New sx_playwright mode="sandbox" — injects the WASM kernel into about:blank
with full FFI, IO suspension tracing, and real DOM. No server needed.
Predefined stacks: core (kernel only), web (full web stack), hs (+ hyperscript),
test (+ test framework). Custom files and setup expressions supported.
Reproduces the host-callback IO suspension bug: direct callFn chains 6/6
suspensions correctly, but host-callback → addEventListener → _driveAsync
only completes 1/6. Bug is in the _driveAsync resume chain context.
Also: debug.sx mock DOM harness, test_hs_repeat.js Node.js reproduction.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
aeaa8cb498