fix: inspector connector status and transport improvements

packages/cli/CHANGELOG.md

@@ -1,5 +1,13 @@
 # @mcp-use/cli
 
+## 2.1.8
+
+### Patch Changes
+
+- Updated dependencies
+  - @mcp-use/[email protected]
+  - [email protected]
+
 ## 2.1.7
 
 ### Patch Changes

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mcp-use/cli",
-  "version": "2.1.7",
+  "version": "2.1.8",
   "description": "Build tool for MCP UI widgets - bundles React components into standalone HTML pages for Model Context Protocol servers",
   "author": "mcp-use, Inc.",
   "license": "MIT",

packages/inspector/CHANGELOG.md

@@ -1,5 +1,13 @@
 # @mcp-use/inspector
 
+## 0.3.8
+
+### Patch Changes
+
+- fix: support multiple clients per server
+- Updated dependencies
+  - [email protected]
+
 ## 0.3.7
 
 ### Patch Changes

packages/inspector/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@mcp-use/inspector",
   "type": "module",
-  "version": "0.3.7",
+  "version": "0.3.8",
   "description": "MCP Inspector - A tool for inspecting and debugging MCP servers",
   "author": "",
   "license": "MIT",

packages/inspector/src/client/components/InspectorDashboard.tsx

@@ -124,8 +124,13 @@ export function InspectorDashboard() {
           }, {} as Record<string, string>),
         }
 
+    // Map UI transport type to actual transport type
+    // "SSE" in UI means "Streamable HTTP" which uses 'http' transport
+    // "WebSocket" in UI means "WebSocket" which uses 'sse' transport
+    const actualTransportType = transportType === 'SSE' ? 'http' : 'sse'
+
     // For now, use URL as both ID and name - this will need proper implementation
-    addConnection(url, url, proxyConfig)
+    addConnection(url, url, proxyConfig, actualTransportType)
   }
 
   const handleClearAllConnections = () => {
@@ -222,7 +227,7 @@ export function InspectorDashboard() {
               >
                 <Badge variant="secondary" className="text-xs cursor-pointer hover:bg-secondary/80 transition-colors">
                   v
-                  {typeof window !== 'undefined' && (window as any).__INSPECTOR_VERSION__ || '1.0.0'}
+                  {(typeof window !== 'undefined' && (window as any).__INSPECTOR_VERSION__) || '1.0.0'}
                 </Badge>
               </a>
             </TooltipTrigger>
@@ -268,7 +273,7 @@ export function InspectorDashboard() {
                           <div className="flex items-center gap-3">
                             <h4 className="font-semibold text-sm">{connection.name}</h4>
                             <div className="flex items-center gap-2">
-                              {connection.error
+                              {connection.error && connection.state !== 'ready'
                                 ? (
                                     <Tooltip>
                                       <TooltipTrigger asChild>
@@ -399,7 +404,7 @@ export function InspectorDashboard() {
               </SelectTrigger>
               <SelectContent>
                 <SelectItem value="SSE">Streamable HTTP</SelectItem>
-                <SelectItem value="WebSocket">WebSocket</SelectItem>
+                <SelectItem value="WebSocket">Server-Sent Events (SSE)</SelectItem>
               </SelectContent>
             </Select>
           </div>

packages/inspector/src/client/components/Layout.tsx

@@ -233,7 +233,7 @@ export function Layout({ children }: LayoutProps) {
       const existing = connections.find(c => c.url === autoConnectUrl)
       if (!existing) {
         setIsAutoConnecting(true)
-        addConnection(autoConnectUrl, 'Local MCP Server')
+        addConnection(autoConnectUrl, 'Local MCP Server', undefined, 'http')
         // Navigate immediately but keep loading screen visible a bit longer to avoid flash
         navigate(`/servers/${encodeURIComponent(autoConnectUrl)}`)
         setTimeout(() => {
@@ -254,7 +254,7 @@ export function Layout({ children }: LayoutProps) {
           const existing = connections.find(c => c.url === config.autoConnectUrl)
           if (!existing) {
             // Auto-connect to the local server
-            addConnection(config.autoConnectUrl, 'Local MCP Server')
+            addConnection(config.autoConnectUrl, 'Local MCP Server', undefined, 'http')
           }
         }
       })
@@ -383,7 +383,7 @@ export function Layout({ children }: LayoutProps) {
                         </span>
                         {selectedServer && (
                           <div className="flex items-center gap-2">
-                            {selectedServer.error
+                            {selectedServer.error && selectedServer.state !== 'ready'
                               ? (
                                   <Tooltip>
                                     <TooltipTrigger asChild>

