[FEATURE] Update GuardContent class to include image field

[JackYPCOnline]

Problem Statement

We're adding a guardrail_latest_message feature flag to the Bedrock model provider. When enabled, only text and image content in the latest user message will be wrapped in guardContent.

Currently our GuardContent class only has text field, we should add image as well.

Proposed Solution

We should add image, reference:

format
The format details for the image type of the guardrail converse image block.

Type: String

Valid Values: png | jpeg

Required: Yes

source
The image source (image bytes) of the guardrail converse image block.

Type: [GuardrailConverseImageSource](https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_GuardrailConverseImageSource.html) object

Note: This object is a Union. Only one member of this object can be specified or returned.

Required: Yes

Use Case

when GuardContent is used.

Alternatives Solutions

No response

Additional Context

No response

[JackYPCOnline]

/strands

[github-actions]

Repository Analysis & Clarifying Questions

Repository Context

I've analyzed the repository structure and current implementation. Here's what I found:

Current State

• GuardContent class: Located in src/strands/types/content.py (lines 30-37)
• Current structure: Only has text field of type GuardContentText
• Usage: Referenced in ContentBlock TypedDict and used in src/strands/models/bedrock.py (lines 412-416)
• AWS API: GuardrailConverseContentBlock is a UNION type - only one of text or image can be present

Implementation Requirements

Based on AWS Bedrock API documentation for GuardrailConverseImageBlock:

1. format: String - Valid values are png | jpeg (more restrictive than the existing ImageFormat)
2. source: GuardrailConverseImageSource object with bytes field

Related Code

The bedrock.py file currently only handles the text field in guardContent (lines 412-416). After adding the image field to the type, this code will need to handle both text and image cases, similar to how regular images are handled at lines 418-426.

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Clarifying Questions

1. Scope of Implementation

Should the bedrock.py update be included in this task?

• The type definition change in content.py is clear
• However, src/strands/models/bedrock.py lines 412-416 will need updating to handle the new image field
• Should this bedrock.py change be part of this PR, or would you prefer a separate follow-up PR?

2. Test Coverage

Should tests be included in this implementation?

• Currently, there are no tests for guardContent functionality
• Should I add tests for:
  • GuardContent with text field
  • GuardContent with image field
  • Bedrock model handling of guardContent with both types
• Or should tests be added in a separate PR?

3. Union Type Constraint

Do we need runtime validation for the union constraint?

• AWS API specifies GuardrailConverseContentBlock is a UNION (only one of text/image)
• The TypedDict will make both fields optional (using total=False)
• Should we add runtime validation to ensure exactly one field is present, or rely on AWS API validation?

4. Documentation Updates

Are there documentation files beyond docstrings that need updating?

• I'll update the docstrings in the type definitions
• Are there any other documentation files (e.g., in docs/ directory) that reference GuardContent and should be updated?

5. Integration Context

Is this change blocking the guardrail_latest_message feature?

• The issue mentions this is needed for the "guardrail_latest_message feature flag"
• Should I be aware of any timeline or dependencies with that feature implementation?

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Please let me know your preferences on these points so I can ensure the implementation meets your expectations!

[JackYPCOnline]

/strands implement

[github-actions]

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[JackYPCOnline]

Summerize the comments:

This is a valid use case , we need to include it. https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_GuardrailConverseImageBlock.html
This is a breaking change, we need to update the code in SDK to handle this case.
https://github.com/strands-agents/sdk-python/blob/main/src/strands/models/bedrock.py#L430
No user requests this for now.
Conclusion, close this ticket for now. Should revisit this in 2.0. Keep the issue open.