[BUG] `claude plugin test`: a plugin's own `$.ui.focus` fails with "no implementation for ui.focus" even with a test hook

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separately for multiple bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

In claude plugin test, a $.ui.focus call made by the plugin under test rejects with HooksError: no implementation for ui.focus. This happens even when the test registers on('ui.focus', ...). The test's hook is never called.

A $.ui.focus call made by the test body itself reaches the same hook and resolves to {}.

So a test can't check which element a plugin focuses. For example, I can't test that my pane moves the focus to a Button that is still drawn after a press removes the focused one, which works around #100874.

What Should Happen?

A plugin's $.ui.focus should go through the test's ui.focus hooks, as the plugin's state.set calls go through the test's state.set hooks. Or the kit should answer it from the mounted site, as it answers $.ui.invalidate.

Error Messages/Logs

HooksError: no implementation for ui.focus

Steps to Reproduce

1. In a plugin, call $.ui.focus({ requestId: <pane id>, key: <a drawn Button's key> }) from a ui.press hook, and record the result or the error.
2. In a test, register on('ui.focus', ($, e) => { calls.push(e.key); return {} }) before the first call on $.
3. Mount the pane with $.ui.mount and press a Button with pane.press.
4. calls stays empty, and the plugin's call rejects with the error above.
5. In the same test, call $.ui.focus({ requestId: <pane id>, key: <the same key> }) from the test body. It resolves to {}, and calls gets the key.

On a desktop mount, the call rejects this way from a ui.press hook and from a timer started in a ui.render hook. On a terminal mount, a focus call from a press handler doesn't reach the test's hook either.

Claude Model

Not model-related.

Is this a regression?

Don't know.

Claude Code Version

2.1.296

Platform

Anthropic API

Operating System

macOS 15.7.3

Terminal/Shell

Terminal (claude plugin test)

Additional Information

None.