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 **rolling 30-day window** per channel: videos older than that are removed from disk, so the
  library stays small and bounded forever (§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) | **Lift, simplify** | Originally slated for deletion — the 30-day window (§5) brings it back. Same aging-out logic and tombstone semantics, minus the disk-cap machinery, and deleting a `.strm` instead of a 500 MB mp4. |
| `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 subscriptions, hourly | `subscriptions.list` | 24/day (1 page) | 24 |
| Backfill one channel's 30-day window (~20 videos) | `playlistItems.list` @50 | 1 | 1 |
| Durations for those videos | `videos.list` @50 ids | 1 | 1 |
| Steady-state incremental discovery | **RSS feed** | — | **0** |
| Durations for the day's new videos | `videos.list` @50 ids | 1 | 1 |

A 20-channel initial build costs about **40 units**. Steady state is **~25 units/day**, nearly all of
it the hourly subscription poll. Against 10,000/day this is not a constraint worth thinking about,
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.** `youtube-automate` needs a yt-dlp
extraction per video to learn an upload date whenever it backfills past the RSS feed, at roughly 2.3s
each. That is the "scan storm" failure mode the original handover warned about: requests to YouTube
from a residential IP, in bulk, for videos nobody asked to watch.

Be honest about the size of the win now that the window is 30 days: at ~20 videos per channel, the
yt-dlp route would be ~400 extractions ≈ 15 minutes, not the 4 hours a 90-day window implied. The
API is still the right answer — it is documented, keyed, quota-metered, indifferent to PO tokens and
SABR, and cannot be rate-limited by YouTube's anti-bot heuristics — but it is now buying
*correctness* (exact dates, real durations) far more than it is buying *safety*.

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**.
   **Do step 2 before this step.** YouTube Data API v3 does not appear in the API-restriction picker
   until it is enabled on the project, so restricting first produces a key that blocks the one API it
   exists for — see §16, which is exactly what happened.
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 — ~8,000
episodes at the measured rate in §5, and 400 backfills' worth of API calls and file writes in one
run. The 30-day window makes this survivable where the earlier 90-day draft did not, but it is still
not something to discover by accident. 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 deletes the channel** — its directory, its `.strm` files, its NFOs and artwork, and
  its rows. Re-subscribing rebuilds it from scratch, which under the 30-day window (§5) is one
  `playlistItems.list` page and ~20 files: cheap enough that keeping a dormant copy around would be
  the more complicated choice. The Jellyfin series disappears, taking its watch state with it.
- `source = 'manual'` channels are exempt from all of the above.

Note how the two halves interact: because the *action* is now destructive and irreversible-ish, the
*detection* rules above are what stand between a transient 403 and a wiped library. They are not
belt-and-braces. Do not weaken the three-sync threshold to make testing more convenient — make the
threshold configurable and set it to 1 in tests.

**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, on the existing shared password

He gets access, which is right — 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.

**Auth does not change.** One shared `admin_password_hash` in the `setting` table, exactly as
`youtube-automate` already does it, matching how every other service on susan is shared. An earlier
draft proposed a two-row `user` table; it is not worth the code. The two things given up are worth
naming once and then forgetting: neither party's access can be revoked without changing the other's
password, and the approval log records *that* something was approved rather than by whom.

`web/auth.py` therefore 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).

---

## 5. Scale — a rolling 30-day window

> **`retention_days = 30`.** A video older than 30 days has its `.strm`, `.nfo` and thumbnail
> deleted and its DB row tombstoned. Backfill on subscribe reaches back the same 30 days. One
> number governs both ends, so the library cannot grow.

This supersedes the earlier "3 months or 300 videos" answer, which was about *backfill depth* while
this is about *retention*; keeping both would mean backfilling 90 days and then immediately deleting
two thirds of it. If the intent was really "go back 3 months, keep everything", set
`retention_days = 90` and this section still holds — only the numbers move.

