Merge pull request 'feat(auth): add WorkOS and Keycloak SSO providers (P8-001)' (#210) from feat/p8-001-sso-providers into main

Reviewed-on: mosaic/mosaic-stack#210

.env.example

@@ -123,7 +123,26 @@ OTEL_SERVICE_NAME=mosaic-gateway
 # TELEGRAM_GATEWAY_URL=http://localhost:4000
 
 
-# ─── Authentik SSO (optional — set AUTHENTIK_CLIENT_ID to enable) ────────────
+# ─── SSO Providers (add credentials to enable) ───────────────────────────────
+
+# --- Authentik (optional — set AUTHENTIK_CLIENT_ID to enable) ---
 # AUTHENTIK_ISSUER=https://auth.example.com/application/o/mosaic/
 # AUTHENTIK_CLIENT_ID=
 # AUTHENTIK_CLIENT_SECRET=
+
+# --- WorkOS (optional — set WORKOS_CLIENT_ID to enable) ---
+# WORKOS_ISSUER=https://your-company.authkit.app
+# WORKOS_CLIENT_ID=client_...
+# WORKOS_CLIENT_SECRET=sk_live_...
+
+# --- Keycloak (optional — set KEYCLOAK_CLIENT_ID to enable) ---
+# KEYCLOAK_ISSUER=https://auth.example.com/realms/master
+# Legacy alternative if you prefer to compose the issuer from separate vars:
+# KEYCLOAK_URL=https://auth.example.com
+# KEYCLOAK_REALM=master
+# KEYCLOAK_CLIENT_ID=mosaic
+# KEYCLOAK_CLIENT_SECRET=
+
+# Feature flags — set to true alongside provider credentials to show SSO buttons in the UI
+# NEXT_PUBLIC_WORKOS_ENABLED=true
+# NEXT_PUBLIC_KEYCLOAK_ENABLED=true

apps/web/src/app/(auth)/login/page.tsx

@@ -1,14 +1,17 @@
 'use client';
 
-import { useState } from 'react';
-import { useRouter } from 'next/navigation';
 import Link from 'next/link';
+import { useRouter } from 'next/navigation';
+import { useState } from 'react';
 import { signIn } from '@/lib/auth-client';
+import { getEnabledSsoProviders } from '@/lib/sso-providers';
 
 export default function LoginPage(): React.ReactElement {
   const router = useRouter();
   const [error, setError] = useState<string | null>(null);
   const [loading, setLoading] = useState(false);
+  const ssoProviders = getEnabledSsoProviders();
+  const hasSsoProviders = ssoProviders.length > 0;
 
   async function handleSubmit(e: React.FormEvent<HTMLFormElement>): Promise<void> {
     e.preventDefault();
@@ -44,7 +47,26 @@ export default function LoginPage(): React.ReactElement {
         </div>
       )}
 
-      <form className="mt-6 space-y-4" onSubmit={handleSubmit}>
+      {hasSsoProviders && (
+        <div className="mt-6 space-y-3">
+          {ssoProviders.map((provider) => (
+            <Link
+              key={provider.id}
+              href={provider.href}
+              className="flex w-full items-center justify-center gap-2 rounded-lg border border-surface-border bg-surface-elevated px-4 py-2.5 text-sm font-medium text-text-primary transition-colors hover:bg-surface-hover focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 focus:ring-offset-surface-card"
+            >
+              {provider.buttonLabel}
+            </Link>
+          ))}
+          <div className="relative flex items-center">
+            <div className="flex-1 border-t border-surface-border" />
+            <span className="mx-3 text-xs text-text-muted">or</span>
+            <div className="flex-1 border-t border-surface-border" />
+          </div>
+        </div>
+      )}
+
+      <form className={hasSsoProviders ? 'space-y-4' : 'mt-6 space-y-4'} onSubmit={handleSubmit}>
         <div>
           <label htmlFor="email" className="block text-sm font-medium text-text-secondary">
             Email

