CLAUDE_CODE_NO_FLICKER=1 (fullscreen rendering) breaks statusLine display

Bug Description

When CLAUDE_CODE_NO_FLICKER=1 is enabled (fullscreen rendering mode), the custom statusLine configured in ~/.claude/settings.json does not appear. When the environment variable is set to 0 or unset, statusLine works correctly.

Steps to Reproduce

1. Configure a statusLine script in ~/.claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "~/.claude/statusline.sh"
  }
}

1. Enable fullscreen rendering by setting export CLAUDE_CODE_NO_FLICKER=1 in shell profile
2. Start Claude Code: claude
3. Send a message → statusLine does not appear at the bottom

Expected Behavior

StatusLine should display correctly even when fullscreen rendering (CLAUDE_CODE_NO_FLICKER=1) is enabled.

Actual Behavior

StatusLine is completely hidden when fullscreen rendering is active. Verified by toggling CLAUDE_CODE_NO_FLICKER between 0 and 1.

Environment

• Claude Code version: 2.1.90
• Terminal: iTerm2 (and others)
• macOS
• Shell: zsh

Additional Context

Fullscreen rendering uses the terminal's alternate screen buffer. The statusLine may be rendered outside of this buffer, making it inaccessible when fullscreen rendering is active. This appears to be a rendering architecture conflict between the two features. Both features are independently useful and users should be able to use them together.