• Semantic menus: #3182
• Settings editor now allows comments and provides setting validation: #3167
• Switch to Yarn as the package manager: #3182
• Support for carriage return in outputs: #2761
• Upgrade to TypeScript 2.6: #3288
• Cleanup of the build, packaging, and extension systems. jupyter labextension install is now the recommended way to install a local directory. Local directories are considered linked to the application. cf #3182
• --core-mode and --dev-mode are now semantically different. --core-mode is a version of JupyterLab using released JavaScript packages and is what we ship in the Python package. --dev-mode is for unreleased JavaScript and shows the red banner at the top of the page. #3270