ytstream/plan.md

# `ytstream` — implementation plan

**Target machine:** `susan`
**Status:** streaming PoC verified end to end against real videos and real Jellyfin — every
measurement behind this plan is written up in **`FINDINGS.md`** alongside this file. Nothing is
installed as a service yet. This document is the plan for turning it into one.

**Repo:** `/opt/ytstream`, pushed to `/disks/git-repos/ytstream.git`, branch `main`. The PoC code
still lives in `/home/susan/ytstream` and is *not* under version control; Phase 2 moves it in and
retires that directory.

**Relationship to `youtube-automate`:** ytstream **replaces** it. The two are entirely separate
trees, databases, services and Jellyfin libraries, and they will run side by side only for as long
as it takes to satisfy §13. `youtube-automate` is then decommissioned (§12). Nothing in
`/opt/youtube-automate` is modified by this work.

---

## 1. What we're building

A DVR-shaped YouTube library for Jellyfin that **stores no video bytes**.

`youtube-automate` downloads each video to disk and points Jellyfin at the file. ytstream writes a
~50-byte `.strm` file containing a URL, and materialises the actual video only when somebody
presses play — fetched on demand by a local proxy, held on tmpfs, dropped when the cache fills.

### Explicitly in scope

- Mirroring **one YouTube account's subscriptions** as Jellyfin TV series, one episode per video —
  that account is the source of truth for what exists (§4)
- **Automatic subscription pickup from a YouTube account's public subscription list** (§4) — the
  new requirement
- A bounded back catalogue per channel — **3 months or 300 videos, whichever comes first** — that
  then grows forward indefinitely (§3, §5)
- Just-in-time streaming via the proxy, with per-video caching
- NFO metadata, episode thumbnails, channel poster/fanart
- An admin UI for subscriptions, status and settings
- Running as real systemd services with real logs and real alerting

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

- Any form of transcoding. susan is a dual Westmere Xeon with **no AVX**; software transcode is off
  the table. The proxy produces `-c copy` fMP4 that Jellyfin direct-plays, and that is the only
  supported path.
- Downloading and keeping video files. If we want a permanent copy of something, that is a
  different tool.
- Playlists, Shorts, livestreams, comments, community posts, memberships.
- Anything that runs on `victoria` (the Linode). susan's residential IP is a load-bearing part of
  not getting flagged by YouTube.
- A YouTube *account* login / cookies. PO tokens only, exactly as `youtube-automate` does it.

---

## 2. This is a fork, not a green-field rewrite

`youtube-automate` is 3,543 lines and most of it is correct, verified, and has nothing to do with
downloading. Rewriting it from scratch would mean re-deriving the RSS filtering, the episode
numbering, the NFO schema and the auth code — all of which were validated on the live machine on
2026-08-11 and are documented in `/opt/youtube-automate/specs.md`.

So: copy the tree, then add, delete and replace.

| `youtube_automate` module | Fate in `ytstream` | Note |
|---|---|---|
| `discovery.py` | **Lift, then extend** | UULF-feed polling is the cheapest correct incremental source and stays. Gains an API-backed full-catalogue backfill (§3). |
| `naming.py` | **Lift unchanged** | Season = upload year, episode = `MMDD*10 + ordinal`. Keep byte-identical so both trees sort the same during the overlap. |
| `nfo.py` | **Lift, small change** | Drop `<fileinfo><streamdetails>` — measured to accomplish nothing (FINDINGS §6). Keep `<durationinseconds>`. |
| `channels.py` | **Lift, minus artwork fetch** | Artwork moves to the API/`i.ytimg.com` path already built in `add_thumbnails.py`. |
| `db.py`, `settings.py`, `util.py`, `config.py` | **Lift** | New DB file and new schema version (§7). |
| `web/` (auth, server, templates) | **Lift** | 838 lines of working scrypt auth + admin UI. New routes for subscription sources. |
| `jellyfin.py` | **Lift, harden** | Library refresh must never be `replaceAllMetadata` (§5). |
| `doctor.py` | **Lift, extend** | Add checks for API key validity, proxy health, `.strm` orphan count. |
| `ytdlp.py` | **Lift, narrow** | Only the proxy calls yt-dlp now. |
| `download.py` (330 lines) | **Delete** | Replaced by `strm.py`, which writes a text file. |
| `reap.py` (150 lines) | **Delete, replace** | Reaping existed to reclaim disk. There is no disk to reclaim (§3). Replaced by a much smaller "retire a video whose channel is gone" path. |
| `runner.py` | **Rewrite** | The run loop changes shape: sync subscriptions → poll → materialise → refresh. |
| — | **New: `strm.py`** | Writes `.strm` + `.nfo` + thumbnail for one video. |
| — | **New: `subsync.py`** | The brother-subscription puller (§4). |
| — | **New: `api.py`** | YouTube Data API v3 client (§3). |
| — | **New: `proxy/`** | `/home/susan/ytstream/ytstream.py`, moved in and split up. |

Everything lifted keeps its tests. `youtube-automate` has 12 test modules; they come across too.

---

## 3. The pivot: the YouTube Data API becomes the metadata source

The subscription feature (§4) forces us to get a Google API key. Once we have one, it is worth
noticing what else it buys, because it resolves the two problems that would otherwise make the
full back catalogue impractical.

