[MCP-SDK] stdio client crashes with "MCP error -32000: Connection closed" when spawned server exits unexpectedly

Describe the bug
A clear and concise description of what the bug is.

🐛 Bug description

When using @modelcontextprotocol/sdk in stdio mode, the child server process exits almost immediately after spawn.
The client then receives MCP error -32000: Connection closed and the whole Node.js process terminates via triggerUncaughtException because the rejection is not handled.

📋 Reproduction steps

1. Clone demo repo

   git clone https://github.com/masx200/mcp-demo-streamable-http-bridge.git
   cd mcp-demo-streamable-http-bridge
   npm i
Build / start the server bundle

npm run build   # outputs dist/server.js
Run the client (stdio mode)

npm run dev     # spawns `node dist/server.js` internally
Observe crash within 1 s.
✅ Expected behavior
Client should either:
keep the connection alive, or
emit a catch-able error instead of killing the entire process.
❌ Actual behavior

McpError: MCP error -32000: Connection closed
    at Client._onclose (file:///D:/github/…/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:130:23)
    …
    at ChildProcess._handle.onexit (node:internal/child_process:305:5)
Node.js v24.10.0 then calls triggerUncaughtException and exits with code 1.

To Reproduce
Steps to reproduce the behavior:
1.

pnpx cross-env "NODE_OPTIONS=--trace-warnings --trace-uncaught" node  D:\github\mcp-demo-streamable-http-bridge\main.js --config "F:\projects\test\settings.json" --port 41111

Expected behavior
A clear and concise description of what you expected to happen.

Logs
If applicable, add logs to help explain your problem.

file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:109
        const error = new McpError(ErrorCode.ConnectionClosed, 'Connection closed');
                      ^

McpError: MCP error -32000: Connection closed
    at Client._onclose (file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:109:23)
    at _transport.onclose (file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:76:18)
    at ChildProcess.<anonymous> (file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/client/stdio.js:95:77)
    at ChildProcess.emit (node:events:508:28)
    at cp.emit (D:\github\mcp-demo-streamable-http-bridge\node_modules\.store\cross-spawn@7.0.6\node_modules\cross-spawn\lib\enoent.js:34:29)
    at maybeClose (node:internal/child_process:1101:16)
    at ChildProcess._handle.onexit (node:internal/child_process:305:5) {
  code: -32000,
  data: undefined
}
Thrown at:
    at _onclose (file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:109:23)
    at _transport.onclose (file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:76:18)
    at file:///D:/github/mcp-demo-streamable-http-bridge/node_modules/.store/@modelcontextprotocol+sdk@1.20.2/node_modules/@modelcontextprotocol/sdk/dist/esm/client/stdio.js:95:77
    at emit (node:events:508:28)
    at cp.emit (D:\github\mcp-demo-streamable-http-bridge\node_modules\.store\cross-spawn@7.0.6\node_modules\cross-spawn\lib\enoent.js:34:29)
    at maybeClose (node:internal/child_process:1101:16)
    at ChildProcess._handle.onexit (node:internal/child_process:305:5)


Node.js v24.10.0

Additional context
Add any other context about the problem here.

 process.on("uncaughtException", (error) => {
   console.error("Uncaught exception:", error);
})

Reproduce the failure with the linked demo commands, then inspect the close path in dist/esm/shared/protocol.js and dist/esm/client/stdio.js shown in the stack trace. Compare the child-process exit handling with the expected catchable-error behavior, and verify the result by rerunning the stdio client without an uncaught process termination.