> **Building with AI coding agents?** Install the authstack plugin with one command. This equips your agent with accurate Scalekit implementation patterns.
>
> **Recommended** (the `-y` flags skip prompts, so the command runs without an interactive terminal):
> ```bash
> npx -y @scalekit-inc/cli setup -y
> ```
>
> Global:
> ```bash
> npm install -g @scalekit-inc/cli
> scalekit setup -y
> ```
>
> Supports Claude Code, Cursor, GitHub Copilot, Codex + skills for other Agent Skills-compatible agents in `~/.agents/skills`.
> Skills: integrate-agentkit, implement-saaskit, add-mcp-oauth, implement-sso, implement-scim.
> [Full setup guide](https://docs.scalekit.com/dev-kit/build-with-ai/)

---

# Choose how to integrate Modular SSO

Pick the Modular SSO guide that matches how your app signs users in today: your own code, Auth0, Amazon Cognito, Firebase, Supabase or Auth.js.
How you add Modular SSO depends on what signs users in to your app today.

| Your app signs users in with | How Scalekit fits in | Guide |
| ---------------------------- | -------------------- | ----- |
| Your own code: your backend checks passwords or sends codes, and creates the session | Your backend calls the Scalekit SDK to start the login and to read the user from the callback | [Quickstart](/authenticate/sso/add-modular-sso/), then [Handle the callback and find the user](/authenticate/sso/handle-callback/) |
| Auth0 | You add Scalekit to Auth0 as an OpenID Connect (OIDC) provider. Auth0 keeps the session | [Auth0](/guides/integrations/auth-systems/auth0/) |
| Amazon Cognito | You add Scalekit to your Cognito user pool as an OIDC identity provider. Cognito keeps the session | [AWS Cognito](/guides/integrations/auth-systems/aws-cognito/) |
| Firebase Authentication | You add Scalekit as an OIDC provider in Firebase, or sign the user in to Firebase from your backend after the Scalekit login | [Firebase](/guides/integrations/auth-systems/firebase/) |
| Supabase Auth | You add Scalekit to Supabase as a custom OIDC provider. Supabase keeps the session | [Supabase](/guides/integrations/auth-systems/supabase/) |
| Auth.js in a Next.js app | You add Scalekit to Auth.js as an OIDC provider | [Add enterprise SSO to Next.js with Auth.js](/cookbooks/add-enterprise-sso-nextjs-authjs/) |

With an auth system, that system talks to Scalekit and creates the session, so your app writes little or no Scalekit code. You still set up Scalekit the same way: put the environment in **Modular Auth** mode, create an organization for each customer, and have their IT admin connect their identity provider (IdP).

Your auth system isn't listed? If it can add an OIDC provider, add Scalekit as one, using your environment URL as the issuer and your client ID and secret. Otherwise, use the SDK from your backend as the quickstart shows.

## Next

Whichever way you integrate, each customer needs an organization and a working connection. See [Onboard an enterprise customer](/sso/guides/onboard-enterprise-customers/).


---

## More Scalekit documentation

| Resource | What it contains | When to use it |
|----------|-----------------|----------------|
| [/llms.txt](/llms.txt) | Structured index with routing hints per product area | Start here — find which documentation set covers your topic before loading full content |
| [/llms-full.txt](/llms-full.txt) | Complete documentation for all Scalekit products in one file | Use when you need exhaustive context across multiple products or when the topic spans several areas |
| [sitemap-0.xml](https://docs.scalekit.com/sitemap-0.xml) | Full URL list of every documentation page | Use to discover specific page URLs you can fetch for targeted, page-level answers |