**Verified quota costs** (`developers.google.com/youtube/v3/determine_quota_cost`): a new project
gets **10,000 units/day** shared across everything except `search.list` and `videos.insert`, which
have their own 100-call/day buckets. `subscriptions.list`, `playlistItems.list`, `videos.list` and
`channels.list` are **1 unit each**, and each returns up to 50 items.

That changes the arithmetic completely:

| Job | Method | Calls | Units |
|---|---|---|---|
| Sync one account's subscriptions, hourly | `subscriptions.list` | 24/day (1 page) | 24 |
| Backfill one channel to the §5 bound (≤300 videos) | `playlistItems.list` @50 | ≤6 | ≤6 |
| Durations for those videos | `videos.list` @50 ids | ≤6 | ≤6 |
| Steady-state incremental discovery | **RSS feed** | — | **0** |

A 20-channel initial build costs at most **240 units** — under 3% of one day's quota, once. Steady
state costs under 100 units/day. **We will never come close to the limit**, provided we never touch
`search.list` (100 calls/day, and we have no use for it).

### Why this matters more than the quota

**It takes yt-dlp out of the cataloguing path entirely.** Today, `youtube-automate` needs a yt-dlp
extraction per video to learn an upload date during backfill, at roughly 2.3s each. For a 20-channel
build at the §5 bound that is 6,000 videos ≈ **4 hours of continuous requests** to YouTube from a
residential IP — the "scan storm" failure mode the original handover warned about, and it recurs
every time a channel is added. The API is a documented, keyed, quota-metered endpoint that does not
care about PO tokens, SABR, or client selection, and cannot be rate-limited by YouTube's anti-bot
heuristics.

So the split becomes:

- **Cataloguing** (what exists, when, how long, what it's called) → **YouTube Data API + RSS**. No
  yt-dlp, no PO token, no IP-flagging risk.
- **Playback** (actual media bytes) → **yt-dlp inside the proxy**, one video at a time, only when a
  human pressed play.

That is a much better boundary than the current one, and it is the main reason to build ytstream as
a new service rather than patch `youtube-automate`.

### It also fixes exact upload dates

Measured during the PoC: `--flat-playlist` reports `timestamp: None`, and
`youtubetab:approximate_date` is **wrong by up to 2 days**. Since season/episode is derived from
the upload date, an approximate date means episodes numbered into the wrong day — and Jellyfin
caches episode numbers, so fixing it later is a metadata-wipe operation. `playlistItems.list`
returns `contentDetails.videoPublishedAt` as an exact RFC-3339 timestamp. Use it.

### One thing to verify before relying on it

`youtube-automate` polls the **UULF** playlist (`UU` with `LF` spliced in), which is undocumented
but excludes Shorts and livestreams at the cheapest possible point — verified in specs.md §4.
Whether `playlistItems.list` accepts a UULF id is **unverified**; only `UU` is documented.

- If UULF works: use it, and the existing filtering carries over unchanged.
- If it 404s: fall back to `UU` (definitely works, includes Shorts and livestreams) and filter with
  the `videos.list` call we are making anyway — `contentDetails.duration < min_duration_seconds`
  drops Shorts, and the presence of `liveStreamingDetails` drops streams.

Either way it is one extra unit per 50 videos. Verify with a single curl on day one:

```sh
curl -s "https://www.googleapis.com/youtube/v3/playlistItems?part=contentDetails\
&playlistId=UULF2EvK7nHUOEw1IvWFpTourQ&maxResults=5&key=$KEY" | head -40
```

---

## 4. Subscription mirroring — the new requirement

**Goal:** the brother subscribes to a channel on YouTube, and it appears in Jellyfin without anyone
touching an admin page.

### The account to mirror — resolved

| | |
|---|---|
| Handle | `@cflux1030` |
| Channel id | **`UCPcTWaLV8zwx4WP4QExHj4Q`** |
| Display name | `C Flux` |

Resolved via yt-dlp on 2026-08-12, so no `channels.list` call is needed at build time — seed it as
the single `source` row.

**This account is the sole source of truth.** There is no second source and no parallel manual
subscription workflow: what he follows on YouTube is what exists in Jellyfin. Tom's own
subscriptions are explicitly not part of this. That is a simplification (§4.3) but it moves all the
weight onto the removal safeguards (§4.4), because nothing else protects a channel any more.

### It works, with one condition on his side

Confirmed against the API reference: `subscriptions.list` accepts a `channelId` filter —
*"The API will only return that channel's subscriptions"* — and unlike `mine`,
`mySubscribers` and `myRecentSubscribers` it is **not** documented as requiring an authorized
request. So a plain API key is enough. The condition is that his subscriptions must be public:
the implementation guide states the API returns **403** if the channel *"does not publicly expose
its subscriptions and the request is not authorized by the channel's owner"*, and the errors table
lists `subscriptionForbidden` (403) — *"The requester is not allowed to access the requested
subscriptions."*

This is a good failure mode: **403, not an empty list.** We can tell "he made his subscriptions
private again" apart from "he has no subscriptions", which matters a lot for §4.4.

**There is no scraping fallback — verified.** `https://www.youtube.com/@cflux1030/channels` returns
200 but silently serves the Home tab: the rendered `ytInitialData` lists exactly four tabs (Home,
Videos, Playlists, Search) and contains **zero** channel ids. YouTube retired the public
subscriptions tab, so the API is the *only* route to this list. That makes the privacy checkbox
genuinely mandatory rather than merely the convenient path, and it means a 403 has no workaround
short of §4.2.

