diff --git a/classes/ActionScheduler_Versions.php b/classes/ActionScheduler_Versions.php
index 4bde8839..6985d010 100644
--- a/classes/ActionScheduler_Versions.php
+++ b/classes/ActionScheduler_Versions.php
@@ -17,6 +17,7 @@ class ActionScheduler_Versions {
 	 * @var array<string, callable>
 	 */
 	private $versions = array();
+	private $sources  = array();
 
 	/**
 	 * Register version's callback.
@@ -28,7 +29,12 @@ public function register( $version_string, $initialization_callback ) {
 		if ( isset( $this->versions[ $version_string ] ) ) {
 			return false;
 		}
+
+		$backtrace = debug_backtrace( DEBUG_BACKTRACE_IGNORE_ARGS );
+		$source    = $backtrace[0]['file'];
+
 		$this->versions[ $version_string ] = $initialization_callback;
+		$this->sources[ $source ] = $version_string;
 		return true;
 	}
 
@@ -39,6 +45,10 @@ public function get_versions() {
 		return $this->versions;
 	}
 
+	public function get_sources() {
+		return $this->sources;
+	}
+
 	/**
 	 * Get latest version registered.
 	 */
diff --git a/classes/WP_CLI/System_Command.php b/classes/WP_CLI/System_Command.php
index 5a585b5c..44b33ce6 100644
--- a/classes/WP_CLI/System_Command.php
+++ b/classes/WP_CLI/System_Command.php
@@ -132,6 +132,35 @@ public function version( array $args, array $assoc_args ) {
 		echo $latest;
 	}
 
+	/**
+	 * Get all system sources.
+	 *
+	 * @param array $args       Positional args.
+	 * @param array $assoc_args Keyed args.
+	 * @uses \ActionScheduler_Versions::get_sources()
+	 * @uses \WP_CLI\Formatter::display_items()
+	 * @uses $this->get_latest_version()
+	 * @return void
+	 */
+	public function sources( array $args, array $assoc_args ) {
+		$instance = \ActionScheduler_Versions::instance();
+		$sources  = $instance->get_sources();
+
+		$rows = array();
+
+		foreach ( $sources as $source => $version ) {
+			$rows[ $source ] = array(
+				'source'  => str_replace( ABSPATH, '', $source ),
+				'version' => $version,
+			);
+		}
+
+		ksort( $rows );
+
+		$formatter = new \WP_CLI\Formatter( $assoc_args, array( 'source', 'version' ) );
+		$formatter->display_items( $rows );
+	}
+
 	/**
 	 * Get current data store.
 	 *