Create and initialize CosmosClient

clientinitializeasync.cs

List<(string, string)> containers = new List<(string, string)> 
{
  ("DatabaseNameForContainer1", "ContainerName1"),
  ("DatabaseNameForContainer2", "ContainerName2")
};

CosmosClientOptions cosmosClientOptions = new CosmosClientOptions
{
    ApplicationName = "MyApplicationName",
    // any other setting I want to customize
};

CosmosClient cosmosClient = await CosmosClient.CreateAndInitializeAsync(connectionString, containers, cosmosClientOptions);

This is kind of getting to my point with the post :)
If you try that code you see that you don't have access to the serviceProvider at that stage.

I understand that my question might be tricky to solve, but at least to me, this looks like a pretty normal setup of a client.

I see what you mean, you cannot read the config because in your case it comes from serviceProvider.

I've seen cases from it coming from the Configuration, which is built before the services are added (so it's available there).

Yes, I went with that option instead. That works too :)
Thanks!