61 tests evaluate the same SX expressions on both Python (sx_ref.py) and JS (sx-browser.js via Node.js), comparing output: - 37 eval tests (arithmetic, strings, collections, logic, HO forms) - 24 render tests (elements, attrs, void elements, components, escaping) All pass — both hosts produce identical results from the same spec. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>