diff --git a/app/chat_store.py b/app/chat_store.py
new file mode 100644
index 0000000..4c8e2b3
--- /dev/null
+++ b/app/chat_store.py
@@ -0,0 +1,20 @@
+# All comments are in English.
+
+import uuid
+
+class ChatStore:
+    """Simple in-memory chat store with multiple conversations."""
+
+    def __init__(self):
+        self.conversations = {}
+
+    def new_conversation(self):
+        cid = str(uuid.uuid4())
+        self.conversations[cid] = []
+        return cid
+
+    def add_message(self, cid, role, content):
+        self.conversations[cid].append({"role": role, "content": content})
+
+    def get_messages(self, cid):
+        return self.conversations.get(cid, [])