# L'Armada — completed-task archive (structured)

Long-term learning + blog/video source material. Each entry = a finished board task
captured in full (description · done · learnings · deps), appended by the `/pre-compact`
ritual before the task is cleared off the active board. Richer than the terse tracker
snapshot in `board-archive.md`. Newest first.

---

## #85 — Pack-level sample grouping (the grouping above the folder)
- **Description:** The Dirt-Samples FOLDER is a loose convention, not the true grouping —
  `rample*` is one bank sliced A0..S57, `808bd/cy/hc/mc` is one drum machine per voice,
  `*_commodore` is one chip sliced by role. PLN wanted the PACK granularity above the
  folder, so we can browse/aggregate at three grains (pack / folder / sample).
- **Done:** `sample_packs.py` + `sample_packs.json` (commit 96bc7bc), captain's log 016.
  A curated REGISTRY (types: drum_machine / bank / chip / source / genre) + an auto-grouper
  (alpha-prefix-before-digit + underscore head/tail tokens, ≥2 folders) that PROPOSES
  packs the registry missed — it caught `trance_*` and `voices_*`, folded in. Reads the
  already-grounded `sample_families.json` (no audio → fast, CPU-light). 22 packs over
  83/150 grounded folders; rolls per-sample family counts up to each pack.
- **Learnings:** Each grain answers a different question — folder = "what did the pack
  author call this slice?", pack = "where did it come from?", sample = "what does it
  actually sound like?". The signal isn't agreement, it's the MISMATCH: 15 of 22 packs
  span multiple audio families BY DESIGN (rample → 8 families, jungle → 11, one Commodore
  chip → bass/lead/pad/fx/synth). A pack defined by ORIGIN is *expected* to scatter across
  the timbre wheel; that scatter is a story (for Unwrapped viz / vibe-search scoping), not
  an error. A 1-folder "pack" is just a folder within the grounded subset — require ≥2
  (may gain siblings when #84 grounds all 718). Same discipline as the folder: a hint to
  compare against, never a law.
- **Deps:** Builds on the grounded `sample_families.json` (#69 resolver); feeds the
  Unwrapped viz (#64 lineage) and vibe-search. Re-run after #84.

## #65 — Fix serve.py Range broken-pipe crash on audio seek
- **Description:** `armada/serve.py copyfile()` threw `ConnectionResetError`/`BrokenPipeError`
  (Errno 104) when a browser aborts/seeks a Range request mid-stream (e.g. `proxy_take89.mp3`
  in the triangle drawer) — the 206 responses worked but the unhandled exception spammed the
  console.
- **Done:** Wrapped both copy branches of `copyfile()` and guaranteed the file handle closes
  in a `finally`; swallow `BrokenPipeError`/`ConnectionResetError`. Verified: a mid-stream
  abort (`curl --max-time` cut) leaves NO traceback and the server keeps serving (206
  follow-up OK). Commit **d70c3ee**.
- **Learnings:** A client disconnect on `<audio>` scrubbing is *normal*, not a failure —
  swallow it, don't log it. This was the keystone QOL fix: it de-frictions every audition
  task (#35 ear-verify, #43/#44 frag-audition, #20 best-take), so cheap-but-high-leverage.
- **Deps:** Blocked nothing formally; unblocks the ear-gating workflow ergonomically.

## #64 — "Information is Beautiful" dataviz of the generated corpus (EPIC)
- **Description:** Phase-2 infodesign of the tide-table corpus (after data-scientist
  exploration) — explorable insights served to a music aficionado.
- **Done:** `corpus.html` narrative + the **Unwrapped** explorable (vibe-search via CLAP,
  dominant-colour density field, zoom/pan) + landing `index.html` + honest style cloud +
  serve.py `/vibe` warm endpoint. Shipped across the prior session's commits; vibe-search,
  field-tuning, label-completion (1490/1501 samples), and zoom all landed.
- **Learnings:** Dots are the stars — the field stays subtle; **don't average hues** (→ mud),
  use the per-cell DOMINANT family colour + purity-fade + desaturate + lift. Cache the field
  offscreen, rebuild on colour/axis/filter change, never on hover. Per-one-shot CLAP
  genre/mood is unreliable (0.3s hits) but CLAP **embeddings are gold for relative
  similarity** (vibe-search / find-similar). Seed free-text search with the user's OWN words.
  DarkReader can fight a dark theme — suspect the inverter before re-tuning to a phantom.
- **Deps:** Spawned #63 (cross-app SPA landing — the tide-table index shipped; tying in the
  React surfaces remains). Set the foundation the emotion-engine work (#89–#92) built on.

---

# The Foundry — phase-2 loops chain (overnight, 2026-06-23)

One session built the entire url→stems→**loops** chain end to end: grader, tierlist,
correlation, finder, naming, GUI, plus engine2 (merge) and audio hardening. Every claim
below is measured; honest negatives kept honest.

## #8 — engine2 Roformer VRAM spike
- **Done:** `research/engine2_spike/spike.sh`; commit 1a201df.
- **Learnings:** Roformer FITS the 6GB RTX 2060 (peak 3051 MiB, ~0.55× realtime) — the
  wall was never VRAM, it was Python: py3.14 breaks (beartype rejects audio-separator's
  `Callable|None` hints); a py3.12 venv works (`~/.virtualenvs/audio-separator`).
- **Deps:** fed #9.

## #10 — Loop grader (the katana), engine/grade.py
- **Done:** pure `grade(wav)->LoopGrade` (S/A/B/C/D + per-rule subscores + flags); commit edb6225.
- **Learnings:** (1) librosa 0.11 tempo is `librosa.feature.tempo`, NOT `.rhythm.tempo` — a
  swallowed AttributeError flat-lined bar-consistency at 0.50 for every file. (2) seam =
  CONTINUITY = the 2nd difference `|x0-2x[-1]+x[-2]|` at the wrap, not the single-sample step
  (the step metric punishes a clean wrap at a zero crossing — a perfect sine scored 0.40).
- **Deps:** reused by #5, #7, #11, #18, #19.

## #11 — Hall of Fame tierlist (data + impeccable viz)
- **Done:** `build_tierlist.py` (1690 loops/97 kits) + `tierlist.html`; commits f88273b, 4c9a831.
- **Learnings:** grade↔.tidal-usage Spearman ρ=+0.34 (rubric points right). The CONFOUND is
  the insight: FX kits (risers 16×, weird_dialogs) tier LOW correctly — sweeps aren't loops,
  so the grader tells loops from transitions; custom `f*` palette validates from the other
  side (fsynth/fguitar A). Only 34/97 kits carry a usage token (folder-name vs `s`-token).
  Showed the confound in the scatter rather than hiding it (trust the instrument).

