verrex: Instructions file for Claude Code

verrex — Effect-native UI framework

Purpose: a TypeScript UI framework where Effect's <A, E, R> channels propagate from every leaf of the view tree to the root. Forgetting to provide a service Layer becomes a compile-time error that names the missing service; symmetrically, forgetting to handle an error with a Catch boundary becomes a compile-time error that names the unhandled error (mount requires Effect<View<never>, never, R>). Errors live in two phases: construction errors ride the Effect E; live errors a rendered subtree can still produce ride the View<E> success — one Catch boundary discharges both.

Honest scope today: the construction channel is fully type-tracked — a forgotten boundary on a failing build is a compile error. The live channel is tracked wherever a rendered subtree can still fail: (1) an Atom/AtomRef child that EMITS an Effect<View, E> — the fold's phase switch puts that E on View<E> (this is how an atom(...)'s failure escalates: <On value={user} Success={…} /> with no failure arm; a tag arm or Failure handles it in place; partial handling narrows E, the residual rides); (2) event handlers: an intrinsic's on* prop returning Effect<_, E, R> stamps E on the element's View<E> and folds R; (3) For rows and Catch fallbacks fold their E/R too. mount's View<never> gate makes a missing boundary a compile error naming E. Reactivity is effect-atom's API with R/E owned by the caller — see "Reactivity model" in src/runtime/AGENTS.md.

The name is built from the channels of an Effect<View, E, R>: V (View — the A, always the View here), E (Error), R (Requirements), plus X, because the JSX/TSX syntax it borrows adds an X too. V + E + R + X spells verx, stylized to verrex (and the .vx source extension).

Status: experimental proof-of-concept. Not production-ready.

The constraint that shaped everything