Bedrock Agent Return Control responses are returned as Java toString() output instead of JSON

[borghol]

Describe the bug

When invoking a Bedrock Agent using the AWS Java SDK (v2), the response event payload is being transformed into a Java object’s toString() output instead of proper JSON. This makes the response unusable without doing custom parsing or regex cleanup.

Environment:
• SDK: aws-java-sdk-v2
• Service: Bedrock Agent Runtime
• Invocation method: InvokeAgentRequest via BedrockAgentRuntimeClient
• Language: Java 17 (adjust if necessary)

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

Responses should be provided as valid JSON strings, or at least as strongly typed objects representing the Bedrock Agent event model. At a minimum, there should be a documented utility for converting the SDK event types to raw JSON.

Current Behavior

The agent returns structured JSON (e.g. {"type": "TEXT", "text": "Hello"}) in the parameter value, but the SDK surfaces it as something like:

{type=TEXT, text=Hello}

Reproduction Steps

• Set up Bedrock Action Group to return control with an API schema that returns an object in its body, i.e.:

{ "productId": "123", "quantity": 3}

When called, the return control value will be:

{ productId=123, quantity=3 }

Possible Solution

Parameters should be returned as the JSON string supplied by the agent and not the marshalled version of Java's SDK

Additional Information/Context

No response

AWS Java SDK version used

2.38.2

JDK version used

17

Operating System and version

MacOS locally, amazoncorretto:17 docker image

[borghol]

Just an example taken from the console:

You can see on the right that the input is actually correct JSON, but the console (and the SDK) seem to drop any double quotes that it encounters in the input