# Notes Gotchas, measured facts, and things already considered and rejected. Measurements carry the date they were taken — several of these are properties of someone else's server and can change. ## MetaBrainz caps a client at ~2 MB/s (measured 2026-07-29) `data.metabrainz.org` serves a single client at roughly 2.1 MB/s, and **concurrency does not help**: one Range stream and four concurrent lanes delivered 32 MB at 2,111,195 B/s and 2,209,000 B/s respectively, while the same machine pulled 66.9 MB/s from a CDN. One of the four lanes starved to 0.5 MB/s. The lanes divide a fixed cap; they do not raise it. Consequences: - No client-side concurrency change will speed up a dump download. Pushing harder earns 503s (the reason `dumpLanes` is 4). - Stage 1 of a full import costs ~11.8 h at best (89 GB after column projection). Before projection it was 205 GB — about 27 h. This is the entire reason the catalog is built centrally and shipped as an artifact rather than derived per install. ## Further stage-1 reductions, not yet taken Both are CI-side options; neither is safe as a silent client default because each changes *what gets counted*. - **Project `recording_mbid` only** (24.1% of row-group bytes instead of 43.4%): ~49 GB, ~6.5 h. `canonical_musicbrainz_data.csv` already carries `recording_mbid`, `release_mbid`, `artist_mbids` and `release_group_mbid`, so release/RG/artist counts can be rolled up locally. Cost: listens with no recording MBID are dropped, and artist totals become "sum of their recordings" rather than direct attribution. - **Stride-sample members** (1-in-4): ~12 GB, ~1.6 h. The dump is flat numbered members (`0.parquet`, …). Sampling is viable because the counts only feed a *ranking* for a top-N cut. Must be a stride, never a prefix — if members are time-ordered a prefix biases hard toward one era. ## Incremental dump retention is 30 days (measured 2026-07-29) The incremental directory held 30 dumps (series 2579–2610), and full dumps land roughly monthly. An artifact older than ~30 days cannot be topped up: the dailies bridging the gap are gone. That is a permanent undercount of that window, not corruption — but it pins the artifact republish cadence at monthly. ## Anonymous package download is UNVERIFIED The client fetches the artifact from a fixed `latest` URL because Gitea's package *listing* API requires a token while a plain file GET appears not to — a probe of the not-yet-published artifact returned 404 rather than 401. **That is suggestive, not proof.** No artifact has been published yet to test against. Confirm before relying on it. Also worth deciding deliberately: every install pulling from a personal Gitea makes its bandwidth and uptime a user-facing dependency. ## Migrations came back (2026-08-08), scoped to avoid the old failure mode The "no migration chain" design below lasted until a real `make sandbox` DB (schema pre-dating the `tagging_items.synthetic`/`parent_group_key` columns) hit `no such column: parent_group_key` — `IF NOT EXISTS` had silently no-op'd the `CREATE TABLE` on the existing table, columns and all. A database written by an older build genuinely needed an upgrade path; there wasn't one. What came back is **not** the old 48-step chain. `sql/schemas/*.sql` stays the single source of truth for the current shape (still what sqlc reads, still what a fresh install gets verbatim). `sql/migrations/*.sql` holds small numbered files — `ALTER TABLE ADD COLUMN`, `CREATE INDEX`, etc. — that run after the schema files, tracked in `schema_migrations`, tolerating "duplicate column name" as a no-op so the exact same files run unconditionally on both a fresh database and an old one and converge on one shape. See the "Schema changes need two things, not one" section in CLAUDE.md for the column-order and index-placement gotchas this implies, and `backend/database/migrations_test.go` for the regression tests. Squashing `sql/migrations/` back into `sql/schemas/` and deleting the migration files is fine pre-1.0 (see CLAUDE.md); stop once real user databases exist. The original decision this replaces, kept for why the old chain died: `applySchema` created the whole schema from `sql/schemas/*.sql` on every open; all DDL was `IF NOT EXISTS`. A database written by an older build was not supported and there was no upgrade path, by design. Two things that removal fixed, worth not reintroducing: - The 48-step chain was ~3,700 of `database.go`'s 4,061 lines, plus helpers that existed only to serve it (`backupDatabase`, `readLibraryDirFromTOML`, `isDuplicateColumnErr`, …). - `sql/schemas/` had drifted badly from the real schema — it still described a `genre_recordings` table that migrations had renamed, and omitted `explore_index`, `http_cache`, `artist_images`, `similar_artist_map`, `release_to_rg`, `lyrics_index` and `artist_metadata` entirely. sqlc reads that directory, so it had been generating against a stale schema and silently missed columns such as `audio_files.modified_at`. The new design's answer to this specific risk: `sql/schemas/` is never edited to describe something migrations already did elsewhere — it's edited to directly declare the target shape, and migrations exist only to carry an old on-disk database to that same shape. There is exactly one hand-maintained description of "what does the schema look like", same as before; migrations don't add a second one. **When regenerating schema files from a live database, remember the seed rows.** `file_types` (the four supported extensions), `player_state` and `queue` each carry `INSERT OR IGNORE` rows that `sqlite_master` does not contain. Dropping them breaks every audio-file foreign key. ## ANALYZE runs after the catalog merge, not at schema creation The old migration 45 ran `ANALYZE` once. With the migration chain gone there is no equivalent moment — an empty database has nothing to measure — so it runs at the end of the artifact import instead (`SearchIndex.analyzeIndex`). Without current statistics the planner mis-estimates the partial expression indexes on `explore_index` (`idx_explore_title_lower`, `idx_explore_artist_lower`) and scans a million rows for queries that should seek. If another path ever populates the catalog, it needs the same call. ## Writers, not readers, are responsible for name quality `resolveArtistName` falls back to returning the artist MBID when it cannot find a name. That is fine for a one-off render but must never be persisted — an MBID stored as a title is unsearchable and shows as a UUID in the UI. This used to be defended at every read (`title != mbid` predicates) and in the upsert's conflict rules. Those defenses are gone; `AddFromCache` now refuses to write a name equal to the MBID and lets the upsert's "non-empty wins" rule fill it in when a real name arrives. `TestAddFromCacheNeverStoresMBIDAsName` guards this. ## Attached databases are invisible to the read pool `database.DB` holds two handles: a single-writer connection and a separate query-only pool. `ATTACH` binds to one connection, so anything touching an attached database must use `ExecContext`/`QueryRowWriter` (the writer) — `QueryContext` routes to the pool, where the attachment does not exist and the query fails with "no such table". ## FTS triggers are defined in Go, not in the schema `explore_index`'s three FTS sync triggers live in `exploreIndexFTSTriggers` in `database.go` rather than in `sql/schemas/explore_index.sql`, because the bulk-load path drops and recreates them (`SuspendExploreIndexFTS`). Defining them in both places would be two copies free to drift. Bulk loads must suspend them: measured on a real import, assembly runs at ~31 rows/s with the triggers attached and ~4,700 rows/s without. They are now **dropped and recreated** on every open rather than created with "already exists" tolerated, because a trigger is a definition: an existing install would otherwise keep the first one it ever got, and these definitions are where this table's write cost is decided. `explore_index_au` is scoped to `UPDATE OF title, artist_name, aliases` with a `WHEN` guard on them having changed, so the common write — an upsert whose merge rules keep every existing value — re-indexes nothing. ## The writer stall that broke playback is only half explained (2026-08-14) The user's report — play an album, the track changes, the transport stays paused, nothing appears in the queue, the play button does nothing — was diagnosed on the running app: 91% of its CPU was `BackfillLibraryDiscographies` → `upsertBatch`, with four of its six workers parked in `sql.(*DB).conn` waiting for the single write connection, while the play path did its writes inline under `q.mu` and `p.mu`. The locking half is fixed and tested (see CLAUDE.md, "Playing a track does not wait for the database to hear about it"). **What is not explained is why those upserts were so expensive.** > **Recovered note, 2026-08-14.** The rest of this section was lost to a > mishandled `git stash --keep-index` before it was ever committed; what > survives above is verbatim, and the two arguments that followed > "Two things argue against the obvious answer" are gone. Re-derive them > from a profile before acting on this — do not treat the question as > answered. ## Explore "library only" toggle was removed (2026-08-06) The Explore UI used to have a "library only" mode toggle (`frontend/src/store/explore-settings.ts`, `explore:libraryOnly` in localStorage) that filtered the Explore UI to owned content only. It was removed outright — the app now always shows full (network-enriched) Explore data. If offline/library-only mode is wanted again, it should be built from scratch rather than restored; the old implementation gated several component code paths in ad hoc ways. A separate `deep_catalog_enabled` backend flag briefly existed for the same idea and was removed earlier, when the dump importer left the app binary. ## The dev server is a real, drivable app (verified 2026-08-10) `wails dev` binds an HTTP + WebSocket server on `localhost:34115` (`internal/frontend/devserver/devserver.go`) that serves the frontend with the generated bindings on `window.go` and bridges every call and every `runtime.EventsEmit` to the **same** Go backend the desktop window uses. A browser pointed at it is not a mock — measured: `queue.Queue.GetState()` returned real JSON, `SetVolume(42)` produced a real `VolumeChanged`. Multiple clients are supported by design (`notifyExcludingSender` fans events to the other web clients *and* the desktop frontend). See plan 005. Four facts that cost time to find: - **The GTK window cannot be suppressed.** `devserver.Run` ends in `d.Frontend.Run(ctx)` with no flag to skip it, so headless needs Xvfb. Nobody upstream has a way around this. - **Build the dev binary directly.** `app_dev.go` parses `-devserver`, `-assetdir`, `-loglevel` from `os.Args`, so `go build -tags "dev webkit2_41"` plus those flags gives the same server with no watcher, no reload broadcast and one PID. - **A binding call with wrong argument types hangs forever.** The backend logs `error parsing arguments` and never fires the callback, so the caller's promise never settles. Always use a timeout; the app log is the only place the reason shows up. - **`dbus-run-session` does not break audio, and fixes MPRIS.