packages/inspector/src/client/context/McpContext.tsx

@@ -21,7 +21,7 @@ interface MCPConnection {
 
 interface McpContextType {
   connections: MCPConnection[]
-  addConnection: (url: string, name?: string, proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }) => void
+  addConnection: (url: string, name?: string, proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }, transportType?: 'http' | 'sse') => void
   removeConnection: (id: string) => void
   getConnection: (id: string) => MCPConnection | undefined
 }
@@ -33,12 +33,14 @@ interface SavedConnection {
   url: string
   name: string
   proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }
+  transportType?: 'http' | 'sse'
 }
 
-function McpConnectionWrapper({ url, name, proxyConfig, onUpdate, onRemove: _onRemove }: {
+function McpConnectionWrapper({ url, name, proxyConfig, transportType, onUpdate, onRemove: _onRemove }: {
   url: string
   name: string
   proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }
+  transportType?: 'http' | 'sse'
   onUpdate: (connection: MCPConnection) => void
   onRemove: () => void
 }) {
@@ -79,6 +81,7 @@ function McpConnectionWrapper({ url, name, proxyConfig, onUpdate, onRemove: _onR
     url: finalUrl,
     callbackUrl,
     customHeaders: Object.keys(customHeaders).length > 0 ? customHeaders : undefined,
+    transportType: transportType || 'http', // Default to 'http' for Streamable HTTP
   })
   const onUpdateRef = useRef(onUpdate)
   const prevConnectionRef = useRef<MCPConnection | null>(null)
@@ -194,12 +197,21 @@ export function McpProvider({ children }: { children: ReactNode }) {
                 && typeof conn.id === 'string'
                 && typeof conn.url === 'string'
                 && typeof conn.name === 'string'
+            }).map((conn: any) => {
+              // Migrate existing connections to include transportType
+              if (!conn.transportType) {
+                conn.transportType = 'http' // Default to 'http' for Streamable HTTP
+              }
+              return conn
             })
           : []
 
-        // If we filtered out any invalid connections, update localStorage
-        if (validConnections.length !== parsed.length) {
-          console.warn('Cleaned up invalid connections from localStorage')
+        // If we filtered out any invalid connections or migrated transport types, update localStorage
+        const hasChanges = validConnections.length !== parsed.length
+          || validConnections.some((conn: any) => conn.transportType === 'http' && !parsed.find((p: any) => p.id === conn.id && p.transportType))
+
+        if (hasChanges) {
+          console.warn('Updated connections in localStorage with transport type migration')
           localStorage.setItem('mcp-inspector-connections', JSON.stringify(validConnections))
         }
 
@@ -218,13 +230,14 @@ export function McpProvider({ children }: { children: ReactNode }) {
     setConnectionVersion(v => v + 1)
   }, [])
 
-  const addConnection = useCallback((url: string, name?: string, proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }) => {
+  const addConnection = useCallback((url: string, name?: string, proxyConfig?: { proxyAddress?: string, proxyToken?: string, customHeaders?: Record<string, string> }, transportType?: 'http' | 'sse') => {
     const connectionName = name || url
     const newConnection: SavedConnection = {
       id: url,
       url,
       name: connectionName,
       proxyConfig,
+      transportType: transportType || 'http', // Default to 'http' for Streamable HTTP
     }
 
     setSavedConnections((prev) => {
@@ -289,6 +302,7 @@ export function McpProvider({ children }: { children: ReactNode }) {
           url={saved.url}
           name={saved.name}
           proxyConfig={saved.proxyConfig}
+          transportType={saved.transportType}
           onUpdate={updateConnection}
           onRemove={() => removeConnection(saved.id)}
         />

packages/mcp-use/CHANGELOG.md

@@ -1,5 +1,13 @@
 # mcp-use
 
+## 1.0.4
+
+### Patch Changes
+
+- fix: support multiple clients per server
+- Updated dependencies
+  - @mcp-use/[email protected]
+
 ## 1.0.3
 
