memlnaut-nisps/ALIGNMENT.md

# ALIGNMENT

> Opinionated diagnosis of how well the codebase serves its mission, ranked by impact. Dated entries; remove when resolved rather than checking off. **Pruned every few weeks** — a stale diagnosis is worse than none.

## Mission

A research platform for interactive ML control of audio. We're building it to figure out what works and what doesn't — different ergonomics and ergodynamics of parameter sets, modes, ML architectures, audio engines, UI, and UX. Therefore: keep most/all parameters tweakable, ML/engine/UI/UX should each be configurable on their own axis, and the codebase has to enable/assist agentic AI coding patterns (confident changes, verifiable without hardware).

**Target vision (operator, 2026-07-20):** (1) one C++20 NISPS core serving RP2350 firmware and the browser, performance-sensitive on the MCU; (2) firmware modes runnable as modes in Manifold; (3) Manifold defaults to curated presets/modes, with the maximalist surface behind an "advanced" dev mode used to author them; (4) PlatformIO for hardware, no more .ino; (5) Manifold doubles as interface/editor for the hardware MEMLNaut (settings, presets, training, examples, visualisation).

The clean-slate rewrite (2026-04-29) consolidated everything into one C++20 codebase compiling to firmware AND WASM. Since 2026-07-13 (P1) the sole browser app is the React Manifold. JSON schemas remain the firmware↔browser parameter contract. A full-repo audit (2026-07-21, `docs/specs/recon/simplification-audit-2026-07.md`) grounds the entries below; mitigations are phased in `docs/specs/plans/simplification-plan.md`.

## Top defects (ranked by mission impact)

### 1. The mode layer is not shared: WASM re-orchestrates modes by hand (2026-07-21)

**What.** `nisps/modes/` — the CRTP layer binding ML config, engine, voice-space and I/O — compiles only into firmware. `nisps/wasm/bindings.cpp` includes engines and ML primitives but zero mode headers, and Manifold re-assembles mode behaviour (jolt stepping, OU, routing) in TS. "Firmware and WASM share the same modes" is true only at the engine level; every ModeBase behaviour must be mirrored browser-side by hand.

**Why it blocks the mission.** Vision bullet 2 is precisely this. Until the control-tick orchestration exists once in C++, every new mode behaviour is a dual implementation with drift risk.

**Rough cost.** Spec first, then ~a week: storage-policy the ModeBase orchestration the way P2 did MLPCore (verified shape in plan §6.5a — *not* binding monolithic mode objects, which would contradict the locked two-instance RT architecture). Related honesty gap: Manifold currently catalogues 4 modes that structurally cannot run in the browser (no mic input, event-only engines) — plan §6.5b (absorbs the old C15/mic-input defect; C15 itself lives on `archive/playground-solidjs`).

### 2. No curated/advanced split and no in-UI mode picker — the UI fights vision 3 (2026-07-21)

**What.** Manifold is 100% dev-maximalist: five drawers of everything, no preset data model to author against, and mode switching exists only via the debug hook — there is no instrument picker in the UI at all (the plumbing, `ctx.modes`/`setModeId`, already exists unused). A stratum of decorative controls (training-param sliders, master volume, bpm, A/B, snapshots, fabricated gradient health) renders real-looking UI that drives nothing.

**Why it blocks the mission.** The default experience is supposed to be curated presets; the advanced surface is the authoring tool. Neither exists, and the decorative stratum actively misleads research use.

**Rough cost.** Product-model decision first (plan §7.6), then incremental: picker is days; the curated-preset model seeds from `backends/presets.ts` + schemas; disclosure via per-drawer depth levels — which as of §6.5e (2026-07-21) has its first genuinely advanced-only consumer, the training-health panel, so the mechanism is proven rather than theoretical. The decorative stratum itself went in the Phase-1 sweep.

### 3. Manifold-as-hardware-editor is a facade (2026-07-21)

**What.** Vision bullet 5 exists as a 237-line Web Serial shell: sound connect lifecycle, zero protocol (`saveModel`/`restoreModel`/`getSettings` are literal stubs), and firmware has no serial command surface or on-device persistence to talk to.