** It replaces the bus, not `/run/user/1000`, so PulseAudio still works and `org.mpris.MediaPlayer2.yellowjacket` registers on the private bus. ## Playwright's WebKit does not run on Arch (measured 2026-08-10) `playwright-cli install-browser webkit` downloads fine and then fails to link: its Linux build wants Ubuntu 24.04 libraries (`libicu74`, `libWPEWebKit-2.0.so.1`, `libflite`) that Arch does not provide, and the dependency check emits `apt-get` advice. So `--browser=webkit` — the cheap way to approximate the WebKit2GTK renderer we actually ship — is a CI-only capability. Local browser work is Chromium, which is unaffected. ## The fixture library is generated, and generated by our own writers `test_data/music_library_test/` is produced by `cmd/gentestdata` (`make testdata`), not committed — 31 tracks across MP3, FLAC, Ogg Vorbis and WAV, ~700 KB, ~1 s to build. Two rules keep it honest: - **Tags are written by `backend/tagwriter`, not by ffmpeg.** ffmpeg only encodes (with `-map_metadata -1`); every tag comes from the same writers the app uses, so a fixture and the reader under test cannot drift into agreeing with each other and disagreeing with reality. `tagwriter.WriteFileTags` exists for this — it is the format switch `WriteUntrackedFileTags` already had, lifted out so tooling with no app to construct can call it. - **The manifest hash covers the spec, not the bytes.** ffmpeg stamps encoder version strings, so identical specs produce different bytes on different ffmpeg builds. `test_data/music_library_test.manifest.json` hashes paths, formats, durations, tags and cover identity instead, and lives *outside* the library root so the scanner never sees it. Fixtures are selected in tests by *case* (`testfixtures.CaseCoverDedup`, `CaseUnicode`, `CaseDuplicates`, …) rather than by path. Deliberately malformed files live in a sibling root, `test_data/music_library_broken/` — the clean library's track count has to stay at exactly 31 for seeds to be verifiable, and a zero-byte `.flac` in the scanned tree used to get swept into `testFlacFiles` and fail the duration parser. ## WAV tags are write-only (found 2026-08-10) `backend/tagwriter` writes WAV tags into a RIFF `id3 ` chunk, and `backend/metadata` reads through `dhowden/tag`, which recognises MP3, FLAC, OGG, MP4 and DSF and has **no RIFF parser at all**. So every tag the app writes to a WAV is invisible to the app that wrote it, and WAV tracks always scan in untitled — visible in the Artists view, where the fixture library's WAV tracks produce no "Field Recordings" artist. The fix is small (unwrap the `id3 ` chunk and hand the payload to `tag.ReadFrom`) but was out of scope for plan 005. `TestWAVTagsAreNotReadableYet` asserts the gap so that fixing the reader turns into a failing test rather than nothing at all. ## The headless harness: how to run this app without a window `make dev-headless [SEED=]` starts the app in the background and returns; `make dev-stop`, `make dev-logs`. It runs the dev *binary* (`go build -tags "dev webkit2_41"`), not `wails dev`, under `dbus-run-session -- xvfb-run`. See plan 005 and `scripts/dev-headless.sh` for why each of those three is load-bearing. **Seeds are built by running the app.** The first-run wizard's dismissal condition is not a config file — it is `GetAllLibrariesWithTrackCounts()` returning something — so `make sandbox-seed NAME=` boots a fresh `YJ_HOME`, calls the real `AddLibrary` binding through `playwright-cli`, waits for the real scan to reach the manifest's track count, stops the app with SIGTERM so the shutdown hooks persist state, and tars the result. Never hand-write a `config.toml` and DB rows: that is a second description of a valid `YJ_HOME`, free to drift, exactly like the migration chain was. Seeding points `YJ_CORE_INDEX_URL` at a dead address on purpose, so no seed depends on what the explore artifact server was serving that day. Two parsing traps, both already paid for: - `playwright-cli` echoes the evaluated source back after the result, so scraping its output for bare digits picks up numbers from your own JavaScript. Return a tagged sentinel (`'YJTRACKS' + '=' + n`) and grep for that. - Waiting on a fixed sleep or on a scan event is worse than waiting on the observable outcome. Polling the track count the app itself reports also validates the fixture manifest against the real scanner. ## Restoring a database needs foreign keys *off*, not deferred `/__test/db/restore` (`backend/testctl`) copies every ordinary table out of an ATTACHed snapshot. The obvious implementation — one transaction with `PRAGMA defer_foreign_keys = ON` — fails at COMMIT with a bare `FOREIGN KEY constraint failed (787)` that names nothing. Deferring postpones the *check*; it does not stop `ON DELETE CASCADE` from firing. Tables are copied in name order, which is not dependency order, so `DELETE FROM libraries` cascades away rows of a child table that was already restored earlier in the loop, and the final state is genuinely inconsistent. `PRAGMA foreign_keys` is a no-op inside a transaction, so it has to be set on the connection around it. That is safe only because the writer is a single connection (`SetMaxOpenConns(1)`); the restore re-enables enforcement afterwards and runs `PRAGMA foreign_key_check`, so a bad restore is reported instead of left in place. `TestRestoreRoundTrip` pins it. Two related traps in the same path: FTS5 virtual tables cannot be written with `SELECT *` and their shadow tables (`_data`, `_idx`, `_docsize`, `_config`) must be rebuilt rather than copied — but the prefix test that excludes them must not swallow `explore_index`, an ordinary table whose name is a prefix of two virtual ones. ## The event bridge hooks EventsNotify, not EventsOn `.playwright/init-events.js` records backend events by wrapping `window.wails.EventsNotify`. That is the single choke point: wails' `ipc_websocket.js` does `case "n": window.wails.EventsNotify(msg)` and fans out to listeners from there, so one wrap captures all 46 events whether or not the app subscribes to them. Wrapping `EventsOn` would have needed 46 registrations and would have missed anything the app does not listen for. `window.wails` does not exist when an initScript runs, so the script installs an accessor on `window` and wraps at assignment time (wails' `main.js` does a plain `window.wails = {...}`), then redefines the property as a plain value so nothing downstream can tell. The buffer lives on `window.__yjEvents` with `wait()`, `reset()`, `names()`, a `ready()` that resolves only when a binding actually round-trips, and a `call()` that **times out** — a binding invoked with wrong argument types never fires its callback, and a 2s rejection naming `.dev/app.log` is worth more than an infinite hang. ## Small harness traps, each of which cost a cycle - **Paths in `.playwright/cli.config.json` resolve against the config file's directory**, not the repo root. `".playwright/init-events.js"` becomes `.playwright/.playwright/init-events.js`. - **`playwright-cli` and `@playwright/test` have separate browser caches.** The CLI working is no guarantee `npx playwright test` can launch; it needs its own `npx playwright install chromium` (the runner wants `chrome-headless-shell`, which the CLI never fetched). - **`getByRole('button', { name: 'Play' })` also matches "Add queue to playlist".** Accessible-name matching is substring by default; the transport controls need `exact: true`. - **Every fixture track except one is 2–6 seconds.** A spec that plays a track and then clicks pause races the track ending and fails against a correct UI. Use the 90-second `Long Player` (`edge-lengths`), exported as `LONG_TRACK` from `e2e/support`. - **`e2e/` needs `"type": "module"`** or Playwright transpiles the specs to CJS and every `import.meta` in the support code throws "Cannot use 'import.meta' outside a module" — reported as "No tests found". ## The component tier fakes two globals, and that is all it fakes `frontend/wailsjs/` is a pure passthrough: every generated binding is `window['go'][svc][Type][Method](args)` and every runtime call is `window.runtime.X(...)`. So `frontend/test/support/wails-fake.ts` replaces those two globals and nothing else, and the tests then run the *real* generated bindings and the *real* store code. No module mocking, and no second description of the Wails layer to drift from the first — the same discipline `sql/schemas/` and the seeds get. The dispatcher mirrors wails' own `internal/frontend/runtime/desktop/ events.js`, which matters in two places: listeners registered with `maxCallbacks` expire and are removed mid-iteration, and `EventsEmit` from the frontend notifies local JS listeners *before* it notifies Go (so a frontend emit is observable in-page). Four things that cost time: - **Store singletons are constructed at module import**, so the fake must be installed from `setupFiles`, and any store that reads config in its constructor loads before a test can stub it. `test/setup.ts` carries import-time defaults for exactly those. Without them a store caches `undefined` where Go would have sent `[]`, and four components then crash on `.length` — which reads as a component bug and is not one. - **`vitest.config.mts`, not `.ts`.** The repo's vite config is `vite.config.mts`; a `.ts` sibling cannot import it, and `mergeConfig` is how the `@go`/`@store`/`@components` aliases get reused rather than restated. - **Vitest 4 takes a provider factory, not a string.** `provider: playwright()` from `@vitest/browser-playwright`, which is a third package beyond `vitest` and `@vitest/browser`, and needs its own `npx playwright install chromium` — a third browser cache after `playwright-cli`'s and `@playwright/test`'s. - **Pre-bundle Web Awesome or Vite reloads mid-test.** Its components are one deep import per element; discovering them lazily makes Vite re-optimise and reload the page underneath a running test. The glob `@awesome.me/webawesome/dist/components/*/*.js` in `optimizeDeps. include` settles it. Screenshots need the app's surface, not the default white page: the setup file imports `@store/theme-store` for its side effect (it applies the `--yj-*` ramp to `:root`) and sets the two `index.css` declarations that matter, or a component renders white-on-white and the baseline is blank. And a `@lit-labs/virtualizer` list never produces two identical frames, so `toMatchScreenshot` on `` fails with "could not capture a stable screenshot" rather than a diff — assert its rows instead. ## Binding drift is now checked, and it is fast `frontend/wailsjs/` is generated by `wails`, **not** by `go generate`, so the pre-commit codegen check never covered it: a renamed Go bound method or struct field first showed up at runtime, in a window, as a call that never settles. `wails generate module` (v2.10.2) rebuilds it in ~1.5 s, which is cheap enough to gate a commit on — `scripts/bindings-check.sh`, `make bindings-check`, and a `lefthook` pre-commit entry. Verified by renaming `queue.GetState` and watching it fail. One quirk: the generator rewrites the three `wailsjs/runtime/` files as mode 755 every run. That is not drift, so the check compares with `git -c core.fileMode=false` and restores the modes afterwards. ## Emitting an event is now one call, and it cannot kill the process `events.Emit(ctx, name, data...)` (`backend/events/emit.go`) is the only supported way to push a Wails event; `TestNoDirectRuntimeEmits` fails the build on any other `runtime.EventsEmit` in the tree. The reason is that `runtime.getEvents` (wails `runtime.go:47`) `log.Fatalf`s — `os.Exit`, unrecoverable — whenever the context lacks its internal `"events"` value. That is any `context.Background()`, so in-process service tests were impossible and background workers that outlived their context could take the app down at launch. Four packages had independently discovered this and hand-rolled a guard (`library.emit`, `download.emit`, `playlist.emitEvent`, and `autotagservice.emitEvent` with a whole `ctxReady` field). Nine other sites guarded on `ctx != nil`, **which does not help** — a non-nil context without the runtime is exactly the fatal case. The wrapper replicates wails' own precondition once and drops at debug level. Three things worth knowing: - **The test sink rides in the context**, `events.WithSink(ctx, rec)`, not in a package global. A global cannot survive `t.Parallel()` and would put a mutex on every production emit. - **`events.Deliver` is `Emit` that returns `ErrNoRuntime`**, and has exactly one caller: `/__test/emit` in `backend/testctl`. That endpoint exists to *impersonate* a backend emit, so answering `200` for an event that reached nobody would send you debugging the frontend for a backend no-op. Ordinary emitters want `Emit`. - **Enforcement is a walk of the tree, not a lint rule.