[BUG]

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x] Other: Claude Code (Web App)
• Claude CLI version: N/A (using web app)
• Operating System: macOS 14.3
• Terminal: N/A

Bug Description

When using Claude Code, after pasting a screenshot and typing Japanese (full-width characters), the previously pasted screenshot is automatically re-inserted after confirming the text input.

Steps to Reproduce

1. Open Claude Code editor
2. Paste a screenshot (e.g., ⌘ + Shift + 4 → ⌘ + V)
3. Type Japanese text (e.g., 「こんにちは」)
4. After confirming the input, the screenshot is re-pasted as a new image (e.g., Image#2)

Expected Behavior

Japanese input should be inserted without triggering any additional image paste.

Actual Behavior

The previously pasted screenshot is automatically inserted again after completing full-width text input.

Additional Context

<img width="691" height="155" alt="Image" src="https://github.com/user-attachments/assets/be74c201-547d-466d-8d94-a8e7f4f3a461" />

<img width="688" height="115" alt="Image" src="https://github.com/user-attachments/assets/c581655f-bc41-446c-8c9b-d43a9d84fe26" />

<img width="689" height="153" alt="Image" src="https://github.com/user-attachments/assets/6a5ab9ac-6f5c-43cd-984f-bcc340860e61" />

This issue only occurs with full-width (e.g., Japanese) input. It does not reproduce with half-width alphanumeric input.