**Why it blocks the mission.** The hardware research loop (train on device, inspect/curate in browser) is closed only by this bridge.

**Rough cost.** Week+, spec-first (plan §6.5d). The right discipline already exists in-repo: useq-celium's C-header wire truth + TS mirror + parity test; settings payloads should derive from schema codegen.

### 4. Dead mass and registry sprawl across every layer (2026-07-21)

**What.** *Phase 1 landed 2026-07-21 and removed the bulk of this:* the dead focus/altitude UI system, the decorative control stratum, 12 dead WASM API entries across the 5-file registration chain, the vendored daisysp tree, retired-playground artifacts and root planning relics, 5 unused primitives, the duplicate backend editor and catalogue, `voice_space.hpp`, `fixed_buffer.hpp`, the dead perf-macro regime, and the OSC bridge twin. What remains is the *registry* half: mode identity spread across ~6 hand-maintained registries with demonstrated drift, MLP dims typed twice, per-mode schema blocks hand-written in C++, and assorted stale specs presenting a deleted world as present tense.

**Why it blocks the mission.** The registries are dual-truth bugs waiting to fire (one already did: the selftest table). Stale specs are agent-confusing surface area.

**Rough cost.** Plan phase 3 (~2–3 days, codegen takes ownership) plus the docs disposition pass (§8). The behaviour bugs found en route (dataset-cap divergence, VCV 2-D input truncation, VCV audio-thread race and JSON) were fixed in phase 2 on 2026-07-21.

### 5. Performance is measured on the host but not on the target that constrains it (2026-07-21)

**What.** *Mostly closed 2026-07-21.* Size: the Phase 4 firmware CI job reports per-variant
flash/RAM on every push. Time: `scripts/bench-engines.sh` now reports per-engine ns/sample,
blocks/s and realtime factor on native AND WASM from one source
(`tests/cpp/engine_bench.cpp`), engines driven into a working state, with `--compare` for
per-engine deltas and a report step in CI. An engine getting 3x slower is now visible.

**What is left.** The numbers are HOST numbers. The mission's performance constraint is the
**RP2350 at 150 MHz**, and nothing measures there — a host realtime factor of 100x says
nothing about whether an engine fits in the MCU's per-block budget, and the two targets have
different FPU, cache and memory behaviour. The honest next step is an on-device timing report
(cycle counter around the audio callback, published over the existing display/serial surface),
which lands naturally with the hardware editor (defect 3) since that is what gives firmware a
command surface to report through.

**Rough cost.** Host half is done. On-device: ~a day, and it wants defect 3's serial protocol
to have somewhere to send the number.

### 6d. One like still heaves the whole mapping (2026-07-25)

**What.** A thumbs-up trains at `lr 1.0 x 1000 iterations` on every gesture. `ml_bench`
U1/U4 measure **lurch** — how far the mapping the musician is playing moves per single
gesture, averaged over the field: `lurch_max` 1.08 against a [0,1] output range, i.e.
one thumbs-up can move the mapping somewhere in the space by more than the entire output
range. Retention (how much of the previous teaching survives) is 0.38; at `iters=1` it
is 0.80.

**Why it blocks the mission.** RMSProp did NOT fix the positive lurch — normalising the
step size does not change its dose. The negative path now exposes upstream-style repeated
small steps (rate/lifetime/LR are live controls), so its old fixed ~70x comparison is no
longer current. Positive teaching remains one enormous blocking train, and the two doses
still need a matched head-to-head rather than independent tuning.

**Rough cost.** Cheap to change, expensive to choose: the tuning space is now measurable
(`ml_bench` U4 sweeps dose; U1 sweeps upstream's soft-target alpha, where alpha=1 is
NISPS today). It wants a matched-N head-to-head, not a guess.

## Open mission questions

### Q1: Per-mode MLP architectures or one shared shape? (2026-04-29)

Schemas declare per-mode dims and since P5.3 both targets honour them. Is the mission served by maintaining per-mode shapes (research diversity) or collapsing to one (simpler ops)? Note the audit found all 9 mode schemas share copy-pasted ML defaults and 20 params are anonymous placeholders — the per-mode diversity is currently nominal (plan L40).

