Code highlighting for diffs, code blocks, and tool use previews has been refactored to use React Suspense with lazy loading. The highlighter module is loaded asynchronously, showing an unhighlighted fallback until ready. This should improve perceived startup time.
Evidence
Suspense-based highlighting wrapper (search for "Suspense" near highlight components)
Strings lifted out of the shipped bundle, so the claim above can be checked against them.