[BUG] "Image uploads convert PNG to JPEG, destroying alpha channel transparency"

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?

All is said in title
Absolute boring bug when you code transparency to BAse64 or whatever

What Should Happen?

RGBA must stay RGBA, and not become RGB

Error Messages/Logs

Steps to Reproduce

-

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Opus 4.6 and @

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_