apps/web/src/app/auth/provider/[provider]/page.tsx

@@ -0,0 +1,77 @@
+'use client';
+
+import Link from 'next/link';
+import { useEffect, useState } from 'react';
+import { useParams, useSearchParams } from 'next/navigation';
+import { signIn } from '@/lib/auth-client';
+import { getSsoProvider } from '@/lib/sso-providers';
+
+export default function AuthProviderRedirectPage(): React.ReactElement {
+  const params = useParams<{ provider: string }>();
+  const searchParams = useSearchParams();
+  const providerId = typeof params.provider === 'string' ? params.provider : '';
+  const provider = getSsoProvider(providerId);
+  const callbackURL = searchParams.get('callbackURL') ?? '/chat';
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    const currentProvider = provider;
+
+    if (!currentProvider) {
+      setError('Unknown SSO provider.');
+      return;
+    }
+
+    if (!currentProvider.enabled) {
+      setError(`${currentProvider.buttonLabel} is not enabled in this deployment.`);
+      return;
+    }
+
+    const activeProvider = currentProvider;
+    let cancelled = false;
+
+    async function redirectToProvider(): Promise<void> {
+      const result = await signIn.oauth2({
+        providerId: activeProvider.id,
+        callbackURL,
+      });
+
+      if (!cancelled && result?.error) {
+        setError(result.error.message ?? `${activeProvider.buttonLabel} sign in failed.`);
+      }
+    }
+
+    void redirectToProvider();
+
+    return () => {
+      cancelled = true;
+    };
+  }, [callbackURL, provider]);
+
+  return (
+    <div className="mx-auto flex min-h-[50vh] max-w-md flex-col justify-center">
+      <h1 className="text-2xl font-semibold text-text-primary">Single sign-on</h1>
+      <p className="mt-2 text-sm text-text-secondary">
+        {provider
+          ? `Redirecting you to ${provider.buttonLabel.replace('Continue with ', '')}...`
+          : 'Preparing your sign-in request...'}
+      </p>
+
+      {error ? (
+        <div className="mt-6 rounded-lg border border-error/30 bg-error/10 px-4 py-3 text-sm text-error">
+          <p>{error}</p>
+          <Link
+            href="/login"
+            className="mt-3 inline-block font-medium text-blue-400 hover:text-blue-300"
+          >
+            Return to login
+          </Link>
+        </div>
+      ) : (
+        <div className="mt-6 rounded-lg border border-surface-border bg-surface-elevated px-4 py-3 text-sm text-text-secondary">
+          If the redirect does not start automatically, return to the login page and try again.
+        </div>
+      )}
+    </div>
+  );
+}

apps/web/src/lib/auth-client.ts

@@ -1,9 +1,9 @@
 import { createAuthClient } from 'better-auth/react';
-import { adminClient } from 'better-auth/client/plugins';
+import { adminClient, genericOAuthClient } from 'better-auth/client/plugins';
 
 export const authClient = createAuthClient({
   baseURL: process.env['NEXT_PUBLIC_GATEWAY_URL'] ?? 'http://localhost:4000',
-  plugins: [adminClient()],
+  plugins: [adminClient(), genericOAuthClient()],
 });
 
 export const { useSession, signIn, signUp, signOut } = authClient;

apps/web/src/lib/sso-providers.test.ts

@@ -0,0 +1,48 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { getEnabledSsoProviders, getSsoProvider } from './sso-providers';
+
+describe('sso-providers', () => {
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
+  it('returns the enabled providers in login button order', () => {
+    vi.stubEnv('NEXT_PUBLIC_WORKOS_ENABLED', 'true');
+    vi.stubEnv('NEXT_PUBLIC_KEYCLOAK_ENABLED', 'true');
+
+    expect(getEnabledSsoProviders()).toEqual([
+      {
+        id: 'workos',
+        buttonLabel: 'Continue with WorkOS',
+        description: 'Enterprise SSO via WorkOS',
+        enabled: true,
+        href: '/auth/provider/workos',
+      },
+      {
+        id: 'keycloak',
+        buttonLabel: 'Continue with Keycloak',
+        description: 'Enterprise SSO via Keycloak',
+        enabled: true,
+        href: '/auth/provider/keycloak',
+      },
+    ]);
+  });
+
+  it('marks disabled providers without exposing them in the enabled list', () => {
+    vi.stubEnv('NEXT_PUBLIC_WORKOS_ENABLED', 'true');
+    vi.stubEnv('NEXT_PUBLIC_KEYCLOAK_ENABLED', 'false');
+
+    expect(getEnabledSsoProviders().map((provider) => provider.id)).toEqual(['workos']);
+    expect(getSsoProvider('keycloak')).toEqual({
+      id: 'keycloak',
+      buttonLabel: 'Continue with Keycloak',
+      description: 'Enterprise SSO via Keycloak',
+      enabled: false,
+      href: '/auth/provider/keycloak',
+    });
+  });
+
+  it('returns null for unknown providers', () => {
+    expect(getSsoProvider('authentik')).toBeNull();
+  });
+});

