fix(agent_api): wire up module lifecycle — auto-start, poll, port 4329

- Call check_cmdline_and_start() from register_types so --agent-api flag works
- Connect poll() to SceneTree::process_frame via deferred callable so
  screenshot/depth/command requests get serviced on the main thread
- Default port changed to 4329 to avoid conflict with C# AgentServer on 4328
- Clean disconnect on stop()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/agent_api/agent_server.cpp

@@ -31,7 +31,7 @@ AgentServer::~AgentServer() {
 }
 
 void AgentServer::_bind_methods() {
-	ClassDB::bind_method(D_METHOD("start", "port", "token"), &AgentServer::start, DEFVAL(4328), DEFVAL(""));
+	ClassDB::bind_method(D_METHOD("start", "port", "token"), &AgentServer::start, DEFVAL(4329), DEFVAL(""));
 	ClassDB::bind_method(D_METHOD("stop"), &AgentServer::stop);
 	ClassDB::bind_method(D_METHOD("is_running"), &AgentServer::is_running);
 	ClassDB::bind_method(D_METHOD("get_port"), &AgentServer::get_port);
@@ -58,6 +58,20 @@ void AgentServer::start(int p_port, const String &p_token) {
 	running = true;
 	server_thread.start(_server_thread_func, this);
 	print_line(vformat("AgentServer: Listening on http://0.0.0.0:%d", port));
+
+	// Connect poll() to the SceneTree's process_frame signal so screenshot/depth/command
+	// requests get serviced on the main thread each frame. Deferred because SceneTree
+	// may not exist yet during module init.
+	callable_mp(this, &AgentServer::_connect_to_scene_tree).call_deferred();
+}
+
+void AgentServer::_connect_to_scene_tree() {
+	SceneTree *tree = SceneTree::get_singleton();
+	if (tree) {
+		tree->connect("process_frame", callable_mp(this, &AgentServer::poll));
+	} else {
+		ERR_PRINT("AgentServer: SceneTree not available, poll() won't run — screenshots will timeout.");
+	}
 }
 
 void AgentServer::stop() {
@@ -68,6 +82,12 @@ void AgentServer::stop() {
 	running = false;
 	server_thread.wait_to_finish();
 
+	// Disconnect from SceneTree if connected.
+	SceneTree *tree = SceneTree::get_singleton();
+	if (tree && tree->is_connected("process_frame", callable_mp(this, &AgentServer::poll))) {
+		tree->disconnect("process_frame", callable_mp(this, &AgentServer::poll));
+	}
+
 	{
 		MutexLock lock(sse_mutex);
 		sse_clients.clear();
@@ -81,7 +101,7 @@ void AgentServer::check_cmdline_and_start() {
 	// Check --agent-api flag or AGENT_API env var.
 	List<String> cmdline_args = OS::get_singleton()->get_cmdline_args();
 	bool should_start = false;
-	int custom_port = 4328;
+	int custom_port = 4329;
 	String custom_token;
 
 	for (const String &arg : cmdline_args) {

modules/agent_api/agent_server.h

@@ -41,7 +41,7 @@ private:
 	Ref<TCPServer> tcp_server;
 	Thread server_thread;
 	bool running = false;
-	int port = 4328;
+	int port = 4329;
 	String auth_token;
 
 	// SSE clients for log/event streaming.
@@ -93,6 +93,7 @@ private:
 	// Server thread function.
 	static void _server_thread_func(void *p_userdata);
 	void _server_loop();
+	void _connect_to_scene_tree();
 	void _handle_connection(Ref<StreamPeerTCP> p_peer);
 
 	// HTTP parsing.
@@ -150,7 +151,7 @@ public:
 	AgentServer();
 	~AgentServer();
 
-	void start(int p_port = 4328, const String &p_token = "");
+	void start(int p_port = 4329, const String &p_token = "");
 	void stop();
 	bool is_running() const { return running; }
 	int get_port() const { return port; }

modules/agent_api/register_types.cpp

@@ -15,6 +15,7 @@ void initialize_agent_api_module(ModuleInitializationLevel p_level) {
 	GDREGISTER_CLASS(AgentServer);
 	agent_server_singleton = memnew(AgentServer);
 	Engine::get_singleton()->add_singleton(Engine::Singleton("AgentServer", AgentServer::get_singleton()));
+	AgentServer::check_cmdline_and_start();
 }
 
 void uninitialize_agent_api_module(ModuleInitializationLevel p_level) {