Custom Credential Resolution Order in AWS SDK for .NET V4

[normj]

We need to provide mechanisms in V4's new DefaultAWSCredentialsIdentityResolver to allow users to change the order of the credential providers. This was a feature the now deprecated FallbackCredentialsFactory had which was used by users like @Vake93 in the discussion below.

In the meantime users will need to continue using the FallbackCredentialsFactory and since the service clients don't use FallbackCredentialsFactory they will need to directly use FallbackCredentialsFactory to resolve credentials and pass the credentials into the service client.

Discussed in #3834

^{Originally posted by Vake93 May 21, 2025}
In AWS SDK for .NET V3, we were able to override the default credential resolution order by configuring:

FallbackCredentialsFactory.CredentialsGenerators = [
    AwsConfigCredentialsFactory.GetAwsCredentials,
    EnvironmentVariablesCredentials.FromEnvironmentVariables,
    AssumeRoleWithWebIdentityCredentials.FromEnvironmentVariables,
];

This allowed us to prioritize AWS Profiles and Environment Variables over Web Identity credentials, which aligns better with our use case.

However, in AWS SDK V4, FallbackCredentialsFactory is deprecated and no longer available. We're looking for guidance on how to achieve a similar customization of credential resolution order in V4.

Could you please advise on the recommended approach in V4 to achieve this?

Thanks in advance!