** golangci-lint runs once per build configuration, so a stray emit in an `indexbuild`- or `dev`-tagged file is only visible to the pass that compiles it. One text walk sees all three, plus anything tagged out entirely. Two traps if you touch that test: the needle has to be built at runtime or the file matches itself, and it has to be the qualified selector (`.EventsEmit(`) or it matches the test's own function name. What it unblocks is a fourth test tier — services, in-process, with no app: `backend/queue/emit_test.go`, `backend/config/emit_test.go`, `backend/playlist/emit_test.go` assert on the payload the *frontend receives*, which had never been covered. Two gotchas found writing them: `config.Save` refuses to write a config that was never `Load`ed (so a test that only calls `applyDefaults` sees its second setter fail, not its first), and `queue.SetQueue` resolves anything over `initialBatchSize` in a background phase, so assert with `rec.Wait` rather than immediately after the call. ## Docs are split by tense, and the split is checkable Three places now describe this repo, and the rule for which one a new paragraph goes in is **grammatical, not topical** — a topical split ("architecture here, testing there") is what rots, because every new fact has two plausible homes. - `.planning/NOTES.md` — **past**: measured, dated, append-only. - `CLAUDE.md` — **present**: what the system is, and why. - `.pi/skills/yellowjacket-dev/` — **imperative**: what to run, in what order, and what it looks like when it fails. So the skill carries the checklist for a schema change and CLAUDE.md carries the reasoning behind the two-file rule; the skill carries the headless lifecycle and CLAUDE.md carries only the invariant that seeds are produced by running the app. Phase 6 deleted about half of CLAUDE.md's harness section on those grounds. `make skill-check` (`scripts/skill-check.sh`, pre-commit) makes it enforceable: every `make ` mentioned under `.pi/**/*.md` must exist. That is the actual anti-drift mechanism — the Makefile is the source of truth for *how* to invoke something and the skill only decides *which*, so a renamed target fails a commit instead of sending an agent confidently at a command that no longer exists. A skill that documents a command slightly wrong is worse than no skill. One shell trap it cost: under `set -euo pipefail`, `x="$(make -pqRr | awk … )"` sinks the whole assignment, because `make -q` exits non-zero whenever a target is out of date and `pipefail` propagates that. Wrap it in `{ …; || true; }`. ## The skill was followed cold, and lost time in exactly one place An agent that did not write `.pi/skills/yellowjacket-dev/` brought the app up from a wiped `.dev/` and no fixture library, drove a flow the skill does not describe (open the queue panel, toggle shuffle, assert on `QueueModeChanged`, confirm against `queue.Queue.GetState`) and stopped it — about a minute of wall clock, no dead ends. All four tiers then re-ran green from that cold state: 313 ui-test, 0 issues × 3 lint configurations, 3 test passes, 19/19 e2e. The one expensive thing was a genuine config bug, not a doc error. `.playwright/cli.config.json` had `outputDir: "../.playwright-cli"`, written on the belief — which `references/harness.md` stated as a flat rule — that every path in that file resolves against the config file's directory. **Only `initScript` does.** `outputDir` resolves against the shell's cwd, so every snapshot and console log was landing in `/home/logan/Development/.playwright-cli`, one level *above* the repo: outside `.gitignore`, outside `find`, and invisible to the obvious `ls .playwright-cli/`. That directory still held a stale snapshot from the previous session, so the obvious `ls -t | head -1` returned it silently, and the transport buttons appeared to have lost their accessible names — a fabricated regression in phase 3's work that took a DOM walk to disprove. Reading a *stale* artifact is much worse than reading none, because it answers. Four smaller corrections, all now in the skill: - `make sandbox-seed` already depends on `make testdata`, so listing both made the fixture step look separately required. It also takes ~10 s with warm caches, not the ~30 s claimed. - `make ui-setup` and `make e2e-setup` are once-per-clone prerequisites and are *not* dependencies of `make ui-test` / `make e2e`. The skill never mentioned them; on a fresh clone both fail with a missing-browser error that reads like a broken test. This matters for CI, which has no warm caches by definition. - `snapshot` prints a *path*, not the tree. Not said anywhere. - `make dev-stop` does not close the browser session; `playwright-cli -s=yj close` is a separate step. And one place the tooling taught the opposite of the skill: `scripts/dev-headless.sh`'s own success banner suggested `eval "async () => await window.go.queue.Queue.GetState()"` — a bare `window.go` call with no timeout, which is precisely the hang the banner's next paragraph warns about. A gotcha documented in prose and contradicted by the copy-pasteable line three inches above it will lose every time; the banner now prints the `__yjEvents.call` form. ## An ALSA null PCM is enough for CI audio, and it clocks Phase 7's job 2 needs playback to actually advance, because `e2e/specs/playback.spec.ts` asserts the elapsed clock moves — a missing audio device fails it in a way that reads like flake, since `app.go` joins `InitSpeaker` failure into `startupErr` and lets everything else work. Measured locally, with PulseAudio made unreachable (`XDG_RUNTIME_DIR` pointed at an empty dir, `PULSE_SERVER=none`) and `ALSA_CONFIG_PATH` pointing at four lines: ``` pcm.!default { type null } ctl.!default { type null } ``` `InitSpeaker` succeeded in 36 ms and all six playback/queue specs passed, including "the elapsed time advances". oto/v3 talks to libasound directly, and ALSA's `null` plugin advances its pointer on a timer rather than discarding instantly, so beep's stream is consumed at real-time rate. **No PipeWire, no PulseAudio and no daemon of any kind is required in the container** — one env var and a file. Also found while setting this up: `scripts/dev-headless.sh` does *not* set `YJ_CORE_INDEX_URL`; only `scripts/seed-sandbox.sh` does. So a seeded run started by hand still reaches for the real explore artifact. Harmless locally, a network dependency and a minute of wall clock in CI — job 2 must set the dead-address override itself. ## CI was prototyped in a container before it was written, and it found a real bug Both jobs of `.gitea/workflows/ci.yml` were built as shell scripts and run to green in a bare `ubuntu:24.04` container (`docker run -v repo:/src -v cache:/cache`) before a line of YAML existed, then the YAML was transcribed back out of the workflow and re-run in the same container to prove the transcription. That is worth the extra half hour on a self-hosted runner: the alternative is push-and-see, and a Gitea Actions run that never starts looks exactly like one that passed. **`make lint` was linting three configurations nothing builds.** All three passes omitted `webkit2_41`, so wails resolved `webkit2gtk-4.0`. Arch still ships `webkit2gtk-4.0.pc`, so it passed locally and had done for the life of the repo; Ubuntu 24.04 dropped 4.0, and the **`dev` pass** fails there — wails' own `app_dev.go` is `dev`-tagged and drags in the 4.0 assetserver, which the other two passes never compile. The tag sets now match `make test` exactly (`webkit2_41`, `webkit2_41 indexbuild`, `webkit2_41 dev`). Still 0 issues × 3 on Arch, and now 0 × 3 on Ubuntu too. Note what this means: "lint passes" and "the thing lint compiled is the thing we ship" were different claims, and only a second distro could tell them apart. Five smaller container facts, all now comments in the workflow: - **`libasound2-dev`, not just `libasound2t64`.** oto/v3 dies at `pkg-config --cflags -- alsa` before a line is compiled. - **`PLAYWRIGHT_BROWSERS_PATH` unifies the location, not the revisions.** `@playwright/cli` bundles its own `playwright-core` pinned to a different Chromium build than `e2e/`'s `@playwright/test`, so both must install into the shared directory. Installing one gives the other "Browser chromium is not installed; expected executable at …/chromium-1237/…". The "three separate browser caches" trap survives being pointed at one path. - **`git config --global --add safe.directory`** or `bindings-check` fails on a clone the container user does not own. - **The runner already mounts and exports `GOMODCACHE`, `GOCACHE` and `GOLANGCI_LINT_CACHE`** for every job via `container.options`, and `valid_volumes` is a glob over the cache root (`/home/logan/docker/gitea/data/runner/cache/**`), so new caches need no runner-side change. Only the Node-side ones had to be declared. - **The fixture hash is deterministic per ffmpeg, not across versions**: `5425fbb454a2` on Arch (ffmpeg n8.1.2), `599a8dd4f152` on Ubuntu 24.04. Nothing asserts a literal hash, so this is harmless — but a test that pinned one would be portable only by accident. **Setting `YJ_CORE_INDEX_URL` for the *app* run, not just for seeding, is worth 8x on the suite.** `scripts/dev-headless.sh` never set it — only `seed-sandbox.sh` did — so a seeded local run still fetches the real explore artifact, and `testctl.spec.ts`'s restore then copies every table of a database full of catalogue: 42 s locally, versus a whole 19-spec suite in 7.3 s in CI with the artifact stubbed out. ## Playwright's WebKit passes, so it gates 19/19, in the same container, ~11 s on top of Chromium's ~7 s. It had never been run anywhere before — Arch cannot start it — so the honest default would have been advisory. Running it once in a throwaway container turned a coin flip into a decision: it is a **required** step. Two things make that safe rather than brave. Nothing in `e2e/` compares pixels — every assertion is an event payload, a `data-testid`, an attribute or backend state, and the `toMatchScreenshot` baselines live in the Chromium-only Vitest tier — so a WebKit failure cannot be antialiasing noise; it is an engine difference in custom-element upgrade, a11y-tree shape or event ordering, which is exactly the WebKit2GTK signal we otherwise have no way to get. And it is cheap enough that the earlier plan to scope it (skip `testctl.spec.ts`, which tests Go and has no engine content) is not worth the complexity at 11 s. ## Every Go typecheck needs a built frontend, and a shared prototype dir hid it `main.go` embeds the built assets (`//go:embed all:frontend/dist`), so `make lint`, `make test` and `make bindings-check` all fail on a fresh clone with `pattern all:frontend/dist: no matching files found (typecheck)` until `pnpm build` has run once. It never bites locally because anyone who has started the app has a `dist/` lying around, and it is not a Go dependency anything declares — which is why CI is the only place it shows up. Job 1 now builds the frontend before linting. **The prototype missed it for an embarrassing and reusable reason.