Merge branch 'modelcontextprotocol:main' into main

.github/workflows/main.yml

@@ -26,6 +26,10 @@ jobs:
       # - run: npm ci
       - run: npm install --no-package-lock
 
+      - name: Check linting
+        working-directory: ./client
+        run: npm run lint
+
       - name: Run client tests
         working-directory: ./client
         run: npm test

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/App.tsx

@@ -647,6 +647,7 @@ const App = () => {
                       setSelectedPrompt={(prompt) => {
                         clearError("prompts");
                         setSelectedPrompt(prompt);
+                        setPromptContent("");
                       }}
                       handleCompletion={handleCompletion}
                       completionsSupported={completionsSupported}

client/src/components/DynamicJsonForm.tsx

@@ -250,7 +250,12 @@ const DynamicJsonForm = ({
     <div className="space-y-4">
       <div className="flex justify-end space-x-2">
         {isJsonMode && (
-          <Button variant="outline" size="sm" onClick={formatJson}>
+          <Button
+            type="button"
+            variant="outline"
+            size="sm"
+            onClick={formatJson}
+          >
             Format JSON
           </Button>
         )}

client/src/components/SamplingRequest.tsx

@@ -0,0 +1,167 @@
+import { Button } from "@/components/ui/button";
+import JsonView from "./JsonView";
+import { useMemo, useState } from "react";
+import {
+  CreateMessageResult,
+  CreateMessageResultSchema,
+} from "@modelcontextprotocol/sdk/types.js";
+import { PendingRequest } from "./SamplingTab";
+import DynamicJsonForm from "./DynamicJsonForm";
+import { useToast } from "@/hooks/use-toast";
+import { JsonSchemaType, JsonValue } from "@/utils/jsonUtils";
+
+export type SamplingRequestProps = {
+  request: PendingRequest;
+  onApprove: (id: number, result: CreateMessageResult) => void;
+  onReject: (id: number) => void;
+};
+
+const SamplingRequest = ({
+  onApprove,
+  request,
+  onReject,
+}: SamplingRequestProps) => {
+  const { toast } = useToast();
+
+  const [messageResult, setMessageResult] = useState<JsonValue>({
+    model: "stub-model",
+    stopReason: "endTurn",
+    role: "assistant",
+    content: {
+      type: "text",
+      text: "",
+    },
+  });
+
+  const contentType = (
+    (messageResult as { [key: string]: JsonValue })?.content as {
+      [key: string]: JsonValue;
+    }
+  )?.type;
+
+  const schema = useMemo(() => {
+    const s: JsonSchemaType = {
+      type: "object",
+      description: "Message result",
+      properties: {
+        model: {
+          type: "string",
+          default: "stub-model",
+          description: "model name",
+        },
+        stopReason: {
+          type: "string",
+          default: "endTurn",
+          description: "Stop reason",
+        },
+        role: {
+          type: "string",
+          default: "endTurn",
+          description: "Role of the model",
+        },
+        content: {
+          type: "object",
+          properties: {
+            type: {
+              type: "string",
+              default: "text",
+              description: "Type of content",
+            },
+          },
+        },
+      },
+    };
+
+    if (contentType === "text" && s.properties) {
+      s.properties.content.properties = {
+        ...s.properties.content.properties,
+        text: {
+          type: "string",
+          default: "",
+          description: "text content",
+        },
+      };
+      setMessageResult((prev) => ({
+        ...(prev as { [key: string]: JsonValue }),
+        content: {
+          type: contentType,
+          text: "",
+        },
+      }));
+    } else if (contentType === "image" && s.properties) {
+      s.properties.content.properties = {
+        ...s.properties.content.properties,
+        data: {
+          type: "string",
+          default: "",
+          description: "Base64 encoded image data",
+        },
+        mimeType: {
+          type: "string",
+          default: "",
+          description: "Mime type of the image",
+        },
+      };
+      setMessageResult((prev) => ({
+        ...(prev as { [key: string]: JsonValue }),
+        content: {
+          type: contentType,
+          data: "",
+          mimeType: "",
+        },
+      }));
+    }
+
+    return s;
+  }, [contentType]);
+
+  const handleApprove = (id: number) => {
+    const validationResult = CreateMessageResultSchema.safeParse(messageResult);
+    if (!validationResult.success) {
+      toast({
+        title: "Error",
+        description: `There was an error validating the message result: ${validationResult.error.message}`,
+        variant: "destructive",
+      });
+      return;
+    }
+
+    onApprove(id, validationResult.data);
+  };
+
+  return (
+    <div
+      data-testid="sampling-request"
+      className="flex gap-4 p-4 border rounded-lg space-y-4"
+    >
+      <div className="flex-1 bg-gray-50 dark:bg-gray-800 dark:text-gray-100 p-2 rounded">
+        <JsonView data={JSON.stringify(request.request)} />
+      </div>
+      <form className="flex-1 space-y-4">
+        <div className="space-y-2">
+          <DynamicJsonForm
+            schema={schema}
+            value={messageResult}
+            onChange={(newValue: JsonValue) => {
+              setMessageResult(newValue);
+            }}
+          />
+        </div>
+        <div className="flex space-x-2 mt-1">
+          <Button type="button" onClick={() => handleApprove(request.id)}>
+            Approve
+          </Button>
+          <Button
+            type="button"
+            variant="outline"
+            onClick={() => onReject(request.id)}
+          >
+            Reject
+          </Button>
+        </div>
+      </form>
+    </div>
+  );
+};
+
+export default SamplingRequest;

