litellm - 💡(How to fix) Fix Anthropic message format validation doesn't reject unsupported image URL sources in /v1/messages endpoint [1 comments, 1 participants]

Expected: HTTP 400 with validation error (matching /v1/chat/completions behavior) Actual: Request passes proxy validation, fails at Anthropic with opaque error

1. Inconsistent Error Messages — Same invalid request format succeeds validation in one endpoint but fails in another
2. Delayed Error Detection — Client gets generic provider error instead of clear proxy validation feedback

• /v1/messages with Anthropic + image URL source → HTTP 400 validation error
• /v1/chat/completions with Anthropic + image URL source → HTTP 400 validation error (existing behavior)

Fix Plan

To address the inconsistency, we need to add provider capability checking in the /v1/messages endpoint. Here are the steps:

• Update the validation logic for the /v1/messages endpoint to check the image source type.
• If the source type is a URL and the provider does not support it, return an HTTP 400 error with a validation message.

Example code snippet in Python:

from flask import request, jsonify

# Define a function to check provider capabilities
def check_provider_capabilities(provider, source_type):
    # For example, Anthropic does not support URL sources
    if provider == "anthropic" and source_type == "url":
        return False
    # Add more provider capabilities as needed
    return True

# Update the /v1/messages endpoint to include validation
@app.route('/v1/messages', methods=['POST'])
def handle_messages():
    data = request.get_json()
    # Check the image source type
    for message in data['messages']:
        for content in message['content']:
            if content['type'] == 'image' and not check_provider_capabilities(data['model'], content['source']['type']):
                return jsonify({'error': 'URL sources are not supported'}), 400
    # If validation passes, proceed with the request
    # ...

Verification

To verify the fix, test the following scenarios:

• Send a request to /v1/messages with Anthropic as the provider and an image URL source. The response should be an HTTP 400 error with a validation message.
• Send a request to /v1/chat/completions with Anthropic as the provider and an image URL source. The response should still be an HTTP 400 error with a validation message (existing behavior).
• Send a request to /v1/messages with a provider that supports image URLs (e.g., OpenAI) and an image URL source. The request should succeed.

Extra Tips

• Ensure that the check_provider_capabilities function is updated to include capabilities for all supported providers.
• Consider adding more robust error handling and logging to help with debugging and monitoring.