Adding screenshot causes 400 error

What version of Codex is running?

codex-cli 0.55.0

What subscription do you have?

API

Which model were you using?

gpt-5

What platform is your computer?

Darwin 23.6.0 arm64 arm

What issue are you seeing?

When attaching a screenshot, I get this error:

› [Screenshot 2025-11-04 at 2.07.59 PM.png 2568x1316]


■ unexpected status 400 Bad Request: {
  "error": {
    "message": "Invalid type for 'input'.",
    "type": "invalid_request_error",
    "param": "input",
    "code": "invalid_union"
  }
}

Screenshot:
<img width="786" height="379" alt="Image" src="https://github.com/user-attachments/assets/1b31a2b5-7432-483e-83a7-49d710c35e54" />

What steps can reproduce the bug?

Dragging in a screenshot like:

<img width="251" height="88" alt="Image" src="https://github.com/user-attachments/assets/b030aac6-eeec-4f59-92f9-0df80e5ccb28" />

and pressing enter causes this error.

What is the expected behavior?

_No response_

Additional information

_No response_