fix: Parse intermediate steps from LangChain into JSON.

PiperOrigin-RevId: 627444864

Author: yeesian

tests/unit/vertex_langchain/test_reasoning_engine_templates_langchain.py

@@ -29,6 +29,7 @@
 from langchain_core import messages
 from langchain_core import outputs
 from langchain_core import tools as lc_tools
+from langchain.load import dump as langchain_load_dump
 from langchain.tools.base import StructuredTool
 
 
@@ -77,6 +78,12 @@ def vertexai_init_mock():
         yield vertexai_init_mock
 
 
+@pytest.fixture
+def langchain_dump_mock():
+    with mock.patch.object(langchain_load_dump, "dumpd") as langchain_dump_mock:
+        yield langchain_dump_mock
+
+
 @pytest.mark.usefixtures("google_auth_mock")
 class TestLangchainAgent:
     def setup_method(self):
@@ -114,7 +121,7 @@ def test_set_up(self, vertexai_init_mock):
         agent.set_up()
         assert agent._runnable is not None
 
-    def test_query(self):
+    def test_query(self, langchain_dump_mock):
         agent = reasoning_engines.LangchainAgent(model=_TEST_MODEL)
         agent._runnable = mock.Mock()
         mocks = mock.Mock()

vertexai/preview/reasoning_engines/templates/langchain.py

@@ -18,6 +18,7 @@
     TYPE_CHECKING,
     Any,
     Callable,
+    Dict,
     List,
     Mapping,
     Optional,
@@ -418,7 +419,7 @@ def query(
         input: Union[str, Mapping[str, Any]],
         config: Optional["RunnableConfig"] = None,
         **kwargs: Any,
-    ) -> Mapping[str, Any]:
+    ) -> Dict[str, Any]:
         """Queries the Agent with the given input and config.
 
         Args:
@@ -433,8 +434,11 @@ def query(
         Returns:
             The output of querying the Agent with the given input and config.
         """
+        from langchain.load import dump as langchain_load_dump
         if isinstance(input, str):
             input = {"input": input}
         if not self._runnable:
             self.set_up()
-        return self._runnable.invoke(input=input, config=config, **kwargs)
+        return langchain_load_dump.dumpd(
+            self._runnable.invoke(input=input, config=config, **kwargs)
+        )