## #12 — Correlation engine (provenance recovery), engine/correlate.py
- **Done:** NCC sample↔stem matcher + `build_provenance.py`; 482/1690 matched (29%),
  cross-stem alignment 0.34; commit 7a79dc8.
- **Learnings:** a hand-cut loop is a literal slice → NCC peaks ~1.0 (foreign ~0.03). TWO
  load-bearing bugs: (a) naive all-pairs full-res took 56 MIN → fixed with coarse-to-fine
  (rank stems on a frame-RMS ENVELOPE, precise NCC on top-3, ~40× cheaper, minutes); (b)
  SILENT-WINDOW BLOWUP — catastrophic cancellation in the sliding-variance cumsum drove the
  normaliser to ~0 in quiet regions, so silence scored ∞ and faked perfect matches (a run
  reported a bogus 55%/0.69, ~440 false positives). Floor the window norm at 5% of global
  energy + clamp NCC to [-1,1]. Also: py3.14 mp defaults to FORKSERVER → COW-global trick
  fails (empty globals per worker); pin `mp.get_context("fork")`.

## #5 + #18 — Loop finder (engine/loops.py) + v2
- **Done:** §1 pipeline (PLP→beat-sync SSM→Foote→scored windows→Takes→export); grid-from-drums;
  chop mode; commits c17dd0d, de0cb11, cdf2f13, 0a2921a, 5ac5cd0.
- **Learnings:** bare PLP latches the eighth-note pulse → ~2× tempo (Loituma read 250 not 125);
  pin tempo_min/max to one octave + min peak distance. Per-stem PLP grids are WEAK on
  sparse-onset vocals → grid-from-drums (one grid from the rhythmic stem, reused for all)
  lifted recall 0.27→0.34 (vocals 0.27→0.50). Chop mode (onset sub-bar) WORKS but recall
  0.13 < loops 0.34 — PLN picks chops by TASTE from many onsets (recall is a harsh metric;
  onsets over-segment, floored chops at 0.25s). Loops=default, chops=opt-in.

## #7 — Finder recall harness, build_finder_eval.py
- **Done:** recall vs provenance GT (distinct-window, uncapped N + precision); commit 09bace6.
- **Learnings:** honest 0.27 recall / 0.24 precision on the 8 most-cut stems — BELOW the 0.70
  target, and that's diagnostic not failure: those are chop-heavy sources (14-42 sub-bar cuts
  /stem); the bar-finder can't reproduce sub-bar chops, and the finder is a SUGGESTER anyway.

## #9 — Merge-of-stems multimodel, engine/separate.py
- **Done:** MultiModelBackend cascade (Roformer vocals → demucs on the instrumental for
  drums/bass/other → merged 4-stem) + wired RoformerBackend + demucs model selector; commits
  853eeaf, 14e69fe.
- **Learnings:** there is NO 4-stem Roformer (all are 2-stem) — the win is an ENSEMBLE.
  htdemucs_ft is a free drop-in 4-stem A/B (vocals SDR 10.8 vs 9.9). Refactored backends to
  declare `produces` + `run_composite`. Verified on Loituma: 4 clean PCM_16 stems.

## #13/#16/#17 + audio fix — supporting wins
- **#13 naming** (engine/naming.py, 146070b): NN_role[_character] derived from the corpus
  (46% indexed, 74% underscore, kit-name not repeated).
- **#16 live MIDI panel** (c0fd5d4): SSE fan-out into the Bridge, colour-by-event.
- **#17 self-updating corpus essay** (24606d4): templated Story 02 from EDA + freshness badge;
  honesty fix — 4→14 gigs is "grew 3.5×", not the hand-copied "tripled".
- **AUDIO STREAMING fix** (7c3154a): stdlib http.server defaults to HTTP/1.0 → `<audio>`
  seeking (many small Range requests) is flaky in real browsers. Set
  `protocol_version="HTTP/1.1"` on the Foundry Handler AND armada RangeHandler (safe: every
  response sets Content-Length). Also preload="metadata" so durations show (0:00/0:00 read as
  "broken"), and offer the ORIGINAL alongside stems. A fleet-wide gotcha for any audio server.

- **Deps:** the chain feeds #19 (auto-tune settings against the grader) and #20 (batch-explore
  many sources). Engine registry now seeds the product/API/service direction PLN wants.

---

# Fourier — birth of the Audio-Intelligence API (2026-06-25)

Designed live with PLN via a long AskUserQuestion co-design (5 rounds), then built lean. The
product: a self-hosted, token-authed, async API in `armada/api/` exposing the fleet's engines
(emotion, samples, features, separation, loops) to hexa (Shipow) + future seats. Full design in
memory `project_fourier_api`. Named after Joseph Fourier — the transform behind `/spectrum` and the feature stack. [Codename renamed 2026-06-29 from the original "Douanier" (Le Douanier Rousseau).]

## #22 / #36 — Scaffold + emotion walking skeleton
- **Description:** stand up the service shell + ONE real endpoint to de-risk the three seams
  (engines import · service runs · client can auth) before building auth/jobs/cache.
- **Done:** FastAPI app (`app.py`) versioned `/v1`; `/v1/healthz` + synchronous
  `POST /v1/analyze/emotion` (upload → valence/arousal via the tide-table CLAP seam
  sample_semantics.embed_audios → emotion_ontology.score); `engines/` lazy-import adapter;
  runs in `~/.virtualenvs/fourier` (--system-site-packages). Commit 7f558a7.
- **Learnings:** lean rewire — the cheap "ears" don't need the job queue/quota for one trusted
  customer, so a walking skeleton (sync + stub token) reaches value in ~1 session vs 6 tasks.
  Arch PEP-668 blocks system pip → venv that INHERITS the multi-GB ML stack, adds only FastAPI.
  CLAP cold-load is ~34 s (→ later #28 warms it once in the worker). Real pipeline proven on a
  synthetic clip end-to-end.
- **Deps:** root of the whole Fourier tree.

