Merge pull request #339 from cliffhall/fix-streamable-endpoint

Fix support for streamable-http connections

client/jest.config.cjs

@@ -1,6 +1,6 @@
 module.exports = {
   preset: "ts-jest",
-  testEnvironment: "jsdom",
+  testEnvironment: "jest-fixed-jsdom",
   moduleNameMapper: {
     "^@/(.*)$": "<rootDir>/src/$1",
     "\\.css$": "<rootDir>/src/__mocks__/styleMock.js",

client/src/lib/hooks/useConnection.ts

@@ -3,6 +3,7 @@ import {
   SSEClientTransport,
   SseError,
 } from "@modelcontextprotocol/sdk/client/sse.js";
+import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
 import {
   ClientNotification,
   ClientRequest,
@@ -278,15 +279,29 @@ export function useConnection({
       setConnectionStatus("error-connecting-to-proxy");
       return;
     }
-    const mcpProxyServerUrl = new URL(`${getMCPProxyAddress(config)}/sse`);
+    let mcpProxyServerUrl;
-    mcpProxyServerUrl.searchParams.append("transportType", transportType);
+    switch (transportType) {
-    if (transportType === "stdio") {
+      case "stdio":
-      mcpProxyServerUrl.searchParams.append("command", command);
+        mcpProxyServerUrl = new URL(`${getMCPProxyAddress(config)}/stdio`);
-      mcpProxyServerUrl.searchParams.append("args", args);
+        mcpProxyServerUrl.searchParams.append("command", command);
-      mcpProxyServerUrl.searchParams.append("env", JSON.stringify(env));
+        mcpProxyServerUrl.searchParams.append("args", args);
-    } else {
+        mcpProxyServerUrl.searchParams.append("env", JSON.stringify(env));
-      mcpProxyServerUrl.searchParams.append("url", sseUrl);
+        break;
+
+      case "sse":
+        mcpProxyServerUrl = new URL(`${getMCPProxyAddress(config)}/sse`);
+        mcpProxyServerUrl.searchParams.append("url", sseUrl);
+        break;
+
+      case "streamable-http":
+        mcpProxyServerUrl = new URL(`${getMCPProxyAddress(config)}/mcp`);
+        mcpProxyServerUrl.searchParams.append("url", sseUrl);
+        break;
     }
+    (mcpProxyServerUrl as URL).searchParams.append(
+      "transportType",
+      transportType,
+    );
 
     try {
       // Inject auth manually instead of using SSEClientTransport, because we're
@@ -304,14 +319,24 @@ export function useConnection({
         headers[authHeaderName] = `Bearer ${token}`;
       }
 
-      const clientTransport = new SSEClientTransport(mcpProxyServerUrl, {
+      // Create appropriate transport
+      const transportOptions = {
         eventSourceInit: {
-          fetch: (url, init) => fetch(url, { ...init, headers }),
+          fetch: (
+            url: string | URL | globalThis.Request,
+            init: RequestInit | undefined,
+          ) => fetch(url, { ...init, headers }),
         },
         requestInit: {
           headers,
         },
-      });
+      };
+      const clientTransport =
+        transportType === "streamable-http"
+          ? new StreamableHTTPClientTransport(mcpProxyServerUrl as URL, {
+              sessionId: undefined,
+            })
+          : new SSEClientTransport(mcpProxyServerUrl as URL, transportOptions);
 
