Roundhouse

The emitted projects compile clean and pass their tests. Correctness is a conformance oracle: the same URL fetched from Rails and from each target must produce the same response — enforced by emitted unit tests, a differential compare gate against live Rails, and end-to-end browser tests.

No annotations are involved: has_many :comments is a type declaration, and whole-program inference recovers the types Rails' conventions already imply. That inference is a product in its own right — an LSP server, an MCP server, and the in-browser IDE answer what's the type here, can this be nil? on unannotated Rails apps, with no app boot and no database: queries answer in milliseconds, and a whole-app pass over Mastodon takes about two seconds, in a browser tab.

It's also the performance story: every decision that can't differ between requests is made once, at transpile time. The emitted Ruby serves ~10× the requests of stock Rails on the same CRuby+YJIT, ~74× under JRuby, and the compiled targets go further — ratios from a CPU-bound microbenchmark; caveats in the posts below.

• Conformance vs Comprehension — the project and its oracle
• Live Types for Rails — the inference as a live type checker
• An IDE You Don't Install — Mastodon analyzed in a browser tab
• The Ruby JRuby Was Built to Run — the 2×2 performance experiment
• Numbers Without Conclusions — benchmark methodology and honest caveats