package.json

{
  "name": "crashtest",
  "version": "1.0.0",
  "main": "dist/server.js",
  "type": "module",
  "scripts": {
    "build": "tsc",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "dependencies": {
    "@modelcontextprotocol/sdk": "^1.11.0",
    "express": "^4.18.2",
    "zod": "^3.22.4"
  },
  "devDependencies": {
    "@types/express": "^4.17.21",
    "@types/node": "^20.12.10",
    "typescript": "^5.8.3"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": ""
}

server.ts

//npm install && npm run build && node ./dist/server.js
import express from "express";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
import { z } from "zod";

const server = new McpServer({
  name: "crashtest",
  version: "1.0.0"
});
server.tool(
  "crashtest0-undefined",
  `Some Description`,
  //  {  },//change to {} to crash
  async (_extra) => {
    return {
      content: [{ type: "text", text: "did it work?" }],
    };
  }
);

server.tool(
  "crashtest1-empty",
  `Some Description`,
  {}, //change to {} to crash
  async (_extra) => {
    return {
      content: [{ type: "text", text: "did it work?" }],
    };
  }
);
server.tool(
  "crashtest2-dummy",
  `Some Description`,
  { dummyArg: z.string() }, //change to {} to crash
  async (_extra) => {
    return {
      content: [{ type: "text", text: "did it work?" }],
    };
  }
);

const app = express();
app.use(express.json());

app.use((req, res, next) => {
  next();
});

const transports = {
  streamable: {} as Record<string, StreamableHTTPServerTransport>,
  sse: {} as Record<string, SSEServerTransport>
};

// Streamable HTTP endpoint placeholder
app.all('/mcp', async (req, res) => {
  console.log(`[MCP HTTP] ${req.method} ${req.originalUrl}`);
});

// SSE endpoint
app.get('/sse', async (req, res) => {
  console.log(`[SSE] New connection from ${req.ip}`);
  const transport = new SSEServerTransport('/messages', res);
  transports.sse[transport.sessionId] = transport;
  res.on("close", () => {
    delete transports.sse[transport.sessionId];
  });
  await server.connect(transport);
});

// Message endpoint
app.post('/messages', async (req, res) => {
  const sessionId = req.query.sessionId as string;
  const transport = transports.sse[sessionId];
  if (transport) {
    await transport.handlePostMessage(req, res, req.body);
  } else {
    res.status(400).send('No transport found for sessionId');
  }
});

// Start server
app.listen(8080, () => {
  console.log(`Server listening on port 8080`);
});

tsconfig.json

{
  "name": "crashtest",
  "version": "1.0.0",
  "main": "dist/server.js",
  "type": "module",
  "scripts": {
    "build": "tsc",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "dependencies": {
    "@modelcontextprotocol/sdk": "^1.10.2",
    "express": "^4.18.2",
    "zod": "^3.22.4"
  },
  "devDependencies": {
    "@types/express": "^4.17.21",
    "@types/node": "^20.12.10",
    "typescript": "^5.8.3"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": ""
}

1.11.1

1.10.2

1.11.0