Add Streamable HTTP transport for remote MCP access

- Convert from stdio-only to dual-mode (stdio + HTTP)
- Add Express server with /mcp endpoint for Streamable HTTP
- Add /health endpoint for Railway health checks
- Update MCP SDK to v1.12.0 for Streamable HTTP support
- Add railway.toml for Railway deployment
- Default to HTTP mode, use --stdio flag for local mode

Dockerfile

@@ -39,9 +39,15 @@ RUN npx tsc && \
 # Switch to production for runtime
 ENV NODE_ENV=production
 
+# Default port for HTTP transport
+ENV PORT=3001
+
 # The API key should be passed at runtime
 # ENV OPENROUTER_API_KEY=your-api-key-here
 # ENV OPENROUTER_DEFAULT_MODEL=your-default-model
 
-# Run the server
+# Expose HTTP port
+EXPOSE 3001
+
+# Run the server in HTTP mode (default)
 CMD ["node", "dist/index.js"]

package.json

@@ -43,14 +43,16 @@
     "node": ">=18.0.0"
   },
   "dependencies": {
-    "@modelcontextprotocol/sdk": "^1.8.0",
+    "@modelcontextprotocol/sdk": "^1.12.0",
     "axios": "^1.8.4",
     "dotenv": "^16.4.7",
+    "express": "^4.21.2",
     "node-fetch": "^3.3.2",
     "openai": "^4.89.1",
     "sharp": "^0.33.5"
   },
   "devDependencies": {
+    "@types/express": "^5.0.0",
     "@types/node": "^22.13.14",
     "@types/sharp": "^0.32.0",
     "shx": "^0.3.4",

railway.toml

@@ -0,0 +1,9 @@
+[build]
+builder = "dockerfile"
+dockerfilePath = "Dockerfile"
+
+[deploy]
+healthcheckPath = "/health"
+healthcheckTimeout = 30
+restartPolicyType = "on_failure"
+restartPolicyMaxRetries = 3

src/index.ts

@@ -1,7 +1,12 @@
 #!/usr/bin/env node
 // OpenRouter Multimodal MCP Server
+// Supports both stdio (local) and Streamable HTTP (remote) transports
+
 import { Server } from '@modelcontextprotocol/sdk/server/index.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
+import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
+import { isInitializeRequest } from '@modelcontextprotocol/sdk/types.js';
+import express, { Request, Response } from 'express';
 
 import { ToolHandlers } from './tool-handlers.js';
 
@@ -15,15 +20,17 @@ interface ServerOptions {
 
 class OpenRouterMultimodalServer {
   private server: Server;
-  private toolHandlers!: ToolHandlers; // Using definite assignment assertion
+  private toolHandlers!: ToolHandlers;
+  private apiKey: string;
+  private defaultModel: string;
 
   constructor(options?: ServerOptions) {
     // Retrieve API key from options or environment variables
-    const apiKey = options?.apiKey || process.env.OPENROUTER_API_KEY;
+    this.apiKey = options?.apiKey || process.env.OPENROUTER_API_KEY || '';
-    const defaultModel = options?.defaultModel || process.env.OPENROUTER_DEFAULT_MODEL || DEFAULT_MODEL;
+    this.defaultModel = options?.defaultModel || process.env.OPENROUTER_DEFAULT_MODEL || DEFAULT_MODEL;
 
     // Check if API key is provided
-    if (!apiKey) {
+    if (!this.apiKey) {
       throw new Error('OpenRouter API key is required. Provide it via options or OPENROUTER_API_KEY environment variable');
     }
 
@@ -31,7 +38,7 @@ class OpenRouterMultimodalServer {
     this.server = new Server(
       {
         name: 'openrouter-multimodal-server',
-        version: '1.0.0',
+        version: '1.5.0',
       },
       {
         capabilities: {
@@ -39,78 +46,204 @@ class OpenRouterMultimodalServer {
         },
       }
     );
-    
+
     // Set up error handling
     this.server.onerror = (error) => console.error('[MCP Error]', error);
-    
+
     // Initialize tool handlers
     this.toolHandlers = new ToolHandlers(
       this.server,
-      apiKey,
+      this.apiKey,
-      defaultModel
+      this.defaultModel
     );
-    
+
     process.on('SIGINT', async () => {
       await this.server.close();
       process.exit(0);
     });
   }
 
