fix(workflow): sync iteration conversation variables (#26368)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/tests/unit_tests/core/workflow/graph_engine/test_update_conversation_variable_iteration.py

@@ -0,0 +1,41 @@
+"""Validate conversation variable updates inside an iteration workflow.
+
+This test uses the ``update-conversation-variable-in-iteration`` fixture, which
+routes ``sys.query`` into the conversation variable ``answer`` from within an
+iteration container. The workflow should surface that updated conversation
+variable in the final answer output.
+
+Code nodes in the fixture are mocked because their concrete outputs are not
+relevant to verifying variable propagation semantics.
+"""
+
+from .test_mock_config import MockConfigBuilder
+from .test_table_runner import TableTestRunner, WorkflowTestCase
+
+
+def test_update_conversation_variable_in_iteration():
+    fixture_name = "update-conversation-variable-in-iteration"
+    user_query = "ensure conversation variable syncs"
+
+    mock_config = (
+        MockConfigBuilder()
+        .with_node_output("1759032363865", {"result": [1]})
+        .with_node_output("1759032476318", {"result": ""})
+        .build()
+    )
+
+    case = WorkflowTestCase(
+        fixture_path=fixture_name,
+        use_auto_mock=True,
+        mock_config=mock_config,
+        query=user_query,
+        expected_outputs={"answer": user_query},
+        description="Conversation variable updated within iteration should flow to answer output.",
+    )
+
+    runner = TableTestRunner()
+    result = runner.run_test_case(case)
+
+    assert result.success, f"Workflow execution failed: {result.error}"
+    assert result.actual_outputs is not None
+    assert result.actual_outputs.get("answer") == user_query