[BUG] Cowork (Windows): arrow-up at top line of input loads prior chat message and hijacks the textarea

Preflight Checklist

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

What's Wrong?

In the Cowork tab of the Claude desktop app on Windows 11, when the typing cursor is on the top line of the input textarea and the user presses arrow-up, the textarea replaces the current draft with the user's previous chat message in the session. Arrow-down restores the current draft. Holding arrow-up iterates back through prior user messages in reverse-chronological order.

Critical secondary failure: while a prior message is loaded into the textarea, typing edits that prior message rather than the current draft, and pressing Enter sends the typed-into-prior-message version. The user can unintentionally edit and re-send a prior message when they only meant to scroll their current draft to the top.

There is no visible indicator that the textarea has been hijacked into a prior-message-edit mode. No setting in Cowork preferences disables this behavior.

What Should Happen?

Arrow-up at the top line of the textarea should either (a) do nothing -- the cursor stays at the top of the current draft -- or (b) provide a clearly-indicated history-recall mode that is opt-in, distinguishable from the current-draft state, and cannot accidentally edit/send a prior message via subsequent typing. The terminal-style up-arrow-recalls-history pattern is a poor fit for a multi-line textarea where the user routinely needs to navigate within their draft.

Error Messages/Logs

None. Failure is silent and visible only in the textarea content.

Steps to Reproduce

1. Open Cowork tab in Claude desktop app on Windows 11.
2. In a session with at least one prior user message, draft a multi-line message in the input textarea.
3. Place cursor on the top line of the textarea.
4. Press arrow-up.
5. Observe: the prior chat message replaces the current draft.
6. Type any character.
7. Observe: typing edits the loaded prior message, not the current draft.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

A week ago this behavior didn't exist.

Claude Code Version

2.1.111 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Non-interactive/CI environment

Additional Information

Practical impact

Holding arrow-up to navigate to the top of a long draft (a routine textarea operation) scrolls the chat history instead, often by many messages. Subsequent typing then corrupts a prior prompt. Recovery requires arrow-down to restore the current draft, but the recovery path is not obvious from the UI and the focus cost is meaningful.