while the agent works, you get a row of ‘instruments’ (model, mode, nb of messages …) and one that shows the current action. you can always prompt your agent directly from HUD, no need to open it in full. its also possible to jump back and forth between HUD and the main coding agent with /hud
on how it works: it uses the official CLIs headless through JSON event streams and the /hud handback for claude code consumes 0 tokens (UserPromptSubmit hook, ~150ms), 0 runtime dependencies.