arr/DESIGN.md

# arr — design

One service that replaces Radarr and Sonarr, and later Bazarr, for a single
household. Rust workspace, API-first, SQLite, no authentication layer.

This document is the contract. Issues reference it by section rather than
restating it.

---

## 1. Why

Five .NET services idle at 600-900 MB to do a job with one loop in it: decide
what you want, find it, fetch it, put it somewhere Jellyfin can read. Each has a
configuration surface an order of magnitude larger than the subset actually
used, and none of them share a model, so the same show is configured three
times in three dialects.

The replacement targets 20-40 MB resident, one binary, one database, one policy
language.

This is not a general-purpose Radarr replacement. Every decision below is
allowed to be narrow.

## 2. Non-goals

Explicitly out of scope, permanently unless stated:

- **Authentication.** The perimeter is a VPN plus Authelia at the proxy. The
  service binds without auth, same trust model as the existing Transmission RPC.
- **Library migration or filesystem scan.** The service knows only what it put
  on disk. Adopting the pre-existing library, if ever wanted, is a one-off
  script against both APIs, not a feature.
- **Automatic quality upgrades.** See §5.4.
- **Multiple quality profiles.** Policy attaches to a root folder. See §5.1.
- **Trakt.** Jellyfin and Stremio already write watch state there and nothing in
  this pipeline reads it.
- **Calendar view, actor/director following, per-indexer UIs.** Prowlarr owns
  indexer configuration and keeps doing so.
- **Books and music.** `shelfmark` and `calibre-web-automated` already cover
  books. If they ever land here they reuse maybe three of the ten crates, so
  nothing is generalised in advance. See §11.

## 3. System context

```
                    ┌──────────────┐
        TMDB ──────▶│              │
                    │     arr      │────▶ Transmission RPC   10.6.10.45:9091
    Prowlarr ──────▶│              │
   (Torznab)        │   (this)     │────▶ ffprobe            local subprocess
                    │              │
   Jellyseerr ─────▶│              │────▶ Jellyfin refresh   10.6.10.18:8096
   (Radarr-compat)  └──────┬───────┘
                           │              ntfy                per-person topics
                           ▼
                    SQLite + media tree on /mnt/media
```

Everything already exists except `arr`. Prowlarr keeps owning tracker auth,
Cloudflare bypass via FlareSolverr, rate limiting and the Cardigann
definitions — replacing it buys nothing.

Transmission runs natively in its own LXC (VMID 130, `10.6.10.45`), RPC
unauthenticated, download dir `/mnt/media/transmission/complete`.

## 4. Domain model

Movies and series are separate aggregates. They share machinery, not a table.

```
Root
  id, kind (movie|tv), audience (main|kids), path, policy_id

Policy
  id, name
  required_audio          rule set, see §5.2
  dub_blacklist           [pt-BR]
  hdr_rules               see §5.3
  size_bands              per resolution: floor, target, penalty curve,
                          all per episode (§5.5)
  resolution_pref         [2160p, 1080p]
  source_weights          small tiebreaker

Movie
  id, tmdb_id, title, year, original_language, root_id
  wanted (bool), overrides (json), state, blocked (bool)
  search_attempts, last_searched_at

Series
  id, tmdb_id, title, year, original_language, root_id
  auto_track (bool), overrides (json), blocked (bool)

Season
  id, series_id, number, tracked (bool)

Episode
  id, season_id, number, title, air_date
  wanted (bool), state
  search_attempts, last_searched_at

MediaFile
  id, owner_kind (movie|episode), owner_id, path, size
  probed (json: resolution, source, hdr, audio_tracks, sub_tracks)
  waiver (json|null)   which rule was relaxed to allow this import

Release
  id, indexer_id, guid, name, size, seeders, publish_date, download_url
  parsed (json)        what the name claims
  score, verdict       eligible | waived | rejected(rule)

Grab
  id, release_id, target_kind, target_id, infohash
  state, grabbed_at, imported_at

Blacklist
  infohash, normalised_name, reason, created_at

Owner
  id, name, ntfy_topic

TitleOwner
  title_kind, title_id, owner_id      many-to-many
```

### 4.1 Intent lives at the leaf

Sonarr's `monitored` conflates "do I want this show" with "is anything
happening right now". It is user-maintained, so it drifts and stops meaning
anything.