       if (onNotification) {
         [

package-lock.json

@@ -17,7 +17,7 @@
         "@modelcontextprotocol/inspector-cli": "^0.10.2",
         "@modelcontextprotocol/inspector-client": "^0.10.2",
         "@modelcontextprotocol/inspector-server": "^0.10.2",
-        "@modelcontextprotocol/sdk": "^1.10.0",
+        "@modelcontextprotocol/sdk": "^1.10.2",
         "concurrently": "^9.0.1",
         "shell-quote": "^1.8.2",
         "spawn-rx": "^5.1.2",
@@ -31,13 +31,14 @@
         "@types/jest": "^29.5.14",
         "@types/node": "^22.7.5",
         "@types/shell-quote": "^1.7.5",
+        "jest-fixed-jsdom": "^0.0.9",
         "prettier": "3.3.3",
         "typescript": "^5.4.2"
       }
     },
     "cli": {
       "name": "@modelcontextprotocol/inspector-cli",
-      "version": "0.10.1",
+      "version": "0.10.2",
       "license": "MIT",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.10.0",
@@ -58,7 +59,7 @@
     },
     "client": {
       "name": "@modelcontextprotocol/inspector-client",
-      "version": "0.10.1",
+      "version": "0.10.2",
       "license": "MIT",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.10.0",
@@ -1399,9 +1400,9 @@
       "link": true
     },
     "node_modules/@modelcontextprotocol/sdk": {
-      "version": "1.10.0",
+      "version": "1.10.2",
-      "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.10.0.tgz",
+      "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.10.2.tgz",
-      "integrity": "sha512-wijOavYZfSOADbVM0LA7mrQ17N4IKNdFcfezknCCsZ1Y1KstVWlkDZ5ebcxuQJmqTTxsNjBHLc7it1SV0TBiPg==",
+      "integrity": "sha512-rb6AMp2DR4SN+kc6L1ta2NCpApyA9WYNx3CrTSZvGxq9wH71bRur+zRqPfg0vQ9mjywR7qZdX2RGHOPq3ss+tA==",
       "license": "MIT",
       "dependencies": {
         "content-type": "^1.0.5",
@@ -5358,6 +5359,19 @@
         "node": "^14.15.0 || ^16.10.0 || >=18.0.0"
       }
     },
+    "node_modules/jest-fixed-jsdom": {
+      "version": "0.0.9",
+      "resolved": "https://registry.npmjs.org/jest-fixed-jsdom/-/jest-fixed-jsdom-0.0.9.tgz",
+      "integrity": "sha512-KPfqh2+sn5q2B+7LZktwDcwhCpOpUSue8a1I+BcixWLOQoEVyAjAGfH+IYZGoxZsziNojoHGRTC8xRbB1wDD4g==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.0.0"
+      },
+      "peerDependencies": {
+        "jest-environment-jsdom": ">=28.0.0"
+      }
+    },
     "node_modules/jest-get-type": {
       "version": "29.6.3",
       "dev": true,
@@ -8550,7 +8564,7 @@
     },
     "server": {
       "name": "@modelcontextprotocol/inspector-server",
-      "version": "0.10.1",
+      "version": "0.10.2",
       "license": "MIT",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.10.0",

package.json

@@ -41,7 +41,7 @@
     "@modelcontextprotocol/inspector-cli": "^0.10.2",
     "@modelcontextprotocol/inspector-client": "^0.10.2",
     "@modelcontextprotocol/inspector-server": "^0.10.2",
-    "@modelcontextprotocol/sdk": "^1.10.0",
+    "@modelcontextprotocol/sdk": "^1.10.2",
     "concurrently": "^9.0.1",
     "shell-quote": "^1.8.2",
     "spawn-rx": "^5.1.2",
@@ -52,6 +52,7 @@
     "@types/jest": "^29.5.14",
     "@types/node": "^22.7.5",
     "@types/shell-quote": "^1.7.5",
+    "jest-fixed-jsdom": "^0.0.9",
     "prettier": "3.3.3",
     "typescript": "^5.4.2"
   }

server/src/index.ts

@@ -12,15 +12,21 @@ import {
   StdioClientTransport,
   getDefaultEnvironment,
 } from "@modelcontextprotocol/sdk/client/stdio.js";
-import { Transport } from "@modelcontextprotocol/sdk/shared/transport.js";
-import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
 import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
+import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
+import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
+import { Transport } from "@modelcontextprotocol/sdk/shared/transport.js";
 import express from "express";
 import { findActualExecutable } from "spawn-rx";
 import mcpProxy from "./mcpProxy.js";
+import { randomUUID } from "node:crypto";
 
 const SSE_HEADERS_PASSTHROUGH = ["authorization"];
-const STREAMABLE_HTTP_HEADERS_PASSTHROUGH = ["authorization"];
+const STREAMABLE_HTTP_HEADERS_PASSTHROUGH = [
+  "authorization",
+  "mcp-session-id",
+  "last-event-id",
+];
 
 const defaultEnvironment = {
   ...getDefaultEnvironment(),
@@ -37,8 +43,12 @@ const { values } = parseArgs({
 
 const app = express();
 app.use(cors());
+app.use((req, res, next) => {
+  res.header("Access-Control-Expose-Headers", "mcp-session-id");
+  next();
+});
 
-let webAppTransports: SSEServerTransport[] = [];
+const webAppTransports: Map<string, Transport> = new Map<string, Transport>(); // Transports by sessionId
 
 const createTransport = async (req: express.Request): Promise<Transport> => {
   const query = req.query;
@@ -97,7 +107,9 @@ const createTransport = async (req: express.Request): Promise<Transport> => {
     console.log("Connected to SSE transport");
     return transport;
   } else if (transportType === "streamable-http") {
-    const headers: HeadersInit = {};
+    const headers: HeadersInit = {
+      Accept: "text/event-stream, application/json",
+    };
 
     for (const key of STREAMABLE_HTTP_HEADERS_PASSTHROUGH) {
       if (req.headers[key] === undefined) {
@@ -127,9 +139,96 @@ const createTransport = async (req: express.Request): Promise<Transport> => {
 
 let backingServerTransport: Transport | undefined;
 