### 4.1 Setup — what has to happen once

**Google side** (Tom, ~5 minutes, free, no billing account required):

1. `console.cloud.google.com` → new project, e.g. `ytstream`.
2. APIs & Services → Library → **YouTube Data API v3** → Enable.
3. Credentials → Create credentials → **API key**.
4. Restrict the key: Application restrictions → *None* (it is called from a server, so referrer and
   Android/iOS restrictions do not apply; an IP restriction is optional and breaks if susan's
   residential IP rotates). API restrictions → **YouTube Data API v3 only**.
5. Paste it into the ytstream admin UI. It is stored in the `setting` table like
   `jellyfin_api_key` already is — never in the repo, never in a systemd unit.

No OAuth consent screen. No app verification. No user-facing consent flow.

**Brother's side** (one checkbox, and it is the only thing he has to do):

- youtube.com → Settings → **Privacy** → uncheck **"Keep all my subscriptions private"**.

**Verify immediately** — before writing any of `subsync.py` — that his account actually returns
data:

```sh
curl -s "https://www.googleapis.com/youtube/v3/subscriptions?part=snippet\
&channelId=UCPcTWaLV8zwx4WP4QExHj4Q&maxResults=50&key=$KEY" \
  | python3 -c 'import json,sys; d=json.load(sys.stdin); \
      print(d.get("pageInfo")); \
      [print(i["snippet"]["resourceId"]["channelId"], i["snippet"]["title"]) \
       for i in d.get("items",[])]'
```

A 200 with `items[]` confirms the design on the real account. A 403 means the privacy checkbox has
not taken effect — and per the finding above, there is no way around it.

**This call also produces the number that sets `subsync_max_new`** (§4.4): `pageInfo.totalResults`
is how many channels he is subscribed to today, which is the one input the cap needs and which
cannot be discovered any other way. Record it here when known:

> `totalResults` = **TBD — Phase 0**

### 4.2 Fallback if `channelId` turns out not to work

Ranked, if and only if the day-one curl fails. Note that all three require him to do something —
there is no silent workaround, because the public HTML route is gone.

1. **OAuth with `mine=true`.** Robust and privacy-setting-independent, but carries a trap:
   confirmed in Google's OAuth 2.0 docs, a project whose consent screen publishing status is
   **"Testing"** is *"issued a refresh token expiring in 7 days"* unless the only scopes are basic
   profile ones. `youtube.readonly` is not, so the token would die weekly. Avoiding that means
   moving the app to "In production", which for a sensitive scope means Google verification — a
   disproportionate amount of process for one brother. Only do this if option 3 is unacceptable.
2. **Google Takeout subscription CSV**, dropped into the admin UI. Manual, but a 30-second job
   whenever he adds channels, and zero moving parts.
3. **Just tell him to use the admin UI.** It already exists and it is one text box.

Design `subsync.py` so the source of a channel list is pluggable (§4.3 makes this fall out
naturally), so swapping between these is a small change rather than a rewrite.

### 4.3 One source of truth — the sync is authoritative

His subscription list *is* the subscription list. So the model is simply "make the DB match the API
response", and it needs no reconciliation machinery:

- A channel in his list is subscribed. A channel that leaves it is unsubscribed, subject to §4.4.
- Two columns on `channel` carry what the sync needs: `source` (provenance) and `missing_syncs` (the
  §4.4 counter). No join table.

An earlier draft modelled this as multi-source *claims*, so that a manually-added channel could not
be deleted by someone else's list. With one source that machinery is dead weight, and speculative
generality in the part of the system that deletes things is the wrong place to spend it. If a second
account is ever mirrored, `source` is already there to key on and the claims model can come back
then.

**One escape hatch survives:** `source = 'manual'` marks a channel the sync will never remove. It is
for pinning something during debugging, not a workflow, and it is not exposed as "subscribe to a
channel" in the UI — the way to add a channel is to subscribe to it on YouTube.

**The cost of this choice, stated plainly:** if he unsubscribes from a channel, its series stops
updating and disappears from the library view. That is the correct behaviour for a mirror, and it is
exactly why §4.4 refuses to act on a single bad response.

### 4.4 Removals must be slow and loud; additions must be capped

Two failure modes here are genuinely destructive, and both are cheap to defend against.

**Runaway additions.** If he has 400 subscriptions, the first sync queues 400 channels — at the §5
bound that is 120,000 Jellyfin episodes, which will not end well. So:

- A sync that would add more than **`subsync_max_new`** channels adds none of them. It records them
  as `pending_approval`, alerts, and waits for a click in the admin UI.
- The cap applies per sync run, so ordinary drip-feed additions never trip it.

**Separate the first sync from steady state.** Otherwise the cap always trips on day one, whatever
it is set to, and the guard trains everyone to ignore it. So a source's **first** sync is an
explicit bulk import: the admin UI shows the whole list with per-channel checkboxes and a count of
the episodes it implies, and nothing is subscribed until someone confirms. From the second sync
onwards the cap is a runaway guard, and `subsync_max_new` is set from the day-one `totalResults`
(§4.1) — a sensible rule is **max(10, ceil(totalResults × 0.2))**, so a genuine burst of activity
gets through but an order-of-magnitude jump does not. Provisional default **25** until Phase 0
produces the real number.

