Rock Band 3 (Wii) — decompilation & browser port

Rock Band 3 for the Wii runs on Harmonix’s Milo engine, compiled with Metrowerks CodeWarrior for PowerPC. A decompilation rebuilds the shipped binary from clean-room C++ until the compiler reproduces the original bytes — progress is a mechanically verified percentage, not an opinion. A community project had reached 628 commits over two and a half years before stalling. In March 2026 I forked it and pointed a fleet of AI coding agents at it.

Four months later the project stands at 99.3% size-weighted fuzzy match across its game and engine targets — the code the port actually reconstructs — and 81.9% fuzzy (63.2% byte-exact) across the entire ~10.9 MiB binary including untargeted SDK and third-party code, with 31,995 of 41,254 functions matched over 3,465 total commits. May 2026 alone produced 1,757 commits, nearly three times the entire prior community history. Along the way the project grew something the original never had: a native Linux/macOS port and an Emscripten/WebAssembly build that plays full songs in a browser tab, with the WASM module optimized down to 6.1 MB (1.5 MB compressed).

The hard problem was not decompilation per se — it was operating LLM agents as a production system. Roughly eight parallel agents run per “wave,” each scoped to a single translation unit with a strict do-not-touch contract, and every candidate win must pass a full-rebuild regression gate across all 41,254 functions before landing. That gate earns its keep: it caught a shared inline “improvement” that scored 97.4% standalone but silently regressed six other functions. A bail-verification protocol refuses to accept an agent’s “this is compiler noise” claim without a mechanical permuter run — which proved two of three such claims premature in one audit. Durable lessons, anti-pattern catalogs, and per-wave economics live in versioned agent memory, so transient sessions accumulate into lasting capability.

Demanding byte-exact matches also surfaced genuine bugs Harmonix shipped in 2010 — an inverted login-retry clause, transposed difficulty branches, a destructor bounds-checking against the wrong container — because a faithful decompilation must first notice them to reproduce them.

The project is active: structural decompilation is mature, and current work focuses on native/web rendering parity and the remaining compiler-forensics long tail. No game assets or copyrighted binaries are stored in the repository — this is preservation through original source.