** Both job scripts were run against the *same* mounted directory, and job 2 runs `dev-headless`, which builds the frontend. So job 1 was silently consuming an artifact job 2 had produced on an earlier run, in an order CI never uses. A container proved the commands work; it did not prove the *inputs* were what CI would have, because the directory had accumulated state exactly the way a developer machine does. The fix for the technique, not just the workflow: verify each job in a **fresh `git clone --no-hardlinks` of the pushed commit** (a plain `git clone` of a repo on the same filesystem fails with "Invalid cross-device link" into `/tmp` on a different device), not in an rsync of the working tree, and never two jobs in one directory. The distinction that matters is not clean-vs-dirty but *whose* dirt: a working-tree copy carries a developer's accumulated build output, which is the one thing CI is supposed to be checking you do not depend on. ## A cached view needs a lifecycle, and so do its controllers Plan 007 phase 1. `index.ts` caches primary views and hides them with a class so `scrollTop` survives navigation — a deliberate, good decision that nothing else was told about. `disconnectedCallback` therefore never fires, and every document listener, interval and subscription a view registers runs for the session. The measured cost was not a leak: pressing `s` on **Settings** skipped albums out of the Autotag queue, because `autotag-view`'s document keydown handler was still live. Three things that were not obvious before doing it: - **A focus-only scope rule would have been a regression.** The shortcut service resolves a panel scope by walking up from the focused element, and this app is driven with the mouse: focus sits on `` almost always. Panel bindings would only have worked after a click landed inside the panel, where the old document listener worked always. Hence the *ambient* scope claimed by the active view (`services/shortcut-scope.ts`) as a fallback after the focus walk. - **Shared reactive controllers have the same bug.** `ContextMenuController` bound three document listeners in `hostConnected`, which for a cached host never un-happens. A controller cannot know whether its host is cached, so `registerViewAware` lets it ask, and it keeps connection-based behaviour on hosts that are not. - **Off-screen views were still rendering.** Store controllers call `requestUpdate()` on every subscriber, so one keystroke in the search box re-rendered eleven pages, ten of them invisible. The mixin withholds the update and replays it on activation, which is why coming back to a view still shows current state. Re-running a view's *load* on activation is not free and is not always right: `autotag-view`'s `startQueue()` resets the selected folder and refetches candidates over the network, so it stays once-per-mount and only the local folder list refreshes on return. ## A local timer is not a clock, and a fixed grid row is not a notice board Plan 007 phase 2. Both halves of the finding were reproduced by hand first, and both reproduced exactly as measured in August: the seek bar read `00:44` against a backend at `73` after four keyboard seeks, and a queue with a moved file in the middle stopped dead at index 0 with nothing emitted and `IsPlaying` false. Four things worth keeping: - **Phase 1 moved the reproduction.** With a track row focused the arrows belong to the grid, so the keyboard seek does not fire from the track list at all any more — the 30 s desync only reproduces with focus off the grid. A fix verified against a stale reproduction would have "passed" without ever running the code path. Re-run the reproduction on the current build, not on the audit's description of it. - **A push of state needs an identity and a sequence.** The store is a singleton and keeps the last position, so a seek bar mounting later adopts it: without `trackChangeId` on the payload that is a stale reading rendered as current. And without a monotonic `seq`, a report of the same second as the last one is indistinguishable from no report, so the interpolation it is supposed to reset keeps running. Both are cheap on the emit side and impossible to add later without touching every consumer. - **`.bottom-bar` is a fixed `4em` grid row.** An inline message laid out inside it squeezes the transport out of its own footer, which looks like a broken player rather than a message. It floats above the bar (`position: absolute; bottom: calc(100% + 4px)`), which is also the right answer for anything else that wants to speak from down there. - **Reporting by event beat returning an error.** The plan wanted the queue bindings to return `error`; the failure that mattered most — auto-advance onto a bad file — has no caller to return to. An event covers both, and the stores kept a `.catch()` per call for the bridge-level rejections that a return value never described anyway. ## A level says how loud, not where, and the bottom band is taken Plan 007 phase 3. The audit's ~30 "the failure is invisible" findings were one problem wearing thirty hats — there was nowhere to put a message — so the surface shipped whole: four levels, one store, one presentation, and the callers routed through it in the same pass. Five things worth keeping: - **A level is not a location.** Blocking, Persistent and Transient say *how loud*; Inline says *not global*, which is not the same as saying where. An inline notification therefore carries a **region** (`player`, and whatever comes next) and the app-level host ignores it. Without that field the "one component with four presentations" would have become two components with two stores, which is the exact thing this phase existed to delete. - **The bottom of the window belongs to the player.** The stack was first anchored above the player bar, beside the player's own floating notice. That looked right at 1440×900 and overlapped at 800×600, because the player's notice grows *upward* by however many lines its sentence needs. The stack moved under the header. Anything anchored to the bottom edge is sharing a band with something whose height is not known in advance. - **Some backend errors are already sentences.** `describeError` maps runtime causes to copy, but the sentinels this app writes for its own conditions ("a library with that name already exists") are the most useful thing that could be shown, and mapping them to a generic line would have been a regression. `explainError` repeats a message with no Go/HTTP noise markers and defers to the map otherwise. The distinction is whether *we* wrote the string, not how long it is. - **C4 and M1 are the same bug from either end.** The library store cached a stale answer because a fetch outlived the selection, and hung its waiters forever because a failed fetch never satisfied the "loaded and not loading" predicate they watched for. Both go away by holding the request itself and stamping it with a cache generation — one change, two findings, and the four hand-written `waitFor*` helpers deleted. - **A reproduction can fail for the wrong reason.** The e2e spec for a rejected binding renamed the decoy library to its own name, which the backend accepts as a no-op: red at the right assertion, having never induced the failure it was named for. It only became a reproduction once it picked its row by the seeded library's name. A failing test is evidence of nothing until you have watched *why* it fails. One operational note: `make bindings-check` requires a clean working tree for `frontend/wailsjs/` and reports staged changes as dirty, so it cannot pass mid-phase on an uncommitted tree. Regenerating and diffing by hand (`go tool wails generate module -tags webkit2_41`, then `git diff -- frontend/wailsjs`) is the equivalent check. ## Measuring is the work; the icon CDN was serving Pro Plan 007 phase 4, items 1–2 of 8. This phase is verified by numbers rather than by assertions, which changes what "first" means: the first deliverable is not a fix, it is a 50 000-track library and a script that takes four measurements against it. Both fixes then landed with a before/after, and both had a reproduction that was watched failing. Six things worth keeping: - **A measurement library is not a fixture library, and should share nothing but its generator.** `test_data/music_library_test` is curated *cases* selected by name; `.dev/music_library_bulk` is a pile whose only interesting property is its size. Generating 50 000 files through ffmpeg is ~40 minutes, so the bulk one encodes six clips once and copies them — but it still tags every file through `backend/tagwriter`, because a library the app cannot read back measures nothing. 11 s, 466 MB, gitignored, and deliberately not a dependency of `make test`. - **The first cover renderer made a 2 GB library.** The fixture cover's diagonal band is ~37 hard edges at 300 px, which is the worst case for a JPEG DCT: ~35 kB per album, nearly all of it artefacts around a pattern nobody looks at. A smooth gradient is ~6 kB and just as distinguishable. 466 MB instead of 2 GB. - **Instrument the bindings, not the symptoms.** "Finishing a track refetches the library" became a fact rather than an inference by wrapping every method on `window.go` and recording call, duration and serialized size. The generated bindings look their target up at call time (`window['go']['library']['Library']['GetAllTracks']()`), so post-hoc wrapping catches a store that imported the wrapper long ago. Pair it with a `longtask` PerformanceObserver: a 25 MB JSON parse on the main thread appears there and nowhere else. - **A debounce will happily measure nothing.** "Keystroke to paint" against the next frame gave 16 ms on every build, because `search-bar` debounces 150 ms and 16 ms is the input echoing its own character — a number that cannot move, and therefore cannot be evidence. The measurement has to wait past the debounce for the render the keystroke caused. - **The icon CDN was serving Font Awesome _Pro_.** Every SVG fetched from the kit host carries a "Commercial License" comment, so the obvious fix — save what the app already downloads — is a licence violation. Font Awesome **Free** 7.3.1 (CC BY 4.0) has all 64 names the app uses, is redistributable with attribution, and moved no `ui-visual` baseline. Check what a CDN is actually serving before vendoring it. - **Some icon names cannot be found statically.** Twenty call sites compute one from state (`jobIcon(job)`, `TONE_ICONS[tone]`, `this.favCtrl.iconName`), so the list is committed and *checked at runtime*: the resolver records a miss and renders a fallback, and an e2e sweep across every view asserts there are none. A missing icon used to be invisible because the CDN had everything; it now has to be findable instead. And two findings that did not survive contact: - **`perf.M1`/`M2` no longer reproduce.** One keystroke costs 49.9 ms net of the debounce with **zero** long-task blocking at 50 000 tracks, not the predicted 50–100 ms across every mounted view — because Phase 1 stopped off-screen views rendering, which was M1's mechanism. An audit finding can be fixed by an unrelated phase, and re-measuring before fixing is how you find out. - **`perf.M7`/`M8`'s unbounded caches did not show as heap growth** across a ten-view scripted browse (37 → 38 MB post-GC). They are real by inspection, but the reproduction has to be a long Explore session, and it should exist before the LRU does. One correction to the audit's own numbering, since two phases cite it: in `perf.md` the icons are **M9** (the plan's Phase 4 prose calls them C1), the whole-library refetch is **C1**, the selection wipe is **C2**, and **C3/C4 were already fixed in Phase 3**. ## A ticker is a hidden dependency for everything that forgot to speak Plan 007 phase 4, items 3–5 (`C5`, `M6`/`H-14`, `M10`). Three fixes, three new measurements, and one bug shipped-and-caught inside the same session — the useful part of which is *how* it was caught. Five things worth keeping: - **Deleting a polling loop is never only a deletion.