#3707 added sse and streamable stransport support for mcp servers (#3747)

* #3707 added sse and streamable stransport support for mcp servers

* #3707 yarn lint changes

* bump MCP SDK to latest

* option chain transport

* small refactor

---------

Co-authored-by: Aleksey Kapustyanenko <kapustyanenko@mercurydevelopment.com>
Co-authored-by: Timothy Carambat <rambat1010@gmail.com>

server/package.json

@@ -32,7 +32,7 @@
     "@langchain/textsplitters": "0.0.0",
     "@mintplex-labs/bree": "^9.2.5",
     "@mintplex-labs/express-ws": "^5.0.7",
-    "@modelcontextprotocol/sdk": "^1.8.0",
+    "@modelcontextprotocol/sdk": "^1.11.0",
     "@pinecone-database/pinecone": "^2.0.1",
     "@prisma/client": "5.3.1",
     "@qdrant/js-client-rest": "^1.9.0",

server/utils/MCP/hypervisor/index.js

@@ -5,6 +5,16 @@ const { Client } = require("@modelcontextprotocol/sdk/client/index.js");
 const {
   StdioClientTransport,
 } = require("@modelcontextprotocol/sdk/client/stdio.js");
+const {
+  SSEClientTransport,
+} = require("@modelcontextprotocol/sdk/client/sse.js");
+const {
+  StreamableHTTPClientTransport,
+} = require("@modelcontextprotocol/sdk/client/streamableHttp.js");
+
+/**
+ * @typedef {'stdio' | 'http' | 'sse'} MCPServerTypes
+ */
 
 /**
  * @class MCPHypervisor
@@ -236,6 +246,81 @@ class MCPHypervisor {
     };
   }
 
+  /**
+   * Parse the server type from the server definition
+   * @param {Object} server - The server definition
+   * @returns {MCPServerTypes | null} - The server type
+   */
+  #parseServerType(server) {
+    if (server.hasOwnProperty("command")) return "stdio";
+    if (server.hasOwnProperty("url")) return "http";
+    return "sse";
+  }
+
+  /**
+   * Validate the server definition by type
+   * - Will throw an error if the server definition is invalid
+   * @param {Object} server - The server definition
+   * @param {MCPServerTypes} type - The server type
+   * @returns {void}
+   */
+  #validateServerDefinitionByType(server, type) {
+    if (type === "stdio") {
+      if (server.hasOwnProperty("args") && !Array.isArray(server.args))
+        throw new Error("MCP server args must be an array");
+    }
+
+    if (type === "http") {
+      if (!["sse", "streamable"].includes(server?.type))
+        throw new Error("MCP server type must have sse or streamable value.");
+    }
+
+    if (type === "sse") return;
+    return;
+  }
+
+  /**
+   * Setup the server transport by type and server definition
+   * @param {Object} server - The server definition
+   * @param {MCPServerTypes} type - The server type
+   * @returns {StdioClientTransport | StreamableHTTPClientTransport | SSEClientTransport} - The server transport
+   */
+  #setupServerTransport(server, type) {
+    // if not stdio then it is http or sse
+    if (type !== "stdio") return this.createHttpTransport(server);
+
+    return new StdioClientTransport({
+      command: server.command,
+      args: server?.args ?? [],
+      ...this.#buildMCPServerENV(server),
+    });
+  }
+
+  /**
+   * Create MCP client transport for http MCP server.
+   * @param {Object} server - The server definition
+   * @returns {StreamableHTTPClientTransport | SSEClientTransport} - The server transport
+   */
+  createHttpTransport(server) {
+    const url = new URL(server.url);
+
+    // If the server block has a type property then use that to determine the transport type
+    switch (server.type) {
+      case "streamable":
+        return new StreamableHTTPClientTransport(url, {
+          requestInit: {
+            headers: server.headers,
+          },
+        });
+      default:
+        return new SSEClientTransport(url, {
+          requestInit: {
+            headers: server.headers,
+          },
+        });
+    }
+  }
+
   /**
    * @private Start a single MCP server by its server definition from the JSON file
    * @param {string} name - The name of the MCP server to start
@@ -245,17 +330,13 @@ class MCPHypervisor {
   async #startMCPServer({ name, server }) {
     if (!name) throw new Error("MCP server name is required");
     if (!server) throw new Error("MCP server definition is required");
-    if (!server.command) throw new Error("MCP server command is required");
-    if (server.hasOwnProperty("args") && !Array.isArray(server.args))
-      throw new Error("MCP server args must be an array");
+    const serverType = this.#parseServerType(server);
+    if (!serverType) throw new Error("MCP server command or url is required");
 
