memlnaut-nisps/docs/specs/plans/one-core-engine-refactor.md

kind	status
plan	active

One Core Engine — Firmware + Manifold Reunification Plan

Dated 2026-07-13. Operator-confirmed scope (see §1). Principle: one core engine (nisps/) for both the resource-constrained RP2350 hardware and the Manifold browser app. Everything with behaviour — ML, feedback, exploration, RNG, DSP, input/output processing, curves — lives once, in C++. TypeScript keeps only UI, reactivity, and transport. This plan supersedes the browser-side "one engine, two skins" framing of ../engine-architecture.md (that seam is built — Manifold is its realisation); the axis of unification now runs vertically, core↔targets, not horizontally, skin↔skin.

0. Where duplication actually lives today (audited 2026-07-13)

Component	Canonical	Duplicate / divergence	Disposition
MLP, training, init, RL move_weights	nisps/ml/	vcv/src/iml.hpp full runtime reimpl ("delta #5")	Reunify (P2, P6)
Feedback explore-and-place	nisps/ml/feedback.hpp	none — firmware + manifold both call it ✓	Keep
Geometric dislike (Mode 1)	(missing from core)	manifold/src/feedback/controller.ts TS approximation, explicit C++ GAP markers (lines ~369, ~436)	Port to core (P3)
Jolt weight-morph	nisps/ml/jolt.hpp	playground/src/ml/jolt.ts TS port; absent in manifold	Expose via WASM (P3)
OU exploration noise	nisps/ml/ou_noise.hpp	playground/src/output/ou-explore.ts TS port; absent in manifold	Expose via WASM (P3)
Deterministic RNG	nisps/core/rng.hpp	manifold/src/feedback/rng.ts (SeededRng, self-described stand-in)	Replace with core stream (P3)
Input pipeline	(TS-only concept)	playground/src/input/pipeline.ts ≡ manifold/src/engine/input-pipeline.ts	Port to core (P4)
Output pipeline + curves	curves mirror nisps/core/math.hpp	byte-identical TS pairs in playground + manifold	Port to core (P4)
Audio DSP engines (×8)	nisps/engines/	none — both targets run the WASM ✓	Keep
TS engine spine (wasm-iml, worker, host, worklet)	—	manifold forked from playground; several files byte-identical	Single home in manifold (P1)
Compiled nisps.wasm	scripts/build-wasm.sh → playground/public/	manifold/public/ byte-identical manual copy	Retarget build (P0)
Mode param schemas	schemas/modes/*.json → codegen	manifold bypasses codegen; hardcodes MF_MODES in console/model.ts	Codegen for manifold (P5)
WASM MLP arity	bindings.cpp MLP<32,10,14,18,126>; nisps_ml_create ignores requested dims	forces clamping, blocks per-mode arch, motivated the VCV reimpl	Runtime-shaped browser MLP (P2)

1. Locked decisions (operator, 2026-07-13)

Decision	Choice
playground/	Retired. Archived to branch archive/playground-solidjs, deleted from main. Manifold is the sole browser app; WASM build, parity-check, codegen all retarget manifold.
Depth of "one core"	All algorithms in C++. Feedback (incl. geometric dislike), Jolt, OU, RNG, input/output pipelines, curves move into nisps/; TS keeps UI/reactivity/transport only.
MLP arity	Template the hardware, dynamic browser. Firmware keeps compile-time MLP<...> (zero-heap contract intact); WASM/VCV targets get a runtime-shaped MLP sharing the same algorithm code. Heap allowed at construction time on non-RP2350 targets only.
VCV	In scope, final phase (P6); may slip without blocking anything else.

Supersedes: BUILD-PLAN.md locked decision "Modular N×M MLP: multiple WASM modules + warm-start; NOT runtime-shaped" (2026-06-27). The runtime-shaped MLP is now the chosen mechanism; warm-start on reshape is retained as a feature of it.

2. Target architecture

                    ┌───────────────────────── nisps/ (ONE CORE) ─────────────────────────┐
                    │ core/   rng, math+curves, buffers, perf attrs                        │
                    │ ml/     algorithms templated on StoragePolicy:                       │
                    │           Fixed<NIn,H1,H2,H3,NOut>  (arrays, zero-heap → RP2350)     │
                    │           Dynamic                    (sized at construction → WASM,VCV)│
                    │         mlp / training / init / rl / jolt / ou_noise / feedback /    │
                    │         geo_push / replay  (geometric dislike lands here)            │
                    │ pipeline/  input chain (deadzone→zoom→curve→smooth→momentum)         │
                    │            output chain (curve→smooth→slew→freeze)      ← NEW        │
                    │ dsp/ engines/ modes/   (unchanged)                                   │
                    └──────────────────────────────────────────────────────────────────────┘
                       ▲ direct #include                ▲ nisps/wasm/bindings.cpp (C ABI)
              ┌────────┴─────────┐            ┌─────────┴──────────┐        ┌───────────────┐
              │ firmware/ glue   │            │ manifold/ (React)  │        │ vcv/ (P6)     │
              │ RP2350, Fixed    │            │ UI + reactive spine│        │ Dynamic       │
              │ storage, no heap │            │ + transports only  │        │ storage       │
              └──────────────────┘            └────────────────────┘        └───────────────┘

Litmus test per file: if it computes behaviour that affects sound, weights, or parameter values, it is C++ in nisps/; if it schedules, renders, or transports, it may be TS. The existing browser litmus (JSX/DOM = skin) still applies inside manifold; this plan adds the vertical one.

