I can create multiple services with the load method.

… but I want each service to have the same tag, with some attributes that can be inferred from the service class itself:

// config/services.php
return static function (ContainerConfigurator $container): void {    
    $services = $container->services()
        ->defaults()
        ->autoconfigure()
        ->autowire();

    $services->load('App\Components\', __DIR__ . '/../src/App/Components')
        ->tag('mytag', [
            'key' => null, // this should depend on service class
        ]);
}

Does Symfony offer a way to accomplish this?

I would, instead (i don’t like both solutions):

In services.php, manually loop src/App/Components and use the reflection to extract the information I need, then call set to register the service

// config/services.php
$files = (new Finder())->files()->name('*.php')->in(__DIR__ . '/../src/App/Components');
foreach ($files as $file) {
    // Extract the FQCN
    $reflection = new ReflectionClass($fqcn);

    $services->set($reflection->getName())
        ->tag('mytag', ['key' => $reflection->getShortName());
}

Another solution would be to assign a “temporary tag”, then use a compiler pass to get the information I need and assign the final tag to it:

// config/services.php
$services->load('App\Components\', __DIR__ . '/../src/App/Components')
  ->tag('temp_tag');


// DependencyInjection/TagPass.php
foreach ($container->findTaggedServiceIds('temp_tag') as $id => $tags) {
    $definition = $container->getDefinition($id);

    $reflection = new ReflectionClass($definition->getClass());

    $definition
        ->clearTags()
        ->addTag('mytag', ['key' => $reflection->getShortName()]);

}