client/src/components/SamplingTab.tsx

@@ -1,11 +1,10 @@
 import { Alert, AlertDescription } from "@/components/ui/alert";
-import { Button } from "@/components/ui/button";
 import { TabsContent } from "@/components/ui/tabs";
 import {
   CreateMessageRequest,
   CreateMessageResult,
 } from "@modelcontextprotocol/sdk/types.js";
-import JsonView from "./JsonView";
+import SamplingRequest from "./SamplingRequest";
 
 export type PendingRequest = {
   id: number;
@@ -19,19 +18,6 @@ export type Props = {
 };
 
 const SamplingTab = ({ pendingRequests, onApprove, onReject }: Props) => {
-  const handleApprove = (id: number) => {
-    // For now, just return a stub response
-    onApprove(id, {
-      model: "stub-model",
-      stopReason: "endTurn",
-      role: "assistant",
-      content: {
-        type: "text",
-        text: "This is a stub response.",
-      },
-    });
-  };
-
   return (
     <TabsContent value="sampling">
       <div className="h-96">
@@ -44,21 +30,12 @@ const SamplingTab = ({ pendingRequests, onApprove, onReject }: Props) => {
         <div className="mt-4 space-y-4">
           <h3 className="text-lg font-semibold">Recent Requests</h3>
           {pendingRequests.map((request) => (
-            <div key={request.id} className="p-4 border rounded-lg space-y-4">
-              <JsonView
-                className="bg-gray-50 dark:bg-gray-800 dark:text-gray-100 rounded"
-                data={JSON.stringify(request.request)}
-              />
-
-              <div className="flex space-x-2">
-                <Button onClick={() => handleApprove(request.id)}>
-                  Approve
-                </Button>
-                <Button variant="outline" onClick={() => onReject(request.id)}>
-                  Reject
-                </Button>
-              </div>
-            </div>
+            <SamplingRequest
+              key={request.id}
+              request={request}
+              onApprove={onApprove}
+              onReject={onReject}
+            />
           ))}
           {pendingRequests.length === 0 && (
             <p className="text-gray-500">No pending requests</p>

