Ruby regular-expression engine

Regex Tools executes Ruby expressions in the actual CRuby 4.0.0 engine built for wasm32-wasi by ruby.wasm. The reviewed runtime is the minimal ruby.wasm from @ruby/4.0-wasm-wasi@2.9.3-2.9.4; the JavaScript host API is @ruby/wasm-wasi@2.9.3-2.9.4.

The fixed bridge.rb module is evaluated once during worker start. Pattern, flags, subject, limits and replacement travel through a bounded, length-prefixed file in the worker-local WASI memory filesystem. Bounded inert JSON returns metadata only; replacement output is written as UTF-8 to a separate bounded worker-local file. No user-controlled value is evaluated or interpolated as Ruby or JavaScript source, and the bridge does not use the ruby.wasm JS.eval conversion path.

CRuby performs compilation and matching and reports character offsets, which the adapter exposes as Unicode code-point native offsets and normalizes to browser UTF-16 ranges. Native String#gsub/String#sub block iteration drives replacement matching without materializing expanded output. A fixed streaming implementation of CRuby 4.0.0's rb_reg_regsub grammar handles \1 through \9, \k<name>, \0, \&, \` , \', \+, and \\; a load-time bounded fixture verifies parity with CRuby. The expander stops on a valid UTF-8 boundary at the configured byte limit. Unpaired browser UTF-16 surrogates are rejected before request encoding. A workbench timeout, cancellation, supersession or crash terminates the dedicated worker and its complete WebAssembly heap.

The deterministic pack contains only:

ruby.wasm;
engine-metadata.json;
SHA256SUMS;
ruby.wasm's exact LICENSE.txt;
ruby.wasm's complete NOTICE.txt, including CRuby and bundled third-party notices; and
the exact browser WASI shim and tslib license texts required by the JavaScript host bundle.