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Critique & Future Work

Snapshot: 0.1.0 (unreleased). This is an honest self-assessment at the first public release, not a marketing document. It records what is solid, what is deliberately narrow, and what is known to be missing.

What is solid

  • Spec conformance. The official WebAssembly 2.0 suite runs at 19,204 assertions / 0 failures. This is the strongest available evidence that the engine is correct, and it is green, not aspirational.
  • Differential agreement. Zero divergences against Wasmtime across a wasm-smith sweep. A second, independent oracle agrees.
  • Embeddability. The no_std core genuinely has no OS dependencies, and the FFI + Swift + AOT surface is exercised by tests, not just sketched.
  • GPU verification is layered and honest. Structural proof runs on every dispatch; numerical proof is opt-in for known-linear kernels with a clearly stated applicability bound (not non-linear ops).

What is deliberately narrow

  • The interpreter is a register-IR interpreter, not a JIT. This is a deliberate 0.1.0 choice for portability and embeddability (no codegen, no platform-specific backend). Throughput is adequate for many embedders but not competitive with Cranelift/Wasmtime on hot loops. A register-block JIT is a future integration-level option (see the Borsalino integration notes).
  • GPU offload is one kernel deep. f32_add is the offloaded operation; the host-module ABI is upload-on-create + read-back. This proves the pipeline end to end; expanding the kernel set and adding partial-write/destroy to the backend trait are follow-ups.
  • Numerical verification covers f32_add. The exact-match protocol applies to linear/bilinear kernels; the reference for each additional kernel must be written. Non-linear kernels are out of scope for this protocol by design.

Known gaps

  • WebAssembly 3.0 is absent. Tail calls, exception handling, memory64, GC, and threads are rejected at validation. These are the roadmap, not a defect of the 2.0 milestone.
  • No hosted documentation site yet at release. This book is the first cut; the API reference points at rustdoc and is intentionally terse.
  • MSRV is asserted (1.85) but CI tests on stable only. A dedicated MSRV CI job would harden the claim.
  • Threading/shared-everything threads are a post-3.0 consideration; the engine is single-threaded by design today.

What this release is not

  • Not a production-hardated server runtime (no observability hooks, no component-model support).
  • Not a JIT (interpreter only).
  • Not a drop-in Wasmtime replacement (smaller surface, different goals).

It is a correct, portable, embeddable WebAssembly 2.0 engine with a real platform-integration story — a credible foundation for the 3.0 work and for running the IA ecosystem on any platform.