Auth0 gives developers the best front door. B5 enforces every action behind it.
Auth0 is the developer’s favorite identity front door — fast login, social, CIAM, and Auth0 FGA for relationship-based authorization. But login is the start of trust, not its enforcement. Once an agent or user is in, B5 decides — per action, in-process, in idiomatic .NET — whether this call, with this delegated scope, is allowed at the method that runs it.
Framing: Use Auth0 for login and the front door. Use B5 to enforce per-action authority in your .NET application tier.Auth0 set the bar for developer-experience in identity.
Auth0’s appeal is real: the cleanest login DX in the market, broad social and enterprise connections, and Auth0 FGA bringing relationship-based authorization to developers. B5 doesn’t compete with the front door — it consumes Auth0’s identities and tokens. The gap Auth0 leaves, by design, is per-action enforcement at the method — which an external FGA call can model but your code must still honor. B5 makes that enforcement a native .NET attribute.
Borrow this, don’t fight it
- Best-in-class login and CIAM developer experience
- Broad social, enterprise, and passwordless connections
- Auth0 FGA for relationship-based, fine-grained authorization
- Rules/Actions extensibility familiar to application developers
Authentication is solved. Per-action enforcement isn’t.
- Auth0 authenticates and issues tokens; the action still executes in your code
- Auth0 FGA externalizes the decision and can require syncing authorization data
- Each per-action check is a call-out to an external service on the hot path
- B5 enforces [Permission] in-process — the agent’s OBO scope is checked at the method itself
Auth0 decides. B5 enforces — at the line of code.
| Auth0 | B5 Secure | |
|---|---|---|
| Locus of enforcement | Edge (login/token) + external FGA service | In-process, at the call site |
| New live attack surface | Yes — operated services | No added service or endpoint |
| Authorization data leaves your boundary | Relationship tuples sync to the FGA store | No — evaluated in-process |
| New sub-processor for the customer | Yes | No |
| .NET integration | SDK, generic | Idiomatic [Permission] attributes & middleware |
| Agent identity model | First-class (CIAM) / resource-scoped (FGA) | First-class + in-process enforcement today; agent OBO + ephemeral scope is a Q4 2026 roadmap extension |
| Best role in your architecture | Authenticate & onboard | Enforce the decision where it executes |
Capability status. In-process [Permission] enforcement Generally Available Agent OBO delegation, ephemeral SPIFFE-compatible agent identity and CAEP/SSF signal ingestion are Q4 2026 roadmap extensions Preview.
The questions a buyer actually asks
Auth0 already handles our auth — why add B5?
Because authentication and per-action authorization are different problems. Auth0 proves who is calling; B5 enforces what that caller — human or agent — may actually do, at each .NET method, with the delegated scope bound in. Keep Auth0; add the enforcement it leaves to your code.
Auth0 FGA does authorization, though.
It models authorization as an external service. B5’s difference is in-process enforcement at the call site with no external store to sync and no round trip per check. You get the decoupled-policy benefit natively in C#.
Will this complicate our stack?
The opposite, for .NET teams: B5 is an attribute and middleware, not another service to operate. And it adds no sub-processor or data-residency question — the enforcement runs inside your own cloud.
Complementary, not competitive.
Auth0 logs them in; B5 governs what they can do.
Let Auth0 own login, CIAM, and token issuance. Let B5 enforce per-action authority inside your .NET services — turning each Auth0-issued identity, including agent OBO tokens, into a binding [Permission] decision at the method (agent OBO on the H2 2026 roadmap) (agent OBO on the H2 2026 roadmap). A great front door still needs a lock on every interior door; B5 is those locks.
Keep the best front door. Add enforcement on every action behind it.
Bring your architecture to a B5 architect. We’ll show you exactly where Auth0 ends and where in-process enforcement begins — and the Trust Center a library, not a platform, gets to publish.
See enforcement at the record. Live.
Thirty minutes with a B5 engineer: your stack, the B1–B5 pipeline, and a data-element authorization decision you can watch happen — for humans, services, and AI agents alike.