Unable to use stack channel logging in Laravel

Question

I'm unable to use 'stack' channel logging, hoping you can help.

In my Laravel (9.x) project, I've setup a 'gelf' channel that logs to my Graylog. I want logs both in Graylog and in storage/logs/laravel.log

My config/logging.php:

'default' => 'stack',

'channels' => [
        'stack' => [
            'driver' => 'stack',
            'channels' => ['single', 'gelf'],
            'ignore_exceptions' => false,
        ],

        'single' => [
            'driver' => 'single',
            'path' => storage_path('logs/laravel.log'),
            'level' => env('LOG_LEVEL', 'debug'),
        ],

        'gelf' => [
            'driver' => 'custom',
            ...
        ]
]

In this configuration, I ONLY get log output in laravel.log. If I set channels.stack.channels to ['single'], I of course still get output to laravel.log. If I set channels.stack.channels to ['gelf'], nothing happens. If I change default to 'gelf', then I get Graylog logging, but of course, nothing in laravel.log.

What am I possibly missing? I don't see others on Google with this issue.

---

Troubleshooting attempts:

• I've done php artisan config:cache on every change, so have ruled out caching issues.

• As a temporary work-around, I've just set it to 'gelf' and registered a reportable in the App\Exceptions\Handler::register() method for the single channel:

public function register():void
{
    $this->reportable(function (Throwable $e) {
        Log::channel('single')->warning($e);
    });
}