Pencils Down, Notation Up

gist

Sam Ruby answers DHH's Rails World 2026 pencils-down keynote by arguing agents still need compact notation at the top of the drill. Using Roundhouse and Spinel, he compiles ONCE Campfire to a 202,000-line C file and shows why agents edit Rails better than the C: context fit, saying each thing once, keeping intent, deterministic rebuilds, and familiar training data. A prompt precise enough to regenerate Campfire is already a program, and Rails is that notation. Compiling Rails to native can still reclaim most of the Rust-scale gains without abandoning the source of truth.

ideas

• Keep notation at the top of the drill. Agents can target Rust, C, or microcode, but the editable source of truth should stay compact and intentional.
• Campfire in Rails beats Campfire in C for agents. The Rails app is about 60k tokens and fits in context; the compiled C is about 4M tokens and about 70× too large.
• Source of truth needs five properties. It must fit in context, say each thing once, keep intent, produce the same result every time, and preferably look like training data.
• A precise prompt is already a program. Pinning every association, validation, callback, and route recreates a web-app DSL that Rails already is.
• Compile-time meaning recovers most of the speed. Emitting Campfire as a native binary yields 7–8× throughput and 92% less memory versus its Dockerfile deploy, and most of Rails' cost was runtime interpretation of declarations.

quotes