### Q2: Engine event taxonomy (2026-04-29)

`ControlEvent` is a flat enum consumed by the two sequencer modes. Revisit when a third event-emitting mode lands.

### Q3: Should Manifold stay desktop-first? (2026-04-29)

Legacy a-immersive was mobile-first; Manifold is desktop-first. Defer until user data exists.

## Deferred / accepted debt

- **EOC effects chain, ShapeSeq sequencer, modular engine (Phase E)** — legacy features consciously out of the v1 rewrite; revisit only if a mode wants them.
- **Inputs multi-source composition** (2026-06-28, reaffirmed 2026-07-21) — mix-and-match pad+gamepad+MIDI is a recorded, unreversed decision; the UI currently enforces exclusive single-source and the composition machinery sits dormant *by design*. Schedule or keep dormant — but the inputs-spec must stop presenting composition as current behaviour (plan §8).
- **Schema content is partially placeholder** (2026-07-21) — 20 anonymous "Param NN" slots across paf_synth/channel_strip/xiasri and copy-pasted ML defaults across all 9 modes. Name them during the first curated-preset pass per mode (plan §6.5c), or shrink `output_size` where the engine allows.
- **Geometric-dislike deliberate divergences** (2026-07-25): (1) the degenerate-branch RNG draws from deterministic `nisps::Rng`, not libc `rand()`; (2) each live rejection computes its liked centroid at its own stored input, rather than upstream reinterpreting every old rejection around the cursor's current position; (3) live negatives are applied as deterministic per-item RMSProp steps rather than one shuffled `TrainBatch`; (4) a repeated nearby rejection refreshes its lifetime (upstream's current dedup path leaves the original timestamp untouched); (5) upstream's default removal of a nearby positive is not yet adopted because Manifold also has a separate positive MLP dataset that would keep pulling; (6) `RandomiseMlp` uses `draw_weights(spread)` rather than old asymmetric ranges. Native↔WASM parity covers the elapsed-time replay path.
- **Manifold dock splits `state`/`muted`/`armed`** (2026-06-28) — deliberate divergence from the deployed conflated `frozen`↔`muted` model (dock-spec §3.3). `muted`-downstream and the `soloMode` gradient-mask variants remain UI-only; the C API exposes `set_focus` but no per-mode gradient masking yet. (The audit found `soloMode` behaviourally inert in the controller — plan L20 trims it until `train_masked` exists.)

## Recently resolved (delete after a few weeks)

- 2026-07-25: **The geometric dislike is re-based on upstream `e291192` (defect 6b).**
  `kGeometricPushScale` 0.5 -> 1.0, `kNegLRBase` 0.5 -> 1.5, and the `/(1+len)` taper
  deleted — upstream's own comment is that a "no" should clearly move the mapping away
  even from a sound already far from the liked region, which is exactly the case the
  taper killed. Cold start folded into the same path (random direction when nothing is
  liked yet) instead of the superseded negative-LR branch, so a "no" now moves the
  mapping before any likes exist (`ml_bench` E1: 0 -> 2.3e-3). One dislike moves the
  mapping **5.3e-2**, up from 1.6e-2 after the RMSProp fix and 5.3e-5 before it — a
  ~1000x change end to end, and now within ~4x of the legacy Diffuse design instead of
  ~4100x (`ml_bench` A4). The follow-up now adopts upstream's repeated-all-negatives
  schedule and full-strength wall-clock lifetime through a deterministic elapsed-time
  core seam. Manifold defaults to 0.001 LR, 200 Hz and 2500 ms, exposes all three in the
  expanded Learning panel, and allows rate/lifetime zero as an explicit one-shot A/B.
- 2026-07-25: **`InterfaceRL` is back in the tree (defect 6c).** Vendored verbatim from
  memllib `e291192` at `firmware/MEMLNaut-NISPS/lib/memllib/reference/` — outside `src/`,
  so PlatformIO never compiles it. Upstream drift in the feedback subsystem is a `diff`
  again rather than an archaeology session.
- 2026-07-25: **The optimiser mismatch (defect 6) is fixed.** `nisps/ml/training.hpp` was
  SGD-only while upstream `memlp` (`ea777502`) applies **RMSProp everywhere**, so every
  learning rate we ported landed in an optimiser that reads it differently — an RMSProp
  `lr` is a normalised step, an SGD `lr` multiplies the raw gradient. `rmsprop_step()`
  now ports `Layer.h:239 ApplyAccumulatedGradients` exactly (decay 0.9, eps 1e-6,
  sq-avg clamp 1e6, one-sided adjusted-LR clamp 1.0), with the per-weight running
  squared-gradient average living in the storage policies so the zero-heap contract
  holds. Measured on `ml_bench` D1: one geometric dislike moves the mapping **1.6e-2,
  up from 5.3e-5**, and repeated presses now converge on the intended 0.5 push (0.12 at
  10 presses, 0.56 at 100) instead of creeping linearly. Golden vector stages 2 and 3
  were re-captured; stages 0 and 1 are pre-training and did not move. What this does NOT
  fix: the dose asymmetry, now tracked as defect 6d.

