Class "GuzzleHttp\Promise" not found - but it is there

I am using CI4, php8.0, guzzlehttp/guzzle 7.9.2 & guzzlehttp/promises: 2.0.3. While guzzle works well, when I gets to promises, it fails.

I load up the classes with:

use GuzzleHttp\Client;
use GuzzleHttp\Promise;

I want to settle the promises like below, however, I get Class "GuzzleHttp\Promise" not found

// Wait for all the asynchronous requests to complete
$responses = Promise::settle($promises)->wait();

My composer.json says:

"require": {
            "php": "^7.3||^8.0",
            "codeigniter4/framework": "^4",
            "phpbu/phpbu": "^6.0",
            "guzzlehttp/guzzle": "^7.9.2",
            "guzzlehttp/promises": "2.0.3",
  

In vendor, I can clearly see: guzzlehttp->guzzle guzzlehttp->promises

Not sure how to further debug so any pointers appreciated.

1.Update Namespace

First, ensure you are using the correct namespace. Update your use statements as follows:

use GuzzleHttp\Client;
use GuzzleHttp\Promise\Utils;

2.Modify Code

Then, update your code to use the Utils class for handling promises:

// Wait for all the asynchronous requests to complete
$responses = Utils::settle($promises)->wait();

3.Regenerate Autoloader

Run the following command to regenerate the Composer autoloader:

composer dump-autoload