-  async run() {
+  getServer(): Server {
+    return this.server;
+  }
+
+  getDefaultModel(): string {
+    return this.toolHandlers.getDefaultModel() || this.defaultModel;
+  }
+
+  async runStdio() {
     const transport = new StdioServerTransport();
     await this.server.connect(transport);
     console.error('OpenRouter Multimodal MCP server running on stdio');
-    
+    console.error(`Using default model: ${this.getDefaultModel()}`);
-    // Log model information
-    const modelDisplay = this.toolHandlers.getDefaultModel() || DEFAULT_MODEL;
-    console.error(`Using default model: ${modelDisplay}`);
     console.error('Server is ready to process tool calls. Waiting for input...');
   }
+
+  async runHttp(port: number) {
+    const app = express();
+    app.use(express.json());
+
+    // Store transports by session ID for stateful mode
+    const transports: Record<string, StreamableHTTPServerTransport> = {};
+
+    // Health check endpoint
+    app.get('/health', (_req: Request, res: Response) => {
+      res.json({
+        status: 'ok',
+        server: 'openrouter-multimodal-mcp',
+        version: '1.5.0',
+        defaultModel: this.getDefaultModel()
+      });
+    });
+
+    // Main MCP endpoint - handles POST and GET
+    app.all('/mcp', async (req: Request, res: Response) => {
+      console.log(`[MCP] ${req.method} request received`);
+
+      // Handle GET for SSE stream (part of Streamable HTTP spec)
+      if (req.method === 'GET') {
+        console.log('[MCP] SSE stream requested');
+        const sessionId = req.headers['mcp-session-id'] as string | undefined;
+
+        if (!sessionId || !transports[sessionId]) {
+          res.status(400).json({ error: 'No active session. Send POST first.' });
+          return;
+        }
+
+        // Let the transport handle the SSE stream
+        const transport = transports[sessionId];
+        await transport.handleRequest(req, res);
+        return;
+      }
+
+      // Handle DELETE for session termination
+      if (req.method === 'DELETE') {
+        const sessionId = req.headers['mcp-session-id'] as string | undefined;
+        if (sessionId && transports[sessionId]) {
+          await transports[sessionId].close();
+          delete transports[sessionId];
+          res.status(200).json({ message: 'Session terminated' });
+        } else {
+          res.status(404).json({ error: 'Session not found' });
+        }
+        return;
+      }
+
+      // Handle POST requests
+      if (req.method !== 'POST') {
+        res.status(405).json({ error: 'Method not allowed' });
+        return;
+      }
+
+      const sessionId = req.headers['mcp-session-id'] as string | undefined;
+      let transport: StreamableHTTPServerTransport;
+
+      // Check if this is an initialization request
+      if (isInitializeRequest(req.body)) {
+        console.log('[MCP] Initialize request - creating new session');
+
+        // Create new transport for stateless mode (no session persistence)
+        transport = new StreamableHTTPServerTransport({
+          sessionIdGenerator: () => crypto.randomUUID(),
+          onsessioninitialized: (newSessionId) => {
+            console.log(`[MCP] Session initialized: ${newSessionId}`);
+            transports[newSessionId] = transport;
+          }
+        });
+
+        // Connect a new server instance for this transport
+        const sessionServer = new Server(
+          { name: 'openrouter-multimodal-server', version: '1.5.0' },
+          { capabilities: { tools: {} } }
+        );
+        sessionServer.onerror = (error) => console.error('[MCP Session Error]', error);
+
+        // Initialize tool handlers for this session
+        new ToolHandlers(sessionServer, this.apiKey, this.defaultModel);
+
+        await sessionServer.connect(transport);
+      } else {
+        // Existing session - find transport
+        if (!sessionId || !transports[sessionId]) {
+          res.status(400).json({
+            error: 'Invalid or missing session ID',
+            message: 'Send initialize request first to create a session'
+          });
+          return;
+        }
+        transport = transports[sessionId];
+      }
+
+      // Handle the request
+      try {
+        await transport.handleRequest(req, res);
+      } catch (error) {
+        console.error('[MCP] Request handling error:', error);
+        if (!res.headersSent) {
+          res.status(500).json({ error: 'Internal server error' });
+        }
+      }
+    });
+
+    // Legacy SSE endpoint for backwards compatibility
+    app.get('/sse', (_req: Request, res: Response) => {
+      res.status(410).json({
+        error: 'SSE transport is deprecated',
+        message: 'Use Streamable HTTP at /mcp endpoint instead'
+      });
+    });
+
+    // Start server
+    app.listen(port, () => {
+      console.log(`OpenRouter Multimodal MCP server running on HTTP port ${port}`);
+      console.log(`MCP endpoint: http://localhost:${port}/mcp`);
+      console.log(`Health check: http://localhost:${port}/health`);
+      console.log(`Using default model: ${this.getDefaultModel()}`);
+    });
+  }
 }
 
