[BUG] System prompt is not passed when using structured output in Bedrock

[jeromevdl]

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

0.2.1

Python Version

3.11

Operating System

macOS 15.5

Installation Method

pip

Steps to Reproduce

1. Install strands using pip (requirements.txt)
2. Use the following code:

bedrock_model = BedrockModel(
            model_id="eu.amazon.nova-lite-v1:0",
            temperature=0.0,
            top_p=0.5,
            region_name="eu-central-1",
            streaming=False,
            cache_prompt="default"  # cache system prompt
        )
agent = Agent(model=bedrock_model, system_prompt="....")
result = agent.structured_output(Model, prompt="...")

Expected Behavior

The model is called both with the prompt and system prompt, and caches the system prompt, and return the structured output.

Actual Behavior

An error occurred (ValidationException) when calling the Converse operation: There is nothing available to cache. Please remove the invalid cache point and try again.

Additional Context

Looking at the code, the system prompt is not passed to the converse method in structured_output() (here)
So it's not an issue of caching, but rather that system prompt is not passed (and therefore caching cannot work).

Possible Solution

No response

Related Issues

No response

[zastrowm]

Hey, thanks for the bug report. This is indeed a bug and I think we need to address this before 1.0 as adding a new parameter could be a breaking change. I will take a look at fixing this.

[zastrowm]

This was merged via #466 and should make it into the next release

[macsir]

Tried using the fix from the main branch but still seeing the same error when cache is enabled with bedrock model.

{'role': 'user', 'content': [{'toolResult': {'toolUseId': 'tooluse_cDzX_sCWQzqsKLspSBiyCA', 'status': 'error', 'content': [{'text': 'Error: ValidationException - An error occurred (ValidationException) when calling the Converse operation: There is nothing available to cache. Please remove the invalid cache point and try again.'}]}}]}