Here, intent is `Episode.wanted` and `Movie.wanted` only.
`Series.auto_track` is not intent — it is a rule one level up: when metadata
reveals a new season, that season becomes tracked. The rule applies from the
second refresh onward: seasons revealed by a series' first refresh — the whole
back catalogue present at add time — are never tracked by it. Only seasons that
appear after the series was added are covered; back-catalogue seasons are picked
by hand. An untracked series where you
manually marked S02 needs no special case: three wanted episodes, nothing else.

`Season.tracked` is also a rule, not intent. Turning tracking on marks every
already-revealed episode in the season wanted, and keeps marking episodes
wanted as metadata reveals them. Turning it off clears `wanted` on every
episode of that season: toggling the flag is itself the explicit act, and the
product offers no other way to withdraw a season's worth of intent. Without
that, untracking leaves a series with every season off and every episode still
wanted, pinned at `incomplete` with no way back. Marking individual episodes
wanted on a season that was never tracked is unaffected by any of this.

Both rules skip season 0. Specials are dozens of undated shorts and recaps
that indexers do not carry, so `auto_track` never marks season 0 tracked. See
§4.2 for how season 0 stays out of derived status.

### 4.2 Status is derived, never stored as intent

Recomputed on metadata refresh and on file change:

| Status | Condition |
|---|---|
| `airing` | an episode aired or airs within ±14 days |
| `incomplete` | wanted episodes missing, nothing currently airing |
| `waiting` | season finished, next unannounced or future-dated |
| `complete` | everything wanted is on disk |
| `ended` | series finished upstream and complete |

Default list view shows `airing` and `incomplete`. Everything else collapses
behind one toggle. A one-off season grab therefore disappears from the default
view by itself once satisfied, and a tracked show reappears by itself when a new
season is announced. Nothing to remember to flip.

Status chips carry state colour, not a single informational hue: green
(`--signal-ok`) for on disk or complete, amber (`--signal-warn`) for wanted but
not yet found, violet (`--status-airing`) for downloading, neutral for
untracked. The word stays present in every chip, so state survives with colour
removed.

Season 0 is invisible to all of it: derived status ignores season 0 episodes
entirely, so a manually wanted special cannot pin a series at `incomplete` or
hold back `ended`. The accepted consequence is that specials are visible and
grabbable in the series detail view, but never affect status.

### 4.3 People are tags, not paths

`Owner` is a many-to-many tag on titles. It drives UI filtering, the default
list, and notification routing. It never appears in a path. A file lives in one
place; audiences overlap.

## 5. Policy engine

The core of the app and the part worth testing hardest. Lives in `arr-core`,
pure, no IO.

### 5.1 Policy attaches to a root

Two roots per media kind (`main`, `kids`), each with one policy. Jellyseerr's
"pick a quality profile per request" model is satisfied by exposing exactly one
fake profile per root and ignoring whatever it sends.

Per-title `overrides` relax the root policy for one title. Same mechanism in
both directions — `only_4k` tightens, `allow_english_audio` loosens.

### 5.2 Language

Requires a concept the release name does not carry: the **original language of
the title**, from TMDB, distinct from a track's language.

```
reject audio track T if  T.lang ∈ dub_blacklist  and  T.lang ≠ title.original_language
```

`dub_blacklist = [pt-BR]` globally. That single expression covers both roots:

- **main** — require a track matching `original_language`. Others may ride
  along. A Brazilian film has `original_language = pt-BR`, so its own
  soundtrack passes; a pt-BR dub of an English film does not.
- **kids** — require pt-PT, or `original_language` when that is already
  Portuguese. pt-BR never satisfies the requirement, because the child does not
  read and a Brazilian dub is not what he should be watching.
- **subtitles** — no blacklist. pt-BR subtitles are always fine.

**The pt-PT / pt-BR detection problem.** ISO-639-2 has one code, `por`, for
both. `ffprobe` reports `por` either way. Three signals in order:

1. Release name markers — Brazilian releases self-identify loudly: `PT-BR`,
   `Dublado`, `Nacional`, `Dual Áudio`.
2. `ffprobe` stream *title* and `handler_name` strings, not the language code —
   often literally `Portuguese (Brazil)`.
3. Container-level BCP-47 tags where present (Matroska can carry `pt-BR`).

