Try it in ten minutes

Fold a file in your browser

The box below holds a TypeScript file. Press the button and the file is folded to its values by tsad-eval, the evaluator written in Rust for the data-host profile, compiled to WebAssembly and loaded into this page, 1255 KB fetched once. Nothing is sent anywhere. The browser’s JavaScript engine never evaluates your file; it only runs the evaluator, which reads the text and produces the values.

Edit the file and fold again. Add something a data file cannot contain, a let or a call to Date.now(), and the answer names the line and the rule that refused it.

The verdict appears here.

What just happened

The page sent the evaluator one request and printed the verdict. It was { "op": "foldProject", "files": { "policy.ts": … }, "host": {} }, the same request the conformance suite sends.

A fold verdict carries the file’s exports as values. A run verdict carries the rule that refused the file and the line it points at. In a full build that file would be executed instead. This page has no runtime, so it reports the refusal and stops.

The module is evaluators/rust compiled for wasm32-unknown-unknown. It has four exports and no imports, so it instantiates against an empty import object. A browser and an editor extension load it the same way. Node or Go call it without a subprocess.

In CI that same module passes every fixture tagged for the data-host profile, agrees with the reference implementation on each, and agrees with the native binary answer for answer. So what this page runs is what the corpus cross-check measured. Add it to your platform shows the calling convention.