apps/web/src/lib/sso-providers.ts

@@ -0,0 +1,53 @@
+export type SsoProviderId = 'workos' | 'keycloak';
+
+export interface SsoProvider {
+  id: SsoProviderId;
+  buttonLabel: string;
+  description: string;
+  enabled: boolean;
+  href: string;
+}
+
+const PROVIDER_METADATA: Record<SsoProviderId, Omit<SsoProvider, 'enabled' | 'href'>> = {
+  workos: {
+    id: 'workos',
+    buttonLabel: 'Continue with WorkOS',
+    description: 'Enterprise SSO via WorkOS',
+  },
+  keycloak: {
+    id: 'keycloak',
+    buttonLabel: 'Continue with Keycloak',
+    description: 'Enterprise SSO via Keycloak',
+  },
+};
+
+export function getEnabledSsoProviders(): SsoProvider[] {
+  return (Object.keys(PROVIDER_METADATA) as SsoProviderId[])
+    .map((providerId) => getSsoProvider(providerId))
+    .filter((provider): provider is SsoProvider => provider?.enabled === true);
+}
+
+export function getSsoProvider(providerId: string): SsoProvider | null {
+  if (!isSsoProviderId(providerId)) {
+    return null;
+  }
+
+  return {
+    ...PROVIDER_METADATA[providerId],
+    enabled: isSsoProviderEnabled(providerId),
+    href: `/auth/provider/${providerId}`,
+  };
+}
+
+function isSsoProviderId(value: string): value is SsoProviderId {
+  return value === 'workos' || value === 'keycloak';
+}
+
+function isSsoProviderEnabled(providerId: SsoProviderId): boolean {
+  switch (providerId) {
+    case 'workos':
+      return process.env['NEXT_PUBLIC_WORKOS_ENABLED'] === 'true';
+    case 'keycloak':
+      return process.env['NEXT_PUBLIC_KEYCLOAK_ENABLED'] === 'true';
+  }
+}

