APPLICATION_LOGS response_payload always null for non-streaming Strands agents

[thiti-sutj]

Description

Problem

response_payload in APPLICATION_LOGS is always null, even though request_payload works fine.

Setup

• Strands Agent deployed via agentcore deploy
• Non-streaming: @app.entrypoint def invoke(...) returns plain dict
• bedrock-agentcore 1.6.3, strands-agents 1.35.0, region us-east-1
• APPLICATION_LOGS delivery: CWL, response_payload is in recordFields

What I see

{
  "request_payload": {"message": "hi", "user_type": "tourist"},
  "response_payload": null
}

What I tried

Changed return format to {"result": "..."} → still null
Toggled recordFields → still null
IAM permissions correct, Tracing enabled

Question

Is response_payload only populated for SSE streaming responses (not plain JSON return)?

Or is there a config I'm missing?

Steps to Reproduce

1. Deploy a Strands agent with agentcore deploy — use non-streaming entrypoint:

   @app.entrypoint
   def invoke(payload, context):
       agent = Agent(model=..., tools=[...])
       result = agent(payload.get("message"))
       return {"result": str(result)}

2.Enable APPLICATION_LOGS delivery to CloudWatch (via console or put-delivery-source)
3.Invoke the deployed agent via Agent Sandbox or invoke_agent_runtime API
4.Open CloudWatch → log group /aws/vendedlogs/bedrock-agentcore/runtime/APPLICATION_LOGS/
5.Observe: response_payload is null while request_payload is populated

Expected Behavior

response_payload in APPLICATION_LOGS should contain the agent's return dict, e.g. {"result": "..."}.

Actual Behavior

response_payload is always null, even though request_payload is populated and the agent responds correctly to clients.

CLI Version

0.8.2

Operating System

Windows

Additional Context

No response