+// Determine transport mode from environment or arguments
+const transportMode = process.env.MCP_TRANSPORT || 'http';
+const httpPort = parseInt(process.env.PORT || '3001', 10);
+
 // Get MCP configuration if provided
 let mcpOptions: ServerOptions | undefined;
 
-// Check if we're being run as an MCP server with configuration
+// Check for config argument
 if (process.argv.length > 2) {
   try {
     const configArg = process.argv.find(arg => arg.startsWith('--config='));
     if (configArg) {
       const configPath = configArg.split('=')[1];
       const configData = require(configPath);
-      
-      // Extract configuration
       mcpOptions = {
         apiKey: configData.OPENROUTER_API_KEY || configData.apiKey,
         defaultModel: configData.OPENROUTER_DEFAULT_MODEL || configData.defaultModel
       };
-      
       if (mcpOptions.apiKey) {
         console.error('Using API key from MCP configuration');
       }
     }
+
+    // Check for --stdio flag
+    if (process.argv.includes('--stdio')) {
+      const server = new OpenRouterMultimodalServer(mcpOptions);
+      server.runStdio().catch(console.error);
+    } else {
+      const server = new OpenRouterMultimodalServer(mcpOptions);
+      server.runHttp(httpPort);
+    }
   } catch (error) {
-    console.error('Error parsing MCP configuration:', error);
+    console.error('Error parsing configuration:', error);
+    process.exit(1);
+  }
+} else {
+  // Default: HTTP mode unless MCP_TRANSPORT=stdio
+  const server = new OpenRouterMultimodalServer(mcpOptions);
+  if (transportMode === 'stdio') {
+    server.runStdio().catch(console.error);
+  } else {
+    server.runHttp(httpPort);
   }
 }
-
-// Attempt to parse JSON from stdin to check for MCP server parameters
-if (!mcpOptions?.apiKey) {
-  process.stdin.setEncoding('utf8');
-  process.stdin.once('data', (data) => {
-    try {
-      const firstMessage = JSON.parse(data.toString());
-      if (firstMessage.params && typeof firstMessage.params === 'object') {
-        mcpOptions = {
-          apiKey: firstMessage.params.OPENROUTER_API_KEY || firstMessage.params.apiKey,
-          defaultModel: firstMessage.params.OPENROUTER_DEFAULT_MODEL || firstMessage.params.defaultModel
-        };
-      }
-    } catch (error) {
-      // Not a valid JSON message or no parameters, continue with environment variables
-    }
-  });
-}
-
-const server = new OpenRouterMultimodalServer(mcpOptions);
-server.run().catch(console.error);