SSE stream disconnected: TypeError: terminated

I got an error "SSE stream disconnected: TypeError: terminated" every 5 minutes with the server connection on the cline or cursor, does anyone know why?
ts code:
`import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import express from 'express';
import * as z from 'zod/v4';

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

// Create the MCP server once (can be reused across requests)
const server = new McpServer({
name: 'example-server',
version: '1.0.0'
});

// Set up your tools, resources, and prompts
server.registerTool(
'echo',
{
title: 'Echo',
description: 'echo',
inputSchema: { name: z.string() },
},
async ({ name }) => {

  return { content: [{ type: 'text', text: `Hello ${name}` }] };
}

);

app.post('/mcp', async (req, res) => {
try {
const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined,
enableJsonResponse: true
});

    res.on('close', () => {
        transport.close();
    });

    await server.connect(transport);
    await transport.handleRequest(req, res, req.body);
} catch (error) {
    console.error('Error handling MCP request:', error);
    if (!res.headersSent) {
        res.status(500).json({
            jsonrpc: '2.0',
            error: {
                code: -32603,
                message: 'Internal server error'
            },
            id: null
        });
    }
}

});

// Reusable handler for GET and DELETE requests
const handleSessionRequest = async (req: express.Request, res: express.Response) => {
const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined,
enableJsonResponse: true
});
await transport.handleRequest(req, res);
};

// Handle GET requests for server-to-client notifications via SSE
app.get('/mcp', handleSessionRequest);

const port = parseInt(process.env.PORT || '3000');
app.listen(port, () => {
console.log(MCP Server running on http://localhost:${port}/mcp);
}).on('error', error => {
console.error('Server error:', error);
process.exit(1);
});
mcp setting:"demo": {
"disabled": false,
"timeout": 1800,
"type": "streamableHttp",
"url": "http://localhost:3000/mcp"
}`
cline version 3.38.3

cursor version 1.4.3

Start by reproducing the reported disconnect with the provided Express /mcp handlers and the StreamableHTTPServerTransport setup. Inspect how the POST and GET handlers manage the transport and compare the behavior with the Cline and Cursor configurations; done means identifying the cause of the five-minute termination and documenting a verified resolution.