[BUG] Image attachment + text message causes messages: text content blocks must be non-empty 400 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?

sent a message with an image attachment + text, got messages: text content blocks must be non-empty repeatedly.

<img width="1482" height="1754" alt="Image" src="https://github.com/user-attachments/assets/d6277ce8-0821-4e1c-b691-215b012b23eb" />

What Should Happen?

It should respond or at least help me fix the issue. The chat is completely offline now.

Error Messages/Logs

Steps to Reproduce

Start a new conversation in Claude Code
Attach an image to a message
Add text to the same message
Send
Observe 400 error: messages: text content blocks must be non-empty
Subsequent messages in the same conversation continue to fail with the same error

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.123 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_