## #23 — Bearer-token auth + scopes + the `fourier` CLI
- **Description:** replace the dev-token stub with a real self-hosted token store.
- **Done:** `db.py` (stdlib sqlite3, WAL for API+worker concurrency); `auth.py` — mint()
  returns plaintext ONCE, stores only sha256 (DB leak unreplayable), verify() → Principal with
  scope/expiry checks, `require_scope()` dependency (401/403); `fourier.py` admin CLI
  (token mint/list/revoke). `/v1/me` echoes identity. Commit fe9ca02.
- **Learnings:** scope='*' wildcard for hexa; dev-token kept as a documented local-only
  bootstrap (prod never sets it) so curl works without minting. 15/15 tests; mint expiry landed
  exactly 31 days out.
- **Deps:** unblocks #24 quota, #33 hexa token; gates every future engine route.

## #26 — Content-addressed cache (the margin lever)
- **Description:** identical audio analyzed once, served forever — the economic core.
- **Done:** `cache.py` — content_id = sha256 of DECODED PCM (re-encodes dedupe) + raw-bytes
  fallback; params_hash folds engine settings; get/put (JSON inline or result_ref path);
  yt-id/url→content_id aliases; LRU/size-cap gc() that unlinks evicted artifacts. Wired into
  `/v1/analyze/emotion` (`X-Fourier-Cache: hit|miss`). Commit 394bec0.
- **Learnings:** **measured 5663× on a real CLAP run** (10.6 s miss → 0.002 s hit). Cache keys
  on the engine so clap/light don't collide. 22/22 tests. This is the margin story vs cloud
  egress that justified self-hosting.
- **Deps:** underpins every engine endpoint + job idempotency; unblocks #27.

## (no task) — Sampling-classics demo sources (Foundry)
- **Done:** `tools/foundry/demos.json` — 10 classics (Amen/Funky Drummer/Apache breaks, Chic
  bass, Loituma vocal, Mozart no-drums, Rickroll, GM Flash, Humpty, Think) + loader + `foundry
  demos` CLI + `/api/demos` + UI quick-picks; `/api/fetch` accepts `ytsearch1:`. Commit fd1fae8.
- **Learnings:** only verified-id URLs ship as links (Loituma from the repo fixture, Rickroll);
  the rest are `ytsearch1:` queries so we never ship a guessed/broken video id. Pedagogically
  diverse on purpose — fuel for #19 autotune + #20 batch-explore.
- **Deps:** feeds #19 / #20.

## #37 — Refit for erable: CPU image + nech.pl platform contract
- **Description:** the SRE replied (SRE.md) that erable has NO GPU / ~2 GB RAM and CLAP/torch
  won't fit; ship a CPU-deployable image. Same letter reframed api.nech.pl as a multi-API
  PLATFORM (we're the `audio` sub-API).
- **Done:** Dockerfile (python:3.12-slim + ffmpeg/libsndfile + torch-free requirements-deploy.txt)
  → **~1 GB image**, <2 GB RAM, default engine=light. Conformed the app: public path `/audio/v1`
  (gateway strips it; routes at root + `root_path`), **central auth** (trust gateway-injected
  X-Tenant/X-Scopes, loopback-only; dropped our SQLite bearer/quota = #23/#24 superseded),
  `/metrics` Prometheus, `/separate` → 503 `compute_unavailable` seam. DEPLOY.md = erable
  contract. Commit 722dade.
- **Learnings:** the SRE EDGE WENT LIVE first (503 warming_up at the public URL) — deploy is
  now a one-command unblock. The container holds ONLY armada/api/ → every engine must be
  self-contained (no tide-table/Foundry import at runtime). 32/32 tests; validated in-container.
- **Deps:** unblocks #42 deploy + #33 onboard; superseded #23/#24.

## #38 — Modular ears building blocks: /features + /analyze/samples
- **Done:** two CPU/torch-free cached endpoints. `/features` (~35-dim spectral/MFCC/chroma/key/
  envelope + rhythm); `/analyze/samples` (per-sample EDA + role percs|bass|melodic|tops|atmos by
  MEASURED spectrum, never the name). `engines/feats.py` self-contained (vendored from
  sample_features/audio_lens). Shared `_cached()` helper (DRY across the 3 analyze routes). Commit 9eb2623.
- **Learnings:** vendoring fixed the librosa-0.11 `feature.rhythm.tempo` bug the tide-table
  original silently swallowed (→ `feature.tempo`). Role-by-measurement upholds feedback_mastering_eda.
  40/40 tests; validated in the torch-free container.
- **Deps:** established the vendoring pattern reused by #39/#41.

## #39 — /grade: the Foundry loop grader as a building block
- **Done:** `/grade` exposes the Foundry mechanical quality grader (composite 0..1 + S/A/B/C/D
  tier + seam/zc/bar/level/dc/bass sub-scores + flags). `engines/grade.py` is a BYTE-FOR-BYTE
  vendored copy; tests/test_grade_endpoint.py is a DRIFT GUARD (imports the Foundry canonical
  standalone, asserts identical grade/tier/sub + WEIGHTS/THRESH). Commit cd3caa7.
- **Learnings:** vendoring + a drift-guard test = DRY-safe deployment when the container can't
  hold the source repo (parsers-over-copy applied to a vendored copy). 43/43 tests.
- **Deps:** the CPU slice of #31 (/loops + /correlate still need a corpus/finder).

## #40 — Low-hanging endpoints: /onsets, /waveform, /analyze
- **Done:** `/onsets` (hit times + tempo + rate), `/waveform` (per-bin [min,max] + 0..1 RMS
  envelope — render-ready), `/analyze` (composite emotion+features+sample in one cached call).
  `engines/signal.py` self-contained librosa. Commit 8c2be60.
- **Learnings:** /onsets+/waveform are aimed at hexa's hydra VISUALS (rhythmic sync + reactive
  envelope) — the API's value isn't just analysis, it's render-ready signal. 50/50 tests.
- **Deps:** —

## #41 — /loudness, /spectrum (FFT-as-a-service), /naming
- **Done:** `/loudness` (BS.1770 integrated LUFS via pyloudnorm + 4×-oversample true-peak +
  crest + gain-to-target -14/-9); `/spectrum` (downsampled mel/linear spectrogram bands×frames,
  0..1, frames=1=avg spectrum — PLN's "FFT-as-a-service" idea); `/naming` (vendored Foundry
  namer, drift-guarded, + feats.character_of). pyloudnorm added to requirements-deploy. Commit f11bef9.
- **Learnings:** /spectrum is the canonical cache-as-margin building block — compute the FFT
  once, serve the bounded matrix forever. **11 engines total.** 58/58 tests.
- **Deps:** —

## #32 — Make it callable: OpenAPI snapshot + zero-dep TS client
- **Done:** `clients/openapi.json` (3.1 snapshot, servers pinned to api.nech.pl/audio/v1, +
  drift-guard test vs the live app), `clients/fourier.ts` (typed, zero-dep, one method/engine,
  `_cache` surfaced, FourierError; tsc --strict clean), `clients/README.md` (Vercel example +
  scope table + codegen one-liner). Commit 11c8f9d.
- **Learnings:** a hand-written zero-dep client beats generated bloat for ~11 simple multipart
  routes; the snapshot-drift test keeps hexa's spec honest as routes evolve. 60/60 tests.
- **Deps:** unblocks #33 (onboard hexa); needs #42 deploy to be live-callable.

