Examples
Enter Does Not Submit While The Roster Is Open
**The composer's Enter behaviour.** Enter with the roster OPEN inserts the highlighted mention and does **not** submit; Enter with the roster CLOSED submits normally and the app clears the draft. This locks the end-to-end behaviour across the two packages. It is **not** a capture-vs-bubble discriminator — `PromptInputTextarea` composes an outer `onKeyDown` manually, so it holds either way (verified by mutating the source and re-running). The binding itself is locked by "T8 Slot handler-order contract" in `packages/ui/src/components/mention-input/mention-input.test.tsx`.