[BUG] "Could not process image" error corrupts session, persists after /exit and restart

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?

After a failed image attachment (400 "Could not process image"), all subsequent messages—including plain text with no image—fail with the same error. The failed image is stuck in the request pipeline.

/exit and restarting claude does NOT fix it. Error persists in a fresh session.

Related to #1747 (locked), still happening on v2.0.76.

Request IDs:

• req_011CWWR6NeBqEi1HiXUy6Ayi
• req_011CWWQxT5cRGi6DJSipfV2o
• req_011CWWR1ha5asqxqqcyXVvM5
• req_011CWWR31eYJcoguJ89W5WyD

What Should Happen?

Failed image should be discarded. Subsequent text messages should work. Restart should clear any stuck state.

Error Messages/Logs

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"Could not process image"},"request_id":"req_011CWWR6NeBqEi1HiXUy6Ayi"}

Steps to Reproduce

1. Work in a session until context is low (~8% remaining)
2. Attach a small PNG image (<1MB) with a message
3. Receive 400 error: {"type":"error","error":{"type":"invalid_request_error","message":"Could not process image"}}
4. Send plain text message (e.g., "Hello")
5. Same image error occurs despite no image
6. /exit and restart claude
7. Error continues in new session

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.76 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_