## #42 — Deploy fourier:latest to erable → green /audio/v1/healthz
- **Done:** First real deploy of the CPU image to erable (pln@nech.pl). Image transferred via
  `docker save | ssh erable docker load`, run loopback-only on 127.0.0.1:9780. Registered
  /openapi.json + /docs as public gateway routes (nechapi 89586eb). DEPLOY.md gotchas captured
  (Tidal fbe1742). Green end-to-end: healthz/openapi/docs 200, authed 401 without token.
- **Learnings:** TWO erable traps — (1) `--security-opt seccomp=unconfined` is MANDATORY:
  Docker 19.03/kernel 4.9 default seccomp blocks the `clone3` syscall that python:3.12-slim's
  glibc 2.36 uses for pthread_create → container boots uvicorn then SIGSEGVs (exit 139) /
  "OpenBLAS pthread_create … Operation not permitted". (2) pin OPENBLAS/OMP/NUMEXPR/MKL
  _NUM_THREADS=1. The _platform service sidesteps #1 by being Alpine/musl on purpose. Data
  volume = ~/srv/fourier/data (no sudo for /srv; pure transient cache).
- **Deps:** unblocked #33; the keystone for the whole live API.

## #43 — Hierarchical scope convention (realm:domain:path) + central enforcement + CLI/docs
- **Done:** Convention `realm:domain:path` (realm=api|admin|future mail/data); required scope
  DERIVED from the path (api:audio:analyze:emotion), subtree wildcards (*, api:*, api:audio:*),
  non-wildcard=exact, api:* never grants admin:*. Canonical matcher `_platform/scopes.py` vendored
  byte-identical into `armada/api/scopes.py` (drift-guarded). Audio app: per-route scope strings
  replaced by ONE path-derived `require` dependency + footgun fix (missing X-Scopes → "" not "*").
  CENTRAL enforcement deployed in `_auth` (derive + 403). CLI validates scopes + `check` cmd.
  nechapi 104748f, Tidal 4197696. Verified: hexa api:*→200, admin admin:*→403 on audio, no-id→401.
- **Learnings:** PLN chose a top-level REALM (vs flat domain root) to future-proof for non-API
  capabilities (mail, personal data). Path-derived scopes = maintenance-free access control
  (add a route, its scope exists). The realm split is what lets a customer hold api:* (everything
  API) while admin stays a separate sealed plane. Tenant migration caveat: the active `maps`
  token has OLD-style geo:read/route — must become api:geo:* BEFORE geo joins the gateway.
- **Deps:** built on #37 platform reframe; enables clean multi-API + selling seats.

## #33 — Onboard Shipow / hexa (the MVP delivery)
- **Done:** hexa minted as tenant 3, plan pro, scope api:* (full platform access). Verified
  end-to-end through https://api.nech.pl/audio/v1 with his real token: /me, /features (cache
  miss→hit), /analyze/emotion. Branded onboarding PDF (clients/onboarding.html template →
  chromium --print-to-pdf; rendered PDF gitignored as it carries the token). Tidal b225ba7.
- **Learnings:** platform tokens DON'T expire (the schema has no expiry — revoke-by-prefix
  instead), so the old "31-day" idea didn't apply. Token plaintext is shown ONCE at mint (only
  the sha256 is stored). Onboarding artifact is transitional — PLN's stance: Scalar /docs +
  landing will replace the PDF; "only token distribution matters." Client SDK renamed
  Fourier→NechAPI (umbrella + .audio namespace) + header X-Fourier-Cache→X-Nech-Cache so the
  internal codename never reaches a consumer.
- **Deps:** was blocked by #42 (deploy) + #43 (scopes); closes the EPIC's MVP.

## #45 — Platform observability: usage analytics, security monitoring, uptime status landing
- **Done:** (1) CAPTURE — `_auth` logs EVERY attempt to usage_log (status 200/401/403 + reason +
  client ip; tenant_id nullable; quota counts 200 only); migration +reason +ip +health_checks.
  (2) ADMIN ANALYTICS (admin:*-gated, self-authed): /admin/usage (totals, by-tenant, top routes,
  14d series) + /admin/security (rejects by reason, offender IPs, recent rejects). (3) PUBLIC
  STATUS — api.nech.pl/ now renders per-API up/down + uptime% (24h/7d/30d) from a 60s background
  probe → health_checks; ca-certificates added for the https probe. nechapi e489d26. Verified:
  landing renders, admin endpoints return real data, hexa api:*→403 on /admin (plane sealed),
  rejects logged with source IP.
- **Learnings:** before this, _auth returned early on reject and logged NOTHING — a total
  security blind spot; logging the decision (not just authorized calls) is the foundation.
  Probing the PUBLIC healthz URL (not loopback) measures the real edge a caller sees — and a
  container can't reach the host's 127.0.0.1 anyway. nginx reload briefly fails one probe → a
  small transient uptime dip that self-heals. The admin/api realm split makes /admin trivially
  safe (an api:* token is auto-403'd).
- **Deps:** built on #43 (admin realm) + #45 capture; Grafana visual layer scheduled as #46.

