[BUG] attaching images to Claude Desktop code occasionally creates API Error 400

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?

multiple times i have experienced dragging an image (screenshot, etc...) into Claude Desktop code and then it throws:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.18.content.0.image.source.base64.data: At least one of the image dimensions exceed max allowed size for many-image requests: 2000 pixels"},"request_id":"req_011CY4jPVe2jbACa1gGFRLC4"}

and the chat is unrecoverable. (requires editing the jsonl file - removing the offending session events before it can be used again)

to be clear, the images used are NOT particularly large (actually fairly small... but i am not clear if it only happens with 2+ images attached, or if it can happen with ONLY 1 image attached.

What Should Happen?

It should NOT throw an API error, and it should NOT kill the chat (and require hand editing the jsonl to fix it)

Error Messages/Logs

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.18.content.0.image.source.base64.data: At least one of the image dimensions exceed max allowed size for many-image requests: 2000 pixels"},"request_id":"req_011CY4jPVe2jbACa1gGFRLC4"}

Steps to Reproduce

1. start Claude Desktop code session
2. drag one (possibly 2+) images into message and send message
3. wait for API error and dead chat session

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.39

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_