The agent's reasoning as a quiet disclosure above its answer: a row with a chevron, "Thinking" and a clock that counts whole seconds, never a shimmer, a pulse or a spinner, then "Thought for 12s". The reasoning sits under it in the quiet text tone with no box. It is open while the agent thinks and closes itself when it stops, unless the reader toggled it.
pnpm dlx shadcn@latest add "https://littmd.vercel.app/r/thinking.json"