... stores in raws and reproduces on toString(). root.walkRules((rule) => { if (rule.selector !== targetSelector) return; rule.walkDecls(prop, (decl) => { decl.value = newValue; }); }); writeFileSync(filePath, root.toString()); // formatting preserved For SCSS, postcss-scss is used it understands SCSS syntax including $variables, nesting, and mixins that standard PostCSS doesn't parse. HMR: from setTimeout to confirmation The first version looked like this: after sending the patch over WebSocket, wait 400ms, then re-read the CSSOM. send({ fileUrl, selector, prop, value }); setTimeout(() => { editor.refresh(); }, 400); // fixed ...