diff --git a/backend/open_webui/migrations/versions/8452d01d26d7_add_chat_message_table.py b/backend/open_webui/migrations/versions/8452d01d26d7_add_chat_message_table.py
index 3b178e60cb..e774ff11d2 100644
--- a/backend/open_webui/migrations/versions/8452d01d26d7_add_chat_message_table.py
+++ b/backend/open_webui/migrations/versions/8452d01d26d7_add_chat_message_table.py
@@ -137,7 +137,7 @@ def upgrade() -> None:
             try:
                 conn.execute(
                     sa.insert(chat_message_table).values(
-                        id=message_id,
+                        id=f"{chat_id}-{message_id}",
                         chat_id=chat_id,
                         user_id=user_id,
                         role=role,
diff --git a/backend/open_webui/models/chat_messages.py b/backend/open_webui/models/chat_messages.py
index bc7508d45e..88d1c9ff7c 100644
--- a/backend/open_webui/models/chat_messages.py
+++ b/backend/open_webui/models/chat_messages.py
@@ -137,7 +137,10 @@ class ChatMessageTable:
             now = int(time.time())
             timestamp = data.get("timestamp", now)
 
-            existing = db.get(ChatMessage, message_id)
+            # Use composite ID: {chat_id}-{message_id}
+            composite_id = f"{chat_id}-{message_id}"
+
+            existing = db.get(ChatMessage, composite_id)
             if existing:
                 # Update existing
                 if "role" in data:
@@ -183,7 +186,7 @@ class ChatMessageTable:
                     info = data.get("info", {})
                     usage = info.get("usage") if info else None
                 message = ChatMessage(
-                    id=message_id,
+                    id=composite_id,
                     chat_id=chat_id,
                     user_id=user_id,
                     role=data.get("role", "user"),