[BUG] Desktop app: input box floods with endless [ / 「 characters (IME composition) while claude-in-chrome browser-selection dialog is open

Environment

• OS: Windows 11 Pro (10.0.26200)
• App: Claude desktop app 1.40609.0.0 (Microsoft Store) with bundled Claude Code 2.1.247
• IME: Japanese IME (Microsoft IME) active
• Terminal: N/A (desktop app chat input)

Description

While a claude-in-chrome "Switch browser" selection dialog (AskUserQuestion listing connected Chrome browsers) was open and the "Claude in Chrome — Open Chrome and click Connect extension to continue" notification was showing, the chat input box began filling with hundreds of 「 characters, growing continuously (roughly one full line every few seconds) with no user input at all.

Details observed in a screen recording:

• The flooded text has an IME composition underline, and the IME candidate window opens with candidates made of 「 sequences — i.e. the app is receiving repeated [ key events which the active Japanese IME converts to 「 and holds as an uncommitted composition string.
• An occasional half-width [ appears mixed into the flood.
• The flood keeps growing indefinitely until the composition is cancelled (Esc) or the text deleted; it resumes while the browser-selection state persists.
• The same corruption leaks into messages actually sent to Claude (messages arrive as [[[[[... / 「「「「... followed by the intended text).

Suspected cause

Looks like the same family as #10375 (focus-reporting sequences leaking into input) / #21766: CSI escape sequences reaching the input with ESC consumed, leaving literal [. In this case something — plausibly the claude-in-chrome connection polling or focus reporting while the browser-selection dialog is pending — injects [ repeatedly, and with a Japanese IME active each one enters the composition buffer as 「, so the input floods indefinitely.

Steps to reproduce (as observed)

1. Windows 11 desktop app, Japanese IME enabled (あ mode).
2. A session uses claude-in-chrome with multiple connected Chrome extensions, so the browser-selection AskUserQuestion dialog appears and the "click Connect extension to continue" notification shows.
3. Leave the dialog unanswered; focus/click around the app.
4. Chat input starts filling with 「 characters continuously without typing.

Workarounds found

• Esc cancels the uncommitted IME composition (clears most of the flood); otherwise Ctrl+A → Delete.
• Answering or skipping the browser-selection dialog stops the flood.

A screen recording of the issue is available and can be provided on request.