diff --git a/inc/class-wp-ultimo.php b/inc/class-wp-ultimo.php
index ed9fee4f..c0967e76 100644
--- a/inc/class-wp-ultimo.php
+++ b/inc/class-wp-ultimo.php
@@ -912,6 +912,14 @@ protected function load_managers(): void {
 		 */
 		WP_Ultimo\Managers\Site_Manager::get_instance();
 
+		/*
+		 * Loads the Post-Signup Activity manager.
+		 *
+		 * Tracks post creation, CPT creation, user registration, and
+		 * WooCommerce orders on managed subsites (issue #399).
+		 */
+		WP_Ultimo\Managers\Post_Signup_Activity_Manager::get_instance();
+
 		/*
 		 * Loads the Checkout Form manager.
 		 */
diff --git a/inc/managers/class-post-signup-activity-manager.php b/inc/managers/class-post-signup-activity-manager.php
new file mode 100644
index 00000000..fa643629
--- /dev/null
+++ b/inc/managers/class-post-signup-activity-manager.php
@@ -0,0 +1,376 @@
+<?php
+/**
+ * Post-Signup Activity Manager
+ *
+ * Tracks actions taken by subsite users after signup:
+ * post creation, custom post type creation, user registration,
+ * and WooCommerce orders. Events are linked to the originating
+ * membership/subsite and viewable by the network admin on the
+ * site edit page's Events widget.
+ *
+ * @package WP_Ultimo
+ * @subpackage Managers
+ * @since 2.5.0
+ */
+
+namespace WP_Ultimo\Managers;
+
+use WP_Ultimo\Models\Event;
+
+// Exit if accessed directly
+defined('ABSPATH') || exit;
+
+/**
+ * Tracks post-signup activity on customer subsites.
+ *
+ * @since 2.5.0
+ */
+class Post_Signup_Activity_Manager {
+
+	use \WP_Ultimo\Traits\Singleton;
+
+	/**
+	 * Post types that are excluded from tracking (internal WP types).
+	 *
+	 * @since 2.5.0
+	 * @var array
+	 */
+	const EXCLUDED_POST_TYPES = [
+		'revision',
+		'auto-draft',
+		'nav_menu_item',
+		'customize_changeset',
+		'oembed_cache',
+		'user_request',
+		'wp_block',
+		'wp_template',
+		'wp_template_part',
+		'wp_global_styles',
+		'wp_navigation',
+		'wp_font_family',
+		'wp_font_face',
+	];
+
+	/**
+	 * Registers hooks.
+	 *
+	 * @since 2.5.0
+	 * @return void
+	 */
+	public function init(): void {
+
+		// Register event types after the event manager has set up.
+		add_action('wu_register_all_events', [$this, 'register_event_types']);
+
+		// Only hook subsite activity on non-main sites.
+		add_action('plugins_loaded', [$this, 'register_subsite_hooks'], 20);
+	}
+
+	/**
+	 * Registers the four post-signup event types.
+	 *
+	 * @since 2.5.0
+	 * @return void
+	 */
+	public function register_event_types(): void {
+
+		wu_register_event_type(
+			'subsite_post_created',
+			[
+				'name'            => __('Subsite Post Created', 'ultimate-multisite'),
+				'desc'            => __('Fired when a customer publishes a new post on their subsite.', 'ultimate-multisite'),
+				'payload'         => fn() => array_merge(
+					[
+						'post_id'        => 1,
+						'post_title'     => 'Example Post',
+						'post_type'      => 'post',
+						'post_status'    => 'publish',
+						'post_author_id' => 1,
+					],
+					wu_generate_event_payload('site'),
+					wu_generate_event_payload('membership')
+				),
+				'deprecated_args' => [],
+			]
+		);
+
+		wu_register_event_type(
+			'subsite_cpt_created',
+			[
+				'name'            => __('Subsite Custom Post Type Entry Created', 'ultimate-multisite'),
+				'desc'            => __('Fired when a customer creates a new entry of a custom post type on their subsite.', 'ultimate-multisite'),
+				'payload'         => fn() => array_merge(
+					[
+						'post_id'        => 1,
+						'post_title'     => 'Example CPT Entry',
+						'post_type'      => 'product',
+						'post_status'    => 'publish',
+						'post_author_id' => 1,
+					],
+					wu_generate_event_payload('site'),
+					wu_generate_event_payload('membership')
+				),
+				'deprecated_args' => [],
+			]
+		);
+
+		wu_register_event_type(
+			'subsite_user_registered',
+			[
+				'name'            => __('Subsite User Registered', 'ultimate-multisite'),
+				'desc'            => __('Fired when a new user is added to a customer subsite.', 'ultimate-multisite'),
+				'payload'         => fn() => array_merge(
+					[
+						'new_user_id'    => 1,
+						'new_user_login' => 'example_user',
+						'new_user_email' => 'user@example.com',
+						'new_user_role'  => 'subscriber',
+					],
+					wu_generate_event_payload('site'),
+					wu_generate_event_payload('membership')
+				),
+				'deprecated_args' => [],
+			]
+		);
+
+		wu_register_event_type(
+			'subsite_woocommerce_order',
+			[
+				'name'            => __('Subsite WooCommerce Order Placed', 'ultimate-multisite'),
+				'desc'            => __('Fired when a WooCommerce order is created on a customer subsite.', 'ultimate-multisite'),
+				'payload'         => fn() => array_merge(
+					[
+						'order_id'     => 1,
+						'order_total'  => '99.00',
+						'order_status' => 'pending',
+						'order_items'  => 1,
+					],
+					wu_generate_event_payload('site'),
+					wu_generate_event_payload('membership')
+				),
+				'deprecated_args' => [],
+			]
+		);
+	}
+
+	/**
+	 * Registers hooks that run on customer subsites.