When none resolve it, tag the track `por-unverified` and surface it. Do not
guess. Guessing toward `kids` gives a child a Brazilian dub; guessing toward
`main` rejects a Brazilian film's own audio.

**Sourcing consequence for `kids`.** European Portuguese dubs live almost
entirely in streaming WEB-DLs (Disney+, Netflix, Max) and essentially never in
BluRay encodes or remuxes. That root biases hard toward WEB-DL sources, and
unlike audio in general it *is* often pre-grab visible, since multi-audio
releases advertise themselves (`MULTi`, `DUAL`, explicit language lists).

When nothing qualifies, the title sits in a visible **no-PT-source queue**
rather than being grabbed in English. That queue is acted on manually,
sometimes for months. A per-title `allow_english_audio` override empties one
item from it with one click, and the resulting file is recorded with a
`waiver` so the UI shows it as "English, no dub" rather than a clean match.

### 5.3 HDR and Dolby Vision

The naive rule "blacklist Dolby Vision" is wrong and would discard a large
share of good 4K releases.

| Profile | Base layer | Behaviour without DV support | Verdict |
|---|---|---|---|
| 5 | none (ICtCp) | green/purple, unwatchable | **reject** |
| 7 | dual-layer BL+EL | depends on player, unreliable | **reject** |
| 8.1 | HDR10 | plays as HDR10 | **accept** |

The existing library is already almost entirely Profile 8.1 with no Profile 5,
and Jellyfin tonemaps it correctly on the current GPU path.

Profile is knowable only from `ffprobe`, never from a release name. A `DV` chip
in search results means "the name claims DV" and its absence means nothing.

### 5.4 Quality, and why there is no upgrade loop

Default: take 4K if it exists now, otherwise 1080p. Per-title `only_4k`
rejects 1080p outright and keeps searching indefinitely — the escape hatch for
the handful of titles worth waiting on.

**No grab delay.** Deliberately rejected. Radarr's delay profile exists to stop
first-match-wins from always yielding 1080p; here the `only_4k` flag solves the
same problem upfront and without making every grab slower.

**No automatic upgrade loop.** An automatic upgrade re-downloads 40-80 GB and
restarts a seeding obligation for something already watched. `needs_upgrade` is
a marker in the UI and a manual "search again" button, not a background job.

### 5.5 Scoring: distance from a target size

Source tier is **not** the dominant term. A remux should win only when nothing
smaller exists.

Per resolution, a floor, a target and a growing penalty above target. For 4K:
floor ~8 GB, target ~22 GB. A 20 GB WEB-DL sits at target and wins; a 60 GB
remux scores badly but stays eligible, so it is picked when it is the only
option. The floor matters — unbounded "smaller is better" selects a 3 GB 4K
encode that looks like mud.

**A band describes one episode.** For a movie the question never arises — one
release is one film. For TV a release may carry a single episode, several, or a
whole season, and the shipped TV numbers are episode numbers: a 1080p target of
2 GiB is what one episode should weigh, not a ten-episode pack. So a release is
measured by its size divided by the number of episodes it covers, and that
per-episode figure is what both the target penalty and the floor are compared
against. A 20 GiB pack of ten episodes is scored as 2 GiB and sits at target,
not ten times above it.

The floor takes the same figure. It is a hard reject rather than a penalty, so
comparing a pack's total against an episode-sized floor lets every pack through
untested — wrong in the opposite direction from the target penalty. The floor
exists to keep a 3 GB 4K encode out, and a pack of ten such encodes has to fail
it just as plainly.

**An unknown episode count is one episode.** A release matched before its
season's episodes have been revealed by a metadata refresh has nothing to divide
by, and the rule does not guess a number: the divisor is 1 and the release is
measured by its full size. That is the behaviour today, and it makes a pack look
oversized rather than undersized — it fails toward rejecting a good pack rather
than grabbing a bad one, and the next search after a refresh has the real count.

