[BUG] Welcome screen disappears instantly on startup

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?

Version: 2.1.124
OS: Windows 10 Pro
Shell: PowerShell / CMD / VS Code (all same)

Issue:
The full welcome screen (with Recent Activity and What's New panels) flashes for ~0.1 seconds on startup, then immediately collapses to a minimal one-line header.

Steps to reproduce:

1. Open a new PowerShell terminal
2. Run claude
3. Welcome screen appears briefly (~0.1s) then disappears

Root cause identified:
The cachedGrowthBookFeatures field in .claude.json contains "tengu_swann_brevity": "focused", which appears to suppress the welcome screen. This value is assigned server-side and cannot be overridden locally — even a completely clean install (no
.claude/ folder, no .claude.json) reproduces the issue, as the server sends the flag immediately on startup.

What Should Happen?

Expected behavior:
The welcome screen should remain visible until the user starts typing, as it did in v2.0.0.

Note:
Other users on the same version do NOT experience this issue, suggesting this is an A/B test group assignment. Please consider adding an opt-out or reverting this behavior for the "focused" brevity group.

Error Messages/Logs

Steps to Reproduce

1. Open a new PowerShell terminal
2. Run claude
3. Welcome screen appears briefly (~0.1s) then disappears

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.124

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_