### What this actually costs, measured

The upload rates matter more than the total catalogue size, so I measured them from the live feeds
on 2026-08-12 rather than guessing:

| Channel | UULF (long-form) | UC feed (everything) | UULF filters |
|---|---|---|---|
| Pitch Side | 0.60/day → **~18 per 30d** | 2.33/day → ~70 per 30d | 74% |
| The Pyramid Podcast | 0.77/day → **~23 per 30d** | 1.91/day → ~57 per 30d | 60% |

So a 30-day window is roughly **20 episodes per channel**, and 20 channels is **~400 episodes,
~1,200 files.** That is two orders of magnitude below the 20,000 the previous draft was braced for,
and it makes the entire scale section boring — which is the point. Pitch Side's 1,249-video back
catalogue simply never enters the library.

It also confirms the UULF feed is doing real work: it filters 60–74% of what the channel publishes,
and that Shorts-and-livestreams majority is exactly what nobody wants as Jellyfin episodes.

### A useful side effect: RSS nearly covers the whole window

The UULF feed returns 15 entries, and for Pitch Side those 15 span **23.3 days** — because the feed
holds 15 *long-form* items, not 15 uploads. At these rates a single free RSS fetch covers most of a
30-day window on its own.

That narrows what the API is for (§3): subscription reading, durations, and topping up the few days
RSS does not reach on a fresh subscribe. It does not eliminate it — RSS carries no duration at all,
and a busier channel would truncate sooner — but nobody should be surprised when the API turns out
to be handling a few dozen calls a day rather than thousands.

### Aging out has two consequences worth stating

1. **Tombstones are mandatory, not optional.** Delete a `.strm` and the next poll finds the video in
   the feed again and re-materialises it, forever. `youtube-automate` already solves this: the DB row
   survives deletion in a terminal state (`aged_out`) and discovery skips it. Lift that behaviour
   exactly; it is the single most likely thing to get wrong here.
2. **Jellyfin loses watch state for aged-out episodes.** Removing the media file removes the item,
   and with it play counts and resume positions. For a 30-day window on a subscription feed that is
   acceptable — this is a "what's new" library, not an archive — but it should be a deliberate choice
   rather than a surprise. Anything worth keeping permanently wants a different tool (§1).

1. **Jellyfin scan cost is now a non-issue, but still worth one measurement.** Every episode is a
   `.strm` + a `.nfo` + a thumbnail. Normal scans were measured to make **0 media probes** (FINDINGS
   §6), which is what makes this viable at all. At ~1,200 files the stat-and-parse cost will not be
   noticeable. **Record it in Phase 3 anyway**, as seconds-per-1,000-episodes, because it is the
   number that would let anyone judge a future change to `retention_days` without re-deriving it.
2. **`replaceAllMetadata` remains the one real hazard.** It is the one operation verified to probe
   media, and at ~400 items it means ~400 cold starts. The cold-start rate limiter (20/hour) contains
   the damage to YouTube's side, but the library-side result is 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, and tombstones are what make it hold.** `MMDD*10 + ordinal` clamps at
   10 uploads/channel/day and is computed against the DB, not the batch. Since aged-out rows stay in
   the DB, the ordinal for a given day never shifts as videos are deleted — which is the second
   reason the tombstones are load-bearing. Season = upload year means a 30-day window usually spans
   one season and occasionally two, which 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 stays resumable** (`channel.backfill_cursor`, commit per page of 50) even though a
   30-day backfill is now one or two pages. It costs a column and it is the difference between a
   crashed first sync resuming and starting over across 20 channels.

---

## 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/` unchanged: shared-password scrypt auth (§4.6), 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) and `uploads_playlist TEXT` (whether
UULF or UU won, §3). **Keep `retention_days`** as a per-channel override of the 30-day window (NULL =
use the global setting) — `youtube-automate` already has this column and the `rescan` semantics that
go with it. No `active` column: unsubscribing now deletes rather than deactivating (§4.4).

**`video`** — drop `size_bytes`, `downloaded_at`, `attempts`, `last_error`; none of them mean anything
when there is no download. **Keep `deleted_at`** — it is the aging-out timestamp now (§5). Keep
`duration` (from `videos.list`; it feeds `<durationinseconds>`). Add `published_at TEXT` (exact
RFC-3339 from the API) alongside the date-only `upload_date` that naming uses.