**A band describes a rate, not a fixed size per episode.** The shipped values
are read against a **reference runtime of 45 minutes**: a 1080p target of 2 GiB
means 2 GiB per 45 minutes of episode. Before the per-episode figure is compared
against them, a band's floor and target are both scaled by
`runtime / 45`, where `runtime` is the series' minutes-per-episode from TMDB
metadata. For a typical drama around 45 minutes the shipped numbers keep exactly
their current meaning; a 22-minute show is judged against roughly half the floor
and half the target instead of being rejected for weighing half of what an hour
of video weighs. The shipped band values themselves do not change — the
reference runtime is chosen so they do not have to.

**A missing or zero runtime is the reference runtime.** When metadata carries no
per-episode runtime, or carries zero, the scale factor is 1 and the band applies
unscaled — exactly today's behaviour. The rule does not guess a duration, for
the same reason the unknown episode count does not guess a number.

**Movies are not scaled.** This applies to episodes only. A movie's bands are
already tuned against feature length, so its floor and target keep their current
meaning regardless of the movie's own runtime.

Source tier (`Remux > BluRay > WEB-DL > WEBRip > HDTV`) survives as a small
tiebreaker. Seeders are log-scaled and small: enough to complete, past that it
does not matter. Telesync, CAM and screener are **hard filters**, not low
scores.

**How resolutions rank against each other.** Size is scored against the band
for the release's own resolution, so on its own it says nothing across
resolutions: an at-target 4K and an at-target 1080p both score the top of the
size term, and a 4K a couple of gigabytes over target loses to a 1080p that is
merely on target. That is wrong — `resolution_pref` is an ordered list, and the
order is a preference, not just an eligibility filter.

So each step up `resolution_pref` is worth a fixed number of points. The last
entry is worth nothing and every earlier one a step more. A resolution the list
does not carry scores nothing rather than being penalised, the same as an
unclaimed resolution: no ranking is no opinion.

The step is sized against the size term, not chosen in isolation. With the
seeded 4K band — target 22 GB, 60 points per gigabyte over — a step of 300 is
five gigabytes of overshoot: a 4K up to about 27 GB beats an at-target 1080p,
and a bloated 40 GB 4K does not. Below target the same arithmetic asks a 4K to
be within about four gigabytes of its target to win, which is what keeps an 8 GB
4K that looks like mud from beating a good 1080p.

Exact numbers are policy rows, tuned by hand. The model is the decision.

### 5.6 Two phases of truth

Release names lie or omit. Files do not.

- **Pre-grab** — parse the name. It is all there is. Use it for hard filters
  (source type, resolution, explicit language markers) and for scoring.
- **Post-download** — `ffprobe` before import. Real audio languages, real HDR
  format and DV profile, real codec, real duration.

Store both, `parsed` on the release and `probed` on the file. The gap between
them is also data: it tells you which release groups mislabel.

### 5.7 Hard fail versus soft fail

A policy violation found by `ffprobe` is not one thing.

- **Hard fail** — useless. No original-language audio track at all, DV Profile
  5, wrong title, corrupt. Do not import, blacklist the release, grab the next
  candidate.
- **Soft fail** — watchable but not what was asked. 1080p while `only_4k` was
  set, PT audio missing on a `kids` title. Import it, record a `waiver`, surface
  it.

Neither deletes the torrent. See §7.3.

**Two hard failures make a decision, and only for 30 days.** A movie, an
episode or a season enters the needs-a-decision queue (§9.5) when two grabs
against *different* releases hard-failed on it, and both of those failures
happened within the last 30 days. One bad torrent is not a decision — a
release that hard-failed is blacklisted (§6.3) and the next candidate is
grabbed, which is the system working.

The window is what lets the queue be emptied. Nothing clears a `grabs` row, so
without it the queue only ever grows and the one season that wants attention
sits behind eight that were dealt with months ago. It is the queue's version of
§6.2's "it never gives up entirely, it goes quiet": a target the operator has
dealt with stops producing failures and drops out once the last one ages past
30 days, while a target that is still broken keeps producing them — the pack
guard retries at worst weekly (§6.2) — and stays queued for exactly as long as
it is genuinely broken. Nothing is dismissed by hand and no acknowledgement
state is stored, so there is no second thing to keep correct.