** The explore index emitted its status every 3 s forever, with an identical payload once ready, which re-rendered the whole settings page for the life of the session. Every path that *mutates* the status already emitted, so the ticker looked purely redundant. It was not: `si.ready = true` and `si.cancel = nil` both change what `emitStatus` derives and neither announced itself, so the ticker was carrying two transitions within three seconds of their happening. Removing it left the header badge reading "Building search index" over an index the settings page called ready. Before removing a poll, enumerate the writes to everything it reports — `rg 'si\.ready = |\.cancel = '` was the whole audit, and it should have come first rather than second. - **The screenshot found it; no test did.** The Go tests passed, the 436 component tests passed, all 36 e2e specs passed, and the numbers were exactly the improvement predicted. The contradiction was two labels 700 px apart in a PNG. "Read the PNG" earns its place in the gate on cases like this — the app was *self-inconsistent*, which no assertion was looking for because nobody had thought to. - **A "0 ms" measurement is usually a broken measurement.** View-open time waited for `#main-content > :not(.view-hidden)`, which matches the view being navigated *away from* — it is still on screen until the incoming chunk resolves. Every view, every build, 0 ms. This is the same failure as the 150 ms debounce from the first pass, and the same tell: a number that cannot move is not evidence. Both times the fix was to wait for the specific thing, not for a generic selector. - **A before/after must differ in exactly one thing, and `git stash` is not a way to arrange that** on a tree carrying four uncommitted phases. Stashing `frontend/index.ts` to measure the pre-split bundle also reverted the bundled-icon registration living in the same file: 22 cross-origin requests, and a baseline for a build that has never existed. The honest baseline was made by *adding the static imports back* to the current file — a change that undoes the one thing being measured and nothing else. - **The cheapest half of a fix is often the one the audit did not name.** `perf.C5` is written as an event handler that over-fetches, and it is. But `playlistStore` is a singleton constructed at import time and eagerly warmed itself as well, so every launch paid the same 2.6 MB whether or not Playlists was ever opened — the event costs that on a user action, the constructor costs it on every start. "Only when there is a subscriber" turned out to be a two-line change that beat the patching logic it was written to support. And one thing about splitting a bundle: **report the trade, not the win.** Route splitting moved 666 kB out of the pre-paint path (1 480 → 814 kB) and cost up to 6 ms on the *first* open of a view, once per session, hidden further by warming the chunks on idle. But first contentful paint did not move at all, because at localhost speeds over a warm cache 666 kB of JS is not what the paint was waiting for. The number that improved is real and is the one that costs on a cold start and under WebKit2GTK; the number a user watches did not change. Saying both is the difference between a measurement and an advertisement. ## "We looked and saw nothing" is only evidence if the thing that fills it ran Plan 007 phase 4, items 6 and 7 (`M7`/`M8`, `M3`/`M4`). Two fixes, two new measurements, and one finding that two previous sessions had come within a sentence of deleting as unreproducible. `perf.M7` says the Explore art caches are never evicted. Two sessions measured a ten-view scripted browse, saw the heap go 37 → 38 MB post-GC, and recorded the finding as "real by inspection but it does not show up". Both were right about the number and wrong about what it meant: **the browse script navigates to Explore and never types in it, and both caches are filled only by a search.** It was measuring a view with two empty maps. A session of twenty-four searches grows the heap 20.58 MB and is still accelerating at the end. Six things worth keeping: - **A negative result inherits the coverage of the thing that produced it.** "We browsed ten views and the heap was flat" sounds like evidence about caches; it is evidence about ten navigations. Before believing a finding did not reproduce, check that the code path it names actually executed — here, one `console.log` of `thumbnailCache.size` would have ended the question two sessions earlier. Phase 4 has now had three findings evaporate on contact (`M1`, `M2`, and half of `M8`) which makes the fourth *look* like the same thing, and that prior is exactly what made it cheap to accept. - **A bound cannot be verified by a run that never reaches it.** The first bounded build measured identical to the unbounded one: twelve searches cached 180 thumbnails against a cap of 192, so nothing was ever evicted. This is the same trap as the 150 ms debounce and the `:not(.view-hidden)` selector, in its third costume — *a number that cannot move is not evidence* — and the tell is the same one every time: before and after are suspiciously equal. - **Two caches holding the same string means bounding one frees nothing.** `explore-view`'s `artistImageCache` and `exploreCache.artists` both hold the artist photo's base64 data URL, ~128 kB each, measured at 2.30 M chars in *both* maps. Capping either alone leaves every string pinned by the other, and the measurement would have read as a fix that did not work. The cap is a shared exported constant now. Before bounding a cache, find every reference to what it holds. - **The audit named the wrong two maps.** `M8` calls out `artistAlbums` and `artistTopTracks` as holding discographies and top-track lists. Nothing in the app has ever written to either — their only callers were a component test. Deleted rather than bounded. The map that actually retains is one the audit does not mention. - **A measurement library optimised for size can remove the property a finding is about.** `M3` is "the Art column renders a 1500×1500 original into a 24 px box". The bulk library's covers are 300×300 and 3.7 kB, because generating 50 000 realistic covers made a 2 GB library and a smooth gradient made a 466 MB one. So the bytes saved here are 3.7 kB → 1.1 kB and prove nothing. The number that is not hostage to the fixture is **which tier was requested** — 26 of 26 originals before, 0 after, true on any library. When the rig cannot show the magnitude, measure the mechanism. - **An audit's arithmetic is a hypothesis too.** `M4` predicts 250 000 comparisons per scroll frame from 5 000 albums × ~50 visible cards. Measured: 24 visible cards, and the scan breaks on its first match, so it costs **1.46 ms per frame** — real, 146× improvable, and far below the long-task threshold, so it moves no user-visible number today. Worth fixing because it stops scaling with the library, not because anything was stuttering. Say which of those two it is. One operational trap that cost a cycle and is now in the skill: **`make e2e` needs `SEED=default`.** Run against the bulk seed left over from a measurement session, 13 of 36 specs fail on fixture content — unicode tracks, fixture artists, the seeded playback file — and the failure list reads exactly like a regression in the change you are holding. ## A virtualizer repaints on its own properties, and the sloppy thing doing that may be load-bearing Plan 007 phase 4, item 8 (`M5`) and part of the tail (`p3`, `m1`, `m7`, `p4`). One large fix, three tail items settled, one audit recommendation rejected as a bug, and a broken feature that no audit had noticed. The mechanism under most of it is one sentence: **``'s rows are rendered by the `virtualize` directive, and that directive runs when one of the *virtualizer's own* properties changes — not when its parent re-renders.** Everything below follows from that. Seven things worth keeping: - **Memoising `items` and hoisting `renderItem` together is how you build a list that never repaints.** Virtualizing the playlist views needed both (that is the point), and selection went silently dead: the controller held exactly the right keys and no row ever showed one. Nothing failed — 447 component tests, 36 e2e specs and every Go test stayed green. A click in the real app found it in ten seconds. The fix is what `track-list` has always done and nobody had written down: push `virtualizer.requestUpdate()` on a selection change and on a playing-track change. - **The same fact makes `perf.m1` a regression.** It asks for `artists-view` and `genres-view` to hoist their per-render arrow functions to stable fields "as `cover-grid` already does". That fresh closure is the only thing changing a virtualizer property on a host update, i.e. the only thing repainting the cards. Measured in the running app: 1 highlighted card before the change, 0 after, both views. There is no compensating win — the host mostly re-renders *because* card state changed — so the closures stay, and `card-grid-repaint.test.ts` fails on the change and exists for no other reason. **An audit's suggested fix is a hypothesis too**, and this is the first one in this phase that was actively harmful rather than merely wrong about magnitude. - **Two of `M5`'s four stated mechanisms did not survive measurement.** "lit removes and re-adds 10 000 listeners per pass" is false on any build: instrumenting `EventTarget.prototype` recorded **zero** add/remove calls per pass, because lit-html's `EventPart` is itself the listener (`handleEvent`) and a changed listener value updates a field rather than the DOM. And one update pass cost 5.3 ms, not a stall. What was real, and worse than predicted, was elements retained: **22 090** for a 2 000-track playlist against the audit's 16 000, and 2 000 eager cover requests. Fixing the two real halves gives 487 elements and 0. - **The suggested fix would have cost two features.** "Render these through `` the way `genre-details` does" holds for `genre-details` because a genre list is just tracks. Both playlist views render phantom rows for missing files, and `playlist-details` is a drag source and a drop target; `track-list` has never had either. Virtualizing in place got the same 45× on elements with none of the risk, and left `track-list` alone for its four other callers. Check what the reference implementation *does not* do before adopting it. - **A row inside a virtualizer needs `width: 100%`.** The virtualizer positions children absolutely, so a grid row shrinks to fit its content: the columns silently stopped lining up with the header above them. Caught by reading the screenshot, not by any assertion — the second time in this phase that a PNG found what the suite could not. - **A write with a `RETURNING` clause is still a write.** `CreateSmartPlaylist` issued its `INSERT ... RETURNING` through `DB.QueryContext`, which routes to the query-only read pool, and failed with "attempt to write a readonly database (8)" — so **no smart playlist could be created at all**, in any real build. It was invisible because `NewTestDB` shares one in-memory connection and leaves `readDB` nil, so `reader()` hands back the *writer* under test: every unit test of that path exercised a handle production does not have. `TestNoWritesOnTheReadPool` now walks the tree for the class, watched failing on the bug first. A test double that collapses two handles into one cannot see a bug about which handle you used. - **`p3` is right about one store and wrong about the other.