3. Phases

Each phase ends green on its test gate and is independently landable. File phases as ergo tasks (one per phase, sub-tasks per bullet); do not start a phase before its predecessor's gate is green.

P0 — Plumbing hygiene (hours, no behaviour change) — ✅ landed 2026-07-13

• ✅ scripts/build-wasm.sh emits to manifold/public/ (keep playground/public/ copy only until P1 lands).
• ✅ scripts/parity-check.sh (and tests/cpp/parity_wasm.mjs) read the manifold artifact.
• ✅ Fix stale doc: the MLP<2,…> line was in docs/AGENT-REFERENCE.md + nisps/wasm/README.md (MAP.md was already correct); both now say MLP<32u,10u,14u,18u,126u>.
• ✅ ml-debug.log/graphify-out/ were already absent from the tree; .claude/worktrees/ gitignored.
• Gate met: run-all-tests.sh green (Playwright leg via the BUILD-PLAN non-snap-node VPS runner); parity PASS reading manifold/public/ (max delta 2.4e-7); manifold typecheck+build green against the freshly-built artifact.

P1 — Retire playground, single TS home (≈1 day) — ✅ landed 2026-07-13

• ✅ Branch archive/playground-solidjs + tag playground-solidjs-final; playground/ deleted from main. Parity fixtures for P4 captured FIRST: manifold/tests/fixtures/ (288-event gesture trace, curve goldens, input/output pipeline goldens under 14+8 configs) + drift-guard pipeline-golden.test.ts. Note: input pipeline's momentum path reads performance.now() — fixtures pin a clock contract (see fixtures README). C15 (stub + c15.wasm) now lives only on the archive branch (ALIGNMENT defect #1).
• ✅ Jolt press + OU explore UI shells in the Learning drawer; interim TS math via get/set_weights in manifold/src/engine/{exploration,jolt,ou-explore}.ts, marked P3 SWAP POINT.
• ✅ Keeper Playwright specs ported: probe-api.spec.ts (15 tests), spine.spec.ts (4). Playground UI/ persistence specs dropped with the playground.
• ✅ References retargeted: run-all-tests stage 5 → manifold, ci.yml manifold-tests job, osc-bridge.yml (was already broken), codegen TS target removed (returns P5), AGENTS/README/MAP/ALIGNMENT/ AGENT-REFERENCE/specs-MAIN. The VPS deploy webhook already built only manifold — no change needed.
• Gate met: full run-all-tests.sh green with playground gone (ctest 4/4, parity PASS, lint clean, manifold 9 unit + 20 e2e).

P2 — Storage-policy split: templated hardware, dynamic browser (the structural centre, ≈1 wk)

• ✅ (landed 2026-07-13) Refactor nisps/ml/ so algorithms (forward, backprop/SGD, init, move_weights) are written once against a storage policy (mlp.hpp MLPCore<Storage>; jolt/OU/feedback already operate on the MLP surface and needed no change). Two models:
  • FixedStorage<NIn,H1,H2,H3,NOut> (nisps/ml/storage.hpp) — std::array, zero heap; MLP<...> is an alias preserving the full compile-time surface. RP2350 contract verified: PAFSynth .text 122324→122692 = +0.30% (±1% budget); ctest + golden vectors + WASM parity bit-stable.
  • DynamicStorage (nisps/ml/dynamic_storage.hpp) — sizes at construction, single arena allocation, nothing per-call. #errors under NISPS_TARGET_EMBEDDED; sole lint-cpp.sh heap-allowlist entry, with a lint check that fails if the guard is ever removed.
• ✅ (landed 2026-07-14, operator-approved) nisps_ml_create(input, output, hidden[]) honours its arguments (non-positive/null → the historical 32→[10,14,18]→126 defaults, keeping pre-P2 callers bit-identical). nisps_ml_reshape = new instance + warm-start copy of overlapping weights (nisps/ml/warm_start.hpp); feedback controller re-created (state resets — front-end modal). FeedbackController got the same storage split (FeedbackControllerCore<FbStorage>, fixed alias for firmware/tests, DynamicFeedbackStorage for the browser). nisps_ml_describe now takes the handle (null → default shape). Verified: reshape ABI smoke (dims honoured, overlap survives, invalid dims rejected), warm-start ctest (grow+shrink), parity PASS unchanged, firmware .text unchanged.
• Manifold drops input clamping/phantom-channel handling; XIASRI/sound-analysis multi-input modes become browser-viable.
• Gate: parity — fixed and dynamic storage produce bit-identical outputs for identical shapes/seeds (new ctest); parity-check.sh native↔WASM ≤1e-5 unchanged; firmware builds byte-comparable (chokepoint B: compile PAFSynth, compare .text size ±1%).

