumerating the uploads**, which
is the cheap way to do this. Pull `channel_id`, `channel`, `description`, `thumbnails`
from the result. If resolution fails or returns no `channel_id`, re-render the form with
an error — don't insert a half-formed row.

Reject duplicates on `channel_id` (not on the submitted URL — the same channel has many
URL forms).

---

## 12. Known gotchas

- **yt-dlp churn is the top operational risk.** Extractor args, client names, and PO
  token requirements change frequently. Weekly `pip install -U yt-dlp` under runitor.
  When something breaks, check the yt-dlp issue tracker before debugging our code.
- **The `UULF` prefix is undocumented** and could vanish. The `channel_id` fallback path
  is not optional.
- **RSS feeds cap at ~15 entries.** Fine for hourly polling, insufficient for backfill —
  hence the separate `--flat-playlist` path in §4.
- **`.work` must share a filesystem with the media root**, or every completed download
  becomes a full copy.
- **Don't transcode.** If Jellyfin is transcoding these files, the format selection in §6
  is wrong — fix it there, not by throwing hardware at it.
- **Descriptions are hostile input** for XML generation. Use `xml.etree`'s serialiser
  rather than string-formatting the NFO by hand.
- **WAL mode is required** — two writers.
- Don't reuse `/disks/Plex/YouTube` (TubeArchivist's tree).

---

## 13. Acceptance criteria

Work through these in order; each is a real check, not a code-reading exercise.

1. `ytsubs doctor` passes on a clean install.
2. Subscribing to a real, active channel creates the directory, `tvshow.nfo`,
   `poster.jpg`, and queues the last 7 days of videos.
3. At least one real video downloads end to end and lands in the right season directory
   with a correct filename, NFO, thumbnail, and subtitle sidecar.
4. `ffprobe` on the downloaded file shows **h264 video and AAC audio**.
5. Jellyfin, after a library scan, shows the channel as a show, the year as a season, and
   the video as an episode with the correct title, description, and air date — with all
   internet metadata providers disabled.
6. The video **direct-plays** on a client with no transcoding (check the Jellyfin
   dashboard's active-streams panel).
7. Re-running `ytsubs run` immediately downloads nothing and errors on nothing
   (idempotency).
8. Manually backdating a video's `upload_date` past the retention window causes `reap` to
   delete it and its sidecars, prune the empty directory, and leave a `deleted` tombstone.
9. Re-running `poll` after that does **not** re-download the deleted video.
10. Marking a video part-watched in Jellyfin protects it from reap (with
    `respect_jellyfin_watch_state` on).
11. Unsubscribing removes the directory and all rows.
12. Killing `ytsubs run` mid-download leaves no orphan in `.work`, and the next run
    recovers the `downloading` row to `pending`.
13. The admin page renders, adds, removes, and persists settings; a bad settings value
    produces an inline error rather than a traceback.
14. Editing `retention_days` in the UI visibly changes reap behaviour on the next run.

---

## 14. Suggested build order

!! tom: we also wants tests through this 
1. Skeleton: DB schema, migrations, settings accessors, `doctor`
2. POT provider + a hardcoded single-video download proving §3 and §6 work — **do this
   before writing anything else of substance**
3. Channel resolution + `subscribe`/`unsubscribe` on the CLI
4. Discovery (`poll`), both feed paths
5. Download worker + NFO/artwork generation + move-into-place
6. Jellyfin library verification (acceptance criteria 5 and 6) — a checkpoint, not a step
7. `reap`, including the watch-state check
8. `run` orchestration, flock, crash recovery, cron + runitor + Healthchecks
9. Admin server
10. systemd unit, nginx on the tailnet, deploy scripts

Steps 2 and 6 are the two places where this design could turn out to be wrong. Hit them
early and report back rather than building on top of an unverified assumption.