Python: Include sub-workflow structure in graph signature for checkpoint validation (#3783)

* Include sub-workflow structure in graph signature for checkpoint validation

* Remove redundant computation

python/packages/core/tests/workflow/test_checkpoint_validation.py

@@ -7,6 +7,7 @@ from agent_framework import (
     WorkflowBuilder,
     WorkflowCheckpointException,
     WorkflowContext,
+    WorkflowExecutor,
     WorkflowRunState,
     handler,
 )
@@ -81,3 +82,87 @@ async def test_resume_succeeds_when_graph_matches() -> None:
     ]
 
     assert any(event.type == "status" and event.state == WorkflowRunState.IDLE for event in events)
+
+
+# -- Sub-workflow checkpoint validation tests --
+
+
+class SubStartExecutor(Executor):
+    @handler
+    async def run(self, message: str, ctx: WorkflowContext[str]) -> None:
+        await ctx.send_message(message)
+
+
+class SubFinishExecutor(Executor):
+    @handler
+    async def finish(self, message: str, ctx: WorkflowContext[Never, str]) -> None:
+        await ctx.yield_output(message)
+
+
+def build_sub_workflow(sub_finish_id: str = "sub_finish"):
+    sub_start = SubStartExecutor(id="sub_start")
+    sub_finish = SubFinishExecutor(id=sub_finish_id)
+    return WorkflowBuilder(start_executor=sub_start).add_edge(sub_start, sub_finish).build()
+
+
+def build_parent_workflow(storage: InMemoryCheckpointStorage, sub_finish_id: str = "sub_finish"):
+    sub_workflow = build_sub_workflow(sub_finish_id=sub_finish_id)
+    sub_executor = WorkflowExecutor(sub_workflow, id="sub_wf", allow_direct_output=True)
+
+    start = StartExecutor(id="start")
+    finish = FinishExecutor(id="finish")
+
+    builder = (
+        WorkflowBuilder(max_iterations=3, start_executor=start, checkpoint_storage=storage)
+        .add_edge(start, sub_executor)
+        .add_edge(sub_executor, finish)
+    )
+    return builder.build()
+
+
+async def test_resume_succeeds_when_sub_workflow_matches() -> None:
+    storage = InMemoryCheckpointStorage()
+    workflow = build_parent_workflow(storage, sub_finish_id="sub_finish")
+
+    _ = [event async for event in workflow.run("hello", stream=True)]
+
+    checkpoints = await storage.list_checkpoints()
+    assert checkpoints, "expected at least one checkpoint to be created"
+    target_checkpoint = checkpoints[-1]
+
+    resumed_workflow = build_parent_workflow(storage, sub_finish_id="sub_finish")
+
+    events = [
+        event
+        async for event in resumed_workflow.run(
+            checkpoint_id=target_checkpoint.checkpoint_id,
+            checkpoint_storage=storage,
+            stream=True,
+        )
+    ]
+
+    assert any(event.type == "status" and event.state == WorkflowRunState.IDLE for event in events)
+
+
+async def test_resume_fails_when_sub_workflow_changes() -> None:
+    storage = InMemoryCheckpointStorage()
+    workflow = build_parent_workflow(storage, sub_finish_id="sub_finish")
+
+    _ = [event async for event in workflow.run("hello", stream=True)]
+
+    checkpoints = await storage.list_checkpoints()
+    assert checkpoints, "expected at least one checkpoint to be created"
+    target_checkpoint = checkpoints[-1]
+
+    # Build parent with a structurally different sub-workflow (different executor id inside)
+    mismatched_workflow = build_parent_workflow(storage, sub_finish_id="sub_finish_alt")
+
+    with pytest.raises(WorkflowCheckpointException, match="Workflow graph has changed"):
+        _ = [
+            event
+            async for event in mismatched_workflow.run(
+                checkpoint_id=target_checkpoint.checkpoint_id,
+                checkpoint_storage=storage,
+                stream=True,
+            )
+        ]