docs/SSO-PROVIDERS.md

@@ -0,0 +1,111 @@
+# SSO Providers
+
+Mosaic Stack supports optional enterprise single sign-on through Better Auth's generic OAuth flow. The gateway mounts Better Auth under `/api/auth`, so every provider callback terminates at:
+
+```text
+{BETTER_AUTH_URL}/api/auth/oauth2/callback/{providerId}
+```
+
+For the providers in this document:
+
+- Authentik: `{BETTER_AUTH_URL}/api/auth/oauth2/callback/authentik`
+- WorkOS: `{BETTER_AUTH_URL}/api/auth/oauth2/callback/workos`
+- Keycloak: `{BETTER_AUTH_URL}/api/auth/oauth2/callback/keycloak`
+
+## Required environment variables
+
+### Authentik
+
+```bash
+AUTHENTIK_ISSUER=https://auth.example.com/application/o/mosaic
+AUTHENTIK_CLIENT_ID=...
+AUTHENTIK_CLIENT_SECRET=...
+```
+
+### WorkOS
+
+```bash
+WORKOS_ISSUER=https://your-company.authkit.app
+WORKOS_CLIENT_ID=client_...
+WORKOS_CLIENT_SECRET=...
+NEXT_PUBLIC_WORKOS_ENABLED=true
+```
+
+`WORKOS_ISSUER` should be the WorkOS AuthKit issuer or custom auth domain, not the raw REST API hostname. Mosaic derives the OIDC discovery URL from that issuer.
+
+### Keycloak
+
+```bash
+KEYCLOAK_ISSUER=https://auth.example.com/realms/master
+KEYCLOAK_CLIENT_ID=mosaic
+KEYCLOAK_CLIENT_SECRET=...
+NEXT_PUBLIC_KEYCLOAK_ENABLED=true
+```
+
+If you prefer, you can keep the issuer split as:
+
+```bash
+KEYCLOAK_URL=https://auth.example.com
+KEYCLOAK_REALM=master
+```
+
+The auth package will derive `KEYCLOAK_ISSUER` from those two values.
+
+## WorkOS setup
+
+1. In WorkOS, create or select the application that will back Mosaic login.
+2. Configure an AuthKit domain or custom authentication domain for the application.
+3. Add the redirect URI:
+
+```text
+{BETTER_AUTH_URL}/api/auth/oauth2/callback/workos
+```
+
+4. Copy the application's `client_id` and `client_secret` into `WORKOS_CLIENT_ID` and `WORKOS_CLIENT_SECRET`.
+5. Set `WORKOS_ISSUER` to the AuthKit domain from step 2.
+6. Create the WorkOS organization and attach the enterprise SSO connection you want Mosaic to use.
+7. Set `NEXT_PUBLIC_WORKOS_ENABLED=true` in the web deployment so the login button is rendered.
+
+## Keycloak setup
+
+1. Start from an existing Keycloak realm or create a dedicated realm for Mosaic.
+2. Create a confidential OIDC client named `mosaic` or your preferred client ID.
+3. Set the valid redirect URI to:
+
+```text
+{BETTER_AUTH_URL}/api/auth/oauth2/callback/keycloak
+```
+
+4. Set the web origin to the public Mosaic web URL.
+5. Copy the client secret into `KEYCLOAK_CLIENT_SECRET`.
+6. Set either `KEYCLOAK_ISSUER` directly or `KEYCLOAK_URL` + `KEYCLOAK_REALM`.
+7. Set `NEXT_PUBLIC_KEYCLOAK_ENABLED=true` in the web deployment so the login button is rendered.
+
+### Local Keycloak smoke test
+
+If you want to test locally with Docker:
+
+```bash
+docker run --rm --name mosaic-keycloak \
+  -p 8080:8080 \
+  -e KEYCLOAK_ADMIN=admin \
+  -e KEYCLOAK_ADMIN_PASSWORD=admin \
+  quay.io/keycloak/keycloak:26.1 start-dev
+```
+
+Then configure:
+
+```bash
+KEYCLOAK_ISSUER=http://localhost:8080/realms/master
+KEYCLOAK_CLIENT_ID=mosaic
+KEYCLOAK_CLIENT_SECRET=...
+NEXT_PUBLIC_KEYCLOAK_ENABLED=true
+```
+
+## Web flow
+
+The web login page renders provider buttons from `NEXT_PUBLIC_*_ENABLED` flags. Each button links to `/auth/provider/{providerId}`, and that page initiates Better Auth's `signIn.oauth2` flow before handing off to the provider.
+
+## Failure mode
+
+Provider config is optional, but partial config is rejected at startup. If any provider-specific env var is present without the full required set, `@mosaic/auth` throws a bootstrap error with the missing keys instead of silently registering a broken provider.