+    this.#validateServerDefinitionByType(server, serverType);
     this.log(`Attempting to start MCP server: ${name}`);
     const mcp = new Client({ name: name, version: "1.0.0" });
-    const transport = new StdioClientTransport({
-      command: server.command,
-      args: server?.args ?? [],
-      ...this.#buildMCPServerENV(server),
-    });
+    const transport = this.#setupServerTransport(server, serverType);
 
     // Add connection event listeners
     transport.onclose = () => this.log(`${name} - Transport closed`);

server/utils/MCP/index.js

@@ -142,7 +142,7 @@ class MCPCompatibilityLayer extends MCPHypervisor {
         tools,
         error: null,
         process: {
-          pid: mcp.transport._process.pid,
+          pid: mcp.transport?.process?.pid || null,
         },
       });
     }

server/yarn.lock

@@ -1599,10 +1599,10 @@
   dependencies:
     ws "^7.5.10"
 
-"@modelcontextprotocol/sdk@^1.8.0":
-  version "1.8.0"
-  resolved "https://registry.yarnpkg.com/@modelcontextprotocol/sdk/-/sdk-1.8.0.tgz#55cdd65054ec24e53800250c70e07429d669db67"
-  integrity sha512-e06W7SwrontJDHwCawNO5SGxG+nU9AAx+jpHHZqGl/WrDBdWOpvirC+s58VpJTB5QemI4jTRcjWT4Pt3Q1NPQQ==
+"@modelcontextprotocol/sdk@^1.11.0":
+  version "1.11.0"
+  resolved "https://registry.yarnpkg.com/@modelcontextprotocol/sdk/-/sdk-1.11.0.tgz#9f1762efe6f3365f0bf3b019cc9bd1629d19bc50"
+  integrity sha512-k/1pb70eD638anoi0e8wUGAlbMJXyvdV4p62Ko+EZ7eBe1xMx8Uhak1R5DgfoofsK5IBBnRwsYGTaLZl+6/+RQ==
   dependencies:
     content-type "^1.0.5"
     cors "^2.8.5"
@@ -1610,7 +1610,7 @@
     eventsource "^3.0.2"
     express "^5.0.1"
     express-rate-limit "^7.5.0"
-    pkce-challenge "^4.1.0"
+    pkce-challenge "^5.0.0"
     raw-body "^3.0.0"
     zod "^3.23.8"
     zod-to-json-schema "^3.24.1"
@@ -6615,10 +6615,10 @@ pirates@^3.0.2:
   dependencies:
     node-modules-regexp "^1.0.0"
 
-pkce-challenge@^4.1.0:
-  version "4.1.0"
-  resolved "https://registry.yarnpkg.com/pkce-challenge/-/pkce-challenge-4.1.0.tgz#95027d7750c3c0f21676a345b48f481786f9acdb"
-  integrity sha512-ZBmhE1C9LcPoH9XZSdwiPtbPHZROwAnMy+kIFQVrnMCxY4Cudlz3gBOpzilgc0jOgRaiT3sIWfpMomW2ar2orQ==
+pkce-challenge@^5.0.0:
+  version "5.0.0"
+  resolved "https://registry.yarnpkg.com/pkce-challenge/-/pkce-challenge-5.0.0.tgz#c3a405cb49e272094a38e890a2b51da0228c4d97"
+  integrity sha512-ueGLflrrnvwB3xuo/uGob5pd5FN7l0MsLf0Z87o/UQmRtwjvfylfc9MurIxRAWywCYTgrvpXBcqjV4OfCYGCIQ==
 
 platform@^1.3.6:
   version "1.3.6"