<PackageReference Include="Microsoft.Identity.Client" Version="4.82.0" />

Microsoft.Identity.Client.Internal.ClientCredential.ClientAssertionDelegateCredential

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

public ClientAssertionDelegateCredential(Func<AssertionRequestOptions, CancellationToken, Task<ClientSignedAssertion>> provider)

public Task AddConfidentialClientParametersAsync(OAuth2Client oAuth2Client, AuthenticationRequestParameters p, ICryptographyManager _, string tokenEndpoint, CancellationToken ct)