client/src/components/__tests__/samplingRequest.test.tsx

@@ -0,0 +1,73 @@
+import { render, screen, fireEvent } from "@testing-library/react";
+import SamplingRequest from "../SamplingRequest";
+import { PendingRequest } from "../SamplingTab";
+
+const mockRequest: PendingRequest = {
+  id: 1,
+  request: {
+    method: "sampling/createMessage",
+    params: {
+      messages: [
+        {
+          role: "user",
+          content: {
+            type: "text",
+            text: "What files are in the current directory?",
+          },
+        },
+      ],
+      systemPrompt: "You are a helpful file system assistant.",
+      includeContext: "thisServer",
+      maxTokens: 100,
+    },
+  },
+};
+
+describe("Form to handle sampling response", () => {
+  const mockOnApprove = jest.fn();
+  const mockOnReject = jest.fn();
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it("should call onApprove with correct text content when Approve button is clicked", () => {
+    render(
+      <SamplingRequest
+        request={mockRequest}
+        onApprove={mockOnApprove}
+        onReject={mockOnReject}
+      />,
+    );
+
+    // Click the Approve button
+    fireEvent.click(screen.getByRole("button", { name: /approve/i }));
+
+    // Assert that onApprove is called with the correct arguments
+    expect(mockOnApprove).toHaveBeenCalledWith(mockRequest.id, {
+      model: "stub-model",
+      stopReason: "endTurn",
+      role: "assistant",
+      content: {
+        type: "text",
+        text: "",
+      },
+    });
+  });
+
+  it("should call onReject with correct request id when Reject button is clicked", () => {
+    render(
+      <SamplingRequest
+        request={mockRequest}
+        onApprove={mockOnApprove}
+        onReject={mockOnReject}
+      />,
+    );
+
+    // Click the Approve button
+    fireEvent.click(screen.getByRole("button", { name: /Reject/i }));
+
+    // Assert that onApprove is called with the correct arguments
+    expect(mockOnReject).toHaveBeenCalledWith(mockRequest.id);
+  });
+});

client/src/components/__tests__/samplingTab.test.tsx

@@ -0,0 +1,55 @@
+import { render, screen } from "@testing-library/react";
+import { Tabs } from "@/components/ui/tabs";
+import SamplingTab, { PendingRequest } from "../SamplingTab";
+
+describe("Sampling tab", () => {
+  const mockOnApprove = jest.fn();
+  const mockOnReject = jest.fn();
+
+  const renderSamplingTab = (pendingRequests: PendingRequest[]) =>
+    render(
+      <Tabs defaultValue="sampling">
+        <SamplingTab
+          pendingRequests={pendingRequests}
+          onApprove={mockOnApprove}
+          onReject={mockOnReject}
+        />
+      </Tabs>,
+    );
+
+  it("should render 'No pending requests' when there are no pending requests", () => {
+    renderSamplingTab([]);
+    expect(
+      screen.getByText(
+        "When the server requests LLM sampling, requests will appear here for approval.",
+      ),
+    ).toBeTruthy();
+    expect(screen.findByText("No pending requests")).toBeTruthy();
+  });
+
+  it("should render the correct number of requests", () => {
+    renderSamplingTab(
+      Array.from({ length: 5 }, (_, i) => ({
+        id: i,
+        request: {
+          method: "sampling/createMessage",
+          params: {
+            messages: [
+              {
+                role: "user",
+                content: {
+                  type: "text",
+                  text: "What files are in the current directory?",
+                },
+              },
+            ],
+            systemPrompt: "You are a helpful file system assistant.",
+            includeContext: "thisServer",
+            maxTokens: 100,
+          },
+        },
+      })),
+    );
+    expect(screen.getAllByTestId("sampling-request").length).toBe(5);
+  });
+});

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(`${getMCPProxyAddress(config)}/sse`);
-    mcpProxyServerUrl.searchParams.append("transportType", transportType);
-    if (transportType === "stdio") {
-      mcpProxyServerUrl.searchParams.append("command", command);
-      mcpProxyServerUrl.searchParams.append("args", args);
-      mcpProxyServerUrl.searchParams.append("env", JSON.stringify(env));
-    } else {
-      mcpProxyServerUrl.searchParams.append("url", sseUrl);
+    let mcpProxyServerUrl;
+    switch (transportType) {
+      case "stdio":
+        mcpProxyServerUrl = new URL(`${getMCPProxyAddress(config)}/stdio`);
+        mcpProxyServerUrl.searchParams.append("command", command);
+        mcpProxyServerUrl.searchParams.append("args", args);
+        mcpProxyServerUrl.searchParams.append("env", JSON.stringify(env));
+        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",
-      "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.10.0.tgz",
-      "integrity": "sha512-wijOavYZfSOADbVM0LA7mrQ17N4IKNdFcfezknCCsZ1Y1KstVWlkDZ5ebcxuQJmqTTxsNjBHLc7it1SV0TBiPg==",
+      "version": "1.10.2",
+      "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.10.2.tgz",
+      "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();
-
-    if (backingServerTransport instanceof StdioClientTransport) {
-      backingServerTransport.stderr!.on("data", (chunk) => {
+    (backingServerTransport as StdioClientTransport).stderr!.on(
+      "data",
+      (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;