fix: mcp enable check (#2049)

* fix: mcp enable check

* chore: changelog

Author: willydouhard

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to Chainlit will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [2.4.301] - 2025-03-24
+
+### Fixed
+
+- Mcp button should not be displayed if `@on_mcp_connect` is not defined
+
 ## [2.4.3] - 2025-03-23
 
 ### Added

backend/chainlit/config.py

@@ -116,9 +116,6 @@
     # Sample rate of the audio
     sample_rate = 24000
 
-[features.mcp]
-    enabled = true
-
 [features.mcp.sse]
     enabled = true
 
@@ -239,7 +236,7 @@ class McpStdioFeature(DataClassJsonMixin):
 
 @dataclass
 class McpFeature(DataClassJsonMixin):
-    enabled: bool = True
+    enabled: bool = False
     sse: McpSseFeature = Field(default_factory=McpSseFeature)
     stdio: McpStdioFeature = Field(default_factory=McpStdioFeature)
 

backend/chainlit/server.py

@@ -761,6 +761,9 @@ async def project_settings(
     if config.code.on_audio_chunk:
         config.features.audio.enabled = True
 
+    if config.code.on_mcp_connect:
+        config.features.mcp.enabled = True
+
     debug_url = None
     data_layer = get_data_layer()
 
@@ -1091,7 +1094,7 @@ async def connect_mcp(
                 status_code=401,
             )
 
-    mcp_enabled = config.features.mcp.enabled and config.code.on_mcp_connect is not None
+    mcp_enabled = config.code.on_mcp_connect is not None
     if mcp_enabled:
         if payload.name in session.mcp_sessions:
             old_client_session, old_exit_stack = session.mcp_sessions[payload.name]

backend/chainlit/version.py

@@ -5,4 +5,4 @@
 except metadata.PackageNotFoundError:
     # Case where package metadata is not available, default to a 'non-outdated' version.
     # Ref: config.py::load_settings()
-    __version__ = "2.4.3"
+    __version__ = "2.4.301"

backend/pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "chainlit"
-version = "2.4.3"
+version = "2.4.301"
 keywords = [
     'LLM',
     'Agents',

frontend/src/components/chat/MessageComposer/Mcp/AddForm.tsx

@@ -23,15 +23,24 @@ import { Translator } from 'components/i18n';
 interface McpAddFormProps {
   onSuccess: () => void;
   onCancel: () => void;
+  allowStdio?: boolean;
+  allowSse?: boolean;
 }
 
-export const McpAddForm = ({ onSuccess, onCancel }: McpAddFormProps) => {
+export const McpAddForm = ({
+  onSuccess,
+  onCancel,
+  allowStdio,
+  allowSse
+}: McpAddFormProps) => {
   const apiClient = useContext(ChainlitContext);
   const sessionId = useRecoilValue(sessionIdState);
   const setMcps = useSetRecoilState(mcpState);
 
   const [serverName, setServerName] = useState('');
-  const [serverType, setServerType] = useState<'stdio' | 'sse'>('stdio');
+  const [serverType, setServerType] = useState<'stdio' | 'sse'>(
+    allowStdio ? 'stdio' : 'sse'
+  );
   const [serverUrl, setServerUrl] = useState('');
   const [serverCommand, setServerCommand] = useState('');
   const [isLoading, setIsLoading] = useState(false);
@@ -131,8 +140,10 @@ export const McpAddForm = ({ onSuccess, onCancel }: McpAddFormProps) => {
                 <SelectValue placeholder="Type" />
               </SelectTrigger>
               <SelectContent>
-                <SelectItem value="sse">sse</SelectItem>
-                <SelectItem value="stdio">stdio</SelectItem>
+                {allowSse ? <SelectItem value="sse">sse</SelectItem> : null}
+                {allowStdio ? (
+                  <SelectItem value="stdio">stdio</SelectItem>
+                ) : null}
               </SelectContent>
             </Select>
           </div>

frontend/src/components/chat/MessageComposer/Mcp/index.tsx

@@ -32,11 +32,14 @@ const McpButton = ({ disabled }: Props) => {
   const { config } = useConfig();
   const [mcps] = useRecoilState(mcpState);
 
-  const isEnabled = !!config?.features.mcp;
   const [open, setOpen] = useState(false);
   const [activeTab, setActiveTab] = useState('add');
 
-  if (!isEnabled) return null;
+  const allowSse = !!config?.features.mcp?.sse?.enabled;
+  const allowStdio = !!config?.features.mcp?.stdio?.enabled;
+  const allowMcp = !!config?.features.mcp?.enabled;
+
+  if (!allowMcp || (!allowSse && !allowStdio)) return null;
 
   const connectedMcps = mcps.filter((mcp) => mcp.status === 'connected');
 
@@ -90,6 +93,8 @@ const McpButton = ({ disabled }: Props) => {
             className="flex flex-col flex-grow gap-6 p-1"
           >
             <McpAddForm
+              allowSse={allowSse}
+              allowStdio={allowStdio}
               onSuccess={() => setActiveTab('list')}
               onCancel={() => setOpen(false)}
             />

libs/react-client/src/types/config.ts

@@ -53,7 +53,15 @@ export interface IChainlitConfig {
     user_message_autoscroll?: boolean;
     latex?: boolean;
     edit_message?: boolean;
-    mcp?: boolean;
+    mcp?: {
+      enabled?: boolean;
+      sse?: {
+        enabled?: boolean;
+      };
+      stdio?: {
+        enabled?: boolean;
+      };
+    };
   };
   debugUrl?: string;
   userEnv: string[];