Python: Fix WorkflowAgent to include thread convo history. Enable checkpointing.

[moonbox3]

Motivation and Context

Fixes #2754 - Workflows wrapped as agents via as_agent() now properly include thread conversation history when running.

When using workflow.as_agent() with an AgentThread, the thread's conversation history was not being passed to the workflow execution. This caused the workflow participants to lose context from previous turns, making multi-turn conversations impossible.

Modified WorkflowAgent._run_stream_impl() to retrieve messages from thread.message_store.list_messages() and prepend them to the input messages before calling workflow.run_stream().

Also added support for checkpoint_id and checkpoint_storage parameters in WorkflowAgent.run() and run_stream() to enable workflow state persistence.

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_agent.py	241	41	82%	56, 64–70, 98–99, 250, 292, 332–335, 341, 347, 351–352, 355–361, 365–366, 405, 412, 418–419, 425, 437, 469, 476, 497, 504, 508, 519
TOTAL	16610	2573	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2392	130 💤	0 ❌	0 🔥	56.664s ⏱️

[Copilot]

Pull request overview

This pull request fixes issue #2754 by enabling WorkflowAgent to properly include thread conversation history when running workflows and adds support for checkpoint storage parameters.

Key changes:

• Modified _run_stream_impl() to retrieve and prepend thread message history to input messages for workflow execution
• Added checkpoint_id and checkpoint_storage parameters to WorkflowAgent.run() and run_stream() methods
• Added comprehensive test coverage for thread history handling and checkpoint storage integration

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
python/packages/core/agent_framework/_workflows/_agent.py	Core implementation: added checkpoint parameters to run/run_stream methods and modified _run_stream_impl to prepend thread history to messages before workflow execution
python/packages/core/tests/workflow/test_workflow_agent.py	Added ConversationHistoryCapturingExecutor test helper and four new test cases covering thread history inclusion, empty threads, and checkpoint storage
python/samples/getting_started/workflows/agents/workflow_as_agent_with_thread.py	New sample demonstrating multi-turn conversations with workflow-as-agent using AgentThread for conversation history persistence
python/samples/getting_started/workflows/checkpoint/workflow_as_agent_checkpoint.py	New sample demonstrating checkpoint storage usage with workflow-as-agent for state persistence and resume capability
python/samples/getting_started/workflows/README.md	Added table entries for the two new sample files in the agents and checkpoint sections

[Copilot]

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