## 6. Sourcing

### 6.1 Prowlarr, per-indexer Torznab

`GET /api/v1/indexer` enumerates. Each indexer is then addressed at its own
Torznab endpoint:

```
GET /{indexerId}/api?apikey=…&t=caps
GET /{indexerId}/api?apikey=…&t=search&q=…
GET /{indexerId}/api?apikey=…&t=movie&imdbid=…
GET /{indexerId}/api?apikey=…&t=tvsearch&tvdbid=…&season=&ep=
```

Prowlarr's aggregate `/api/v1/search` is deliberately not used: Torznab is the
stable standard rather than an internal UI API, it gives real RSS semantics, and
per-indexer addressing keeps indexer identity in hand — which the per-tracker
seeding rules need anyway.

`t=caps` per indexer records which search modes each tracker supports. Not all
do ID-based search; some are text-only.

### 6.2 Three triggers, three cost profiles

| Trigger | Cost | Cadence |
|---|---|---|
| RSS sync | one call per *indexer*, independent of library size | ~10 min, never backs off |
| Targeted search | one call per *wanted item* per attempt | exponential backoff |
| Manual | one call, user-initiated | on demand |

RSS is an empty-query Torznab call whose results are matched against the wanted
list locally. Because its cost does not scale with the wanted list, every wanted
item is matched against every RSS result forever — with one guard: the RSS lane
skips a season pack for a season that already has episodes on disk, the same
guard §14 applies to re-grabs. Both lanes agree, so a season does not behave
differently depending on which lane sees a release first. A pack for a season
with nothing on disk stays eligible. When a single episode cannot be found on
its own, the escape hatch is the season release deck, not a lane exception.

Targeted search backs off `1h → 6h → 1d → 3d`, capped at 7d, reset when the
title's metadata changes. It never gives up entirely, it goes quiet.

**Do not search before the release exists.** TMDB carries release dates; a
movie with no digital release date gets zero targeted searches. This is the
single largest source of wasted queries in Radarr and it is free to avoid.

### 6.3 Blacklist

Keyed on infohash and normalised release name. Anything that hard-failed
post-`ffprobe` is never grabbed again, including by RSS.

A manual `blocked` flag stops targeted search for a title entirely while
leaving RSS matching on.

## 7. Download and import

### 7.1 Transmission

RPC at `10.6.10.45:9091`, no credentials. Labels are `movies-main`, `tv-kids`
and so on — enough to find things in Transmission's own UI, and distinct from
Radarr's existing `radarr`/`sonarr` labels so both stacks can run side by side.

### 7.2 Hardlink

Verified: Radarr's only media bind is `/mnt/media-v2:/mnt/media`, one mount,
one dataset, and the existing arrs hardlink-import today. So `link()` succeeds.

Implementation still falls back to copy on `EXDEV` rather than trusting that
forever — no configuration flag, no way to get it wrong.

Hardlinking gives the library file and the seeding file independent names at
zero extra disk. Copy would double storage for the entire seeding window, which
at 4K is 40-80 GB per title.

### 7.3 Two lifecycles, deliberately decoupled

The torrent and the library entry are separate state machines.

Seeding obligation is **per tracker**, configured locally because Prowlarr does
not expose tracker rules — `ratio` and `min_seed_time`. Set `seedRatioLimit`
and `seedIdleLimit` on the torrent at add time and let Transmission enforce
them. A reaper deletes torrents Transmission reports as done seeding.

Consequently a hard-failed release is blacklisted and never imported, but its
torrent keeps seeding until the obligation clears. Nothing is deleted early to
satisfy the library.

### 7.4 Layout

```
/mnt/media/movies/main/Dune Part Two (2024) [tmdbid-693134]/
    Dune Part Two (2024) [tmdbid-693134] - [2160p][WEB-DL][HDR10].mkv

/mnt/media/tv/kids/Bluey (2018) [tmdbid-82728]/
    Season 01/
        Bluey (2018) - S01E02 - Hospital [1080p][WEB-DL][pt-PT].mkv
```

Media kind first, hard audience boundary second, people nowhere.

