[BUG] Opus 4.6 - Image Generation size issue causing recursive loop

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 asking Opus 4.6 to generate thumbnail images, it doesn't seem to be able to control the dimensions of the image generated, but it doesn't know this, so it keeps trying over and over to generate the correct size image only to get the wrong size each time.

The generated file is always 1376x768,

<img width="342" height="1374" alt="Image" src="https://github.com/user-attachments/assets/325973b5-1a1b-470f-8e1a-f01c969ae9ff" />

What Should Happen?

Option 1: Claude warns me that it cannot create custom sized images.
Option 2: Claude handles the failure more gracefully without churning through my usage.

Error Messages/Logs

Steps to Reproduce

Resources - Existing wide thumbnails

<img width="2048" height="1536" alt="Image" src="https://github.com/user-attachments/assets/bf2e1084-563a-4c68-95fb-5dfeb6d9f0e7" />

<img width="2048" height="1536" alt="Image" src="https://github.com/user-attachments/assets/1b429471-92e2-4bff-8a20-191c8574a4b0" />

Resources - Existing Tall Thumbnails

<img width="1536" height="2048" alt="Image" src="https://github.com/user-attachments/assets/3dd32e94-5cc4-4f02-a5a2-a015cdf44454" />

<img width="1536" height="2048" alt="Image" src="https://github.com/user-attachments/assets/6ee4dfa1-ef53-4837-8c7d-e5c480f22da5" />

Resources - Model Picture

<img width="1000" height="750" alt="Image" src="https://github.com/user-attachments/assets/1995ba36-9b64-4e3d-aeaf-baef1533991f" />

Step 1: Tell claude to make a wide thumbnail for the model "ExoGuitar - Head - Arrow" using the Model Picture above, in the style of the other wide thumbnails. (this will create a file that's the wrong size, but it won't recursively fail because it's still "wide"

Step 2: Tell Claude to make a Tall version of the Wide thumbnail it created.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Unsure, this is being run by the latest version of Cursor

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This is the GH project if you'd like to take a look: https://github.com/spikeon/exoguitar