API Error 400 – invalid_request_error for tool_result image media type

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?

When Claude Code reads files (in this case, 3 files were read), it crashes with an HTTP 400 Invalid Request Error from the Anthropic API. The error message is:

messages.9.content.0.tool_result.content.0.image.source.base64.media_type: Input should be 'image/jpeg', 'image/png', 'image/gif' or 'image/webp'

What's happening:
Claude Code is passing an image inside a tool_result message to the API, but the media_type field contains an unsupported or malformed value. The API only accepts image/jpeg, image/png, image/gif, or image/webp, so the request is rejected.
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Additional Bug / Core Impact:

After the 400 invalid_request_error is returned, the Claude Code session becomes unrecoverable. The CLI does not handle the error gracefully — it crashes entirely rather than skipping the problematic file or prompting the user to continue. The only way to recover is to start a completely new session, losing all context and conversation history.

Expected behavior:
The session should catch the 400 error, warn the user about the unsupported file type, and allow the session to continue.
Actual behavior:
The session dies permanently after the error. No recovery is possible.

What Should Happen?

even after an error the session should return so not only we are having an error, we are losing the session

Error Messages/Logs

Steps to Reproduce

ask it to open a file

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

-

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

<img width="1833" height="117" alt="Image" src="https://github.com/user-attachments/assets/edb0692a-ea7e-48b2-8874-f6ca60075785" />