Use node echo probe for transport e2e

Author: pallyoung

tests/e2e/fixtures/agent-stdin-echo.mjs

@@ -0,0 +1,15 @@
+process.stdin.setEncoding('utf8');
+
+let buffer = '';
+
+process.stdin.on('data', (chunk) => {
+  buffer += chunk;
+  const newlineIndex = buffer.search(/[\r\n]/u);
+  if (newlineIndex === -1) {
+    return;
+  }
+
+  const line = buffer.slice(0, newlineIndex);
+  process.stdout.write(`${line}\n`);
+  process.exit(0);
+});

tests/e2e/transport.spec.ts

@@ -83,6 +83,7 @@ const BACKEND_WS_PATH = '/ws';
 const WS_RECONNECT_DELAY_MS = 800;
 const WORKSPACE_PATH = process.cwd();
 const WORKSPACE_PROBE_FILE = path.join(WORKSPACE_PATH, 'package.json');
+const AGENT_STDIN_ECHO_SCRIPT = 'tests/e2e/fixtures/agent-stdin-echo.mjs';
 const execFileAsync = promisify(execFile);
 
 const incrementCounts = (counts: PollCounts) => ({
@@ -648,15 +649,13 @@ function buildTerminalProbeInput(target: WorkspaceHandle['target']) {
 }
 
 function buildAgentProbeCommand(target: WorkspaceHandle['target']) {
-  return isWindowsNativeTarget(target)
-    ? 'cmd /Q /D /K'
-    : 'cat';
+  void target;
+  return `node ${AGENT_STDIN_ECHO_SCRIPT}`;
 }
 
 function buildAgentProbeInput(target: WorkspaceHandle['target']) {
-  return isWindowsNativeTarget(target)
-    ? 'echo transport-agent'
-    : 'transport-agent';
+  void target;
+  return 'transport-agent';
 }
 
 function countTrackedSockets(tracker: TransportTrackerSnapshot, fragment: string) {