HEXAW: a tiny time machine for WebAssembly

A developer has released HEXAW, an experimental MIT-licensed text format for WebAssembly that replaces WAT's nested parentheses with readable mnemonics and a retro assembler feel. The accompanying CLI assembles HEXAW into .wasm, dumps binaries back into annotated instructions with their hex bytes, and steps execution forwards and backwards, and it includes an AI mentor powered by the open-weight gpt-oss-120b model via Groq that is grounded in the opcode table and current VM state. In the demo shell, CALL factorial 5 computes 5! = 120 and BACK reverses the last execution step.

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 3: Slow and Steady https://dev.to/challenges/hacktoberfest-week3-2026-10-19 I once wrote a Z80 game on a Videoton TV Computer. I still miss typing an instruction and seeing the exact bytes it becomes. WebAssembly brought back the possibility. WAT brought me a parenthesis jungle. My brain wanted an assembler listing. So I started building HEXAW: a new, experimental text format for WASM , with readable mnemonics and a retro assembler feeling. It is still totally beta. The syntax and tooling are evolving. Expect rough edges. The CLI can assemble HEXAW into .wasm , dump binaries back into readable instructions, and step through code forwards and backwards. There is also an AI mentor you can ask when the bytes stop making sense. Clone the repository https://github.com/Pengeszikra/hexaw , run npm ci , and save the example below as factorial.hexaw in the repository folder. Then: npm run shell -- factorial.hexaw Inside the shell: CALL factorial 5 G BACK That computes 5 = 120 , then reverses the last execution step. The shell also has an SST-inspired A mode: type an instruction, press Enter, see its hex bytes, and continue at the next address. An empty Enter applies the completed draft. Here is the factorial loop: EXP "factorial" 0 FN 0 PAR 0 ; n RES LOC 1 ; result CONST 1 SET 1 BLOCK LOOP GET 0 EQZ BRIF 1 ; leave the outer block when n = 0 GET 1 GET 0 MUL SET 1 GET 0 CONST 1 SUB SET 0 BR 0 ; repeat the loop END END GET 1 END The default numeric type is i32 . Prefixes L , F , and D select i64 , f32 , and f64 . This is still WASM: a typed stack, locals, and structured control flow. The dump keeps the bytes beside the instructions: 00000032 : 20 00 : GET 0 00000034 : 45 : EQZ 00000035 : 0D 01 : BRIF 1 Source: https://github.com/Pengeszikra/hexaw https://github.com/Pengeszikra/hexaw I built it with Codex, using my TS+| TypeScript fork for the CLI and a shared assembly/debugging engine. The mentor uses the open-weight gpt-oss-120b https://console.groq.com/docs/model/openai/gpt-oss-120b model through Groq, carried over from my Terminal Is Your Friend project. Its teaching material now focuses on HEXAW and WASM, grounded in the actual opcode table and a limited snapshot of the current code, assembly draft, VM state, and recent errors. With GROQ API KEY set before starting the shell, I can ask: // What does BRIF 1 mean here? AI ERROR The reply arrives while I keep working. Suggested code stays an example until I enter it myself. I can change the language, the compiler fork, and the mentor’s teaching material. Anyone else can too: HEXAW is MIT-licensed. An open-weight model leaves a future route to self-hosting. Today the mentor uses Groq’s hosted API; the assembler and debugger work locally. Less manual byte decoding. Fewer trips between code, documentation, and a separate AI chat. Apparently I am lazy enough to want all of that in one terminal. Just not lazy enough to leave assembly alone.