- **Provider ID in the folder name** turns Jellyfin matching from fuzzy string
  guessing into exact lookup.
- **Attribute tags come from `ffprobe`**, not from the release name, so they are
  true. The filename doubles as an audit surface: `ls` shows which files are DV
  or which of the kids' files are still English-only, with the app stopped.
- **One folder per title even for a single file**, so sidecar subtitles and
  artwork stay contained and deletes are atomic.
- **Release group is deliberately absent.** It is not a selection criterion and
  it makes filenames long enough to break a terminal.

Changing a title's root relocates its title folder into the new root; roots are assumed to share one filesystem, so the move is a rename, never a copy. Changing a root's path is the same move over every title under it, and it is all or nothing: one folder that cannot move puts back the ones that already did and leaves the root's path alone, so the stored path always describes the disk.

During transition, write into the existing roots so Jellyfin needs no
reconfiguration and new content appears immediately. Radarr will not touch a
folder it has no record of.

### 7.5 Jellyfin

On successful import, call Jellyfin's refresh endpoint for the affected
library. Its filesystem watcher misses things. One HTTP call at the end of
import.

## 8. The reconcile loop

There is no job queue.

The database rows are the work list. A wanted episode with no file is a pending
grab. A torrent past its seeding rule is a pending delete. A downloaded file not
yet probed is a pending import. Every tick, compare desired state to actual
state and act on the gap.

This is idempotent and crash-safe by construction. Kill the process mid-grab and
the next tick recomputes the same gap and continues. A job table would need
retry counts, dead-lettering and reconciliation against Transmission anyway,
because Transmission is an external system that changes underneath the app.

Transient state — a search in flight, download progress — is in memory and
rebuilt from Transmission on startup.

Ticks are staggered: reconcile every 30 s, RSS every 10 min, metadata refresh
daily, reaper every 5 min.

## 9. API and UI

### 9.1 API-first

The HTTP API is the product surface; the web UI is a client of it with no
privileged path. OpenAPI spec generated from handler annotations, served
alongside the app, and used to generate the TypeScript client.

Own schema first. Radarr-compatible endpoints are a **later, separate,
lower-priority crate** (§9.4), not the primary shape.

### 9.2 Unified search

One box. Two grouped result sets: **in library** first, **on TMDB** below. Both
sets are titles — series and movies. Episode rows never appear, under any
query, and there are no season rows. Enter on a TMDB result opens the add flow
with root and policy pre-filled.

The same box accepts a raw TMDB or IMDb ID, and a pasted magnet or `.torrent`,
which skips to the manual-grab flow.

There is never a moment where the user has to know whether they are searching or
adding.

Result rows are enriched: a poster thumbnail and a rating, under the same rules
as title detail (§9.6) — images hotlinked from path fragments, the rating being
TMDB's `vote_average` with its `vote_count`. A trailer chip renders per row and
resolves only when clicked (§9.6).

### 9.3 Manual search results

Radarr's manual search is unusable because the raw release name is the dominant
column, pushing everything that actually decides the choice off-screen.

Invert it. The policy engine has already classified every candidate:

- **Three buckets.** `eligible` shown by default, sorted by score. `waived`
  (fails a soft rule, grabbable with one click that writes an override) and
  `rejected` collapse to a count, expandable.
- **Columns are parsed attributes as chips** — score, resolution, source, HDR,
  audio languages, size, seeders. Fixed width, no horizontal scroll.
- **Release name is secondary**, truncated, full string on expand. It is
  evidence for when you disagree with the parse, not the primary key.
- **Every rejected row names the rule that killed it**, so over-strict filters
  are visible without reading names.

Pre-grab, HDR and audio chips are best-effort from the name (§5.6).

### 9.4 Jellyseerr compatibility

Jellyseerr stays. It already does Jellyfin user auth, discovery and request
approval — none of which is the problem being solved, and rebuilding it doubles
the project.

A thin `arr-compat` crate exposes the slice Jellyseerr actually calls:

```
GET  /api/v3/system/status
GET  /api/v3/rootfolder            → the real roots
GET  /api/v3/qualityprofile        → one fake profile per root
GET  /api/v3/tag
GET  /api/v3/movie                 existence check
POST /api/v3/movie                 add
GET  /api/v3/movie/lookup
```

plus the `series` equivalents. Thin mappings onto the real domain, isolated in
one crate that never leaks into `arr-core`.

Lower priority than everything in §5-8.