+	 *
+	 * Only registers on non-main sites that are WU-managed.
+	 *
+	 * @since 2.5.0
+	 * @return void
+	 */
+	public function register_subsite_hooks(): void {
+
+		// Skip the main site — we only track customer subsites.
+		if (is_main_site()) {
+			return;
+		}
+
+		// Track post/CPT creation (fires on publish transition).
+		add_action('transition_post_status', [$this, 'track_post_published'], 10, 3);
+
+		// Track new user added to this subsite.
+		add_action('add_user_to_blog', [$this, 'track_user_added_to_blog'], 10, 3);
+
+		// Track WooCommerce orders (fires when a new order is created).
+		add_action('woocommerce_new_order', [$this, 'track_woocommerce_order'], 10, 2);
+	}
+
+	/**
+	 * Tracks when a post transitions to "publish" status for the first time.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string   $new_status The new post status.
+	 * @param string   $old_status The old post status.
+	 * @param \WP_Post $post       The post object.
+	 * @return void
+	 */
+	public function track_post_published(string $new_status, string $old_status, \WP_Post $post): void {
+
+		// Only fire on the first publish transition.
+		if ('publish' !== $new_status || 'publish' === $old_status) {
+			return;
+		}
+
+		// Skip excluded/internal post types.
+		if (in_array($post->post_type, self::EXCLUDED_POST_TYPES, true)) {
+			return;
+		}
+
+		$blog_id = get_current_blog_id();
+		$wu_site = $this->get_wu_site($blog_id);
+
+		if ( ! $wu_site) {
+			return;
+		}
+
+		$is_cpt = 'post' !== $post->post_type && 'page' !== $post->post_type;
+		$slug   = $is_cpt ? 'subsite_cpt_created' : 'subsite_post_created';
+
+		$payload = $this->build_site_membership_payload($wu_site);
+		$payload = array_merge(
+			$payload,
+			[
+				'post_id'        => $post->ID,
+				'post_title'     => $post->post_title,
+				'post_type'      => $post->post_type,
+				'post_status'    => $post->post_status,
+				'post_author_id' => (int) $post->post_author,
+				'object_type'    => 'site',
+				'object_id'      => $wu_site->get_id(),
+			]
+		);
+
+		wu_create_event(
+			[
+				'severity'    => Event::SEVERITY_INFO,
+				'slug'        => $slug,
+				'initiator'   => 'system',
+				'object_type' => 'site',
+				'object_id'   => $wu_site->get_id(),
+				'payload'     => $payload,
+			]
+		);
+	}
+
+	/**
+	 * Tracks when a user is added to a subsite.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param int    $user_id The user ID being added.
+	 * @param string $role    The role assigned.
+	 * @param int    $blog_id The blog ID the user is being added to.