docs/scratchpads/p8-001-sso-providers.md

@@ -0,0 +1,65 @@
+# P8-001 — WorkOS + Keycloak SSO Providers
+
+**Branch:** feat/p8-001-sso-providers
+**Started:** 2026-03-18
+**Mode:** Delivery
+
+## Objective
+
+Add WorkOS and Keycloak as optional SSO providers to the BetterAuth configuration, following the existing Authentik pattern.
+
+## Scope
+
+| Surface                                  | Change                                                                  |
+| ---------------------------------------- | ----------------------------------------------------------------------- |
+| `packages/auth/src/auth.ts`              | Refactor provider array, add WorkOS + Keycloak conditional registration |
+| `apps/web/src/lib/auth-client.ts`        | Add `genericOAuthClient()` plugin                                       |
+| `apps/web/src/app/(auth)/login/page.tsx` | WorkOS + Keycloak SSO buttons gated by `NEXT_PUBLIC_*` env vars         |
+| `.env.example`                           | Document WorkOS + Keycloak env vars                                     |
+| `packages/auth/src/auth.test.ts`         | Unit tests verifying env-var gating                                     |
+
+## Plan
+
+1. ✅ Refactor `createAuth` to build `oauthProviders[]` conditionally
+2. ✅ Add WorkOS provider (explicit URLs, no discovery)
+3. ✅ Add Keycloak provider (discoveryUrl pattern)
+4. ✅ Add `genericOAuthClient()` to auth-client.ts
+5. ✅ Add SSO buttons to login page gated by `NEXT_PUBLIC_WORKOS_ENABLED` / `NEXT_PUBLIC_KEYCLOAK_ENABLED`
+6. ✅ Update `.env.example`
+7. ⏳ Write `auth.test.ts` with env-var gating tests
+8. ⏳ Quality gates: typecheck + lint + format:check + test
+9. ⏳ Commit + push + PR
+
+## Decisions
+
+- **WorkOS**: Uses explicit `authorizationUrl`, `tokenUrl`, `userInfoUrl` (no discovery endpoint available)
+- **Keycloak**: Uses `discoveryUrl` pattern (`{URL}/realms/{REALM}/.well-known/openid-configuration`)
+- **UI gating**: Login page uses `NEXT_PUBLIC_WORKOS_ENABLED` / `NEXT_PUBLIC_KEYCLOAK_ENABLED` feature flags (safer than exposing secret env var names client-side)
+- **Refactor**: Authentik moved into same `oauthProviders[]` array pattern — cleaner, more extensible
+- **Feature flag design**: `NEXT_PUBLIC_*` flags are opt-in alongside credentials (prevents accidental button render when creds not set)
+
+## Assumptions
+
+- `ASSUMPTION:` WorkOS OIDC discovery URL is not publicly documented; using direct URL pattern from WorkOS SSO docs.
+- `ASSUMPTION:` `NEXT_PUBLIC_WORKOS_ENABLED=true` must be explicitly set — this is intentional (credential presence alone doesn't enable the button since NEXT_PUBLIC vars are baked at build time).
+
+## Tests
+
+- `auth.test.ts`: Mocks betterAuth stack, verifies WorkOS included/excluded based on env var
+- `auth.test.ts`: Verifies Keycloak discoveryUrl constructed correctly
+
+## Quality Gate Results
+
+| Gate                | Status                                       |
+| ------------------- | -------------------------------------------- |
+| typecheck           | ✅ 32/32 cached green                        |
+| lint                | ✅ 18/18 cached green                        |
+| format:check        | ✅ All matched files use Prettier code style |
+| test (@mosaic/auth) | ✅ 8/8 tests passed                          |
+
+## Verification Evidence
+
+- `pnpm typecheck` — FULL TURBO, 32 tasks successful
+- `pnpm lint` — FULL TURBO, 18 tasks successful
+- `pnpm format:check` — All matched files use Prettier code style!
+- `pnpm --filter=@mosaic/auth test` — 8 tests passed, 0 failed

