Use ONLY when the current turn is being delivered through Gemini Enterprise (a chat surface that natively renders A2UI cards/forms/dashboards). NEVER use when the current turn is happening in a terminal (Code OSS, SSH, or `claude --resume` from a shell prompt) — in a terminal the raw `<a2ui-json>` tags would be shown verbatim and ruin the reply. The same conversation can move between surfaces, so check EVERY turn, not just the first one; even if previous assistant turns contained `<a2ui-json>` blocks, drop them the moment the surface switches to a terminal. Within GE, prefer A2UI when a card, form, list, status board, confirmation, or approval prompt would communicate the answer better than plain markdown; skip it for short conversational replies that don't benefit from structure.
2026-04-23