**Runaway removals.** A transient 403, a network blip, or him re-ticking the privacy box all look
like "he unsubscribed from everything". Deleting 20 channels' worth of Jellyfin metadata on that
basis would be unrecoverable in any pleasant way. So:

- **A 403, a 5xx, a timeout, or a zero-item 200 is never treated as a removal.** It increments the
  source's failure counter, alerts, and changes nothing. A genuinely empty list is
  indistinguishable from a broken one in consequence, and we prefer the harmless reading.
- A channel missing from an otherwise-healthy response increments `missing_syncs`. Only at
  **`subsync_missing_threshold`** (default **3** consecutive syncs, so ~3 hours) is it unsubscribed.
- Unsubscribing **does not delete anything on disk**. It sets the channel `inactive`: polling stops,
  the tree stays, and re-subscribing on YouTube restores it with no refetching. Actual deletion is a
  separate, explicit, human-initiated admin action. `.strm` files cost ~50 bytes each; there is no
  pressure to reclaim anything, so there is no reason to ever delete automatically.
- `source = 'manual'` channels are exempt from all of the above.

**Ordering:** the sync runs *before* the poll in the same run, so a channel added at 14:00 has its
catalogue built in the same pass.

### 4.5 Alerting

Existing convention on susan is `runitor` + healthchecks.io at `hc.jihakuz.xyz`, one UUID per job.
Follow it. A sync that hits 403, trips the add cap, or accumulates failures must exit non-zero so
the check goes red — a silently-broken subscription mirror is the worst possible outcome, because
nothing appears to be wrong until someone asks why a channel never showed up.

### 4.6 The brother gets admin access, so auth becomes multi-user

This is the right call — the approval queue (§4.4) and the "channel went missing" alerts are about
*his* subscriptions, so they should be his to action rather than landing on Tom every time. But it
does mean a change: `youtube-automate` has exactly one credential, `admin_password_hash` in the
`setting` table. Sharing it would mean neither party can have their access revoked or their password
changed independently, and the approval log would not record who approved what.

So replace the single setting with a minimal `user` table (§7): `username`, `password_hash`
(scrypt, same parameters), `created_at`, `last_login_at`. Two rows. **No roles, no permissions
system** — both accounts can do everything, which is correct for two brothers and one media server,
and the alternative is a permission model nobody will maintain.

Everything else in `web/auth.py` carries over unchanged, and it is adequate for an
internet-facing login: scrypt hashing and per-address failed-login throttling that reads
`X-Forwarded-For` (which nginx must set — it already does, see §12 step 4).

Record `approved_by` on `pending_approval` resolutions. It costs one column and it answers "why is
this channel here" six months later.

---

## 5. Scale — bounded backfill, unbounded growth

Measured during the PoC: **Pitch Side has 1,249 videos.** The `youtube-automate` DB holds 15 of
them, because a 9-day retention window and 1.3 TB of free disk is what bounded it. `.strm` files
remove that bound entirely, so the bound is now a policy choice, and the choice is:

> **Backfill 3 months or 300 videos per channel, whichever comes first.**

Both settings exist (`backfill_max_days` = 90, `backfill_max_videos` = 300) and whichever is reached
first stops the walk. The two are well matched in practice: a channel uploading 2–3 times a day —
which is what Pitch Side's episode numbering implies — produces roughly 270 videos in 90 days, so
neither bound dominates. A weekly uploader gets ~13 videos and is bounded by time; a daily-podcast
firehose gets 300 and is bounded by count. That is the right behaviour in both directions.

**This bounds the *initial* build, not the library.** Nothing ages out — `.strm` files cost ~50
bytes and there is no disk to reclaim, so aging out would destroy metadata for no gain. The
consequence is honest and worth stating: the library **grows forever from the subscribe date**. At
20 channels averaging 2 uploads/day that is ~15,000 new episodes a year, so the 20,000-episode
question in point 1 below is deferred by about eighteen months, not answered. The lever, if it ever
bites: a `hidden` video state that removes the `.strm` and `.nfo` from disk while keeping the DB row,
so the catalogue stays re-materialisable. **Do not build it now** — build the measurement that tells
us when we need it.

