What
A new act interface, with actions like find, findAll, press, input, select, key, pointer, post, advance, resize, redraw, and unmount, plus supporting functions (mount, act, refresh, releaseAll), can now drive Claude Code's terminal-rendered plugin UI components (Button, Link, Markdown, Code, Input, Select, Client) programmatically: clicking buttons, typing into inputs, selecting values, sending key or pointer events, advancing a virtual clock, and resizing, redrawing, or unmounting a mounted UI.
Why
This is a testing/automation tool for exercising plugin UI components without a person at the keyboard, useful for scripted checks of how plugin interfaces behave.