Day 6: my language now compiles to WebAssembly — and I emit the bytes by hand

A solo developer building LOOM, an open-source language designed as a machine-checked trust layer for AI-written code, has added a WebAssembly backend by manually emitting the binary bytes. The language now compiles to WebAssembly, running on Node's built-in WebAssembly module, and passes 298 checks across all backends. The developer also landed a new provenance rule, proposed autonomously by the AI organism that grows the language, allowing attestation of specific foreign components.

I'm building LOOM — a small open-source language that is a machine-checked trust layer for AI-written code. I don't write it by hand anymore: an organism I built grows it, day and night, on my own machine. This is Day 6, and the whole day went to one thing — WebAssembly . LOOM already runs three ways: an interpreter, and backends that compile checked code to Python and JavaScript. The thesis is "trust survives translation" — effects and provenance, proven once, hold the same on every target. WebAssembly is the strongest test of that: a low-level stack machine with linear memory, nothing like Python or JS. And there was a constraint. This machine's clang has no wasm target, and I install nothing paid or heavy. So I don't compile to wasm through a toolchain — I emit the wasm bytes myself LEB128, the type / function / memory / global / export / code sections, the i32 stack machine and run them through node's built-in WebAssembly . Zero dependencies. fib to a value runtime, in a day Every step was prototyped and proven wasm output == interpreter output before it touched the kernel: if , first-order calls and recursion. fib 10 becomes 61 bytes of real WebAssembly and returns 55, identically on the interpreter, Python, Node and wasm. let and integer $cons cell allocator; head / tail are i32.load , empty is i32.eqz . A list sums and folds by recursion, inside wasm. variant Tag e becomes a tagged cell tag-id | payload ; match loads the tag, compares, binds the payload, branches.You can watch it: the live playground has a Compile → WAT button and WASM · fib / list-sum / match examples. Type a program, see it become real assembly, in your browser. Honest scope: ints, let , integer lists and sum types compile to wasm today. Records, closures and effects are the next frontiers closures are the hard one — a function table plus a heap environment . Anything outside the supported set fails closed — it never emits wrong code. While I worked on wasm, the organism worked on the trust layer. I'd landed D26 — a rule that provenance does not survive an opaque foreign FFI call, so the host can vouch for what foreign code is granted but never for what it returns . D26 left an honest gap in its own comments: a vetted, signed library was treated no better than an arbitrary .so . The organism, on its own overnight pass, proposed the answer — and I reviewed it and landed it. vouch ROLE WHO COMP : a non-AI authority signs a specific foreign component, so that component's output carries the authority's anchor instead of being stripped. It's an attestation — traceability to a named, non-AI auditor of that exact component — not a claim the component is correct. It fails closed everywhere an AI vouching for itself, a name mismatch, a value laundered through the call — all rejected . A machine I built found and closed a gap in my own design. 298 checks, all green. Across every day, the language has only ever gotten greener. Built solo, in the open, from Ukraine 🇺🇦. ⭐ Code MIT : https://github.com/umbraaeternaa/loom https://github.com/umbraaeternaa/loom ▶ Try it live: https://umbraaeternaa.github.io/loom/play.html https://umbraaeternaa.github.io/loom/play.html ☕ Support: https://send.monobank.ua/jar/AHaziFXjYX https://send.monobank.ua/jar/AHaziFXjYX