+	 * @return void
+	 */
+	public function track_user_added_to_blog(int $user_id, string $role, int $blog_id): void {
+
+		$wu_site = $this->get_wu_site($blog_id);
+
+		if ( ! $wu_site) {
+			return;
+		}
+
+		$user = get_userdata($user_id);
+
+		$payload = $this->build_site_membership_payload($wu_site);
+		$payload = array_merge(
+			$payload,
+			[
+				'new_user_id'    => $user_id,
+				'new_user_login' => $user ? $user->user_login : '',
+				'new_user_email' => $user ? $user->user_email : '',
+				'new_user_role'  => $role,
+				'object_type'    => 'site',
+				'object_id'      => $wu_site->get_id(),
+			]
+		);
+
+		wu_create_event(
+			[
+				'severity'    => Event::SEVERITY_INFO,
+				'slug'        => 'subsite_user_registered',
+				'initiator'   => 'system',
+				'object_type' => 'site',
+				'object_id'   => $wu_site->get_id(),
+				'payload'     => $payload,
+			]
+		);
+	}
+
+	/**
+	 * Tracks when a WooCommerce order is created on a subsite.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param int       $order_id The WooCommerce order ID.
+	 * @param \WC_Order $order    The WooCommerce order object.
+	 * @return void
+	 */
+	public function track_woocommerce_order(int $order_id, $order): void {
+
+		$blog_id = get_current_blog_id();
+		$wu_site = $this->get_wu_site($blog_id);
+
+		if ( ! $wu_site) {
+			return;
+		}
+
+		$order_total  = $order ? $order->get_total() : 0;
+		$order_status = $order ? $order->get_status() : '';
+		$order_items  = $order ? count($order->get_items()) : 0;
+
+		$payload = $this->build_site_membership_payload($wu_site);
+		$payload = array_merge(
+			$payload,
+			[
+				'order_id'     => $order_id,
+				'order_total'  => (string) $order_total,
+				'order_status' => $order_status,
+				'order_items'  => $order_items,
+				'object_type'  => 'site',
+				'object_id'    => $wu_site->get_id(),
+			]
+		);
+
+		wu_create_event(
+			[
+				'severity'    => Event::SEVERITY_INFO,
+				'slug'        => 'subsite_woocommerce_order',
+				'initiator'   => 'system',
+				'object_type' => 'site',
+				'object_id'   => $wu_site->get_id(),
+				'payload'     => $payload,
+			]
+		);
+	}
+
+	/**
+	 * Looks up the WU site object for a given WordPress blog ID.
+	 *
+	 * Returns false if the blog is not a WU-managed customer site.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param int $blog_id The WordPress blog ID.
+	 * @return \WP_Ultimo\Models\Site|false
+	 */
+	protected function get_wu_site(int $blog_id) {
+
+		if ( ! function_exists('wu_get_site')) {
+			return false;
+		}
+
+		$wu_site = wu_get_site($blog_id);
+
+		if ( ! $wu_site || ! $wu_site->get_membership_id()) {
+			return false;
+		}
+
+		return $wu_site;
+	}
+
+	/**
+	 * Builds the site and membership payload arrays for an event.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param \WP_Ultimo\Models\Site $wu_site The WU site object.
+	 * @return array
+	 */
+	protected function build_site_membership_payload($wu_site): array {
+
+		$payload = wu_generate_event_payload('site', $wu_site);
+
+		$membership = $wu_site->get_membership();
+
+		if ($membership) {
+			$payload = array_merge($payload, wu_generate_event_payload('membership', $membership));
+		}
+
+		return $payload;
+	}
+}
diff --git a/tests/WP_Ultimo/Managers/Post_Signup_Activity_Manager_Test.php b/tests/WP_Ultimo/Managers/Post_Signup_Activity_Manager_Test.php
new file mode 100644
index 00000000..26147ea6
--- /dev/null
+++ b/tests/WP_Ultimo/Managers/Post_Signup_Activity_Manager_Test.php
@@ -0,0 +1,186 @@
+<?php
+/**
+ * Unit tests for Post_Signup_Activity_Manager.
+ *
+ * @package WP_Ultimo\Tests\Managers
+ */
+
+namespace WP_Ultimo\Tests\Managers;
+
+use WP_Ultimo\Managers\Post_Signup_Activity_Manager;
+
+/**
+ * Tests for the post-signup activity tracking manager (issue #399).
+ */
+class Post_Signup_Activity_Manager_Test extends \WP_UnitTestCase {
+
+	/**
+	 * The manager instance under test.
+	 *
+	 * @var Post_Signup_Activity_Manager
+	 */
+	protected $manager;
+
+	/**
+	 * Set up the test.
+	 *
+	 * @return void
+	 */
+	public function setUp(): void {
+
+		parent::setUp();
+
+		$this->manager = Post_Signup_Activity_Manager::get_instance();
+	}
+
+	/**
+	 * The manager is a singleton and returns the same instance.
