fix: flush CLI stdio before forced exit

src/cli.ts

@@ -403,15 +403,21 @@ function flushWriteStream(stream: NodeJS.WriteStream, timeoutMs: number): Promis
     const finishAfterDrain = () => {
       setImmediate(cleanup);
     };
+    const finishWhenDrained = () => {
+      if (settled) {
+        return;
+      }
+      if (stream.destroyed || stream.writableEnded || (!stream.writableNeedDrain && stream.writableLength === 0)) {
+        cleanup();
+        return;
+      }
+      setImmediate(finishWhenDrained);
+    };
 
     timeout = setTimeout(cleanup, timeoutMs);
     stream.once('drain', finishAfterDrain);
     stream.once('error', cleanup);
-    setImmediate(() => {
-      if (stream.destroyed || stream.writableEnded || !stream.writableNeedDrain) {
-        cleanup();
-      }
-    });
+    setImmediate(finishWhenDrained);
   });
 }
 

tests/cli-force-exit-behavior.integration.test.ts

@@ -50,6 +50,7 @@ const [cliEntry, configPath] = process.argv.slice(2);
 process.env.MCPORTER_DISABLE_AUTORUN = '1';
 
 let cleanupErrorListenerSeen = false;
+let cleanupEmptyWriteSeen = false;
 let cliRunning = false;
 Object.defineProperty(process.stdout, 'writableNeedDrain', {
   configurable: true,
@@ -70,6 +71,13 @@ process.stdout.once = (event, listener) => {
   }
   return result;
 };
+const originalWrite = process.stdout.write.bind(process.stdout);
+process.stdout.write = (chunk, encoding, callback) => {
+  if (cliRunning && chunk === '') {
+    cleanupEmptyWriteSeen = true;
+  }
+  return originalWrite(chunk, encoding, callback);
+};
 
 const { runCli } = await import(pathToFileURL(cliEntry).href);
 cliRunning = true;
@@ -78,6 +86,10 @@ if (!cleanupErrorListenerSeen) {
   console.error('expected force-exit cleanup to observe stdout errors');
   process.exitCode = 1;
 }
+if (cleanupEmptyWriteSeen) {
+  console.error('expected force-exit cleanup not to write to stdout');
+  process.exitCode = 1;
+}
 `;
   const scriptPath = path.join(tempDir, 'cleanup-stdout-error.mjs');
   await fs.writeFile(scriptPath, script, 'utf8');