diff --git a/nemoguardrails/integrations/langchain/runnable_rails.py b/nemoguardrails/integrations/langchain/runnable_rails.py
index 54b68d383..74ad50937 100644
--- a/nemoguardrails/integrations/langchain/runnable_rails.py
+++ b/nemoguardrails/integrations/langchain/runnable_rails.py
@@ -16,9 +16,11 @@
 from __future__ import annotations
 
 import logging
-from typing import Any, AsyncIterator, Dict, Iterator, List, Optional, Union
+from typing import Any, AsyncIterator, Dict, Iterator, List, Optional, Union, cast
 
-from langchain_core.language_models import BaseLanguageModel
+from langchain_core.language_models import BaseChatModel, BaseLanguageModel
+from langchain_core.language_models.llms import BaseLLM
+from langchain_core.messages import AIMessage, HumanMessage, SystemMessage
 from langchain_core.prompt_values import ChatPromptValue, StringPromptValue
 from langchain_core.runnables import Runnable, RunnableConfig
 from langchain_core.runnables.utils import Input, Output, gather_with_concurrency
@@ -33,7 +35,7 @@
     message_to_dict,
 )
 from nemoguardrails.integrations.langchain.utils import async_wrap
-from nemoguardrails.rails.llm.options import GenerationOptions
+from nemoguardrails.rails.llm.options import GenerationOptions, GenerationResponse
 
 logger = logging.getLogger(__name__)
 
@@ -62,7 +64,7 @@ class RunnableRails(Runnable[Input, Output]):
     def __init__(
         self,
         config: RailsConfig,
-        llm: Optional[BaseLanguageModel] = None,
+        llm: Optional[Union[BaseLLM, BaseChatModel]] = None,
         tools: Optional[List[Tool]] = None,
         passthrough: bool = True,
         runnable: Optional[Runnable] = None,
@@ -110,7 +112,7 @@ def __init__(
         if self.passthrough_runnable:
             self._init_passthrough_fn()
 
-    def _init_passthrough_fn(self):
+    def _init_passthrough_fn(self) -> None:
         """Initialize the passthrough function for the LLM rails instance."""
 
         async def passthrough_fn(context: dict, events: List[dict]):
@@ -134,7 +136,8 @@ async def passthrough_fn(context: dict, events: List[dict]):
 
             return text, _output
 
-        self.rails.llm_generation_actions.passthrough_fn = passthrough_fn
+        # Dynamically assign passthrough_fn to avoid type checker issues
+        setattr(self.rails.llm_generation_actions, "passthrough_fn", passthrough_fn)
 
     def __or__(
         self, other: Union[BaseLanguageModel, Runnable[Any, Any]]
@@ -687,6 +690,9 @@ def _full_rails_invoke(
         res = self.rails.generate(
             messages=input_messages, options=GenerationOptions(output_vars=True)
         )
+        # When using output_vars=True, rails.generate returns a GenerationResponse
+        if not isinstance(res, GenerationResponse):
+            raise Exception(f"Expected GenerationResponse, got {type(res)}")
         context = res.output_data
         result = res.response