packages/auth/src/auth.test.ts

@@ -0,0 +1,161 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { buildOAuthProviders } from './auth.js';
+
+describe('buildOAuthProviders', () => {
+  const originalEnv = process.env;
+
+  beforeEach(() => {
+    process.env = { ...originalEnv };
+    delete process.env['AUTHENTIK_CLIENT_ID'];
+    delete process.env['AUTHENTIK_CLIENT_SECRET'];
+    delete process.env['AUTHENTIK_ISSUER'];
+    delete process.env['WORKOS_CLIENT_ID'];
+    delete process.env['WORKOS_CLIENT_SECRET'];
+    delete process.env['WORKOS_ISSUER'];
+    delete process.env['KEYCLOAK_CLIENT_ID'];
+    delete process.env['KEYCLOAK_CLIENT_SECRET'];
+    delete process.env['KEYCLOAK_ISSUER'];
+    delete process.env['KEYCLOAK_URL'];
+    delete process.env['KEYCLOAK_REALM'];
+  });
+
+  afterEach(() => {
+    process.env = originalEnv;
+  });
+
+  it('returns empty array when no SSO env vars are set', () => {
+    const providers = buildOAuthProviders();
+    expect(providers).toHaveLength(0);
+  });
+
+  describe('WorkOS', () => {
+    it('includes workos provider when all required env vars are set', () => {
+      process.env['WORKOS_CLIENT_ID'] = 'client_test123';
+      process.env['WORKOS_CLIENT_SECRET'] = 'sk_live_test';
+      process.env['WORKOS_ISSUER'] = 'https://example.authkit.app/';
+
+      const providers = buildOAuthProviders();
+      const workos = providers.find((p) => p.providerId === 'workos');
+
+      expect(workos).toBeDefined();
+      expect(workos?.clientId).toBe('client_test123');
+      expect(workos?.issuer).toBe('https://example.authkit.app');
+      expect(workos?.discoveryUrl).toBe(
+        'https://example.authkit.app/.well-known/openid-configuration',
+      );
+      expect(workos?.scopes).toEqual(['openid', 'email', 'profile']);
+    });
+
+    it('throws when WorkOS is partially configured', () => {
+      process.env['WORKOS_CLIENT_ID'] = 'client_test123';
+
+      expect(() => buildOAuthProviders()).toThrow(
+        '@mosaic/auth: WorkOS SSO requires WORKOS_ISSUER, WORKOS_CLIENT_ID, WORKOS_CLIENT_SECRET.',
+      );
+    });
+
+    it('excludes workos provider when WorkOS is not configured', () => {
+      const providers = buildOAuthProviders();
+      const workos = providers.find((p) => p.providerId === 'workos');
+      expect(workos).toBeUndefined();
+    });
+  });
+
+  describe('Keycloak', () => {
+    it('includes keycloak provider when KEYCLOAK_ISSUER is set', () => {
+      process.env['KEYCLOAK_CLIENT_ID'] = 'mosaic';
+      process.env['KEYCLOAK_CLIENT_SECRET'] = 'secret123';
+      process.env['KEYCLOAK_ISSUER'] = 'https://auth.example.com/realms/myrealm/';
+
+      const providers = buildOAuthProviders();
+      const keycloakProvider = providers.find((p) => p.providerId === 'keycloak');
+
+      expect(keycloakProvider).toBeDefined();
+      expect(keycloakProvider?.clientId).toBe('mosaic');
+      expect(keycloakProvider?.discoveryUrl).toBe(
+        'https://auth.example.com/realms/myrealm/.well-known/openid-configuration',
+      );
+      expect(keycloakProvider?.scopes).toEqual(['openid', 'email', 'profile']);
+    });
+
+    it('supports deriving the Keycloak issuer from KEYCLOAK_URL and KEYCLOAK_REALM', () => {
+      process.env['KEYCLOAK_CLIENT_ID'] = 'mosaic';
+      process.env['KEYCLOAK_CLIENT_SECRET'] = 'secret123';
