🐛 Bug Report: Anthropic instrumentation fails to serialize pydantic messages from previous assistant responses

[dinmukhamedm]

Which component is this bug for?

Anthropic Instrumentation

📜 Description

When I send the content of a previous response as a history message instrumentation fails to add this to attributes

Very similar issue in the past with OpenAI: #2976

👟 Reproduction steps

image_content_block = {
    "type": "image",
    "source": {
        "type": "base64",
        "media_type": "image/jpeg",
        "data": base64.b64encode(
            open(
                Path(__file__).parent.joinpath("data/logo.jpg"),
                "rb",
            ).read()
        ).decode("utf-8"),
    },
}

client = Anthropic()
user_message1 = {
    "role": "user",
    "content": "Are you capable of describing an image?"
}
user_message2 = {
    "role": "user",
    "content": [
        {"type": "text", "text": "What do you see?"},
        image_content_block, # a base64 or url encoded image content
    ]
}

response1 = client.messages.create(
    max_tokens=1024,
    model="claude-3-5-haiku-latest",
    messages=[
        user_message1,
    ],
)

response2 = client.messages.create(
    max_tokens=1024,
    model="claude-3-5-haiku-latest",
    messages=[
        user_message1,
        {"role": "assistant", "content": response1.content},
        user_message2,
    ],
)

👍 Expected behavior

For the second span,

gen_ai.prompt.2.role=user
gen_ai.prompt.2.content='{"type": "text", "text": "What do you see?"}'

👎 Actual Behavior with Screenshots

There's no attributes for the last message on the second span

🤖 Python Version

3.13

📃 Provide any additional context for the Bug.

The error causes the function to fail, but @dont_throw results in it just dropping the last attributes

👀 Have you spent some time to check if this bug has been raised before?

• I checked and didn't find similar issue

Are you willing to submit PR?

Yes I am willing to submit a PR!