-app.get("/sse", async (req, res) => {
+app.get("/mcp", async (req, res) => {
+  const sessionId = req.headers["mcp-session-id"] as string;
+  console.log(`Received GET message for sessionId ${sessionId}`);
   try {
-    console.log("New SSE connection");
+    const transport = webAppTransports.get(
+      sessionId,
+    ) as StreamableHTTPServerTransport;
+    if (!transport) {
+      res.status(404).end("Session not found");
+      return;
+    } else {
+      await transport.handleRequest(req, res);
+    }
+  } catch (error) {
+    console.error("Error in /mcp route:", error);
+    res.status(500).json(error);
+  }
+});
+
+app.post("/mcp", async (req, res) => {
+  const sessionId = req.headers["mcp-session-id"] as string | undefined;
+  console.log(`Received POST message for sessionId ${sessionId}`);
+  if (!sessionId) {
+    try {
+      console.log("New streamable-http connection");
+      try {
+        await backingServerTransport?.close();
+        backingServerTransport = await createTransport(req);
+      } catch (error) {
+        if (error instanceof SseError && error.code === 401) {
+          console.error(
+            "Received 401 Unauthorized from MCP server:",
+            error.message,
+          );
+          res.status(401).json(error);
+          return;
+        }
+
+        throw error;
+      }
+
+      console.log("Connected MCP client to backing server transport");
+
+      const webAppTransport = new StreamableHTTPServerTransport({
+        sessionIdGenerator: randomUUID,
+        onsessioninitialized: (sessionId) => {
+          webAppTransports.set(sessionId, webAppTransport);
+          console.log("Created streamable web app transport " + sessionId);
+        },
+      });
+
+      await webAppTransport.start();
+
+      mcpProxy({
+        transportToClient: webAppTransport,
+        transportToServer: backingServerTransport,
+      });
+
+      await (webAppTransport as StreamableHTTPServerTransport).handleRequest(
+        req,
+        res,
+        req.body,
+      );
+    } catch (error) {
+      console.error("Error in /mcp POST route:", error);
+      res.status(500).json(error);
+    }
+  } else {
+    try {
+      const transport = webAppTransports.get(
+        sessionId,
+      ) as StreamableHTTPServerTransport;
+      if (!transport) {
+        res.status(404).end("Transport not found for sessionId " + sessionId);
+      } else {
+        await (transport as StreamableHTTPServerTransport).handleRequest(
+          req,
+          res,
+        );
+      }
+    } catch (error) {
+      console.error("Error in /mcp route:", error);
+      res.status(500).json(error);
+    }
+  }
+});
+
+app.get("/stdio", async (req, res) => {
+  try {
+    console.log("New connection");
 
     try {
       await backingServerTransport?.close();
@@ -150,15 +249,14 @@ app.get("/sse", async (req, res) => {
     console.log("Connected MCP client to backing server transport");
 
     const webAppTransport = new SSEServerTransport("/message", res);
-    console.log("Created web app transport");
+    webAppTransports.set(webAppTransport.sessionId, webAppTransport);
 
-    webAppTransports.push(webAppTransport);
     console.log("Created web app transport");
 
     await webAppTransport.start();
-
+    (backingServerTransport as StdioClientTransport).stderr!.on(
-    if (backingServerTransport instanceof StdioClientTransport) {
+      "data",
-      backingServerTransport.stderr!.on("data", (chunk) => {
+      (chunk) => {
         webAppTransport.send({
           jsonrpc: "2.0",
           method: "notifications/stderr",
@@ -166,9 +264,51 @@ app.get("/sse", async (req, res) => {
             content: chunk.toString(),
           },
         });
-      });
+      },
+    );
+
+    mcpProxy({
+      transportToClient: webAppTransport,
+      transportToServer: backingServerTransport,
+    });
+
+    console.log("Set up MCP proxy");
+  } catch (error) {
+    console.error("Error in /stdio route:", error);
+    res.status(500).json(error);
+  }
+});
+
+app.get("/sse", async (req, res) => {
+  try {
+    console.log(
+      "New SSE connection. NOTE: The sse transport is deprecated and has been replaced by streamable-http",
+    );
+
+    try {
+      await backingServerTransport?.close();
+      backingServerTransport = await createTransport(req);
+    } catch (error) {
+      if (error instanceof SseError && error.code === 401) {
+        console.error(
+          "Received 401 Unauthorized from MCP server:",
+          error.message,
+        );
+        res.status(401).json(error);
+        return;
+      }
+
+      throw error;
     }
 
+    console.log("Connected MCP client to backing server transport");
+
+    const webAppTransport = new SSEServerTransport("/message", res);
+    webAppTransports.set(webAppTransport.sessionId, webAppTransport);
+    console.log("Created web app transport");
+
+    await webAppTransport.start();
+
     mcpProxy({
       transportToClient: webAppTransport,
       transportToServer: backingServerTransport,
@@ -186,7 +326,9 @@ app.post("/message", async (req, res) => {
     const sessionId = req.query.sessionId;
     console.log(`Received message for sessionId ${sessionId}`);
 
-    const transport = webAppTransports.find((t) => t.sessionId === sessionId);
+    const transport = webAppTransports.get(
+      sessionId as string,
+    ) as SSEServerTransport;
     if (!transport) {
       res.status(404).end("Session not found");
       return;