** Coalescing `search-store`'s notify to a microtask makes a subscriber that unsubscribes synchronously after a `setTerm` miss the notification entirely — a semantic change, and one an existing test had already pinned deliberately. `playlist-store` took the fix; the keystroke store did not. "Make these five consistent" is a fine instinct and a bad rule when one of them is on a different path. And two operational notes, both now in the skill: - **A frontend edit is not live until the app restarts.** Vite HMR updates the module, but an already-registered custom element class cannot be re-registered, so the running page keeps the old one — the edit reads as having done nothing. Worse, a *build error* leaves the dev server serving the last good bundle, silently: a stray backtick inside a comment in a `css` tagged template literal ended the literal, esbuild failed, and the page kept rendering the previous CSS while `make dev-headless` printed nothing about it. - **`tsc --noEmit` is in CI and was not in the documented gate.** The previous pass left the tree failing it, under a fully green `make lint && make test && make ui-test && make e2e` — none of which typechecks `frontend/test/`. ## An audit's magnitude and its mechanism are two claims, and the fix is a third Plan 007 phase 4, fifth pass: the `track-details` chunk split and `m6`. Two items, both landed, and the pass's one useful generalisation is that a finding is really *three* hypotheses — how big it is, why it is that big, and what to do about it — which can be independently right and wrong. `perf.m6` got the first right, the second wrong, and the third half wrong: - **Right about size.** "Select all → Edit tags at 50 000 tracks will hang the renderer." Measured through the real opener: **3.0–6.3 s** of blocked main thread, varying that much run to run on one build. It is the largest single stall this phase has found, and it was in the *minor* tier of the audit. - **Wrong about why.** The audit calls it O(selection × total) — 2.5 × 10⁹ comparisons. It is not: select-all hands the opener its keys *in list order*, so each `find` matches at index *i* and the real cost is N²/2, quadratic in the **selection**. That matters for what it predicts about everything else: the audit's formula says a ten-track selection costs 500 000 comparisons (it costs about 50), and says nothing about the genuine worst case, which is a selection built from the *bottom* of the list. - **Half wrong about the fix.** "Keep an index-ordered selection, and build a `Map` for the batch lookup." The map is the entire 50× (**3 051–6 298 ms → 68 ms**), and it is now `utils/track-index.ts`, a `WeakMap` keyed on the array's identity — the invalidation signal this app already relies on everywhere else. The index-ordered selection is the unsafe half: an index goes stale on any re-sort, re-filter or refetch while a file path survives all three, which is exactly why `retain()` drops `lastSelectedIndex` and keeps the keys. The helper it would have replaced measures **3 ms**. Three milliseconds does not buy a silently mis-ordered queue insert. That is the second audit recommendation in two passes that would have shipped a bug, after `m1`. Both times the reason was the same: the audit reasoned from the shape of the code and not from what the rest of the file already knew about it. Five more things worth keeping: - **A `longtask` entry arrives after the task that produced it.** The new measurement's first run reported `blocking: 0 ms` next to a six-second wall time, because it read the buffer synchronously after the await. Sixth variant of this phase's most-repeated trap, and the first one caught by *another number in the same row* contradicting it rather than by suspicion. Two numbers that must agree are worth more than one number you have to be sceptical about. - **The first load after a rebuild is not a measurement of first load.** FCP read 96–112 ms on every run taken immediately after `make dev-headless`, and 28–32 ms on the very next run of the same build. A cold Vite module graph, not variance. The plan had been describing this as "±100 ms run to run" for three passes without naming it. - **Measurement labels are a flat namespace; audit IDs are case sensitive.** `before-m6`/`after-m6` already existed — the *second* pass's capital `M6`, an unrelated finding about a 3 s ticker. Naming a baseline after a finding would have overwritten two of them. - **An unreachable code path still costs bundle size, and “dead code” can mean “missing feature”.** `cover-grid` is one of the five components that opened `track-details`, and it cannot: its album dropdown is rendered by `renderSplitGrid`, which `connectedCallback` references only to satisfy `noUnusedLocals` and which is, by its own comment, never invoked. Expanding an album fetches its ten tracks and draws nothing. The audit files this as `perf.p2`, "an unreferenced `renderSplitGrid`", under housekeeping. It is a whole interaction that does not exist, and it was only visible from trying to use it. - **What keeps a chunk out of a bundle is the absence of an import, which nothing notices.** Five static imports were what put `track-details`'s 42 kB before first paint; adding one back costs nothing anybody would see, because the chunk is also warmed on idle and the dialog carries on working. `lazy-track-details.test.ts` reads the five sources and fails on a returning import — the same shape as `TestNoDirectRuntimeEmits`, and for the same reason: the invariant is about what the code *does not* say. ## A finding's magnitude is measured where the work runs, not where it is written Plan 007 phase 4, sixth pass: `m5`, `m4`, `m2` — the end of the tail, and the phase. Three items, one of which was measured and then *dropped*, which is the outcome the discipline exists to allow. The generalisation the pass added to the previous one's "an audit's magnitude and its mechanism are two claims": **a mechanism can be exactly as described and still cost nothing, because the cost depends on state the reading cannot see.** `perf.m5` is right that `now-playing.updated()` interleaves layout reads with style writes on every pass, and right that the component updates while playing. It is wrong by two orders of magnitude, because a 1 Hz position report changes nothing that component renders — so the layout is clean when the reads happen and they cost 3 µs. The interleave only flushes when the DOM actually changed, measured at 0.103 ms, 34× more. The fix is still right (52 forced layouts over six seconds of playback became 2), but the number that justifies it had to be found by making the DOM dirty on purpose. Seven things worth keeping: - **A guard is only correct if it lists everything the measurement depends on, including things a CSS rule adds.** `.will-scroll .scroll-content` has `padding-right: 2em`, so applying the scroll class changes the distance the marquee has to travel: −128 px before the class, −158 px after it. The audit's "guard on the value/flag they already track" reads as "guard on the text", and a text-only guard would have left every first hover scrolling 30 px short — silently, with no test in any tier able to see it. That is the **third** audit recommendation in three passes that would have shipped a bug, after `m1` and `m6`, and all three failed the same way: reasoning from the shape of a function instead of from what the rest of the file already knows about it. - **Measuring is also how you decline to fix something.** The same finding names `artists-view` and `genres-view`, which do one `querySelector` and two `style.setProperty` per pass and **no layout read at all** — 0.0033 ms, one percent of their own update pass. They are the two files `perf.m1` was rejected in, where a guard risks stopping the virtualizer seeing a changed property. Three microseconds does not buy that risk, and "measured, declined" is a better record than a silent omission. - **A finding can be half-fixed by a phase that was not about it.** `m4` describes two components registering document `mousemove` in `connectedCallback` "for the process lifetime". Phase 1 had already moved `track-list`'s onto `listenWhileActive`, so half the finding described a build a year of work had passed. Check the line the audit cites still says what it said. - **An N+1 finding is usually also an N-bytes finding, and the audit's fix may only address the N.** All three `m2` sites want `FilePath` and ask for whole track rows to get it: five genres cost **6 MB over the IPC**, which the suggested `GetTracksByGenres([]string)` would have preserved exactly while removing four round trips. Returning paths made it 1.29 MB. Ask what the caller does with the answer before batching the question. - **Return grouped, not flattened, when the caller owns the order.** An album list is sorted by name and a genre selection by click order; a flattened result would have reordered a queue silently. The new bindings return `map[int64][]string` / `map[string][]string`, which also serves the drag cache — a fourth N+1 site the audit does not name, and the one that fires most, since it warms on every selection change rather than on a menu action. - **`make generate` was emitting TypeScript that does not parse.** `genevents` prefixed only the *first* line of a const block's doc comment with `//`; Phase 4's first pass gave `events.go` two multi-paragraph comments; so regenerating `frontend/src/events.ts` wrote bare prose into an object literal. It is a pre-commit hook, so the failure was waiting for whoever next touched a `.sql`, a `.templ` or an event constant. Nothing caught it because nobody had run the generator since the comments were written. **A generator is only verified by running it**, and a hook that regenerates is a hook that can break a clean tree. - **The `wailsjs` delta is 13 lines across *two* files**, both `autotagservice/Service.*`, not five as three sessions of notes have said. It is 25 across four now, the extra 12 being this pass's two library bindings. And three on measuring, all of which produced a wrong number first: - **"First run cold, second warm" is not a rule.** First contentful paint read 100 then 96 on one build this pass, and 28 then 76 on another — the second run warmer in neither. FCP varies ±50 ms here for reasons the harness does not control. The honest response is to report it as unattributable, not to take a third run until it agrees. - **A confirming run against the wrong seed looks like a result.** A re-run taken straight after `make e2e` measured the *default* library, because `make e2e` needs `SEED=default` and the app was still on it: "Play 20 albums" went from a number to a dash and the artist's bytes fell 40×. Plausible in shape, meaningless. The tell was a row that stopped having a value at all. - **Selection highlighting read from an inactive view measures Phase 1, not a repaint bug.