### 9.5 Notifications

`ntfy`, one topic per `Owner`. Three events only — Radarr's failure mode is
notifying on everything and being muted within a week.

- **Imported** → to the title's owners. The only good-news notification.
- **Needs a decision** → to the operator alone. Entered the no-PT-source queue,
  or hard-failed twice on different releases.
- **Broken** → to the operator alone. Prowlarr, Transmission or TMDB
  unreachable, disk full.

Not notified: grabs, searches, downloads starting or finishing, soft fails.

### 9.6 Title detail

One detail surface per kind: `/movies/{id}` and `/series/{id}` (#129). For a
movie the release deck becomes a section of the page, and `/movies/{id}/releases`
keeps resolving; series keeps its season-and-episode shape, seasons ordered
newest-first within the series and episodes newest-first within each season —
the seasons you are deciding about now are at the top, not after nine rows of
back catalogue.

**TMDB is the only metadata source.** The rating shown anywhere is TMDB's
`vote_average` with its `vote_count`, rendered as amber stars (`--signal-warn`
— the same state colour a wanted chip carries). No OMDb, no IMDb or Rotten
Tomatoes scores — each would need a second upstream, a second key and a second
thing that can be down.

**Images are hotlinked** from `image.tmdb.org`. The API returns TMDB path
fragments, never URLs; the browser composes the URL and chooses the size. No
image proxy and no image cache in the service.

**Rich detail is not persisted.** It is served through arr-meta's 24-hour
response cache, which lives on disk in a directory alongside the database
(§10), bounded by both age and total size (#158) — not the database itself,
and not an image cache; images stay hotlinked as above. The single exception
is `poster_path`, `backdrop_path`
and `vote_average`, stored on `movies` and `series` and written by the daily
metadata refresh (§8), so library views render without a TMDB call.

**External links** are TMDB always, IMDb for movies, TVDB for series — all from
ids the app already holds — plus a Rotten Tomatoes *search* link, which is a
query URL, not a resolved title page.

**Trailers resolve on click.** TMDB's search responses carry no videos, so a
trailer key costs a detail call. Rendering one chip per title and resolving the
one clicked keeps that cost at one call, and the 24h cache makes a repeat free.

**Library view.** A poster grid by default with a list toggle; the list keeps
the derived-status columns §4.2 built it around.

Out of scope here, because they are the adjacent scope most likely to creep:
watch providers, recommendations or similar titles, collections, person pages
inside the app, review text.

### 9.7 The shell

**The library is the homepage.** `/` renders the library view described in
§9.6. It is what the operator opens the app to look at, so it is what the app
opens on.

**The signal chain is a settings section.** The four upstreams — tmdb,
prowlarr, arr, transmission — and their lamps live inside `/settings`, and have
no route of their own. Per-upstream health is something you check when
something is wrong, not a homepage.

**The master lamp stays on the rail**, so the at-a-glance read that the chain
is healthy survives the move and no navigation is needed to get it.

**The wordmark is a link home.** `arr` on the rail navigates to `/`.

## 10. Persistence

SQLite via `sqlx`, compile-time-checked queries, migrations in `arr-db`.

A few thousand rows, single writer. Postgres would buy nothing and cost a
service.

Policy lives in the database, not a config file — size targets and DV rules get
tuned by hand during testing and a restart-to-reload loop gets old immediately.
Only bootstrap settings (bind address, Prowlarr URL, Transmission URL, TMDB key,
media root, TMDB response cache directory) come from config/env.

Backup is `sqlite3 .backup` on a timer.

## 11. Crate layout

Cargo workspace, `members = ["crates/*"]`, versions pinned once in
`[workspace.dependencies]`, following `~/tea/maestro`.

```
arr-core      domain types, policy engine, scoring     no IO, no heavy deps
arr-parse     release name parsing                     no IO
arr-meta      TMDB client
arr-indexer   Torznab via Prowlarr
arr-dl        Transmission RPC
arr-probe     ffprobe wrapper
arr-db        sqlx + migrations
arr-api       axum + OpenAPI
arr-compat    Radarr/Sonarr v3 shim for Jellyseerr
arr-daemon    reconcile loop, wires everything
arr-e2e       cross-process integration tests
web/          Vite + TypeScript SPA, embedded via include_dir
```

The rule: `arr-core` and `arr-parse` hold the logic worth testing constantly and
must not depend on axum, sqlx or reqwest. Everything expensive is downstream of
them.

