A set of tools can drive a single app window instead of your whole screen.
Thirteen per-app control tools are registered but every call returns "not available in this build" without a host implementation.
What's wrong with this entry?
A new tier of computer-use tools operates a single application through Accessibility instead of taking over the whole display: app_screenshot, app_click, app_type, app_key, app_scroll, app_drag, app_menu, app_list_windows, app_ax_find, app_batch, app_release, app_bring_to_current_space and list_apps. They only work when the host program running Claude Code provides an app-scoped implementation; otherwise every call returns "Per-app background tools are not available in this build."
- Each call re-checks an enabled flag, so remote configuration can switch the family off part-way through a session. When that happens the message is "Per-app background control (the app_* tools) was just turned off for this device by a remote configuration change."
- app_screenshot returns a JPEG plus an <ax-summary> listing interactive elements; the indices in that summary can be passed back as element_index to click or type into a specific control.
- None of these tool names existed in v2.1.241, and the implementation module moved position in the bundle.
Per-app background tools are not available in this build.
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Related
Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.
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v2.1.248
Computer-use app blocklists extended on Windows
Both mention computer