 ### Patch Changes

packages/mcp-use/package.json

@@ -1,7 +1,7 @@
 {
   "name": "mcp-use",
   "type": "module",
-  "version": "1.0.3",
+  "version": "1.0.4",
   "packageManager": "[email protected]",
   "description": "Opinionated MCP Framework for TypeScript (@modelcontextprotocol/sdk compatible) - Build MCP Agents and Clients + MCP Servers with support for MCP-UI.",
   "author": "mcp-use, Inc.",
@@ -88,7 +88,7 @@
     "example:observability": "tsx examples/client/observability.ts"
   },
   "peerDependencies": {
-    "@mcp-use/inspector": "^0.3.7",
+    "@mcp-use/inspector": "^0.3.8",
     "cors": "^2.8.5",
     "express": "^4.18.2",
     "langfuse": "^3.32.0",

packages/mcp-use/src/server/mcp-server.ts

@@ -46,7 +46,7 @@ export class McpServer {
     this.app.use((req, res, next) => {
       res.header('Access-Control-Allow-Origin', '*')
       res.header('Access-Control-Allow-Methods', 'GET, POST, DELETE, OPTIONS')
-      res.header('Access-Control-Allow-Headers', 'Content-Type')
+      res.header('Access-Control-Allow-Headers', 'Content-Type, Accept, Authorization, mcp-protocol-version, mcp-session-id, X-Proxy-Token, X-Target-URL')
       next()
     })
 
@@ -296,7 +296,8 @@ export class McpServer {
    * 
    * Sets up the HTTP transport layer for the MCP server, creating endpoints for
    * Server-Sent Events (SSE) streaming, POST message handling, and DELETE session cleanup.
-   * Uses stateless mode for session management, making it suitable for stateless deployments.
+   * Each request gets its own transport instance to prevent state conflicts between
+   * concurrent client connections.
    * 
    * This method is called automatically when the server starts listening and ensures
    * that MCP clients can communicate with the server over HTTP.
@@ -314,30 +315,53 @@ export class McpServer {
     if (this.mcpMounted) return
 
     const { StreamableHTTPServerTransport } = await import('@modelcontextprotocol/sdk/server/streamableHttp.js')
-
-    // Create StreamableHTTPServerTransport in stateless mode
-    const httpTransport = new StreamableHTTPServerTransport({
-      sessionIdGenerator: undefined // Stateless mode
-    })
-
-    // Connect the MCP server to the transport
-    await this.server.connect(httpTransport)
 
     const endpoint = '/mcp'
 
+    // POST endpoint for messages
+    // Create a new transport for each request to support multiple concurrent clients
+    this.app.post(endpoint, express.json(), async (req, res) => {
+      const transport = new StreamableHTTPServerTransport({
+        sessionIdGenerator: undefined,
+        enableJsonResponse: true
+      })
+
+      res.on('close', () => {
+        transport.close()
+      })
+
+      await this.server.connect(transport)
+      await transport.handleRequest(req, res, req.body)
+    })
+
     // GET endpoint for SSE streaming
     this.app.get(endpoint, async (req, res) => {
-      await httpTransport.handleRequest(req, res)
-    })
+      const transport = new StreamableHTTPServerTransport({
+        sessionIdGenerator: undefined,
+        enableJsonResponse: true
+      })
 
-    // POST endpoint for messages
-    this.app.post(endpoint, express.json(), async (req, res) => {
-      await httpTransport.handleRequest(req, res, req.body)
+      res.on('close', () => {
+        transport.close()
+      })
+
+      await this.server.connect(transport)
+      await transport.handleRequest(req, res)
     })
 
     // DELETE endpoint for session cleanup
     this.app.delete(endpoint, async (req, res) => {
-      await httpTransport.handleRequest(req, res)
+      const transport = new StreamableHTTPServerTransport({
+        sessionIdGenerator: undefined,
+        enableJsonResponse: true
+      })
+
+      res.on('close', () => {
+        transport.close()
+      })
+
+      await this.server.connect(transport)
+      await transport.handleRequest(req, res)
     })
 
     this.mcpMounted = true