.NET: [Bug]: Declarative Workflows - Gracefully handle agent scenarios where no response is returned

[peibekwe]

Description

Declarative workflow runs that include InvokeAzureAgent actions could crash with:

Unhandled workflow failure - #<action_id> (InvokeAzureAgent)
→ System.InvalidOperationException: Sequence contains no elements

The crash is deterministic whenever an invoked agent returns an AgentResponse with zero Messages (e.g., a tool-only
turn where the model emits remote_function_call / mcp_call items without a final assistant text message,
content-filtered responses, or streams that close before the terminal assistant message).

Code Sample

Error Messages / Stack Traces

Package Versions

Microsoft.Agents.AI.Workflows.Declarative

.NET Version

No response

Additional Context

No response