... 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 wait The problem: after writing the file, Vite goes through several steps the file watcher detects the change, Vite recompiles ... ... slow machines 400ms wasn't enough. On fast ones wasted time. The fix: the server sends a confirmation only after writing the file. The client waits for this signal, not a timer. // server after writeFileSync: socket.send(JSON.stringify({ type: "patched