## #34 — Ops: systemd units, observability, SRE deploy runbook
- **Description:** the ops half of the audio-API rollout — keep-alive units, observability,
  a deploy runbook for SRE.
- **Done:** closed as SUBSUMED by the platform's paved road (which appeared in a parallel SRE
  session between sessions). Observability shipped earlier (nechapi f89d7f9 — per-call capture,
  /admin analytics, public uptime status page); the systemd-restart + deploy-runbook half is now
  the golden base image (nechapi/py) + `nechapi ship` CLI + the onboarding runbook in the SRE
  repo, not bespoke units here. Reconciliation documented in armada/api/SRE.md (Tidal d228966).
- **Learnings:** the platform repo had DIVERGED — my 3 unpushed control-plane commits
  (observability, scope convention, audio-LIVE) vs origin's 10-ahead paved-road refactor (golden
  base, ship CLI, edge-cache tiers, geo/v1 + iris/v1 onboarded). Resolved by rebasing mine onto
  origin/main: only docs + the registry + the generated vhost conflicted; the core observability
  code (_platform/app.py, scopes.py, schema.sql) was untouched upstream and replayed clean. The
  generated vhost (api.nech.pl.conf) is re-rendered, never hand-merged. PARKED RISK flagged: geo
  is live with old-style scopes (geo:read) but my central enforcement derives api:geo:* — so if
  _platform is redeployed WITH central enforcement, geo tokens 403 until re-minted; enforcement
  stays parked (audio self-enforces) and that reconcile is SRE's.
- **Deps:** part of the EPIC #21 thread; observability lineage = #45.

## #35 — Test suite + CI for the API
- **Description:** a real test suite for the audio API plus a CI pipeline.
- **Done:** the 67-test suite already existed and was green, but only under a
  --system-site-packages venv (quietly host-dependent). Made it hermetic:
  requirements-test.txt pins the true test surface (fastapi/uvicorn/multipart + numpy + soundfile
  + librosa + pyloudnorm + httpx + pytest), NOT system-site-packages; .gitea/workflows/api-ci.yml
  runs it on git.plnech.fr for any push/PR touching armada/api/**. Tidal 213eb8a. Clean-venv
  rehearsal: 67 passed.
- **Learnings:** a system python bump to 3.14 had dropped fastapi/httpx from the old venv → the
  whole suite reported "no tests collected" (red for an ENV reason, not a code reason) — exactly
  what a site-packages-inheriting CI would hide. Rehearsing in a clean throwaway venv surfaced
  TWO deps the system venv had silently supplied: librosa (lazy-imported inside engine functions,
  not at module load — so a grep for eager imports missed it) and pyloudnorm (the LUFS engine).
  The heavy ML stack (torch/laion_clap/demucs) is NOT needed by the tests, so CI installs fast.
  CI is dormant until an act_runner is registered for the repo; the workflow is correct + locally
  rehearsed.
- **Deps:** part of EPIC #21; was a blocker on #21.

## #25 — Async job model + worker daemon (SQLite)
- **Description:** the async backbone so heavy work (sources/separate/loops) runs out-of-band and the API stays responsive.
- **Done:** committed 17d3f46. Four design decisions taken with PLN (AskUserQuestion w/ sketches): HYBRID sync/async (cheap analyses stay sync, heavy = jobs), PER-ENGINE submit (202 {job_id}) + SHARED poll (GET /jobs/{id}) + cancel (DELETE), SINGLE serialized worker, X-Accel-Redirect for artifacts. Built: jobs table (db.py), jobs.py (enqueue + born-done idempotent fast path, atomic claim, progress/finish/fail-requeue-under-cap, crash recovery, cooperative cancel), worker.py (serialized recover→claim→dispatch→webhook loop, SIGTERM-graceful, @jobs.handler registry), typed JobStatus endpoints, deploy/fourier-worker.service (systemd --user). 11 new tests (67→78), incl. a real 6-thread×25-job no-double-claim concurrency test. OpenAPI refreshed (15 ops) + @nech/api regenerated (getJob/cancelJob).
- **Learnings:** SQLite WAL serializes writers, so the claim race reduces to candidate-select → `UPDATE ... WHERE id=? AND status='pending'` + rowcount-0 retry — no locks needed, provably exactly-once across threads. typescript-fetch's generated instanceOf guard indexes a camel/snake key union that trips TS7053 under noImplicitAny → relaxed noImplicitAny for the 100%-generated package (emitted .d.ts stays fully typed). MID-BUILD: the btrfs disk hit ENOSPC at 98% (20G "free" but unallocated, metadata-full) — writes failed intermittently; cleared ~5.7G of regenerable caches (npm + ~/.cache browser/HF, user-approved) to continue. Disk still 97% — flagged for real cleanup.
- **Deps:** was blocked by scaffold + central auth (done); unblocks #29 → #30 → #31. Worker prod container-vs-host wiring is a paved-road residual (SRE/#34).

## #27 — Artifact store (local disk on erable; freebox deferred)
- **Description:** somewhere to keep the big rebuildable binaries (fetched sources, later stems/loops) that don't belong inline in SQLite, served efficiently to hexa.
- **Done:** committed c7e5392. `artifacts.py`: content-addressed layout `ARTIFACTS_ROOT/<cid>/<name>`, tracked as ordinary `cache` rows (kind→result_ref→path, bytes) so the **existing LRU `cache.gc()` evicts them for free** under `FOURIER_ARTIFACTS_MAX_MB` (1 GB). `resolve()` refuses path traversal / escapes outside the root. Serving = zero-copy nginx `X-Accel-Redirect` (`FOURIER_X_ACCEL`), `FileResponse` fallback in dev. `GET /artifacts/{cid}/{name}` endpoint (auth-gated, any tenant holding the opaque ref). DEPLOY.md §5b documents the internal nginx location. The cache schema's `result_ref` column + `gc()` unlink were pre-built in #25/#26 *for* this — #27 was mostly wiring.
- **Learnings:** PLN dropped freebox-as-SSOT ("forget freebox storage for now") → the store collapsed from "signed Range URLs over a remote mount" to "local dir + nginx internal location", much simpler. Reusing the cache table for artifacts means one eviction policy, one stats surface, one GC — no separate artifact lifecycle. The `_meter` middleware had to switch from `request.url.path` to the **route template** (`request.scope["route"].path_format`) or `/artifacts/{cid}` + `/jobs/{id}` would each mint an unbounded Prometheus series.
- **Deps:** was blocked-by-nothing once #25 landed; unblocks #30 (stems need somewhere to live). Go-live (nginx location + FOURIER_X_ACCEL) tracked in #47.