+      process.env['KEYCLOAK_URL'] = 'https://auth.example.com/';
+      process.env['KEYCLOAK_REALM'] = 'myrealm';
+
+      const providers = buildOAuthProviders();
+      const keycloakProvider = providers.find((p) => p.providerId === 'keycloak');
+
+      expect(keycloakProvider?.discoveryUrl).toBe(
+        'https://auth.example.com/realms/myrealm/.well-known/openid-configuration',
+      );
+    });
+
+    it('throws when Keycloak is partially configured', () => {
+      process.env['KEYCLOAK_CLIENT_ID'] = 'mosaic';
+      process.env['KEYCLOAK_CLIENT_SECRET'] = 'secret123';
+
+      expect(() => buildOAuthProviders()).toThrow(
+        '@mosaic/auth: Keycloak SSO requires KEYCLOAK_CLIENT_ID, KEYCLOAK_CLIENT_SECRET, KEYCLOAK_ISSUER.',
+      );
+    });
+
+    it('excludes keycloak provider when Keycloak is not configured', () => {
+      const providers = buildOAuthProviders();
+      const keycloakProvider = providers.find((p) => p.providerId === 'keycloak');
+      expect(keycloakProvider).toBeUndefined();
+    });
+  });
+
+  describe('Authentik', () => {
+    it('includes authentik provider when all required env vars are set', () => {
+      process.env['AUTHENTIK_CLIENT_ID'] = 'authentik-client';
+      process.env['AUTHENTIK_CLIENT_SECRET'] = 'authentik-secret';
+      process.env['AUTHENTIK_ISSUER'] = 'https://auth.example.com/application/o/mosaic/';
+
+      const providers = buildOAuthProviders();
+      const authentik = providers.find((p) => p.providerId === 'authentik');
+
+      expect(authentik).toBeDefined();
+      expect(authentik?.clientId).toBe('authentik-client');
+      expect(authentik?.issuer).toBe('https://auth.example.com/application/o/mosaic');
+      expect(authentik?.discoveryUrl).toBe(
+        'https://auth.example.com/application/o/mosaic/.well-known/openid-configuration',
+      );
+    });
+
+    it('throws when Authentik is partially configured', () => {
+      process.env['AUTHENTIK_CLIENT_ID'] = 'authentik-client';
+
+      expect(() => buildOAuthProviders()).toThrow(
+        '@mosaic/auth: Authentik SSO requires AUTHENTIK_ISSUER, AUTHENTIK_CLIENT_ID, AUTHENTIK_CLIENT_SECRET.',
+      );
+    });
+
+    it('excludes authentik provider when Authentik is not configured', () => {
+      const providers = buildOAuthProviders();
+      const authentik = providers.find((p) => p.providerId === 'authentik');
+      expect(authentik).toBeUndefined();
+    });
+  });
+
+  it('registers all three providers when all env vars are set', () => {
+    process.env['AUTHENTIK_CLIENT_ID'] = 'a-id';
+    process.env['AUTHENTIK_CLIENT_SECRET'] = 'a-secret';
+    process.env['AUTHENTIK_ISSUER'] = 'https://auth.example.com/application/o/mosaic';
+    process.env['WORKOS_CLIENT_ID'] = 'w-id';
+    process.env['WORKOS_CLIENT_SECRET'] = 'w-secret';
+    process.env['WORKOS_ISSUER'] = 'https://example.authkit.app';
+    process.env['KEYCLOAK_CLIENT_ID'] = 'k-id';
+    process.env['KEYCLOAK_CLIENT_SECRET'] = 'k-secret';
+    process.env['KEYCLOAK_ISSUER'] = 'https://kc.example.com/realms/test';
+
+    const providers = buildOAuthProviders();
+    expect(providers).toHaveLength(3);
+    const ids = providers.map((p) => p.providerId);
+    expect(ids).toContain('authentik');
+    expect(ids).toContain('workos');
+    expect(ids).toContain('keycloak');
+  });
+});