`state` becomes `{listed, materialised, skipped_short, skipped_live, skipped_old, aged_out}`. No
`pending`/`downloading`/`failed`, because materialising a `.strm` cannot meaningfully fail. The two
terminal states matter and are not the same thing:

- **`skipped_old`** — discovered already outside the window; never materialised. `youtube-automate`'s
  `rescan` can revive these if `retention_days` is raised.
- **`aged_out`** — was materialised, then deleted by the sweep. **Never revived**, or raising
  `retention_days` would resurrect months of episodes into Jellyfin as "new". These are tombstones
  and discovery must skip them unconditionally (§5).

**`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`).

**`setting`** — carry over what still applies (`jellyfin_url`, `jellyfin_api_key`,
`pot_provider_url`, `max_height`, `min_duration_seconds`, `admin_password_hash`, `session_secret`,
`last_run_at`), including **`retention_days`** — now **30**, and governing both the aging-out sweep
and the backfill reach (§5). Drop `disk_cap_gb`, `write_subs`, `sub_langs`, `sponsorblock_mark`,
`max_attempts`, `backfill_days` — download-era concepts. Add `youtube_api_key`, `subsync_max_new`
(25, provisional — §4.4), `subsync_missing_threshold` (3), `proxy_base_url`
(`http://127.0.0.1:8099`), and `backfill_max_videos` (**300**) purely as a runaway guard on a channel
that turns out to upload 50 times a day.

**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.

Four keys, all in `setting`: `youtube_api_key` (new), `jellyfin_api_key`, `session_secret`, and
`admin_password_hash` — one shared admin password, as everywhere else on susan (§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.** Mostly **done, 2026-08-12** — see §16 for
what was verified and what is still blocked. Remaining: paste the API key in and run

```sh
python3 /opt/ytstream/tools/verify_api.py --key AIza...
```

which performs all three API checks, costs ~5 quota units, prints the `subsync_max_new` value, and
exits non-zero if anything fails.
→ *Done when: `verify_api.py` reports ALL PASS and its numbers are written into §4.1 and §16.*

**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 and retention.** `api.py`, `strm.py`, the 30-day bounded resumable backfill, the
aging-out sweep with its tombstones, the hourly run. Build **Pitch Side alone** (expect ~18 episodes)
and time a Jellyfin scan for the §5 record.
→ *Done when: the expected episode count is visible with correct titles, dates, durations and
thumbnails; one of them plays; scan time per 1,000 episodes is recorded in §5; and — the part most
likely to be wrong — a video forced past the window is deleted from disk, and the **next two polls do
not bring it back**.*

**Phase 4 — subscription sync.** `subsync.py`, the first-sync bulk import, the add cap, the
missing-threshold, channel deletion on unsubscribe, the admin routes, the healthchecks UUID.
→ *Done when: he 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. Then
the destructive half: he unsubscribes, and after three syncs the channel and its tree are gone. Plus
a forced 403 and a forced empty response, each of which must leave the DB untouched and turn the check
red — test these before trusting the deletion path, not after.*

**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. **Retention:** a **rolling 30-day window** — anything older is deleted from disk and tombstoned
   (§5). This supersedes the earlier "3 months or 300 videos" answer, which was about backfill depth;
   holding both would mean backfilling 90 days and deleting two thirds of it immediately. If the
   intent was "reach back 3 months and keep it", `retention_days = 90` is a one-line change and §5
   still holds. Measured consequence: **~400 episodes total**, not 20,000.
3. **`subsync_max_new`:** still open — set from `pageInfo.totalResults` on the first
   `subscriptions.list` call, which `tools/verify_api.py` prints. Provisional 25; rule of thumb
   `max(10, ceil(totalResults × 0.2))` (§4.4).
4. **Brother gets admin access:** yes, on the **existing shared password** — no `user` table, no
   per-account credentials (§4.6). `web/auth.py` carries over untouched.
5. **Unsubscribe deletes the channel** rather than deactivating it, since re-subscribing is one API
   page and ~20 files under the 30-day window (§4.4). This makes the removal *detection* safeguards
   load-bearing rather than precautionary.

