php - Lumen changed log format from raw json after update

one text

I've upgraded lumen from 5.8 to 9.1 and php from 7.x to 8.1

In my env we load json logs to kibana, but after update log format has changed to something like this:

2022-11-08 11:56:47 App\Domain\Email\Listeners\MoveEmailToProcessed{"message":"Marked email as processed","context":{"object_key":"incoming/0i02qrl9t4llea3fhfm2t6184r3nv9rs7nb4cu01","email":"wx1vx6fnek7rqhcr@lead-import.test.com"},"level":200,"level_name":"INFO","channel":"production","datetime":"2022-11-08T11:56:48.006053+00:00","extra":{}}
  447.64ms DONE

while it was and should stay raw JSON like this:

{"message":"Marked email as processed","context":{"object_key":"incoming/0i02qrl9t4llea3fhfm2t6184r3nv9rs7nb4cu01","email":"wx1vx6fnek7rqhcr@lead-import.test.com"},"level":200,"level_name":"INFO","channel":"production","datetime":"2022-11-08T11:56:48.006053+00:00","extra":{}}

I have config for this as different channel in lumen using monolog:

'stdout-json' => [
    'driver' => 'monolog',
    'handler' => StreamHandler::class,
    'with' => [
        'stream' => 'php://stdout',
    ],
    'formatter' => Monolog\Formatter\JsonFormatter::class,
],

And since format has changed it don't end up in kibana as expected. Question is what am I missing? Config didn't changed and I didn't saw anything specific in any upgrade guide I was following. Any idea what might be wrong?

Oh, and I don't use any lumen 'shortcuts' so logger is injected as it should. So code looks like this i.e.

public function __construct(Cloud $s3, LoggerInterface $logger)
{
    $this->s3 = $s3;
    $this->logger = $logger;
}

public function handle(EmailProcessed $emailProcessed): void
{
    $filename = explode('/', $emailProcessed->getObjectKey())[1];
    $newPath = sprintf('%s/%s', self::PROCESSED_DIR, $filename);

    if ($this->s3->exists($newPath)) {
        $this->s3->delete($newPath);
    }

    $this->s3->move($emailProcessed->getObjectKey(), $newPath);

    $this->logger->info(
        'Marked email as processed',
        [
            'object_key' => $emailProcessed->getObjectKey(),
            'email' => $emailProcessed->getEmail(),
        ]
    );
}