** Driving `artists-view` after navigating with a raw `navigate` event showed the controller holding one selected artist and zero highlighted cards — the exact signature of the virtualizer hazard, and entirely an artifact: `viewActive` was `false` and an off-screen view does not render. Through a real sidebar click: one highlighted card, `aria-selected="true"` on the right one, in both card grids. Check `viewActive` before believing a view did not repaint. ## A reproduction read too early is a fix applied to nothing Plan 007 phase 5, first pass: the track list's arithmetic, a window minimum the layout can actually hold, and one page header for nine views. Three items, one inherited one-liner, and the pass's own contribution to this plan's longest-running theme — *a number that cannot move is not evidence* — which appeared twice more here, both times in a **reproduction** rather than in a measurement. `config-page`'s rename bug is real: the library name's click bubbles to the document handler that closes the rename editor, so it opens and closes it in the same click. But the probe that "reproduced" it read `.edit-input` synchronously after a synthetic `.click()`, and Lit renders on a microtask — so it reported "not editing" on the broken build *and* on the fixed one. The fix looked like it had done nothing, which nearly bought a second, unnecessary fix; the real check needed one `await`. The same shape then failed an e2e spec of mine, which captured a header count immediately after a navigation and got `null`, making every assertion after it vacuous. Seven things worth keeping: - **A screenshot disagreeing with a number is the useful signal, not a puzzle to explain away.** A viewport ladder reported the top bar overflowing by 0 px at every width while the PNG showed the job indicator cut off at the edge. The badge was `display: none` — no job was running by then — so nothing was overflowing and the "bug" was a rendering of the app working. Two numbers that must agree are worth more than one number you have to be sceptical about, and a picture counts as one of the two. - **An audit's symptom can outlive its mechanism.** `H-11` says the app title "wraps into the nav" below 700 px. It does — but the title block is 80 px tall inside a 64 px bar at *every* width, including 1440; what changes at 780 px is the *subtitle* taking a second line. Fixing the visible half is a breakpoint on the subtitle. The permanent 16 px was never the finding and is still there. - **Fixing the stated cause does not always remove the stated symptom.** With the 40 px arithmetic fixed, Duration still reads "Durat…" at 800 px — because the column is at its 50 px floor and the *label* no longer fits, while the values do. Same screenshot, different mechanism. Worth writing down, or the next reader reasonably concludes the arithmetic fix did not land. - **Count the copies before calling something a duplicate pair.** The audit names Albums and Tracks as the two views with a sort toolbar; `playlist-view` had a third copy of the same twenty lines. The fix was worth 1.5× what the finding implied. - **What a model carries decides what a control can offer.** "Artists and Genres have no sort control" is one finding and two different fixes: genres have a track count to sort by, and `library.Artist` carries nothing countable at all. A select with one option is a control that does nothing, so that view gets a label and a direction button. - **Backend state outlives the page, and a spec that spends it fails the *next* run.** `view-lifecycle.spec.ts` toggled shuffle and never toggled it back, so a second `make e2e` against the same app failed `playback.spec`'s shuffle assertion — in a list that reads exactly like a regression in the change you are holding, which is what I assumed for half an hour. Stashing the phase's source changes and re-running the same specs is what proved it pre-existing; the same file also skips an autotag album per run, out of eleven, which is inherent and now in the skill. **Restart the app before believing an e2e failure you did not cause.** - **A header that appears with the data is the layout problem it was meant to fix.** The first version of `` rendered only once a view had loaded, and showed "0 playlists" while loading. Both were caught by reading a screenshot rather than by any assertion. The header now renders during load and omits the count until there is an answer — `null` meaning "no answer yet", which is a different thing from zero and has to be a different value. ## An audit ages against the code, and the oldest claims are the least checked Plan 007 phase 5, second pass: the five hand-rolled dialogs, the context menu's keyboard model, the ARIA tail, and landing on Home. `a11y.md` was the least verified material in the repo — three of its 34 findings had been touched before this pass — and treating each one as a hypothesis was worth it three times over. The generalisation the pass adds to "an audit's magnitude and its mechanism are two claims": **a finding also has a date, and the code has moved since.** Three of the findings here describe a build that no longer exists, in three different ways: - **Fixed by a phase that was not about it.** `a11y.12` lists five silent async surfaces. The first is `config-page`'s private toast, which Phase 3 *deleted* — and the surface that replaced it has had `role="status" aria-live="polite"` since the day it was written. Two of five bullets were already closed. - **Half-fixed, so the stated mechanism is now wrong.** `H-9` says the Home card's missing-art placeholder "has no background". It has one; it is `--yj-bg-surface`, which is almost exactly the page colour, and it holds a `wa-icon` — which has rendered at all only since Phase 4 bundled the icons. "Renders as nothing" was *literally* true offline when the audit was written and is now merely nearly true. Fixing the stated cause would have changed one line and nothing visible. - **Reproduces differently.** `H-9`'s other half says "all three shelves show the same seven albums". There are five shelves and the duplication is one adjacent *pair*. The fix is still right; a rule written from the sentence rather than from the page would have been aimed at three shelves that do not exist. Seven more things worth keeping: - **The existing tests caught two bad versions of a new rule; the new test caught neither.** "Suppress a shelf that repeats the one above" is one line of intent and three of policy. Version one collapsed a four-album library to a single shelf. Version two, guarded by a fixed shelf size, let an 11-album library keep three identical shelves while a 13-album one lost them. The rule that survives is **"a repeat is a fault only if a different row was possible"** — the shelf must not be showing the whole library — and the reason it is right is that it is about the library rather than about a constant. A test written for a change tests the change; the tests already there are what test the system. - **A default that is a behaviour has to be changed in two places, and one of them is a test suite.** Landing on Home broke **eleven** e2e specs. Nine assumed the track list is on screen at startup. One failed because every primary view stays in the DOM and Home names the same artists, so an unscoped `getByText().first()` matched a card on a `.view-hidden` page. And one was a real bug: `getByRole('button', {name: 'Shuffle'})` resolved to *two* elements, because Home's page-header action and the transport's shuffle mode had the same accessible name and had never been on screen together. A cached view is in the accessibility tree from the first paint, so "these two controls are on different pages" stopped being true the moment the app started on one of them. - **A component test against hand-built markup cannot see a web component's own lifecycle.** Two of the three things that made the menu keyboard model work are invisible to it: `wa-dropdown-item` sets its `role` in its *own* first update, so a query at the host's `updateComplete` finds no items at all; and `focus()` on a `wa-popup` that has not positioned itself is a silent no-op. Both produce a menu that opens and refuses to take focus. Both were found by driving the real app, and the e2e spec exists because the component test passes either way. - **The rule for a live region is about ordering, not markup.** Most screen readers announce a *change* to a region they are already watching and ignore one that appears with its content already in it — which is why `catalog-scope-notice` had a `role="status"` that announced nothing. So the regions render unconditionally and empty and only their text changes, and `now-playing`'s is in **both** render branches, because the branch with no track is the one that has to be mounted before the first track arrives. - **`aria-selected` on `role="button"` is not useless, it is dropped.** Four grids whose entire ctrl/shift interaction exists to produce a selection were publishing it into a void. The fix is not an attribute but a role: `listbox`/`option`. - **A backtick in a comment inside a `css` tagged template literal ends the literal.** The skill has warned about this for two plans. I did it twice in one session — once in a component, where `tsc` pointed at the line, and once in `tokens.css.ts`, where **every test file in the suite failed to import** and the output reads like a broken test runner. If the whole tier dies at once, suspect the shared module. - **Migrating a dialog can delete feedback nobody listed.** `config-page`'s remove-library spinner lived *in* the hand-rolled overlay, so moving the confirmation to `confirmAction()` left a backend call of unknown length with no indication it had started. The state field it used had no reader afterwards, which is the tell: `removingLibraryId` now means "which row is busy" and the row says so. And one on the harness, stated carefully because it is the kind of thing that gets over-claimed: **`e2e` has failed in CI on every push this session, including one that changed no application code at all** — `9f03b3f`, a workflow file and a shell script. `check` passed on all of them. Together with `9e92721` (docs only, recorded last pass) that is two failures which cannot have been caused by the commit they ran on. But **it does not follow that this session's failures are the same one**, and I could not check: this Gitea build does not expose the job-log endpoint, and the runner is not on this machine, so the log tail the skill describes is out of reach from here. The suite passes locally, twice consecutively, all 48 specs — **on Chromium only**. CI also runs **WebKit**, which cannot run on Arch at all, and this pass changed focus management, dialog modality and roles, which is exactly the area where the two engines differ. Treat the WebKit half as unverified rather than as the known audio-clock flake until someone reads the log. ## "Out of reach" is a claim about a tool, not about the information Plan 007 phase 5, third pass: Settings' keyboard reach, the `?` overlay and the arrows, an Album column, and the CI question two sessions had recorded as unanswerable. The generalisation the pass adds: **when a tool says it cannot get something, that is a fact about the tool.** `gitea_ci job_logs` returns a 404 on this Gitea build and says so clearly, and two sessions read that as "the log is out of reach from here" and reasoned from the commits instead. The REST API on the same server answers fine, with the token that was already in the environment: ``` GET /api/v1/repos/{owner}/{repo}/actions/runs/{run}/jobs # per-step status GET /api/v1/repos/{owner}/{repo}/actions/jobs/{id}/logs # the whole log ``` Ten minutes, after a session and a half of careful hedging about what the failure might be. The hedging was correct — it just cost more than checking would have. What the log said, in two parts: - **The failure is the container's audio clock**, on both engines. Not a regression in the dialog/focus/menu work, which was the live worry. `playback.spec`'s elapsed time and two `player-truth.spec` cases: the UI interpolates while the backend position stays at zero, 17–18 s adrift. `ci.yml` says the ALSA null plugin advances at real time; it was measured once and no longer does. - **WebKit had never run.