[BUG] iTerm2 Screen Erratic Flashing Before First Claude Response

# Bug Report

## Environment

• Platform (select one):
• [x] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.25 (Claude Code)
• Operating System: macOS (Darwin 24.3.0)
• Terminal: iTerm2

## Bug Description
Erratic screen flashing occurs in iTerm2 when using Claude Code, particularly after pasting long text content. The flashing happens both when typing and when Claude Code is generating responses. The flashing goes away after Claude finishes its first response.

## Steps to Reproduce

1. Open iTerm2
2. Launch Claude Code
3. Paste a long length of text into the terminal
4. Begin typing
5. Observe screen flashing while typing
6. Request Claude Code to generate a response
7. Observe screen flashing during generation
8. Wait for Claude to finish its first response
9. Notice that the flashing stops after the response is complete

## Expected Behavior
The terminal display should remain stable without any flashing or visual artifacts during typing or when Claude Code is generating responses.

## Actual Behavior
The screen flashes erratically in iTerm2 when:

• Typing after pasting long text content
• Claude Code is generating responses