Statusline renders vertically for ~10s on startup (Windows/MINGW)

Description

On Windows (MINGW64/Git Bash), the statusline renders vertically (each segment stacked) for approximately 10 seconds after launching Claude Code, then corrects itself to horizontal.

Environment

• OS: Windows 10 (MINGW64_NT-10.0-26200)
• Shell: Git Bash (MINGW64)
• Claude Code version: Latest (as of 2026-02-22)

Reproduction

1. Configure a statusline in ~/.claude/settings.json:

``json
{
"statusLine": {
"type": "command",
"command": "printf 'colab | main | test-ok'"
}
}
``

1. Launch Claude Code
2. Observe the statusline displays vertically for ~10 seconds before settling to horizontal

Debugging done

• Tested with a hardcoded inline printf (no script, no stdin parsing) — same behavior
• Tested with a bash script — same behavior
• Verified script output via xxd — clean single-line output, no \r, no ANSI codes, no trailing newlines
• Conclusion: not caused by the statusline command/script itself — appears to be a TUI renderer timing issue on Windows

Expected

Statusline should render horizontally immediately on startup.

Actual

Statusline segments stack vertically for ~10 seconds, then snap to correct horizontal layout.