** The step had no `if:`, so a chromium failure skipped it — `conclusion: skipped`, in the same JSON that held the answer. The previous pass's "treat the WebKit half as unverified" was more literally true than intended: the one place WebKit gets any coverage had produced no signal at all for as long as chromium had been red. With `if: !cancelled()` it runs, and both engines pass 48 and fail the same three. Seven more things worth keeping: - **A reproduction of the *fix* can be as invalid as one of the bug.** After making `←`/`→` reach the player again, the check measured zero `Player.Seek` calls — the same answer as the broken build, because nothing was playing and the dispatch records nothing with no track loaded. Seventh costume of this plan's most-repeated trap, and the first on the *after* side: "the fix did nothing" and "the probe cannot see anything" produce identical output. - **A shortcut a dialog swallows is a promise the shortcut layer cannot keep.** The `?` overlay was written as a toggle. It cannot be: `focusedControlOwnsKey` yields every unmodified key to anything inside an open dialog, so the second `?` never reaches the service. Escape closes it, as it does every dialog here. The rule that protects focused controls is the rule that forbids the toggle, and an e2e spec is what noticed. - **Every `wa-dialog` in this app is an unnamed dialog.** `a11y.md` lists them under "what is already correct" and says every one passes a `label` — true, and the label never reaches the accessibility tree. Web Awesome renders it into an `

` in the same shadow root as the `` and never sets `aria-labelledby`. Found by writing `getByRole('dialog', {name})` and getting nothing. Two more facts about locating one, both costing a spec run: the host is `display: contents` so it always reports hidden, and the slotted content lives in the *host's* shadow root, not in the dialog's subtree. - **A fix can be right while the finding's stated benefit is wrong.** `H-15` wants an Album column so the three `Tideline / Aurora Fields / 00:06` rows can be told apart. They are duplicates of the same album, so they still read identically; what distinguishes them is the duplicate-detection feature or a path column. The column is still the right default for every other row. Visible only in a screenshot — nothing failed, and the finding's sentence would have been ticked off without looking. - **A section of controls that do nothing is worse than admitting the section does not exist.** `H-22` asks for a Playback/Audio section; `backend/config` has no output device, gapless, crossfade or replay gain to expose. Same judgement as "Artists cannot have a sort *select*" two passes ago, and the same tell: the audit describes the UI it wants without checking what the model carries. - **A default the seed has already persisted is not a default you can see.** Changing `tracklist.DefaultColumns` changed nothing in the running app, because `.dev/seeds/default.tar` carries a `config.toml` from before it — while CI builds its seed by running the app and would have exercised the *new* one. A local run and a CI run testing different defaults is worse than either being wrong. `make sandbox-seed NAME=default`. - **`aria-controls` has to name an element that exists**, which decides how a disclosure renders: `config-section`'s body is rendered unconditionally and toggled with `hidden` rather than added and removed. Nothing is paid for it — the slot's light-DOM children are in the DOM either way; a conditional `` only stops projecting them. ## A dependency with a rate has to be checked at its rate Same pass, after the plan's three landings: the `e2e` job's red history turned out to be one measurement being wrong, and the fix was worth the generalisation. `ci.yml` had made ALSA's `null` plugin the container's default device, with a comment saying it "advances its pointer on a timer, so playback is consumed at real-time rate". It does not. Measured in the CI image under Docker, through beep and oto with the same `speaker.Init` arguments `player.InitSpeaker` uses: | default device | 3000 ms of audio consumed in | |---|---| | `type null` | **2.96 ms** | | PulseAudio null sink | **3762 ms** | A thousand times too fast. Every track finished instantly, so the position reset to zero while the UI kept interpolating, and three specs failed on a clock that never moved — 17–19 s adrift, which reads exactly like the `H-3` bug Phase 2 fixed. `check` and `e2e` are both green now, 54 specs on Chromium and 54 on WebKit. Five things worth keeping: - **A dependency with a *rate* needs a check at its rate.** Installing a sound device and asserting it exists is not the same as asserting it plays. The job now plays three seconds and fails if they take under two, in a step called "The sink plays at real time" — so the next regression names itself instead of surfacing three steps later as an app bug. - **A failure that succeeds quietly is the expensive kind.** `InitSpeaker` returns nil in ~3 ms against both devices. Nothing logged, nothing errored; the only symptom was arithmetic in three specs. Two sessions read that as a flake and one as a possible WebKit regression. - **The CI container is reproducible locally, and nobody had tried.** `docker run --rm ubuntu:24.04` reproduced the whole thing in four minutes and let the fix be verified — including under the private session bus and Xvfb `dev-headless.sh` runs the app in — before it was pushed. Every previous attempt to reason about this job reasoned from the *commits* instead, because the log looked unreachable (which it was not either). - **Test the stack you ship, not one that resembles it.** `aplay` showed the same 1000× gap and would have been enough to *diagnose*. It would not have shown that oto opens the pulse-backed device at all, which is the thing that had to be true for the fix to work; a fifteen-line Go program using the app's own `speaker.Init` did. - **The comment was the bug's hiding place.** "Measured: InitSpeaker succeeds in ~36 ms and all six playback specs pass" was true when written and had been carried forward through every subsequent read of that file, including two this session. A measurement in a comment needs the same expiry as one in a plan. ## A finding creates the conditions for the next one Plan 007 phase 5, fourth pass: naming every `wa-dialog`, drawing `cover-grid`'s album dropdown, and giving the album page a primary action. The generalisation this pass adds: **a finding is a door, and what is behind it has never been looked at.** Three of the four items here had a second bug hiding *behind* the one the audit named, and none of them could have been found by reading — each was only reachable once the first fix made the code path run for the first time. - `perf.p2` files `renderSplitGrid` as "dead code carried in the bundle", housekeeping, delete it. It was a **missing feature** whose data path already worked, and behind it sat 1 463 lines that had never executed: `scroll-manager.ts` (916) and `album-dropdown.ts` (461). Drawing it revealed that **the albums grid could not scroll at all** — `.grid-scroll-container` is the markup `artists-view` uses and `cover-grid` had the class with no rule for it, so 186 984 px of albums sat in a 772 px box at 5 000 albums, unreachable by wheel, keyboard or scrollbar — which in turn revealed that the scroll manager had spent its whole life saving and restoring a `scrollTop` that was permanently 0. And *that* revealed the shared context menu labelled "Album actions" on a track row, which nothing could observe while the only menu that could open on a track was unreachable. - `H-13` asks for a Play button. The button needs file paths; the obvious key is `MBTrack.LocalID`, which is declared, is in the generated bindings, and **is never written by anything in the backend**. Ownership is decided by recording MBID. Keying on that produced a button that was wired, labelled correctly, clicked cleanly and **queued nothing** — a library-only album has no recording MBIDs, because its tracks are synthesised with `mbid: RecordingMBID || ''`. Every component test passed. It was caught by clicking the button in the running app and reading the queue. Seven more things worth keeping: - **A count of call sites in an audit is a count as of its date.** `a11y.md` lists five `wa-dialog`s; last pass estimated eight; there are eleven. Three of the six added since were added by *this plan*. The fix was written as a helper called from each host rather than a list, so the number stopped mattering — which is the right response to a number that drifts. - **Reaching into another library's shadow root is acceptable when the failure is bounded.** `name-dialog.ts` queries Web Awesome's open shadow root, which is not API. If the structure moves, the query misses, nothing is written, and the dialog is exactly as unnamed as it was — no state to get wrong, nothing to throw. The alternative, patching `WaDialog.prototype`, fixes every call site for free and fails loudly and strangely instead. The bound is the argument, not the tidiness. - **`aria-labelledby` beats `aria-label` when the label can change.** Three call sites compute their label at render time. An IDREF to the heading the component re-renders anyway stays correct with nothing resyncing it, so the helper can be a one-shot call. - **A web component's shadow root is populated in its own update, not its host's.** Naming a `wa-dialog` from the host's `firstUpdated` finds an element with an empty shadow root and names nothing. Same lifecycle trap as `wa-dropdown-item`'s role two passes ago, which suggests it is not a trap so much as a rule: **never query inside a child custom element without awaiting its `updateComplete`.** - **The a11y snapshot cannot see a dialog's accessible name.** `playwright-cli snapshot` prints a bare `- dialog [ref=…]` whether the dialog is named by `aria-labelledby`, by `aria-label`, or not at all — checked all three ways against the running app. Twenty minutes went into "the fix did not work" before the probe was suspected. `getByRole('dialog', {name})` and CDP's `Accessibility.getFullAXTree` both answer, and CDP additionally reports *where* the name came from. The e2e spec was watched failing on a probe-disabled build before it was believed, which is the only reason the twenty minutes did not become an hour. - **An assertion that cannot fail will pass a bug, and the fix is to make the probe move.** "The scroll position is preserved when the dropdown opens" passed against a `scrollTop` of 0 both times on an eight-album fixture. Shrinking the viewport until the grid genuinely scrolled turned it red — and the red was **correct**: `scrollToShowDropdown` deliberately moves the scroll to reveal the dropdown (80 → 4, with the content *taller* after, so not clamping). The premise was wrong, not the app. Two lessons in one: a vacuous assertion hides a bug *and* a false claim, and the way to tell them apart is to make the number move before deciding what it means. - **A parameter name is not a specification.** `Queue.SetQueue`'s `shuffleStart` does not start a shuffle: it picks a random first track *if shuffle mode is already on*. A Shuffle button written from the name plays track 1 and looks broken. Reading the Go was thirty seconds. And one on the audit's own accounting: **`H-13`'s "unexplained ✓ badges" was half-aged before it was read.** The indicator has carried a `title` and an `aria-label` reading "Album “X” is in your library" all along, so a hover and a screen reader were both already answered; what was missing was a key for a sighted user scanning a column of green circles. The same element turns out to be a `