Auth0 Token Forwarding to Backend APIs

What problem does it solve?

When a frontend authenticated with Auth0 OIDC makes HttpClient calls to protected backend APIs, the user's access_token is not automatically propagated which causes 401 Unauthorized errors; this skill shows how to attach the token from the user's authentication session to outgoing requests.

Core Features & Use Cases

• Automatic token attachment: Use a DelegatingHandler to read the access_token from the current HttpContext and set Authorization: Bearer {token} on outgoing HttpClient requests.
• Framework scope: Designed for Blazor Server and ASP.NET Core frontends calling separate backend APIs that validate JWT bearer tokens.
• Operational guidance: Covers registration of IHttpContextAccessor, enabling SaveTokens in OIDC options, handler registration on HttpClient, testing patterns, and common pitfalls.

Quick Start

Create a TokenForwardingHandler, register IHttpContextAccessor, set SaveTokens = true in your Auth0 OIDC options, and add the handler to each HttpClient registration so outgoing requests include the Bearer token.