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jellytau/docs/specs/README.md
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docs(specs): add backend-owned stream selection
Rust becomes the single owner of which stream to play — direct play or
transcode, at what ceiling, over what transport — and hands every player
backend a self-describing StreamSelection instead of a bare URL. mpv,
ExoPlayer and the HTML5/hls.js path all consume one decision rather than
three places re-deriving it.

The motivating leak is concrete. VideoPlayer.svelte determines transport with
`currentStreamUrl.includes(".m3u8")`, in two places, for a URL Rust
constructed and therefore already knows the shape of. That is the boundary
rule in miniature: not item-type taxonomy, but the same error of
reconstructing a domain fact in the presentation layer because the wire shape
did not carry it. A tagged Transport enum deletes it.

The design line, which ExoPlayer forces: Rust decides *what stream*, the
player decides *how to deliver it*. ExoPlayer has genuine adaptive track
selection; this spec must not reimplement or fight it. Rust only adapts where
the player cannot (mpv) and the server actually offers a ladder.

Six phases, and phase 1 stands alone as pure ownership movement with no
behaviour change. Phase 4 (direct-play negotiation) is what removes the
transcode and unblocks the Linux native-video work. Phase 5 (adaptation) is
gated on counting EXT-X-STREAM-INF entries in a real playlist — the
acceptance criteria require that count be recorded before it is either
started or dropped.

Takes DR-121 from read-through-media-cache.md, which specced Rust-owned
quality reporting but never built it; that spec keeps its capture half.
2026-08-21 19:41:32 +02:00

5.6 KiB

Specs index

Feature specs for JellyTau. Start a new one from SPEC-TEMPLATE.md and run it past SPEC-REVIEW-CHECKLIST.md before accepting it.

What lives here

Only work that has not shipped. Once a spec is fully implemented its design is folded into the architecture docs — which are the maintained description of the build — and the spec file is deleted. Git history keeps the original, including its rejected alternatives and acceptance criteria; the architecture docs keep the reasoning that a future change still needs.

So: a file in this directory is a promise, not a description. If you want to know how something works, read docs/architecture/. If you want to know what is planned, read here.

Status vocabulary

Status Meaning
Proposed Written, not accepted. Nothing built.
Accepted Agreed as the design; implementation not started or not finished.
Partially implemented Some parts shipped; the spec names what is left.
Design authority No code of its own — it records a decision later specs act on.

Next free requirement ids (always re-check requirements.md before allocating): UR-079, IR-033, DR-219. Three specs below suggested ids that have since been taken by other work; each carries a ⚠️ note at the top.

Partially implemented

Spec What landed What is left
frontend-domain-model.md Catalog surface: MediaKind, from_jellyfin isolated, ticks → ms primaryImageTagimageId (~30 sites); player/session/reporting tick math; stream.type
libmpv2-migration.md LICENSE The libmpvlibmpv2 crate swap
read-through-media-cache.md DR-126…128, DR-133…138 — cache entries are download rows; local playback of downloads DR-121/122/124/125 — the player quality selector and the read-through capture
scoped-search-boundary-implementation.md Stage 1: SearchScope owned by Rust (DR-063…067) Stage 2: result-side grouping (GROUP_ITEM_TYPES still in searchScope.ts)

Not started

Spec Blocked on / note
backend-owned-stream-selection.md Rust owns direct-play-vs-transcode, transport and quality; players consume one StreamSelection. Phase 1 (delete the .m3u8 sniff) stands alone. Unblocks Linux native video.
build-provenance.md build.rs is still bare. ⚠️ suggested id DR-093 is taken.
player-facade-enforcement.md ~60 commands.player* sites still outside the facade; no lint rule. ⚠️ suggested id DR-095 is taken.
windows-native-audio-backend.md Blocked on the libmpv2 swap. ⚠️ suggested id IR-030 is taken.
linux-native-video-spike.md Spike run 2026-08-21: compositing works on Linux, X11 and Wayland. G1-G6 green bar the Tauri default_vbox() half of G1. Needs an implementation spec that answers adaptive bitrate.

Design authority

Spec Role
playback-backend-unification.md Why video cannot unify onto one native engine and audio can. The audio half has since shipped on Android; Windows has not.
scoped-search-boundary.md The boundary design the check:boundary rule came from. Stage 1 built.
scoped-search.md Superseded in part — its "frontend only, no Rust changes" decision is the leak the boundary spec reversed. UX still current.

Where the shipped specs went

Sixteen specs were folded into the architecture docs and deleted (2026-08-21). Where to look for each:

Shipped work Now documented in
Account menu & global chrome 02-svelte-frontend.md — App Shell and Chrome
Library mosaic 02-svelte-frontend.md — Library Mosaic
Series current-episode navigation 02-svelte-frontend.md — Series and Episode Navigation
Downloads as an offline library 02-svelte-frontend.md — Downloaded Browse
Favourites browsing 01-rust-backend.md — Favorites System
Streaming bitrate cap 01-rust-backend.md — Streaming quality ladder
Locally-indexed search 03-data-flow.md — Search Flow; 01-rust-backend.md — Background workers
Offline downloaded-only filter 06-downloads-and-offline.md — Offline Catalog Visibility
Audio equalizer · Android audio settings parity 05-platform-backends.md — Audio settings on ExoPlayer
Android native video spike 05-platform-backends.md — Native Video Compositing
Video background audio 05-platform-backends.md — Background Audio Handoff
Traceability gate repair traceability-ci.md
Boundary tripwire hardening scripts/check-frontend-boundary.sh (its header is the spec)
Playback docs corrections · req-coverage script removal Nothing to document — both were corrections that have been applied