+	 */
+	public function test_singleton_returns_same_instance(): void {
+
+		$a = Post_Signup_Activity_Manager::get_instance();
+		$b = Post_Signup_Activity_Manager::get_instance();
+
+		$this->assertSame($a, $b);
+	}
+
+	/**
+	 * register_event_types registers all four expected event slugs.
+	 */
+	public function test_register_event_types_registers_all_slugs(): void {
+
+		// Trigger registration.
+		$this->manager->register_event_types();
+
+		$expected_slugs = [
+			'subsite_post_created',
+			'subsite_cpt_created',
+			'subsite_user_registered',
+			'subsite_woocommerce_order',
+		];
+
+		foreach ($expected_slugs as $slug) {
+			$event = wu_get_event_type($slug);
+			$this->assertIsArray($event, "Event type '{$slug}' should be registered.");
+			$this->assertArrayHasKey('name', $event, "Event type '{$slug}' should have a 'name' key.");
+			$this->assertArrayHasKey('desc', $event, "Event type '{$slug}' should have a 'desc' key.");
+		}
+	}
+
+	/**
+	 * on_post_published does nothing when the post status is not 'publish'.
+	 */
+	public function test_on_post_published_ignores_non_publish_status(): void {
+
+		$post = $this->factory->post->create_and_get(
+			[
+				'post_status' => 'draft',
+				'post_type'   => 'post',
+			]
+		);
+
+		$events_before = wu_get_events(['number' => 9999]);
+
+		// Simulate a draft-to-draft transition (should be ignored).
+		$this->manager->on_post_published('draft', 'draft', $post);
+
+		$events_after = wu_get_events(['number' => 9999]);
+
+		$this->assertCount(
+			count($events_before),
+			$events_after,
+			'No new event should be created for a non-publish transition.'
+		);
+	}
+
+	/**
+	 * on_post_published does nothing when old and new status are both 'publish'.
+	 */
+	public function test_on_post_published_ignores_re_save_of_published_post(): void {
+
+		$post = $this->factory->post->create_and_get(
+			[
+				'post_status' => 'publish',
+				'post_type'   => 'post',
+			]
+		);
+
+		$events_before = wu_get_events(['number' => 9999]);
+
+		// Simulate a publish-to-publish transition (re-save, should be ignored).
+		$this->manager->on_post_published('publish', 'publish', $post);
+
+		$events_after = wu_get_events(['number' => 9999]);
+
+		$this->assertCount(
+			count($events_before),
+			$events_after,
+			'No new event should be created when re-saving an already-published post.'
+		);
+	}
+
+	/**
+	 * on_post_published does nothing for excluded post types.
+	 */
+	public function test_on_post_published_ignores_excluded_post_types(): void {
+
+		$post = $this->factory->post->create_and_get(
+			[
+				'post_status' => 'draft',
+				'post_type'   => 'revision',
+			]
+		);
+
+		$events_before = wu_get_events(['number' => 9999]);
+
+		$this->manager->on_post_published('publish', 'draft', $post);
+
+		$events_after = wu_get_events(['number' => 9999]);
+
+		$this->assertCount(
+			count($events_before),
+			$events_after,
+			'No event should be created for excluded post types like "revision".'
+		);
+	}
+
+	/**
+	 * get_wu_site returns false when wu_get_site is not available.
+	 */
+	public function test_get_wu_site_returns_false_for_unknown_blog(): void {
+
+		// Use reflection to call the protected method.
+		$reflection = new \ReflectionClass($this->manager);
+		$method     = $reflection->getMethod('get_wu_site');
+		$method->setAccessible(true);
+
+		// Blog ID 99999 should not exist.
+		$result = $method->invoke($this->manager, 99999);
+
+		$this->assertFalse($result, 'get_wu_site should return false for an unknown blog ID.');
+	}
+
+	/**
+	 * EXCLUDED_POST_TYPES constant contains expected internal types.
+	 */
+	public function test_excluded_post_types_contains_revision(): void {
+
+		$this->assertContains(
+			'revision',
+			Post_Signup_Activity_Manager::EXCLUDED_POST_TYPES,
+			'"revision" must be in the excluded post types list.'
+		);
+	}
+
+	/**
+	 * EXCLUDED_POST_TYPES constant contains auto-draft.
+	 */
+	public function test_excluded_post_types_contains_auto_draft(): void {
+
+		$this->assertContains(
+			'auto-draft',
+			Post_Signup_Activity_Manager::EXCLUDED_POST_TYPES,
+			'"auto-draft" must be in the excluded post types list.'
+		);
+	}
+}