diff --git a/src/wcgw/client/tools.py b/src/wcgw/client/tools.py
index 47f39ea..662fe67 100644
--- a/src/wcgw/client/tools.py
+++ b/src/wcgw/client/tools.py
@@ -744,6 +744,7 @@ class Mdata(BaseModel):
         | ResetShell
         | FileEditFindReplace
         | FullFileEdit
+        | str
     )
 
 
@@ -768,6 +769,8 @@ def register_client(server_url: str, client_uuid: str = "") -> None:
                 # Wait to receive data from the server
                 message = websocket.recv()
                 mdata = Mdata.model_validate_json(message)
+                if isinstance(mdata.data, str):
+                    raise Exception(mdata)
                 try:
                     output, cost = get_tool_output(
                         mdata.data, default_enc, 0.0, lambda x, y: ("", 0), None
diff --git a/src/wcgw/relay/serve.py b/src/wcgw/relay/serve.py
index 9e8d6f9..cd83208 100644
--- a/src/wcgw/relay/serve.py
+++ b/src/wcgw/relay/serve.py
@@ -35,6 +35,7 @@ class Mdata(BaseModel):
         | ResetShell
         | FileEditFindReplace
         | FullFileEdit
+        | str
     )
     user_id: UUID
 
@@ -65,7 +66,10 @@ async def register_websocket(websocket: WebSocket, uuid: UUID) -> None:
     sem_version_server = semantic_version.Version.coerce(CLIENT_VERSION_MINIMUM)
     if sem_version_client < sem_version_server:
         await websocket.send_text(
-            f"Client version {client_version} is outdated. Please upgrade to {CLIENT_VERSION_MINIMUM} or higher."
+            Mdata(
+                user_id=uuid,
+                data=f"Client version {client_version} is outdated. Please upgrade to {CLIENT_VERSION_MINIMUM} or higher.",
+            ).model_dump_json()
         )
         await websocket.close(
             reason="Client version outdated. Please upgrade to the latest version.",