Rust Phase 2 Native-Core Boundary And WASM Feasibility Review

Review Status

The native Phase 2 boundary is approved and Phase 3 KiCad-native PCB reader/writer work may proceed. The typed footprint and symbol-library reader/writer proofs and shared footprint/symbol plotter-IR proofs are implemented. WASM feasibility is demonstrated, but WASM packaging is not approved; the remaining adapter findings are deferred to Phase 7. Downstream pcb_a0 work remains outside this plan. The durable ordering and ownership decision is recorded in ADR-011.

Implemented Boundary

Surface	Native core	WASM	Write/parity evidence
S-expression scan/build/patch	Yes	Yes	Rack L0/L1 corpus, semantic reparse, stable second write
Standalone footprint view/edit	Yes	Yes	Unknown-byte preservation and focused-property writeback
Symbol-library iterator/edit	Yes	Yes	Python summary oracle, flag replacement/insertion, stable write
Footprint plotter IR	Yes	Yes	Python vectors; graphics, strokes, pads, drills, point bounds
Library-symbol plotter IR	Yes	Yes	Python vectors; body, pins, and inheritance

Architecture Audit

kicad-monkey-core has no normal third-party dependency, platform API, FFI type, or package-owned unsafe code. Source views own spans and borrow caller bytes. Typed hot paths never build a generic tree for the complete file; selected forms are materialized only when their local semantics require it.
kicad-monkey-contracts contains TypeSpec-generated DTOs and depends only on Serde. Handwritten semantic validators sit beside generated structural types and prevent contradictory union states.
kicad-monkey-wasm is a thin operation adapter over core and contracts. Source and auxiliary request bytes are separate arrays. Large result payloads are returned out of band from small metadata envelopes; no base64 is used.
Invalid request JSON, identity, or platform-sized limit strings are transport failures and reject the call. Valid requests that encounter source, model, or resource failures return structured diagnostics and no partial output. This distinction is intentional and must remain stable for downstream wrappers.
TypeSpec is authoritative for every public operation in this slice. JSON Schema, Rust, strict Python/msgspec, and TypeScript projections are generated and checked for drift through Rack.
The workspace conforms to wn-dev-std 2026.8.12. The Rust structural ratchet, warnings-denied Clippy, rustfmt, complete Cargo tests, and real wasm32 execution pass. No provisional standards exception remains.

Copy And Artifact Evidence

WASM inputs are borrowed slices. Read operations serialize one result buffer. Edit and plot operations allocate the produced KiCad or JSON bytes plus a separate metadata buffer. Paired-output objects retain compatibility clone getters and also expose takeOutputBytes. Complete non-empty execution evidence for every paired result remains a deferred packaging gate.

Locked release wasm32 builds before JavaScript glue, compression, or wasm-opt measure 292,798 bytes for sexpr, 409,815 bytes for footprint, 556,646 bytes for symbol, and 787,825 bytes with every default feature. The three operation families compile independently under isolated feature checks; actual isolated artifact build/link evidence remains a deferred packaging gate. The default remains an all-operations development artifact.

Deferred WASM Packaging Gates

Shared plotter DTO. Before adding PCB, graph, or other WASM plotter producers, generate one canonical Rust PlotterOperation type for footprint and symbol documents and remove the symbol adapter's per-operation JSON round-trip.
Bounded symbol-library read. Add max_output_bytes to the read contract, serialize through a bounded writer, and return a structured resource-limit result without partial summaries.
Take-once execution evidence. Add non-empty ownership tests for footprint edit, footprint plot, and symbol plot, including at least one direct invocation of the generated JavaScript method.
Artifact build evidence. Replace the isolated cargo check feature test with actual build/link evidence when WASM packaging resumes. Until then, describe the current evidence as independent feature compilation.

Retained Native Gates

PyO3 acceleration remains optional after native parity.
Text/render parity retains the FontBundle, HarfRust shaping-record, outline extraction, and render-cache gates.
Native Windows kicad-cruncher and Rack parity remain the product critical path. Linux and real-browser evidence apply only to later artifacts that claim those platforms.

Recorded Review Decision

Approve the Phase 2 native boundary and authorize Phase 3 KiCad-native PCB reader/writer work. Record WASM as feasibility demonstrated and packaging not approved; the four findings above must close before future WASM expansion. No public Cargo compatibility promise is created by this decision; all crates remain publish = false during incubation.