[BUG] Custom statusline renders character-by-character during startup message transitions

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?

Status line displays character-by-character during startup when temporary messages (like "Claude Code has switched from npm...") disappear and transition to the custom status line
Each character appears on its own line temporarily, then corrects itself

What Should Happen?

Status line should render as a single complete line

Error Messages/Logs

N/A

Steps to Reproduce

Happens intermittently when Claude Code starts with a custom status hook configured

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.42 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

_No response_