P3 — Exploration + feedback fully in core (≈3–4 days)

• Geometric dislike: port firmware k-NN centroid push (upstream InterfaceRL.cpp:602-738) into nisps/ml/geo_push.hpp + replay.hpp + mlp.train_targets, per docs/adr/rl-feedback-design.md §4. Expose via nisps_ml_feedback_dislike_geometric. Delete the TS approximation + both C++ GAP blocks in manifold/src/feedback/controller.ts.
• Jolt / OU: expose nisps/ml/jolt.hpp + ou_noise.hpp through bindings (nisps_ml_jolt_press/release, nisps_ml_explore_intensity); manifold's P1 UI shells switch to them. The playground TS ports die with P1.
• RNG: feedback/exploration randomness in the browser comes from the core's seeded Rng streams (already per-instance, ctor-seeded). Delete manifold/src/feedback/rng.ts.
• Gate: new cross-platform parity test — scripted feedback session (seeded) produces identical weight trajectories native↔WASM; firmware spot-check on hardware (chokepoint A) for geometric dislike feel.

P4 — Input/output pipelines + curves into core (≈3 days)

• New nisps/pipeline/: input chain and output chain as plain structs satisfying the perf contract (usable per-sample on firmware if ever wanted; per-pointer-event in browser — JS↔WASM call cost is trivial at that rate).
• Curves: single catalog in nisps/core/math.hpp (already canonical); bindings expose nisps_curve_apply(id, x) and batch variant; TS curves.ts (both copies) deleted, UI curve previews render by sampling the WASM.
• Manifold input-pipeline.ts / output-pipeline.ts become thin calls into the main-thread WASM instance (state lives C++-side, per-instance, serialisable for persistence).
• Golden TS-vs-C++ tests retire; replaced by direct use.
• Gate: spine e2e unchanged; recorded-gesture regression: same pointer trace → same routed output pre/post migration (capture fixture before starting).

P5 — Schema/codegen serves manifold (≈2 days)

• codegen/generate.ts emits manifold/src/modes/generated/ alongside the C++ headers (playground target removed in P1). MF_MODES in console/model.ts is derived from generated schemas, not hand-written — labels/ordering may stay a manifold-side overlay, but params/ranges/ml-config come from schema truth.
• With P2's dynamic MLP, per-mode ml.input_size/output_size/hidden in schemas becomes real in the browser; codegen gains a check that firmware modes still fit the fixed template.
• Gate: codegen idempotence golden test extended to manifold output; e2e per-mode param count/range assertions driven from schema.

P6 — VCV reunification (later; may slip)

• vcv/src/iml.hpp deleted; module consumes nisps/ml/ with DynamicStorage (its 8→16 runtime shape is exactly the P2 case). DetRng replaced by nisps/core/rng.hpp. Closes vcv-module.md delta #5.
• OSC server stays vcv-local (transport, not behaviour).
• Gate: vcv builds; seeded train/infer parity vs native ctest.

4. Risks

Risk	Mitigation
P2 template refactor destabilises firmware perf (chokepoint B)	Fixed-storage path stays std::array + same attrs; compare .text/RAM and audio-callback timing before/after; land behind a ctest parity gate.
Dynamic storage leaks heap use into firmware paths	Compile-time guard (#if NISPS_TARGET_EMBEDDED excludes DynamicStorage); lint-cpp.sh already fails heap under nisps/ — carve an explicit allowlist for the dynamic TU only.
Per-event WASM calls for pipelines add latency	Pointer-rate ≈120 Hz, one call each — negligible; batch API as fallback. rAF/canvas never calls WASM.
Geometric-dislike port changes feel vs firmware	Port from upstream source verbatim, seeded-trajectory parity test, then hardware A/B (chokepoint A) before deleting the TS fallback.
Retiring playground loses a working reference	Archive branch + tag; parity fixtures (recorded gestures, golden outputs) extracted before deletion in P1.
Manifold worklet + main thread now both depend on retargeted wasm build	P0 gate builds manifold from fresh artifact in CI, killing the manual-copy hazard permanently.

5. Doc-sync obligations

• On each phase landing: update MAP.md (it is the shipped-behaviour authority) and burn down this plan's phase table; when all phases land, set status: executed.
• MAIN.md registry: this file added; engine-architecture.md remains authoritative for the browser-side seam only; BUILD-PLAN.md's MLP row annotated as superseded (done 2026-07-13).
• ALIGNMENT.md defect #3 (fixed WASM arity) closes at P2; the accepted-divergence log entries for Jolt/OU TS ports and vcv delta #5 close at P3/P6.