[BUG] Windows: Claude startup welcome/header UI not visible in some folders

Summary

On Windows, Claude Code startup welcome/header UI is not visibly persistent in some folders, while it appears in others. Claude still works (prompt, /help), so this looks like a terminal rendering/startup UI bug.

Environment

• OS: Windows 11
• Shell/terminal: PowerShell + Windows Terminal
• Claude Code version: 2.1.39
• Account type: Claude Pro

Reproduction

1. Run:

• cd <REPO_PATH_A>
• claude

1. Run:

• cd <REPO_PATH_B>
• claude

Expected

Startup welcome/header UI should appear consistently in both folders.

Actual

• In one folder, trust/setup flow appears.
• In another folder, Claude works (Claude >, /help works), but startup welcome/header is not visibly persistent (appears missing/cleared).

Notes

• This is not correlated with folder file count alone.
• Behavior is folder-dependent on same machine/session.

Troubleshooting already done

• claude --setting-sources user
• Reset project trust/onboarding flags in <HOME>/.claude.json
• pwsh -NoProfile
• claude --no-alt-screen
• Cleared env styling vars (NO_COLOR, TERM, FORCE_COLOR variants)
• Verified functionality is intact (prompt commands work)

Additional context

• Startup debug logs show different startup paths between folders.
• Looks similar to prior Windows terminal welcome/banner visibility regressions.