[BUG] Bedrock provider has stricter Message requirements than other providers

[zastrowm]

Checks

• I have updated to the lastest minor and patch version of Strands
• I have checked the documentation and this is not expected behavior
• I have searched ./issues and there are no duplicates of my issue

Strands Version

source

Python Version

3.13

Operating System

macOS

Installation Method

git clone

Steps to Reproduce

With a local image, attempt to use the following code/tool:

@tool
def tool_with_image_return():
    with open(test_image_path, "rb") as image_file:
        encoded_image = image_file.read()

    return {
        "status": "success",
        "content": [
            {
                "image": {
                    "format": "png",
                    "filename": test_image_path, # this is the problem!
                    "source": {"bytes": encoded_image},
                }
            },
        ],
    }

agent = Agent(tools=[tool_with_image_return])
agent("Run the the tool and analyze the image")

Expected Behavior

The agent runs and succeeds when using Bedrock, or Anthropic, or OpenAI

Actual Behavior

The agent runs and succeeds when using Anthropic or OpenAI, but throws the following error in Bedrock:

E strands.types.exceptions.EventLoopException: Parameter validation failed:
E Unknown parameter in messages[2].content[0].toolResult.content[0].image: "filename", must be one of: format, source

../src/strands/event_loop/event_loop.py:248: EventLoopException

Additional Context

This is most likely due to the fact that messages are passed through to the Bedrock provider directly, while for the other providers they're transformed, ignoring extra content.

Possible Solution

Update Bedrock to transform contents in the same way as other providers

-- or --

Make other providers fail in the same way

Related Issues

No response

[zastrowm]

There's two parts here:

• Long-term, we'd like to see the Bedrock provider be much more strict in what data is passes/what the inputs are. But that would be a 2.0 thing as it'd probably be a breaking change
• For this this bug specifically, we're going to exclude the field when passing to bedrock. [FEATURE] Support of image source URL in image content #343