diff --git a/generic_rag/app.py b/generic_rag/app.py
index 274a7ac..c76a253 100644
--- a/generic_rag/app.py
+++ b/generic_rag/app.py
@@ -98,9 +98,8 @@ async def process_response(message):
 
     chainlit_response = cl.Message(content="")
 
-    response = graph.invoke(message.content, config=config)
-
-    await chainlit_response.stream_token(f"{response}\n")
+    for response in graph.stream(message.content, config=config):
+        await chainlit_response.stream_token(response)
 
     pdf_sources = graph.get_last_pdf_sources()
     if len(pdf_sources) > 0:
diff --git a/generic_rag/graphs/ret_gen.py b/generic_rag/graphs/ret_gen.py
index c30d6e2..3c332ed 100644
--- a/generic_rag/graphs/ret_gen.py
+++ b/generic_rag/graphs/ret_gen.py
@@ -3,7 +3,10 @@ from pathlib import Path
 from typing import Any, Union
 
 from langchain import hub
+from langchain_chroma import Chroma
 from langchain_core.documents import Document
+from langchain_core.embeddings import Embeddings
+from langchain_core.language_models.chat_models import BaseChatModel
 from langgraph.checkpoint.memory import MemorySaver
 from langgraph.graph import END, START, StateGraph
 from typing_extensions import List, TypedDict
@@ -19,7 +22,7 @@ class State(TypedDict):
 
 
 class RetGenLangGraph:
-    def __init__(self, vector_store, chat_model, embedding_model):
+    def __init__(self, vector_store: Chroma, chat_model: BaseChatModel, embedding_model: Embeddings):
         self.vector_store = vector_store
         self.chat_model = chat_model
         self.embedding_model = embedding_model
@@ -32,15 +35,15 @@ class RetGenLangGraph:
         graph_builder.add_edge("_generate", END)
 
         self.graph = graph_builder.compile(memory)
-        self.last_invoke = None
+        self.last_retrieved_docs = []
 
-    def invoke(self, message: str, config: dict) -> Union[dict[str, Any], Any]:
-        self.last_invoke = self.graph.invoke({"question": message}, config=config)
-        return self.last_invoke["answer"]
+    def stream(self, message: str, config: dict) -> Union[dict[str, Any], Any]:
+        for response, _ in self.graph.stream({"question": message}, stream_mode="messages", config=config):
+            yield response.content
 
     def _retrieve(self, state: State) -> dict:
-        retrieved_docs = self.vector_store.similarity_search(state["question"])
-        return {"context": retrieved_docs}
+        self.last_retrieved_docs = self.vector_store.similarity_search(state["question"])
+        return {"context": self.last_retrieved_docs}
 
     def _generate(self, state: State) -> dict:
         docs_content = "\n\n".join(doc.page_content for doc in state["context"])
@@ -54,30 +57,30 @@ class RetGenLangGraph:
         """
         pdf_sources = {}
 
-        if self.last_invoke is None:
+        if not self.last_retrieved_docs:
             return pdf_sources
 
-        for context in self.last_invoke["context"]:
+        for doc in self.last_retrieved_docs:
             try:
-                Path(context.metadata["source"]).suffix == ".pdf"
+                Path(doc.metadata["source"]).suffix == ".pdf"
             except KeyError:
                 continue
             else:
-                source = context.metadata["source"]
+                source = doc.metadata["source"]
 
             if source not in pdf_sources:
                 pdf_sources[source] = set()
 
             # The page numbers are in the `page_numer` and `page` fields.
             try:
-                page_number = context.metadata["page_number"]
+                page_number = doc.metadata["page_number"]
             except KeyError:
                 pass
             else:
                 pdf_sources[source].add(page_number)
 
             try:
-                page_number = context.metadata["page"]
+                page_number = doc.metadata["page"]
             except KeyError:
                 pass
             else:
@@ -94,15 +97,15 @@ class RetGenLangGraph:
         """
         web_sources = set()
 
-        if self.last_invoke is None:
+        if not self.last_retrieved_docs:
             return web_sources
 
-        for context in self.last_invoke["context"]:
+        for doc in self.last_retrieved_docs:
             try:
-                context.metadata["filetype"] == "web"
+                doc.metadata["filetype"] == "web"
             except KeyError:
                 continue
             else:
-                web_sources.add(context.metadata["source"])
+                web_sources.add(doc.metadata["source"])
 
         return web_sources