- 2026-07-21: **Q4 (who owns memllib) closed.** Vendored at `firmware/MEMLNaut-NISPS/lib/memllib/`
  from upstream `e291192`; the submodule and the fork are both gone. **Q5 (legacy feedback modes)
  closed** — operator kept all four (`RandomiseOutputs`/`RandomiseMlp`/`Diffuse`/`on_drag`) as
  building blocks for comparing how instruments feel under different behaviours, which upholds
  rather than reverses `docs/adr/rl-feedback-design.md`.
- 2026-07-21: **Training-health telemetry (old defect 6) is gone** — the browser reads the real
  per-iteration loss the core records, both fabrication sites are deleted (`wasm-worker.ts`'s
  1-element array AND `wasm-iml.ts`'s sync-train twin, which the audit missed), and the display
  sits behind the existing `expanded` drawer depth. The firmware buffer stays, per the L25 call.

- 2026-07-21: **Training-health telemetry (old defect 6) is real.** `nisps_ml_loss_history` now
  crosses all five WASM registration layers, so the browser reads the SAME per-iteration curve the
  firmware MLP records; `wasm-worker.ts`'s 1-element `new Float32Array([loss])` fake is gone from
  both the sync and the async train paths; and the curve + the already-plumbed `get_layer_stats`
  render in `manifold/src/console/TrainingHealth.tsx` at the Learning drawer's `expanded` depth.
  The firmware buffer stays, per the operator call — it is the record the hardware editor
  (defect 3) will read. One more fabrication went with it: `ConsoleCtx.loss`, a synthetic
  `prev * 0.82` series no drawer read. With no history the panel says "no training run yet"
  rather than drawing a plausible curve.

- 2026-07-21: **Arduino-CLI build machinery (old defect 3) is gone.** Phase 4 replaced it with a
  PlatformIO project: one `[env:]` per variant is now the only variant registry, the `.ino`-mutating
  Python/sed machinery and the `NISPS_ST_*` token-paste table and the sketch symlink forest and the
  global TFT_eSPI mutation are all deleted, memllib is vendored (no submodule), and firmware finally
  entered CI — three representative envs per run, which is what would have caught the SelfTest
  variant sitting broken. All 16 envs build; sizes match arduino-cli within ~520 bytes.

- 2026-07-21: Full-repo simplification audit landed (recon + plan + this rewrite). Superseded entries removed: "browser-only engines incomplete" (→ defect 2/plan 5b), "loss curve not plumbed" (→ defect 7), "NISPS_AUDIO_FUNC misshapen" (→ plan Phase 1, S21/L13), stale "VCV not currently maintained" note (vcv/ is active and consumes `nisps/` directly post-P6).
- 2026-07-18: Browser curve maths unified onto the canonical `nisps/core/math.hpp` catalog at P4; four silently-divergent TS curves re-baselined.
- 2026-07-14: WASM MLP fixed-architecture defect resolved by P2 (`MLPCore<Storage>`; browser runtime-shaped, firmware zero-heap fixed).