fix: convert local file paths to base64 in AddImageTool for Anthropic compatibility

[devin-ai-integration]

Summary

Fixes #3984

AddImageTool now converts local file paths to base64 data URLs before returning them to the LLM. This enables multimodal functionality with Anthropic models (Claude 3.5 Sonnet, etc.) which require images in base64 format rather than raw file paths.

The new _normalize_image_url method handles:

• HTTP/HTTPS URLs → returned unchanged
• Data URLs → returned unchanged
• file:// URLs → converted to base64 data URLs
• Local file paths (absolute, relative, ~ expansion) → converted to base64 data URLs
• Unknown schemes (e.g., s3://) → returned unchanged (allows downstream handling)

Review & Testing Checklist for Human

• Test with Anthropic API: The unit tests verify base64 conversion logic but don't test actual Anthropic API calls. Please test a multimodal agent with Claude 3.5 Sonnet using a local image file to confirm the fix works end-to-end.
• Regression test with OpenAI: Verify that HTTP URLs still work correctly with OpenAI's vision models (should be unchanged behavior).
• Large file behavior: No size limit is enforced when reading files into memory. Consider testing with a large image (10MB+) to verify acceptable behavior.

Recommended Test Plan

from crewai import Agent, Task, Crew

agent = Agent(
    role="Image Analyst",
    goal="Analyze images",
    backstory="Expert at analyzing images",
    llm="anthropic/claude-3-5-sonnet-20241022",  # or your Anthropic model
    multimodal=True,
)

task = Task(
    description="Describe the image at /path/to/local/image.png",
    expected_output="A description of the image",
    agent=agent,
)

crew = Crew(agents=[agent], tasks=[task])
result = crew.kickoff()

Notes

• Link to Devin run: https://app.devin.ai/sessions/4ccdc6014e954ba09a668688c516918f
• Requested by: João ([email protected])

[devin-ai-integration]

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