**Initial build:** ~20 channels × ≤300 = **≤6,000 episodes, ≤12,000 files.** Comfortable.

1. **Jellyfin scan cost is still unmeasured**, and is the number that decides everything above.
   Every episode is a `.strm` + a `.nfo` + a thumbnail. Normal scans were measured to make **0 media
   probes** (FINDINGS §6), which is the thing that makes this viable at all — but stat-ing and
   NFO-parsing 12,000 files on a Westmere with the library DB on spinning disk is its own cost.
   **Measure in Phase 3** by building one channel to the bound, timing a full scan, and recording
   seconds-per-1,000-episodes here. That single figure sizes both the initial build and the growth
   runway.
2. **`replaceAllMetadata` remains a catastrophe rather than an annoyance.** It is the one operation
   verified to probe media, and at 6,000 items it means 6,000 cold starts. The cold-start rate
   limiter (20/hour) contains the damage to YouTube's side, but the library-side result is 6,000
   items whose metadata got wiped and not re-derived. Defences, all of them:
   - the proxy 503s past the budget (built, tested — `test_limits.py`)
   - `ytstream` never itself issues a refresh with `replaceAllMetadata=true`
   - the admin UI documents "do not click Replace all metadata" in the place where someone would be
     tempted to
   - **NFOs are the source of truth**, so recovery is a re-materialise pass over the tree, not a
     re-fetch from YouTube. Make sure that pass exists and is one CLI command.
3. **Episode numbering holds.** `MMDD*10 + ordinal` clamps at 10 uploads/channel/day, computed
   against the DB rather than the batch, so it is stable across a 300-video backfill. Season =
   upload year means a 3-month window usually spans one season and occasionally two (a January
   subscribe reaches back into the previous year), which is correct and needs no special handling.
4. **The `.strm` URL is baked into every file.** Changing the proxy's host or port means rewriting
   all of them. Cheap (it is a tree walk) but it must be a supported CLI command, not a `sed`
   someone invents under pressure. Settle the URL now: `http://127.0.0.1:8099/watch/<id>`. Jellyfin
   is the only client that ever reads it, it runs on the same host, and 127.0.0.1 means the proxy is
   unreachable from the network by construction.
5. **Backfill must be resumable.** Quota is a non-issue but a crash halfway through 12,000 files
   needs to resume, not restart. Track progress per channel (`channel.backfill_cursor`), commit per
   page of 50.

---

## 6. Components

Four processes. Two are long-running services, two are cron jobs.

### 6.1 `ytstream-proxy` — systemd service

The PoC, productionised. `/home/susan/ytstream/ytstream.py`, 31 KB, currently running by hand.

Already built and verified: `/watch/<id>` and `/healthz`, single extraction reused by both
yt-dlp legs via `--load-info-json`, FIFO→ffmpeg `-c copy` fMP4 on tmpfs, correct HTTP range
handling (25 assertions), LRU cache, concurrency cap, retry-on-403, cold-start rate limiter
(18 assertions), counters.

Outstanding before it is a service:

- **Install the unit.** `ytstream.service` is written but not installed; susan has **no
  passwordless sudo**, so this goes in `deploy/deploy.sh` for the operator to run once. The unit
  pins `Environment=PATH=/var/lib/ytstream/venv/bin:...` (load-bearing — the venv yt-dlp is the
  only one with the POT plugin), `User=susan Group=mediaserver UMask=0002`, and
  `Requires=docker.service` for the POT provider container.
- **Startup sweep of the work dir.** Sessions live in memory; a restart orphans whatever is in
  `/dev/shm/ytstream`. Wipe it on start.
- **Prove LRU eviction.** It has never fired in testing. Add a test with a tiny `--cache-gb`.
- **Decide the tmpfs budget.** `/dev/shm` is 24 GB of 47 GB RAM; throughput measured at ~480
  MB/hour of video. `--cache-gb 8` holds ~16 hours of content, which is ample. Do not raise it
  without thinking about what else on susan wants RAM.
- **Log to journald** rather than a scratch file, and keep the access log behind a flag.

**Unresolved, and staying that way:** the intermittent 403 has no known cause. Ruled out during the
hardening pass: rate limiting, `--load-info-json` round-tripping, concurrency, and — the
plausible-sounding one — missing PO tokens. Pinning `player_client=mweb` to get token-bearing URLs
measured **0 ok / 6 fail**, while token-less `ANDROID_VR` URLs work; had that "fix" shipped it would
have broken every playback. Retry with a fresh extraction is the mitigation, it works, and it fires
roughly once per dozen cold starts. Keep the `retried` counter visible so a change in that rate is
noticeable.

### 6.2 `ytstream-admin` — systemd service

Lifted from `youtube_automate/web/`. scrypt password hashes, now per user in the `user` table (§4.6)
rather than one shared setting, per-address failed-login throttling reading `X-Forwarded-For`, behind
nginx on `127.0.0.1:8086` (8085 is `youtube-automate`'s during the overlap).

New routes beyond what exists: subscription **sources** (add/remove a mirrored YouTube account, show
its last sync, its failure count, its `pending_approval` queue with an approve/reject action), the
first-sync bulk-import screen, per-channel backfill-depth controls, account management for the two
users, and the API key field.

**Two people use this**, so the copy matters more than it did with a single operator: the
"do not click Replace all metadata" warning (§5) has to be where someone would be tempted, and the
approval screen has to show what a channel implies — an episode count — before it is approved.

### 6.3 `ytstream run` — hourly cron

`sync sources → poll feeds → materialise → refresh Jellyfin`. Under `flock` on
`/var/lib/ytstream/run.lock`, under `runitor` with its own healthchecks UUID, via
`sg mediaserver "..."` to match the existing convention.

### 6.4 `ytstream backfill` — manual / one-off per channel

The expensive path (§3, §5). Deliberately not on a timer: it runs when a channel is first
subscribed, and when someone explicitly asks for a deeper catalogue.

---

## 7. Data model

`/var/lib/ytstream/ytstream.db`. Start from `youtube-automate`'s schema — `channel`, `video`,
`setting` are the right shape — with these changes:

**`channel`** — add `backfill_cursor TEXT` (resumable backfill), `backfill_max_videos INTEGER` and
`backfill_max_days INTEGER` (per-channel overrides of the §5 bounds; NULL = use the global setting),
`active INTEGER NOT NULL DEFAULT 1` (§4.4 soft-delete), `uploads_playlist TEXT` (whether UULF or UU
won, §3). Drop `retention_days`.