Nothing is generic over media kind. Movies are built concretely, then TV
concretely, and shared machinery is extracted only once both exist. An
abstraction derived from one example fits one example.

## 12. CI

Lints declared once in the root manifest:

```toml
[workspace.lints.rust]
unused_crate_dependencies = "warn"
missing_debug_implementations = "warn"

[workspace.lints.clippy]
pedantic = { level = "warn", priority = -1 }
unwrap_used = "warn"
```

Member crates carry only `[lints] workspace = true`.

**Per-push gate**, target under 5 minutes:

| Step | Tool |
|---|---|
| format | `cargo fmt --check` |
| lint | `cargo clippy --all-targets -- -D warnings` |
| unused deps | `cargo machete` (stable; `cargo udeps` needs nightly and a full rebuild) |
| test | `cargo nextest run` |
| frontend | `biome ci web/` and `tsc -b --noEmit` |

**Off the gate**, scheduled: `cargo deny` for advisories and licenses.
Coverage, if ever, likewise. Neither blocks a push.

Total wall-clock on the self-hosted Gitea runner is an explicit constraint. The
lever is caching, not step selection: cache `~/.cargo/registry`, `~/.cargo/git`
and `target/`, keyed on `Cargo.lock` plus `rust-toolchain.toml`. Never build
`--release` in the gate.

**End-to-end tests, only at the seams that actually break:**

- Prowlarr and TMDB — `wiremock` with recorded real responses as fixtures.
  Never live: trackers rate-limit, and it would leak credentials into CI.
- Transmission — a real container as a CI service. RPC semantics are the most
  likely source of surprise and it starts in a second.
- `ffprobe` — tiny committed clips, a few KB each. The Jellyfin LXC already has
  the right fixtures at `/srv/jellyfin-test`, including a real **DV Profile 5**
  clip. That is the test proving the policy engine rejects Profile 5 and accepts
  8.1 — the subtlest rule in the system.

E2E runs on `main` and on pull requests touching those crates, not every push.

## 13. Build order

Each phase ends at something usable end to end. No phase is a refactor of the
previous one.

1. **Skeleton** — workspace, CI gate, config, SQLite migrations, health
   endpoint, embedded empty SPA.
2. **Parse and score** — `arr-parse` and `arr-core` against fixture release
   names. Pure, fast, heavily tested. No network.
3. **Read-only sourcing** — TMDB lookup, Prowlarr enumeration and search,
   classified results over the API. Still grabs nothing.
4. **Movies, end to end** — add a movie, grab, download, `ffprobe`, hardlink,
   rename, Jellyfin refresh, seeding reaper. The first real cutover test is one
   movie Radarr does not know about.
5. **UI** — unified search, manual search buckets, library views, the queues.
6. **TV** — seasons, episodes, `auto_track`, per-episode versus season-pack
   grabbing, derived status.
7. **Owners and notifications** — tags, per-person ntfy topics, filtered views.
8. **Jellyseerr compat** — `arr-compat`.
9. **Subtitles** — replaces Bazarr. Out of scope for this document.

Movies before TV because TV adds season packs, air-date calendars and
per-episode state on top of an otherwise identical pipeline. Doing it second
means that pipeline is already proven.

## 14. Open questions

- **Remux playback.** Whether a 4K remux streams cleanly to the Shield is
  untested. The usual failure is audio, not bitrate: BluRay remuxes carry
  TrueHD/DTS-HD MA, and if the Shield cannot bitstream that downstream, Jellyfin
  transcodes audio and playback stutters while video direct-plays. Test before
  fixing the 4K size ceiling in §5.5. The outcome changes the conclusion from
  "remuxes are bad" to "remux audio needs a downmix".
- **Size band numbers** in §5.5 are placeholders pending that test.
- **Season-pack re-grab.** When an airing season completes, the episodes are
  already present individually. Nothing re-grabs the pack, and per §6.2 the
  RSS lane obeys the same guard — it skips packs for any season with episodes
  on disk. Whether a re-grab is ever wanted remains unresolved and deliberately
  deferred.