<PackageReference Include="Microsoft.Identity.Client" Version="4.84.0" />

Microsoft.Identity.Client.Internal.ClientCredential.ClientAssertionDelegateCredential

sealed class ClientAssertionDelegateCredential : IClientCredential, IClientSignedAssertionProvider
Handles client assertions supplied via a delegate that returns a ClientSignedAssertion (JWT + optional certificate bound for mTLS-PoP).
public AssertionType AssertionType { get; }

public Task<CredentialMaterial> GetCredentialMaterialAsync(CredentialContext context, CancellationToken cancellationToken)