Starting from Atom v1.13.0, the contents of atom-text-editor elements are no longer encapsulated within a shadow DOM boundary. This means you should stop using :host and ::shadow pseudo-selectors, and prepend all your syntax selectors with syntax--.
At the time of writing Atom will automatically translate the unsupported selectors, but this will be removed in a few release cycles.
At the time of writing Atom will automatically translate the unsupported selectors, but this will be removed in a few release cycles.