**`video`** — drop `size_bytes`, `downloaded_at`, `deleted_at`, `attempts`, `last_error`; none of
them mean anything when there is no download. Keep `duration` (now from `videos.list`, and it feeds
`<durationinseconds>`). `state` collapses to `{listed, materialised, skipped_short, skipped_live,
hidden}` — no `pending`/`downloading`/`failed`, because materialising a `.strm` cannot
meaningfully fail. Add `published_at TEXT` (exact RFC-3339 from the API) alongside the existing
date-only `upload_date` that naming uses.

**`channel`, continued** — two more columns instead of the join table an earlier draft had (§4.3):
`source TEXT NOT NULL` (`'youtube'` for synced, `'manual'` for the pinning escape hatch) and
`missing_syncs INTEGER NOT NULL DEFAULT 0` (the §4.4 counter).

**`source`** — new, and in practice **exactly one row**: `key`, `label`, `channel_id`, `enabled`,
`last_sync_at`, `last_sync_ok`, `consecutive_failures`, `last_error`. A one-row table rather than six
`setting` keys, because these are fields of one thing and they change together.

**`pending_approval`** — new, the §4.4 add-cap and first-sync import queue: `source`, `channel_id`,
`title`, `seen_at`, `resolved_at`, `resolution` (`approved`/`rejected`), `approved_by`.

**`user`** — new (§4.6), replacing the single `admin_password_hash` setting: `username` (PK),
`password_hash` (scrypt, same parameters as `youtube-automate`), `created_at`, `last_login_at`. Two
rows, no roles.

**`setting`** — carry over what still applies (`jellyfin_url`, `jellyfin_api_key`,
`pot_provider_url`, `max_height`, `min_duration_seconds`, `session_secret`, `last_run_at`). Drop
`retention_days`, `disk_cap_gb`, `write_subs`, `sub_langs`, `sponsorblock_mark`, `max_attempts`,
`backfill_days`, `admin_password_hash` — download-era concepts plus the credential that moved to
`user`. Add `youtube_api_key`, `subsync_max_new` (25, provisional — §4.4),
`subsync_missing_threshold` (3), `proxy_base_url` (`http://127.0.0.1:8099`), `backfill_max_videos`
(**300**), `backfill_max_days` (**90**).

**No migration from `subs.db`.** It holds 2 channels and 18 videos. Re-subscribe by hand and let
the backfill do the rest; a migration script would be more code than the data is worth.

---

## 8. On-disk layout and the `.strm` contract

Media root: **`/disks/Plex/_ytstream/`** — already created and already wired to the *YouTube
(stream)* Jellyfin library, with 2 channels in it from the PoC. Keep it. (The name has a leading
underscore matching `_ingest`/`_cache` on that volume; `/disks/Plex/YouTube` stays with
`youtube-automate` until §12 retires it.)

```
/disks/Plex/_ytstream/
└── Pitch Side/
    ├── tvshow.nfo
    ├── poster.jpg                                  # channel avatar
    ├── fanart.jpg                                  # channel banner
    └── Season 2026/
        ├── Pitch Side - S2026E8120 - Title [dQw4w9WgXcQ].strm
        ├── Pitch Side - S2026E8120 - Title [dQw4w9WgXcQ].nfo
        └── Pitch Side - S2026E8120 - Title [dQw4w9WgXcQ]-thumb.jpg
```

Naming, sanitisation and `dir_name` stability rules are `youtube-automate`'s, unchanged
(specs.md §5) — identical rules in both trees is what makes the overlap period sane.

**`.strm` contents:** one line, no trailing newline required:

```
http://127.0.0.1:8099/watch/dQw4w9WgXcQ
```

**NFO:** `episodedetails` with `title`, `season`, `episode`, `aired`, `plot`, `runtime`,
`durationinseconds`, `uniqueid type="youtube"`. **No `<fileinfo><streamdetails>`** — pre-seeding it
was measured to change nothing about whether Jellyfin probes (FINDINGS §6), so it is dead weight.

**No `.work/` dir under the media root.** The proxy's scratch space is `/dev/shm/ytstream`, outside
the library entirely, which is strictly better than the dot-dir-plus-`.ignore` belt-and-braces that
`youtube-automate` needs.

---

## 9. Environment and paths

Verified on the machine, 2026-08-12.

| Purpose | Path |
|---|---|
| Source (bare repo) | `/disks/git-repos/ytstream.git` — **exists but is not yet `git init --bare`** |
| Checkout | `/opt/ytstream` — exists, `susan:automation` `0770` |
| Entry point | `/usr/local/bin/ytstream` (needs root, → `deploy.sh`) |
| Virtualenv | `/var/lib/ytstream/venv` |
| State DB | `/var/lib/ytstream/ytstream.db` |
| Lock file | `/var/lib/ytstream/run.lock` |
| Media root | `/disks/Plex/_ytstream/` |
| Proxy scratch | `/dev/shm/ytstream` (tmpfs, 24 GB available) |
| Admin UI | `127.0.0.1:8086`, nginx → `tube.jihakuz.xyz` (§12) |
| Proxy | `127.0.0.1:8099`, not exposed |

Facts that constrain the design:

- **Ownership:** the media tree convention is `susan:mediaserver`, dirs `0770`, files `0664`.
  `/disks/Plex` is `0770` with no setgid; Jellyfin reaches the tree only through its `mediaserver`
  supplementary group. Both units run `User=susan Group=mediaserver UMask=0002`; cron goes through
  `sg mediaserver`. `/disks/Plex/_ytstream` already has the setgid bit — keep it.
- **No passwordless sudo.** Everything touching `/usr/local/bin`, `/etc/systemd/system` or
  `/etc/nginx` belongs in `deploy/deploy.sh`.
- **yt-dlp:** `/usr/local/bin/yt-dlp` is a **2023.11.16** binary, far too old to work. Nothing
  references it; leave it alone. ytstream gets its own venv with `yt-dlp[default]` (the extra that
  ships `yt-dlp-ejs`, mandatory for JS challenge solving), `bgutil-ytdlp-pot-provider==1.3.1`
  matching the container tag, and `curl-cffi<0.16`. Note that during the overlap **two** venvs will
  hold yt-dlp; keep both current, and do not let a bare `yt-dlp` on `PATH` be what either service
  resolves.
- **POT provider:** container on `127.0.0.1:4416`, `--restart unless-stopped`, Docker enabled at
  boot. Shared with `youtube-automate` during the overlap and inherited afterwards. It is the
  reason the proxy unit declares `Requires=docker.service`.
- **Client selection is settled — do not re-litigate it.** `CLIENT_ARGS =
  "youtube:player_client=default"`. `mweb` is deliberately absent: its formats 403 on every
  attempt, and it was the sole source of the DRC and dubbed-language variants behind both original
  format-picker bugs. `web`/`ios`/`web_safari`/`tv` are SABR-only and yield nothing usable. Left as
  `default` rather than pinned to `android_vr` so a yt-dlp update can follow YouTube.
- **Jellyfin 10.11.4**, native systemd, `0.0.0.0:8096`, API key already in the DB.

---

## 10. Playback UX — state it plainly

Measured: wait-for-complete is ready in **20 s** for a 21-minute video and **~55 s** for a
46-minute one, at ~8 MB/s (~60× realtime). `--growing` mode gives TTFB of **6.5–7.1 s** but ffmpeg
writes `mvhd.duration=0` and no `mehd` box regardless of what it knows about the input — verified,
including an attempt to patch the boxes afterwards, which ffmpeg ignores — so the player sees a
video of unknown, growing length. Seeking and progress bars misbehave.

**Ship wait-for-complete.** A ~20–55 s spinner that then behaves like a normal file beats instant
playback with a broken timeline. Keep `--growing` as a flag for experimentation. Revisit only if
someone complains, and if they do, the fix is a pre-warm on library browse rather than a change to
the mux.

---

## 11. Configuration and secrets

Secrets live in `/var/lib/ytstream/ytstream.db`, mode `0640` `susan:automation`, and are entered
through the admin UI. Never in the repo, never in a systemd unit, never in a cron line. This matches
`youtube-automate`, where `jellyfin_api_key` and `session_secret` already live that way.

Three kinds: `youtube_api_key` (new) and `jellyfin_api_key` in `setting`; `session_secret` in
`setting`; and two scrypt password hashes in `user` (§4.6).

The YouTube API key is restricted to the YouTube Data API v3 and has read-only reach over public
data. Worst case on leak is quota exhaustion; rotation is a two-minute job in the console.

---

## 12. Decommissioning `youtube-automate`

Not until §13 phase 5 passes. Order matters — the point is that every step is reversible until the
last one.

1. **Stop new work.** Comment out the `17 * * * *` cron entry. Leave the service running so the
   admin UI still answers.
2. **Watch for a week** with both libraries live in Jellyfin. This is the real acceptance test:
   does anyone reach for the old library?
3. **Retire the Jellyfin library.** Remove *YouTube* (`/disks/Plex/YouTube`) via
   `/Library/VirtualFolders`. Rename *YouTube (stream)* → *YouTube*. **Note from the PoC:**
   deleting and recreating a library at the same path returns the **same** `ItemId` and reuses the
   old items — if a clean slate is ever needed, use a fresh path, as `_ytstream` already is.
4. **Free the hostname.** `tube.jihakuz.xyz` is served by a leftover TubeArchivist `server` block
   inside `sites-available/jihakuz.xyz`, which owns the Let's Encrypt cert and wins because nginx
   takes the first matching block. Repoint it at 8086 the same way `deploy/fix-nginx-tube.sh` did
   for 8085; do not install a competing vhost file.
5. **Disable the service.** `systemctl disable --now youtube-automate.service`; remove the unit.
6. **Reclaim the bytes.** Estimated 5–10 GB under `/disks/Plex/YouTube`. Delete only after step 2
   has actually elapsed.
7. **Keep, do not delete:** `/var/lib/youtube-automate/subs.db` (copy it aside — it is the only
   record of what was subscribed and when), `/opt/youtube-automate` and its bare repo, and
   `specs.md`, which remains the reference for every rule ytstream inherited.

`update-ytdlp.sh` (Mondays 04:40) must be **repointed, not removed** — it becomes ytstream's, and it
is the thing that keeps playback working as YouTube changes.

---

## 13. Build order

Each phase ends in something checkable. Do not start the next one until it does.

