> ## Documentation Index
> Fetch the complete documentation index at: https://docs.esperr.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Anubis Challenge

> Esper-managed proof-of-work challenge for customers who want to avoid a third-party CAPTCHA provider when a mitigation resolves to Challenge.

## When to choose Anubis

* You want a locally verified challenge path.
* You prefer browser proof-of-work over a hosted CAPTCHA flow.
* You want to reduce external challenge-provider dependency.

<Tip>
  **Best fit**

  Anubis is a strong fit for environments where a short burst of client-side CPU
  work is acceptable and avoiding a hosted challenge vendor matters more than
  minimizing device effort.
</Tip>

## What the customer configures

You configure Anubis at the mitigation layer:

1. In the console, create or edit a mitigation with `Mode = Challenge`.
2. Select `Anubis` as the challenge provider.

Esper's runtime must also have Anubis enabled:

* `ESPER_ANUBIS_DIFFICULTY`

The difficulty controls how much work the browser performs before Esper accepts
the challenge solve.

<Info>
  **Operational note**

  Higher difficulty increases resistance to commodity automation, but it also
  increases solve time and device battery usage for legitimate users.
</Info>

## How to verify the setup

Open `Settings > Challenge` and run `Test challenge setup`.

Green means:

* Anubis is enabled on the runtime
* your enabled `Challenge` mitigations that use Anubis are valid

Red means one or more of the following:

* Anubis is disabled in runtime config
* a challenge mitigation is missing its provider selection
* the tenant has no enabled challenge mitigations to validate

## What users experience

When a policy resolves to a `Challenge` mitigation using Anubis:

* Esper creates a challenge session
* the browser loads an Esper-managed challenge page
* the page solves a short proof-of-work locally
* Esper verifies the proof and issues the challenge proof token
* the user is redirected back to the original return URL

<Tip>
  **UX expectation**

  Anubis can feel slower on older mobile devices than Turnstile. If your
  customer-facing flow is sensitive to client CPU spikes, compare both providers
  before standardizing on one.
</Tip>

## Tradeoffs

* Pros: no third-party challenge provider, local verification, simple runtime
  dependencies
* Cons: higher client CPU cost, device variability, tuning difficulty is an
  operational decision