[BUG] - Invalid image data error when using `to_solver()` with InspectAI evaluations containing inline images

[karangattu]

Description

When running InspectAI evaluations with datasets containing base64-encoded images (data URLs), the evaluation fails with:

BadRequestError: Error code: 400 - 
{'error': {'message': "The image data you provided does not represent a valid image. Please check your input and try again with one of the supported image formats: ['image/jpeg', 'image/png', 'image/gif', 'image/webp'].", 'type': 'invalid_request_error', 'param': 'input', 'code': 'invalid_value'}}

Steps to Reproduce

1. Create an evaluation dataset with inline images using chat.export_eval()
2. Use chat.to_solver() to create an InspectAI solver
3. Run the evaluation with inspect eval

Reproducible code

from chatlas import ChatOpenAI
from inspect_ai import Task, task
from inspect_ai.dataset import json_dataset
from inspect_ai.scorer import model_graded_qa

chat = ChatOpenAI(model="gpt-5-nano-2025-08-07")


@task
def my_eval():
    return Task(
        dataset=json_dataset("pic_only_eval_dataset.jsonl"),
        solver=chat.to_solver(),
        scorer=model_graded_qa(),
        model="openai/gpt-5-nano-2025-08-07",
    )

Contents of jsonl file for reference

{"input":[{"id":"TmBUSKu2WyoXGvjFnfEy5F","content":"You can inspect the provided image and document attachments to answer questions accurately. Reference both when forming your response.","role":"system"},{"id":"YyjFMLrekQuCwYnec3fwTU","content":[{"type":"text","text":"Review the attached materials to answer the question."},{"type":"image","image":"https://www.allrecipes.com/thmb/GMjVlmWXRMGPuIK2FRh8MBvIXgA=/1500x0/filters:no_upscale():max_bytes(150000):strip_icc()/AR-151595-Campbells-green-bean-casserole-DDMFS-4x3-49f408d95f4d40a39cb14ce6fa9544a5.jpg","detail":"auto"},{"type":"text","text":"What is the recipe shown in the image?"}],"role":"user"}],"target":"The recipe shown in the image is a generic Green Bean Casserole."}