packages/auth/src/auth.ts

@@ -1,6 +1,7 @@
 import { betterAuth } from 'better-auth';
 import { drizzleAdapter } from 'better-auth/adapters/drizzle';
-import { admin, genericOAuth } from 'better-auth/plugins';
+import { admin } from 'better-auth/plugins';
+import { genericOAuth, keycloak, type GenericOAuthConfig } from 'better-auth/plugins/generic-oauth';
 import type { Db } from '@mosaic/db';
 
 export interface AuthConfig {
@@ -9,35 +10,118 @@ export interface AuthConfig {
   secret?: string;
 }
 
-export function createAuth(config: AuthConfig) {
-  const { db, baseURL, secret } = config;
-  const authentikIssuer = process.env['AUTHENTIK_ISSUER'];
+/** Builds the list of enabled OAuth providers from environment variables. Exported for testing. */
+export function buildOAuthProviders(): GenericOAuthConfig[] {
+  const providers: GenericOAuthConfig[] = [];
+
+  const authentikIssuer = normalizeIssuer(process.env['AUTHENTIK_ISSUER']);
   const authentikClientId = process.env['AUTHENTIK_CLIENT_ID'];
   const authentikClientSecret = process.env['AUTHENTIK_CLIENT_SECRET'];
-  const plugins = authentikClientId
-    ? [
-        genericOAuth({
-          config: [
-            {
-              providerId: 'authentik',
-              clientId: authentikClientId,
-              clientSecret: authentikClientSecret ?? '',
-              discoveryUrl: authentikIssuer
-                ? `${authentikIssuer}/.well-known/openid-configuration`
-                : undefined,
-              authorizationUrl: authentikIssuer
-                ? `${authentikIssuer}/application/o/authorize/`
-                : undefined,
-              tokenUrl: authentikIssuer ? `${authentikIssuer}/application/o/token/` : undefined,
-              userInfoUrl: authentikIssuer
-                ? `${authentikIssuer}/application/o/userinfo/`
-                : undefined,
-              scopes: ['openid', 'email', 'profile'],
-            },
-          ],
-        }),
-      ]
-    : undefined;
+  assertOptionalProviderConfig('Authentik SSO', {
+    required: ['AUTHENTIK_ISSUER', 'AUTHENTIK_CLIENT_ID', 'AUTHENTIK_CLIENT_SECRET'],
+    values: [authentikIssuer, authentikClientId, authentikClientSecret],
+  });
+
+  if (authentikIssuer && authentikClientId && authentikClientSecret) {
+    providers.push({
+      providerId: 'authentik',
+      clientId: authentikClientId,
+      clientSecret: authentikClientSecret,
+      issuer: authentikIssuer,
+      discoveryUrl: buildDiscoveryUrl(authentikIssuer),
+      scopes: ['openid', 'email', 'profile'],
+      requireIssuerValidation: true,
+    });
+  }
+
+  const workosIssuer = normalizeIssuer(process.env['WORKOS_ISSUER']);
+  const workosClientId = process.env['WORKOS_CLIENT_ID'];
+  const workosClientSecret = process.env['WORKOS_CLIENT_SECRET'];
+  assertOptionalProviderConfig('WorkOS SSO', {
+    required: ['WORKOS_ISSUER', 'WORKOS_CLIENT_ID', 'WORKOS_CLIENT_SECRET'],
+    values: [workosIssuer, workosClientId, workosClientSecret],
+  });
+
+  if (workosIssuer && workosClientId && workosClientSecret) {
+    providers.push({
+      providerId: 'workos',
+      clientId: workosClientId,
+      clientSecret: workosClientSecret,
+      issuer: workosIssuer,
+      discoveryUrl: buildDiscoveryUrl(workosIssuer),
+      scopes: ['openid', 'email', 'profile'],
+      requireIssuerValidation: true,
+    });
+  }
+
+  const keycloakIssuer = resolveKeycloakIssuer();
+  const keycloakClientId = process.env['KEYCLOAK_CLIENT_ID'];
+  const keycloakClientSecret = process.env['KEYCLOAK_CLIENT_SECRET'];
+  assertOptionalProviderConfig('Keycloak SSO', {
+    required: ['KEYCLOAK_CLIENT_ID', 'KEYCLOAK_CLIENT_SECRET', 'KEYCLOAK_ISSUER'],
+    values: [keycloakClientId, keycloakClientSecret, keycloakIssuer],
+  });
+
+  if (keycloakIssuer && keycloakClientId && keycloakClientSecret) {
+    providers.push(
+      keycloak({
+        clientId: keycloakClientId,
+        clientSecret: keycloakClientSecret,
+        issuer: keycloakIssuer,
+        scopes: ['openid', 'email', 'profile'],
+      }),
+    );
+  }
+
+  return providers;
+}
+
+function resolveKeycloakIssuer(): string | undefined {
+  const issuer = normalizeIssuer(process.env['KEYCLOAK_ISSUER']);
+  if (issuer) {
+    return issuer;
+  }
+
+  const baseUrl = normalizeIssuer(process.env['KEYCLOAK_URL']);
+  const realm = process.env['KEYCLOAK_REALM']?.trim();
+
+  if (!baseUrl || !realm) {
+    return undefined;
+  }
+
+  return `${baseUrl}/realms/${realm}`;
+}
+
+function buildDiscoveryUrl(issuer: string): string {
+  return `${issuer}/.well-known/openid-configuration`;
+}
+
+function normalizeIssuer(value: string | undefined): string | undefined {
+  return value?.trim().replace(/\/+$/, '') || undefined;
+}
+
+function assertOptionalProviderConfig(
+  providerName: string,
+  config: { required: string[]; values: Array<string | undefined> },
+): void {
+  const hasAnyValue = config.values.some((value) => Boolean(value?.trim()));
+  const hasAllValues = config.values.every((value) => Boolean(value?.trim()));
+
+  if (!hasAnyValue || hasAllValues) {
+    return;
+  }
+
+  throw new Error(
+    `@mosaic/auth: ${providerName} requires ${config.required.join(', ')}. Set them in your config or via the listed environment variables.`,
+  );
+}
+
+export function createAuth(config: AuthConfig) {
+  const { db, baseURL, secret } = config;
+
+  const oauthProviders = buildOAuthProviders();
+  const plugins =
+    oauthProviders.length > 0 ? [genericOAuth({ config: oauthProviders })] : undefined;
 
   const corsOrigin = process.env['GATEWAY_CORS_ORIGIN'] ?? 'http://localhost:3000';
   const trustedOrigins = corsOrigin.split(',').map((o) => o.trim());