A bug has been found in older versions of Electron causing slowdowns on macOS 26 when the app is running or minimized. Macintosh.js is using electron 23.1.3 and needs to be updated to fix this.
❌ macintosh.js.app (Electron 23.1.3) - Contents/Frameworks/Electron Framework.framework/Versions/A/Electron Framework
See issue: electron/electron#48311 (comment)