[BUG] Passing SageMakerAIEndpointConfig additional_args raises error

[athewsey]

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

1.10

Python Version

3.13.3

Operating System

macOS 15.7

Installation Method

pip

Steps to Reproduce

1. Create a Strands SageMakerAIModel with a dict of additional_args in the endpoint config, for example:

model = SageMakerAIModel(
    endpoint_config={
        "endpoint_name": "{your-endpoint}",
        "additional_args": {
            "TargetContainerHostname": "my-cool-container",
        },
    },
)

2. Try to invoke the model (either direct or via an agent)

Expected Behavior

The additional_args should be passed through to the SageMaker AI endpoint.

Actual Behavior

Invocation fails with error at this line:

AttributeError: 'dict' object has no attribute '__dict__'

Additional Context

(At least in CPython 3.12 and 3.13 on macOS), it seems that dictionary objects don't have a __dict__ property. Maybe there are some other versions or platforms where this is/was working? I couldn't tell for sure from the Python docs.

The equivalent section in Strands BedrockModel is not broken, because it just directly passes through the self.config["additional_args"] rather than attempting to fetch .__dict__ of it.

Possible Solution

Since additional_args is type-hinted as a Python dictionary, I suggest the fix should be to remove the unnecessary .__dict__ accessor and just stick with:

# Add additional args if provided
if self.endpoint_config.get("additional_args"):
    request.update(self.endpoint_config["additional_args"])

Related Issues

No response