No need for class

lib/api-event-iterator.js

@@ -0,0 +1,17 @@
+import {on} from 'node:events';
+
+export async function * asyncEventIteratorFromApi(api) {
+	for await (const [plan] of on(api, 'run')) {
+		yield {
+			type: 'run',
+			plan,
+		};
+
+		for await (const [stateChange] of on(plan.status, 'stateChange')) {
+			yield {
+				type: 'stateChange',
+				stateChange,
+			};
+		}
+	}
+}

lib/cli.js

@@ -8,6 +8,7 @@ import figures from 'figures';
 import yargs from 'yargs';
 import {hideBin} from 'yargs/helpers'; // eslint-disable-line n/file-extension-in-import
 
+import {asyncEventIteratorFromApi} from './api-event-iterator.js';
 import Api from './api.js';
 import {chalk} from './chalk.js';
 import validateEnvironmentVariables from './environment-variables.js';
@@ -19,7 +20,6 @@ import {loadConfig} from './load-config.js';
 import normalizeModuleTypes from './module-types.js';
 import normalizeNodeArguments from './node-arguments.js';
 import pkg from './pkg.cjs';
-import { ExternalRunObserver } from './external-run-observer.js';
 
 function exit(message) {
 	console.error(`\n  ${chalk.red(figures.cross)} ${message}`);
@@ -472,7 +472,11 @@ export default async function loadCli() { // eslint-disable-line complexity
 		});
 	}
 
-	const externalRunObserver = combined.observeRun ? new ExternalRunObserver(api, combined.observeRun) : null;
+	if (combined.observeRun) {
+		combined.observeRun({
+			events: asyncEventIteratorFromApi(api),
+		});
+	}
 
 	api.on('run', async plan => {
 		reporter.startRun(plan);