fix: handle EPIPE errors in StdioServerTransport

Add error handling for stdout write failures to prevent uncaught EPIPE
exceptions when clients disconnect unexpectedly.

Changes:
- Add stdout error listener in start() to catch EPIPE and other errors
- Trigger graceful close when stdout errors occur
- Handle write errors in send() by rejecting the promise
- Clean up stdout error listener in close()

This prevents the Node.js process from crashing when a client disconnects
while the server is writing to stdout.

Fixes #1564

Author: User

packages/server/src/server/stdio.ts

@@ -37,6 +37,14 @@ export class StdioServerTransport implements Transport {
     _onerror = (error: Error) => {
         this.onerror?.(error);
     };
+    _onstdouterror = (error: Error) => {
+        // Handle stdout errors (e.g., EPIPE when client disconnects)
+        // Trigger close to clean up gracefully
+        this.close().catch(() => {
+            // Ignore errors during close
+        });
+        this.onerror?.(error);
+    };
 
     /**
      * Starts listening for messages on `stdin`.
@@ -51,6 +59,7 @@ export class StdioServerTransport implements Transport {
         this._started = true;
         this._stdin.on('data', this._ondata);
         this._stdin.on('error', this._onerror);
+        this._stdout.on('error', this._onstdouterror);
     }
 
     private processReadBuffer() {
@@ -72,6 +81,7 @@ export class StdioServerTransport implements Transport {
         // Remove our event listeners first
         this._stdin.off('data', this._ondata);
         this._stdin.off('error', this._onerror);
+        this._stdout.off('error', this._onstdouterror);
 
         // Check if we were the only data listener
         const remainingDataListeners = this._stdin.listenerCount('data');
@@ -87,12 +97,25 @@ export class StdioServerTransport implements Transport {
     }
 
     send(message: JSONRPCMessage): Promise<void> {
-        return new Promise(resolve => {
+        return new Promise((resolve, reject) => {
             const json = serializeMessage(message);
+            
+            // Handle write errors (e.g., EPIPE when client disconnects)
+            const onError = (error: Error) => {
+                this._stdout.off('error', onError);
+                reject(error);
+            };
+            
+            this._stdout.once('error', onError);
+            
             if (this._stdout.write(json)) {
+                this._stdout.off('error', onError);
                 resolve();
             } else {
-                this._stdout.once('drain', resolve);
+                this._stdout.once('drain', () => {
+                    this._stdout.off('error', onError);
+                    resolve();
+                });
             }
         });
     }