---

## 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'`.
- **Google returns 403 `forbidden` for two unrelated setup mistakes**, and the useful signal is in
  `error.details[].reason`, not `error.errors[].reason`. `SERVICE_DISABLED` means the API is not
  enabled on the project (and carries an `activationUrl` naming the project number);
  `API_KEY_SERVICE_BLOCKED` means the API is enabled but *this key's* restrictions exclude it. They
  are fixed on different console screens. `tools/verify_api.py` distinguishes them and prints the fix.

---

## 16. Phase 0 results — 2026-08-12

### Done

- **Bare repo initialised.** `/disks/git-repos/ytstream.git` existed as an empty directory; it is now
  a real `--bare --shared=group` repo with `HEAD` → `refs/heads/main`, matching
  `youtube-automate.git`. `/opt/ytstream` is a checkout with `origin` pointed at it.
- **The mirrored channel is resolved.** `@cflux1030` → `UCPcTWaLV8zwx4WP4QExHj4Q` ("C Flux", 55
  subscribers). No `channels.list` call needed at build time.
- **There is no scraping fallback** — `/@cflux1030/channels` serves the Home tab with zero channel
  ids (§15). The privacy checkbox is mandatory.
- **UULF feeds work for both existing channels**, and the filtering is substantial — 60–74% of what
  these channels publish is Shorts or livestreams that UULF correctly excludes.
- **Upload rates measured**, which is what sized §5: ~18–23 long-form videos per channel per 30 days,
  so ~400 episodes for a 20-channel library. Pitch Side's UULF feed spans **23.3 days in 15 entries**,
  meaning RSS alone nearly covers the retention window.
- **`tools/verify_api.py` written and self-tested** (ISO-8601 duration parser unit-checked against six
  cases; argparse and import verified). It runs all three API checks in one command.

### Key created, project 510818173753 — two setup steps deep, one to go

Progress on the key itself, all of it diagnosed from the error bodies:

1. **Key created** and reaching Google — it authenticates, so the key string is good.
2. **`SERVICE_DISABLED`** — YouTube Data API v3 was not enabled on project `510818173753`. Fixed by
   enabling it.
3. **`API_KEY_SERVICE_BLOCKED`** ← *current state.* The API is now enabled, but the key's own API
   restrictions exclude it, so every method returns "Requests to this API youtube method … are
   blocked". Fix at
   `https://console.cloud.google.com/apis/credentials?project=510818173753` → the key → API
   restrictions → *Don't restrict key*, or tick YouTube Data API v3.

The ordering trap is worth remembering rather than rediscovering: the API must be enabled **before**
the key can be restricted to it, because it is absent from the picker until then. §4.1 step 4 now
says so.

Until the key answers, these three assumptions remain unverified:

| # | Assumption | Consequence if it fails |
|---|---|---|
| 1 | `subscriptions.list?channelId=` returns his subscriptions | **Feature is impossible as designed.** Falls back to §4.2, all of which need him to do something. |
| 2 | `playlistItems.list` accepts a `UULF…` playlist id | Take the documented `UU` fallback and filter Shorts/livestreams via `videos.list` duration + `liveStreamingDetails`. Costs one extra unit per 50. |
| 3 | `videos.list` returns parseable `contentDetails.duration` | No `<durationinseconds>` in NFOs without a yt-dlp extraction per video. Degrades, does not block. |

Only #1 is a genuine blocker, and it also carries the number that sets `subsync_max_new`. Two
external prerequisites remain: **the key's API restriction** (above), and **his brother unchecking
"Keep all my subscriptions private"** — note that nothing so far has tested the second, because every
call has failed at the key before reaching YouTube's privacy check. Then one command closes Phase 0:

```sh
python3 /opt/ytstream/tools/verify_api.py --key AIza...
```