## #29 — /sources endpoint (yt-dlp fetch as a job)
- **Description:** turn a URL into analysis-ready audio — the front door of the heavy chain (sources→separate→loops).
- **Done:** committed c7e5392. `engines/sources.py` registers the `sources` job handler: yt-dlp → `bestaudio` → 44.1k WAV (PLN's choice: analysis-ready PCM over keep-source-codec), content-address, store as a `source` artifact, `put_alias(url→cid)`. `POST /sources` returns `202 {job_id}`; a re-fetched URL (alias hit + artifact still on disk) is a **born-`done` job** — no re-download. `normalize_url()` validates: http(s) only, lowercases host, drops fragment (so trivially-different URLs dedupe), and hard-blocks SSRF footguns (localhost, RFC1918/loopback/link-local/reserved IP literals, incl. the 169.254.169.254 cloud-metadata classic). The fetch is a thin seam (`_fetch_audio_wav`) so tests mock the network with a synthetic WAV — 17 new tests (78→95), zero network. healthz reports yt-dlp presence honestly.
- **Learnings:** PLN chose OPEN url scope (any http(s)) over an allowlist, explicitly leaning on "our apikey + nechapi monitoring" as the protection layer — so the code accepts any public URL but still refuses the SSRF set in-process (defense the gateway can't do). yt-dlp+ffmpeg are **worker-only** deps (the API container stays torch/yt-dlp-free) → added to requirements-deploy, not requirements-test. The idempotent born-done path falls out of the #25 `enqueue(..., result=...)` fast path + #26 aliases — the URL→cid alias table was designed in #26 *for* exactly this.
- **Deps:** blocked-by #25 (done); unblocks #30 (separate consumes the fetched WAV). Go-live (yt-dlp install on erable) tracked in #47.

## #48 — Gate /docs + /openapi.json behind a cross-cutting api:docs scope
- **Description:** PLN noticed `api.nech.pl/docs` "down" + asked if docs should be token-protected. Investigation found two things: (1) root `/docs` is 404 (the platform Scalar portal was never built; the 404 catch-all's "See /docs" hint dangles), and (2) the real issue — audio's `public_routes` exposed `/audio/v1/{docs,openapi.json}` ANONYMOUSLY: the full API surface advertised to the internet.
- **Done:** deployed live 2026-06-29. `required_for()` special-cases `docs|openapi.json|redoc` → `{realm}:docs` (canonical `nechapi/_platform/scopes.py` commit on branch `claude/docs-scope`, rebased onto upstream + merged to main `0ab148b`; vendored byte-identical into `armada/api/scopes.py`, commit `d4d27a4`). Dropped docs/openapi from `audio.public_routes` (kept `/healthz`), re-rendered the vhost. Rebuilt + shipped `nechapi-platform:latest` (Alpine, Postgres-backed so no token loss), recreated the container on `nechapi-net`, installed the re-rendered vhost (diffed-first: only my 2 blocks removed), `nginx -t && reload`. VERIFIED LIVE: anon /docs+/openapi.json → 401 (was 200), /healthz → 200; a minted `api:docs` token → /docs 200 but POST /analyze/emotion → 403 (decoupling proven); test token revoked. `api:*` (hexa/pln) keeps docs access via subtree.
- **Learnings:** the cross-cutting scope (`api:docs`, not per-API `api:audio:docs`) decouples "read the specs" from "call the API" — a docs-reader token can't invoke anything, and `api:*` still covers both via the subtree wildcard. The drift guard reads the MAIN `~/Work/nechapi` checkout, so the canonical + vendored copies must merge in LOCKSTEP — committing the vendored copy ahead of the canonical merge turns the local suite red (CI skips it when the canonical is absent). Resolved by reverting the premature vendor, staging on a branch, and re-vendoring only after the nechapi merge. Also re-learned the shared-repo race: origin/main had advanced (a parallel SRE `bin/nechapi` drift-guard commit) — rebased onto it (no overlap), and ALWAYS diff the rendered vhost vs the LIVE one before `sudo tee` so a parallel session's work isn't clobbered.
- **Deps:** spun out of the #29/#27 deploy session; touched the security control plane (gated). Follow-up: build the platform `/docs` Scalar portal (basic-auth RTFM/PLN per registry) + fix the 404 "See /docs" dangling hint.

## #44 — Official generated clients + private npm (Verdaccio)
- **Description:** ship a real, never-drifts client for hexa + future seats, distributed from a private registry — replacing the interim hand-written `nech.ts` drop-in.
- **Done:** deployed live 2026-06-29. (a) Generated `@nech/api` TS client from the OpenAPI snapshot (openapi-generator typescript-fetch → tsup ESM bundle; clean operationIds → `audio.analyzeEmotion()`; subpath exports). (b) Stood up **Verdaccio 6** on erable (loopback `:4873`, `~/srv/verdaccio/{storage,conf}`, `unless-stopped`) behind an LE-TLS nginx vhost **`npm.nech.pl`**; seeded publisher `pln` via the user API, locked signups (`max_users:-1`), creds 0600 at `~/.config/nechapi/verdaccio.pln.{pw,token}`. (c) Published `@nech/api@0.1.0` and install-verified as a consumer (AudioApi/Configuration import clean). (d) Retired `nech.ts` (`git rm`), updated README + onboarding.html to the `@nech/api` install path. Commits: client `ed77ee9`/regens, retire `851767f`; VERDACCIO.md marked DEPLOYED.
- **Learnings:** three Verdaccio gotchas the bare runbook missed — `listen: 0.0.0.0:4873` (else binds localhost INSIDE the container, dead `-p` map), `chown -R 10001:65533` the bind-mount (verdaccio uid), and `ssl_protocols TLSv1.2;` ONLY (erable's old OpenSSL rejects TLSv1.3 and fails `nginx -t`). Non-interactive publish: create the user via `PUT /-/user/org.couchdb.user:<name>` to get a token, then `npm publish --userconfig <temp .npmrc with _authToken>` — no interactive `npm adduser`/`login` needed. KEY DECISION: `@nech/*` reads are `$authenticated` (not public) — consistent with the bearer-gated `/openapi.json` (#48); so consumers need an npm READ token, a deliberate consistency call over install-convenience.
- **Deps:** unblocked by the OpenAPI snapshot (#32); part of EPIC #21. Follow-ups (in `armada/api/TODO.md`): a `nech_api` Python client; mint hexa a read token.

