[BUG] Narrow pane doesn't clip content in Claude Desktop - session header text overlaps

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

<img width="278" height="101" alt="Image" src="https://github.com/user-attachments/assets/5ecf7f82-b87c-4d1c-926c-4888d805e12a" />

What's Wrong?

When one of the open panes in the Claude Desktop app is sized to a small/narrow width, its content does not clip or truncate to the pane bounds. Instead, overlapping elements render on top of each other and become unreadable.

Concretely, in the session header / composer area of a narrow pane, the session number (#3362), the change-count indicator (+118), and the repo/session label (compute-platform) collapse onto the same space and overlap into an illegible string.

What Should Happen?

Content should clip to the pane width - long labels should truncate with an ellipsis, and elements should keep their own position/line rather than overlapping. The header should stay legible at any pane width.

Steps to Reproduce

1. Open the Claude Desktop app with more than one pane visible.
2. Shrink one pane to a small width (narrow enough that the session header no longer fits).
3. Observe the session header / composer area of the narrow pane.
4. The session number, change count (+NNN), and session/repo label overlap on top of each other instead of truncating.

Claude Code Version

2.1.175 (Claude Code)

Is this a regression?

I don't know

Claude Model

Opus

Platform

Anthropic API

Operating System

macOS (Darwin 24.6.0)

Terminal/Shell

Other - this is Claude Code running inside the Claude Desktop app (CLAUDE_CODE_ENTRYPOINT=claude-desktop, bundle id com.anthropic.claudefordesktop), not a terminal. The bug is in the desktop app's pane/layout rendering.

Additional Information

This is a UI/layout bug in the Claude Desktop app rather than the terminal CLI. A screenshot showing the overlapping header text in a narrow pane is available and will be attached to this issue.