**Phase 0 — verify the assumptions the plan rests on, and get the one number it is missing.**
~15 minutes, before any code. `git init --bare /disks/git-repos/ytstream.git`. Get the API key
(§4.1). Then three curls:

1. `subscriptions.list` on `UCPcTWaLV8zwx4WP4QExHj4Q` returns 200 with items — **and record
   `pageInfo.totalResults`**, which is what sets `subsync_max_new` (§4.4). This is a hard blocker:
   there is no fallback that does not involve him doing something (§4.2).
2. `playlistItems.list` accepts a UULF playlist id — or does not, and we take the documented `UU`
   fallback plus duration filtering (§3).
3. `videos.list` returns `contentDetails.duration` for a batch of 50 ids.

→ *Done when: all three answers are written back into this file as verified facts or corrections,
and `subsync_max_new` has a real value.*

**Phase 1 — skeleton and lift.** Fork the tree, new package name, new DB path, new schema (§7),
lifted modules and their tests passing. No new behaviour.
→ *Done when: `pytest` is green and `ytstream doctor` reports a healthy environment.*

**Phase 2 — the proxy as a service.** Move it in, split it up, add the startup sweep and the LRU
test, write `deploy/deploy.sh`, operator runs it.
→ *Done when: `systemctl status ytstream-proxy` is active after a reboot, `/healthz` answers, and
Jellyfin direct-plays a cold video end to end.*

**Phase 3 — catalogue.** `api.py`, `strm.py`, the 3-month/300-video bounded resumable backfill, the
hourly run. Build **Pitch Side alone** and **time a Jellyfin scan** — the §5 measurement. Worth
doing twice, once at the 300-video bound and once unbounded at 1,249, since the second gives the
seconds-per-1,000-episodes figure that sizes the growth runway for free.
→ *Done when: the bounded episode count is visible with correct titles, dates, durations and
thumbnails; scan time per 1,000 episodes is recorded in §5; and one of them plays.*

**Phase 4 — subscription sync.** `subsync.py`, the first-sync bulk import, the add cap, the
missing-threshold, the `user` table and two accounts (§4.6), the admin routes, the healthchecks UUID.
→ *Done when: the brother logs in with his own credentials and approves the first import; then he
subscribes to a new channel on YouTube and within an hour it is a series in Jellyfin with episodes
that play, nobody having touched the admin UI. Plus: a forced 403 and a forced empty response both
leave the DB untouched and turn the check red.*

**Phase 5 — cut over.** §12 steps 1–2, run for a week.
→ *Done when: nothing has broken and nobody has used the old library.*

**Phase 6 — decommission.** §12 steps 3–7.

---

## 14. Decisions — answered 2026-08-12

1. **Account to mirror:** `@cflux1030` → `UCPcTWaLV8zwx4WP4QExHj4Q` ("C Flux"), resolved and
   recorded in §4. **Sole source of truth** — Tom's own subscriptions are not part of this at all,
   which removed the multi-source claim model from §4.3 and put the weight on §4.4 instead.
2. **Catalogue depth:** 3 months or 300 videos, whichever comes first. §5 rewritten around it, and
   both bounds are settings with per-channel overrides. Note the consequence recorded there: this
   bounds the initial build, not the library, which grows forward indefinitely.
3. **`subsync_max_new`:** to be set from `pageInfo.totalResults` on the day-one
   `subscriptions.list` call, since that is the only way to learn how many channels he follows.
   Provisional 25; rule of thumb `max(10, ceil(totalResults × 0.2))` (§4.4). **The one open number
   in this plan** — Phase 0 closes it.
4. **Brother gets admin access:** yes, which turns the single shared password into a two-row `user`
   table (§4.6) and adds `approved_by` to the approval log.

---

## 15. Gotchas carried forward

Things already paid for once. All of these are verified.

- **A normal Jellyfin scan makes 0 media probes**, which is the single fact this design depends on.
  `replaceAllMetadata=true` **does** probe. Pre-seeded `streamdetails` do not prevent it.
- **`--load-info-json` reuses the extraction** — confirmed twice, once during the original PoC and
  again while hunting the 403. Both yt-dlp legs run from one `-J`.
- **ffmpeg will not write a duration into a fragmented MP4**, and will not accept one patched in
  afterwards. Hence wait-for-complete (§10).
- **Two picker bugs, both silent, both from `mweb`:** `140-drc` was chosen over `140` on an `abr`
  tie and 403'd; `140-0` was chosen on a 9-language video and produced German audio. The audio sort
  key ranks `language_preference` **first**, deliberately above the DRC check — a 403 is a loud
  failure, wrong-language audio is a silent one that would have shipped.
- **`row["title"]` ambiguity renamed every series once.** The channel/video join has `title` on both
  sides. Pass show fields explicitly, never `row["title"]`. Caught only by accident.
- **Jellyfin's `/Items/{id}` needs user context** — use the `/Items?ids=` form.
- **`youtubetab:approximate_date` is wrong by up to 2 days.** Do not derive episode numbers from
  it; use `playlistItems.list` (§3).
- **YouTube's public subscriptions tab is gone.** `/@handle/channels` returns 200 and silently
  serves Home — four tabs, zero channel ids in `ytInitialData`. Verified 2026-08-12. Nobody should
  spend an afternoon trying to scrape it; the API is the only route (§4).
- **`pkill -f 'ytstream.py'` kills the shell that runs it**, because the command string contains its
  own pattern. Bracket it: `pkill -f 'ytstrea[m].py'`.