## #63 — The silent-orbit epidemic: `doNotReadYet` loads WAV headers only
- **Description:** for two evenings, orbits in `the_revolution_will_be_sampled` (d4/d5/d9-d12, varying per boot) made no sound. Events were visible in the Pulsar highlighter, no error appeared anywhere, and every static check — patterns, g* helpers, sample banks, libsndfile readability, orbit count, PipeWire links, Ardour routing, saved faders — pronounced the rig healthy while it was demonstrably not.
- **Done:** root cause identified 2026-07-28. SuperDirt `DirtSoundLibrary.sc:221` reads `Buffer.readWithInfo(server, path, onlyHeader: doNotReadYet)`. With `~dirt.doNotReadYet = true` (start_and_midi.scd:202) it reads **only the WAV header**: the buffer is allocated with a correct frame count and duration but contains NO AUDIO DATA. That is verbatim the `Buffer UGen: no buffer data` message. The deferred real read is what decides whether an orbit sounds, so which orbits die changes per boot, and a re-eval sometimes revives one by retriggering the read. Fix (eager-load the set's banks) spun out to #26 and deliberately NOT shipped at J-7 without index-integrity validation. Tooling shipped alongside: `872676a` (probe-chain contamination guard), `a43f428`+`d3de9bd` (remote control channel + CLI), `66af326` (eager package activation, which also closed #59).
- **Learnings:** THE METHODOLOGICAL ONE, worth more than the bug: every measurement used a 4-8 second window, and at that timescale a TIME-VARYING failure looks STATIC. "These two sample banks are dead" was overwhelmingly convincing and completely wrong; six hypotheses were built and demolished on top of it (banks, symlinks, 24-bit depth, filename characters, buffer exhaustion, xfade). The decisive observation took one command: play `arpy`, measure at t+3s (-37.0 dBFS rms, healthy) and again at t+26s (-inf, gone), no re-eval between. Patterns play, then die. Sampling ONE subject at TWO times would have found this in five minutes. Second lesson, more uncomfortable: probe-chain FABRICATED signal — contaminated capture taps reported five orbits at an identical +0.0 dBFS peak (twelve independent orbits don't do that; it was the mix measured five times), and that false table said d4/d5 had recovered while PLN's ears and Ardour's meters said otherwise. A measurement tool that invents signal outranks the human in an argument it should always lose; it now refuses to report unverified rows. Also: `find` does NOT follow symlinked directories without `-L`, which produced a confident "these files don't exist" about 69 files that do; and a bank name doesn't reveal its loader (`Dirt-Samples/kick` doesn't exist as a folder, yet `s "kick"` plays, because banks also come from `Samples/extra/*` and tidal-drum-machines).
- **Deps:** absorbed the `no buffer data` half of #45 (whose remaining 69 `zz._` AppleDouble warnings are harmless junk); handed the fix to #26, now the gig blocker; unblocked #59 as a side effect.

## #59 — "Sound broke after a Window Reload, fixed by a Tidal reboot"
- **Description:** a Pulsar `Window: Reload` reliably killed audio, and rebooting Tidal reliably restored it. Filed as a mysterious interaction between the reload and the audio stack.
- **Done:** fixed 2026-07-28 (`66af326`, pulsar-tidalcycles). Nothing was breaking. `activationHooks: ["source.tidalcycles:root-scope"]` plus `activationCommands` made Pulsar DEFER loading the package, so a reload landed in a window where the Tidal package was simply DORMANT — no ghci, none of its three UDP ports bound, and nothing saying so. `tidalcycles:reboot` happened to be the first *activationCommand* in the list, so "rebooting Tidal" worked by WAKING the package, not by fixing anything. Removed both keys; the package is now eager.
- **Learnings:** the remedy worked for a reason unrelated to the story we told about it, which is exactly why the cause stayed hidden for so long — a reliable workaround stops anyone asking why. Proof was structural rather than inferred: the renderer's `~/.pulsar/blob-store` contained no compiled tidalcycles code at all, so `lib/tidalcycles` had never been required (a good general check for "did this package actually load?"). Design consequence worth keeping: lazy activation and remote control are mutually exclusive on principle — a channel whose purpose is removing the manual keypress cannot itself require a keypress to come into existence. And shipping package JS always costs exactly one reload, because new code cannot be injected into a running Electron renderer.
- **Deps:** found while debugging why the new remote channel (#44/a43f428) wasn't listening; unblocks unattended launch work (#44).

---

## #26 — GIG-CRITICAL: silent orbits (root cause was OUR preload, not SuperDirt)

**Description.** For two evenings, orbits went silent mid-set. *Which* ones changed every
boot. The boot log looked perfect — every bank registered with the right file count — and
19,741 `Buffer UGen: no buffer data` messages piled up in one 6h session where no
performer would ever see them. Six orbits of `the_revolution_will_be_sampled` were dead on
stage. J-7 to OPAL 2026.

**Done.** `b4f6275` (branch `claude/preload-eager-banks`), in `tools/setlist_samples.py`'s
emitter, plus `setlist_opal2026.txt` and `gig-up.sh`. Also `0ae4116` (probe timeline +
check-mix session resolution) and, in the fork, `374d8a3` (stop swallowing GHC errors).

**Learnings.**

*It was a two-part interaction, and part two was ours.* Upstream, `doNotReadYet = true`
registers banks from WAV **headers only**; the audio read is fired *asynchronously* by
`readFileIfNecessary` (`DirtSoundLibrary.sc:268-274`), which returns immediately — so the
synth for the very event that triggered it gets a bufnum with no samples. That alone is a
first-hit glitch. What made it fatal: our generated `preload.scd` set
`doNotReadYet = false` and **never set it back**, and that flag gates the *only* caller of
`readFileIfNecessary` (`:259-261`). Flag false ⇒ a header-only buffer is never read. Not
late — **never**. So any bank the whitelist missed was permanently silent.

*And the whitelist missed banks by design.* `gig-up.sh` built it from the N
most-recently-**edited** tracks. `the_revolution_will_be_sampled` hadn't been touched
recently, so `like_sugar` and `the_revolution` were never warmed — exactly the banks
feeding the six dead orbits. Whitelist-by-mtime is also why *which* orbits died changed
every boot. The thing that made this feel haunted was file timestamps.

*The load-bearing line is one line.* Restoring `doNotReadYet = true` after warming demotes
the whitelist from load-bearing to a mere optimisation: a miss becomes a slow first hit
instead of a dead orbit. That is the only thing it is safe to be on stage.

*A reload REPLACES a bank, it does not append.* `addBuffer` defaults
`appendToExisting = false` and frees the old bank on the first file (`:42-46`), so a plain
re-load is index-stable — `like_sugar:21` keeps its meaning. An earlier session's worry
about *doubled* indices was wrong, and that wrong belief had made the fix look far more
delicate than it was. Measured: **0 of 1428** bank names even collide across the three
loaders.

