[BUG] Pasting a screenshot into a coding session causes all subsequent messages to fail with an API error

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?

I created a screenshot using Windows + Shift + S and pasted it directly into the message input of a Claude Code session. After that, every message I type returns the following error. The issue is reproducible. I'm on Windows 11 with a German locale.

What Should Happen?

User input should be accepted and Claude should respond as expected.

Error Messages/Logs

API-Fehler
API Error: 400 messages.222.content.1.text: cache_control cannot be set for empty text blocks

API-Fehler
API Error: 400 messages: text content blocks must be non-empty

Steps to Reproduce

1. Open Claude Code on the web (https://claude.ai/code) in a browser on Windows 11 (German locale).
2. Open or start a coding session for any repository.
3. Press Win + Shift + S to open the Windows Snipping Tool and capture a screenshot of any area.
4. Click into the Claude Code message input field and paste the screenshot using Ctrl + V.
5. Send the message (with or without additional text).
6. Type any follow-up message (e.g. "test") and send it.

Result: Every subsequent message in the session fails with:
API Error: 400 messages: text content blocks must be non-empty

Expected: User input should be accepted and Claude should respond as expected.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Code 2.1.131 is running in the current container.

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Non-interactive/CI environment

Additional Information

_No response_