*The count assertion caught a bug in itself on its first run,* which is the best possible
outcome for a guard: `jbk_kick: expected 508, got 254`. Exactly 2×, and the *tool* was
wrong. That folder symlinks into the rhadamanthe pack, which carries an AppleDouble
`._X.wav` beside every real `X.wav`; `glob('*.wav')` matches both, SuperDirt's
`pathMatch("*")` skips dotfiles, and `ls` hides them so the folder looks clean.

*Red herring worth remembering:* SuperDirt's "Required 0 MB of memory" is not evidence the
eager read failed — `memoryFootprint` counts frames from the header, so header-only
buffers already report full size. Only audio measurement can prove a preload worked.

**Validation (instrumental, no ears — PLN was at work).** Before: d4/d5/d9/d10/d11/d12 all
`-inf` at source. After: all 11 declared orbits carry signal *and still do* on a second
probe ~95 s later with no re-eval (stable to ~0.2 dB) — the two-timepoint check being
mandatory for this bug class. `no buffer data` 19,741-in-6h → **1** (a boot artifact at the
instant the preload completed). Preload asserts **47/47** banks, 2352 files, 2.2 s, 1.2 GB.
Also green: `perfect` 12/12, `gimme_acid` 10/10, `mafia_sans_serif` 7/7, `wap` 5/5. Bare
`s "like_sugar*4"` audible. Confirmed by PLN's ears later that day: *"i hear indeed all
sounds in the track, so it sounds good to me!"*

*Two harness failures during validation, both worth more than the fix.* A batch loop
returned four EMPTY results that read exactly like "nothing is playing" — cause: **zsh does
not word-split unquoted variables**, so `-d $ORB` passed one bogus argument and the tool
exited 2 with a usage error my grep hid. And the readiness gate passes ~4 s too early,
because `listening to Tidal` is printed by `~dirt.start` well before the warm-up. *When a
batch of measurements all come back empty, suspect the harness before the rig.*

**Deps.** Closed #26 and #63. Unmasked #61 (which then measured *clean* for the OPAL set —
all 41 seeded CCs cover it). Spawned #65 (an undefined `crackles` silencing nine orbits,
which is a compile error, not audio), #66, #67. Feeds #44 (readiness gate) and #24.

---

## #66 — Prove all 10 OPAL tracks playable + every control audibly effective

**Description.** PLN left the laptop running at J-7 and authorised autonomous work:
*"ensure all tracks from gig are playable. you can send fake midi events for each, thus
test all controls have impact on sound ;) even the crushes should change noticeably what
you see/'hear'"*. No ears in the room — every claim instrumental, every failure reported.

**Done.** `check-tracks.sh` end-to-end: **10/10 tracks, 91 orbits, zero silent, zero eaten
by an Ardour fader.** Two were broken at the start of the day — `desire.tidal` at **0/9**
(`off 0.125 (|+ note 12 . (|* gain 0.6))`: `.` binds tighter than the section, so it
composed a function into a ValueMap; one pair of parens → 9/9, `cfa56b6`) and
`vague_de_crime` (PLN's own `crackles` fix, saved). Every control measured effective with
the lens that suits it: `gF1` centroid 112→3681 Hz, `gF3` 384→2765 Hz (+529%), `gMute2`
−23 dB→silence, `crushbus` 125→189 Hz (+37%), `ply ^89` 8.1→4.7 onsets/s, `gMask` −33%
onsets, `gMute1`+`gM1` silencing four orbits at once. `ply ^91` on d7 reported
**INCONCLUSIVE** and left that way. Shipped `tools/control-lens.py`,
`tools/check-tracks.sh`, `tools/tempo-lens.py`; commits `cfa56b6` `708c2ae` `7b2e5b4`
`16429b0` `36466a4` `4836d74` `104fb03` `156444d`.

**Learnings — the instruments were wrong more often than the rig, six times, and the
arithmetic was never the bug.**
1. *rms is blind to a filter or a crusher* — they move timbre at constant loudness.
   `gMask` read "NO CHANGE, 0.5 dB": right sum, wrong question; on the density lens, −42%.
2. *`ply` reported "+inf %, EFFECTIVE" off a division by zero* — the envelope onset
   detector read 0.0/s on a sustained bass. The tool invented an effect, the one thing it
   promises never to do. Fixed with spectral flux + an INCONCLUSIVE floor.
3. *A decay crosses its own midpoint exactly once.* A healthy `mask "<t f!7>"` riser was
   called "DECAYING, almost certainly an xfade tail" twice. Two quartile averages cannot
   answer a monotonicity question; counting crossings can.
4. *One low FINAL bin is the window closing, not a fade* — `perfect`'s d4, steady for
   twelve bins, condemned on the thirteenth.
5. *A uniform +1.8% tempo bias* came from a threshold rule sliding down the left flank of
   the RIGHT peak — comparing points on one hill as if they were different hills. (I first
   blamed `np.correlate`'s unnormalised overlap and fixed that too; the bias didn't budge.
   **Fixing a real-but-irrelevant flaw is not evidence you found the cause.**)
6. *The observer was the effect.* Ardour's xrun counter climbed +816 in 25 s under the ply
   stress test — which reads exactly like "heavy patterns cause dropouts on gig week" and
   matched PLN's own crackle report. Remove the ~18 PipeWire capture nodes probe-chain
   creates, repeat the identical musical load: **zero xruns**, scsynth ERR = 1 all session.

*And the discipline that makes the rest survivable:* **A-B-A**. These patterns vary per
cycle by themselves (`d2` of `vague_de_crime` plays a different bar every cycle), so
re-measure the baseline at the END and treat any swing under 2× the self-drift as
inconclusive. Plus: take the baseline **twice** — a single closing repeat agreed with the
opening one by luck and reported drift 0.0% when the true within-condition spread was 33%.

*Also:* `you_my_sunshine`'s alarming "144 vs 166" tempo mismatch was **a commented-out
`setcps` line** — a parser miss masquerading as a data conflict, again. And the RUNBOOK's
pre-set checklist had been telling PLN to put the DJ filters DOWN for bypass; **centre is
bypass**, down is a hard low-pass.

**Deps.** Closed #65. Fed #62 (the live mixer is clean; the SAVED file still isn't),
#56 (event density exonerated as a crackle cause), #12 (one of three tempo questions
dissolved), #33. Spawned #68 (orphan orbits). Ran alongside #67 (LED painter) in a
parallel agent.
