Authentication Patterns - Tuturuuu Docs

The Tuturuuu platform uses Supabase Auth for user authentication with support for email/password, OAuth providers, multi-factor authentication (MFA), and cross-app token authentication.

The server helpers in @tuturuuu/supabase/next/server resolve cookies (and an optional request argument) asynchronously, so createClient() and createDynamicClient() are async and must be awaited. createAdminClient() is synchronous, but its return type allows awaiting, so existing call sites that await createAdminClient() still work — never await createClient() results without the keyword.

Authentication Flow

┌──────────────┐      ┌──────────────┐      ┌──────────────┐
│   Client     │──1──>│  Supabase    │──2──>│  Database    │
│ (Browser/App)│      │  Auth        │      │  (RLS)       │
└──────────────┘      └──────────────┘      └──────────────┘
       │                      │                      │
       │<─────────3───────────│                      │
       │  Session Token       │                      │
       │                      │                      │
       │──────4──────────────────────────────────────>│
       │  Authenticated Request (w/ session)          │
       │<─────────────────────────────────────────────│
       │  Data (filtered by RLS)                      │

User signs in via Supabase Auth
Supabase validates credentials against database
Client receives session token
Subsequent requests include session token for RLS

Cross-App Supabase Cookies

Production Tuturuuu browser sessions use one canonical Supabase auth cookie for the configured Supabase project and share it across *.tuturuuu.com by setting Domain=.tuturuuu.com. Portless local development does the same across *.tuturuuu.localhost with Domain=.tuturuuu.localhost. Keep the cookie host-only for plain localhost, preview deployments, and unrelated domains. Registered satellite apps still keep Tuturuuu app-session JWTs as a fallback and API isolation mechanism, so do not remove app-session refresh or handoff paths when updating shared Supabase cookie behavior.

Web Multi-Account Sessions

apps/web stores multi-account sessions in a server-owned vault instead of browser localStorage. The browser keeps only an HttpOnly device cookie and loads account summaries from /api/v1/auth/accounts; Supabase access and refresh tokens remain encrypted in private.web_account_sessions. Use WEB_MULTI_ACCOUNT_SESSION_SECRET for vault encryption when available. If it is not configured, the server falls back to SUPABASE_SECRET_KEY, SUPABASE_SERVICE_ROLE_KEY, then SUPABASE_SERVICE_KEY. Never expose those values to client components or upload legacy browser-stored sessions into the vault; users should re-add accounts after storage migrations.

Keeping stored sessions usable

Supabase rotates the refresh token every time the browser refreshes a session, so a stored copy is only good until the account it belongs to refreshes. A switch therefore writes the outgoing account’s live session into its row before calling setSession for the incoming one — without that, switching back fails, the row is deleted as unusable, and a retry reports the account as missing entirely. When a switch does fail, the response carries requiresReauth: true and the account has already been dropped from the vault. Clients must re-read /api/v1/auth/accounts on failure so the dead entry disappears, and should tell the user to sign into that account again rather than surfacing the raw error. A switch redirect is a navigation instruction, not a stored route: /login and /add-account are rejected for last_route on purpose, so never resolve an explicit targetRoute through the persistable-route filter or you will drop a sign-in that is still in flight.

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";
import { redirect } from "next/navigation";

export async function signUp(formData: FormData) {
  const supabase = await createClient();

  const email = formData.get("email") as string;
  const password = formData.get("password") as string;
  const displayName = formData.get("displayName") as string;

  const { data, error } = await supabase.auth.signUp({
    email,
    password,
    options: {
      data: {
        display_name: displayName,
      },
      emailRedirectTo: `${process.env.NEXT_PUBLIC_APP_URL}/auth/callback`,
    },
  });

  if (error) {
    return { error: error.message };
  }

  redirect("/verify-email");
}

Client Component

"use client";

import { signUp } from "./actions";
import { useState } from "react";

export function SignUpForm() {
  const [error, setError] = useState<string | null>(null);

  async function handleSubmit(formData: FormData) {
    const result = await signUp(formData);
    if (result?.error) {
      setError(result.error);
    }
  }

  return (
    <form action={handleSubmit}>
      <input name="displayName" placeholder="Display Name" required />
      <input name="email" type="email" placeholder="Email" required />
      <input name="password" type="password" placeholder="Password" required />
      {error && <p className="text-dynamic-red">{error}</p>}
      <button type="submit">Sign Up</button>
    </form>
  );
}

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";
import { redirect } from "next/navigation";

export async function signIn(formData: FormData) {
  const supabase = await createClient();

  const email = formData.get("email") as string;
  const password = formData.get("password") as string;

  const { data, error } = await supabase.auth.signInWithPassword({
    email,
    password,
  });

  if (error) {
    return { error: error.message };
  }

  redirect("/dashboard");
}

The providers offered on the login page and in account linking come from AUTH_OAUTH_PROVIDERS in apps/web/src/lib/auth/oauth-providers.ts — one list drives the buttons, the /api/v1/users/me/identities/link/[provider] route, and the settings linked-accounts card. Adding a provider anywhere means adding it there.

The Supabase Azure provider must be pinned to a single tenant. Microsoft (azure) is offered with the email scope, and Supabase links an OAuth identity into an existing account when the provider reports that address as verified. On the shared multi-tenant common issuer that claim is only an assertion by whichever directory the user signed in from, so anyone who controls any Azure directory could claim a Tuturuuu address and take over the matching account. Set the provider’s URL override to your tenant, not common.

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function signInWithOAuth(provider: "google" | "github") {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.signInWithOAuth({
    provider,
    options: {
      redirectTo: `${process.env.NEXT_PUBLIC_APP_URL}/auth/callback`,
    },
  });

  if (error) {
    return { error: error.message };
  }

  return { url: data.url };
}

Client Component:

"use client";

import { signInWithOAuth } from "./actions";

export function OAuthButtons() {
  async function handleOAuthSignIn(provider: "google" | "github") {
    const result = await signInWithOAuth(provider);
    if (result.url) {
      window.location.href = result.url;
    }
  }

  return (
    <div>
      <button onClick={() => handleOAuthSignIn("google")}>
        Sign in with Google
      </button>
      <button onClick={() => handleOAuthSignIn("github")}>
        Sign in with GitHub
      </button>
    </div>
  );
}

OAuth Callback State

For provider-specific OAuth callbacks that need to carry ephemeral verifier or CSRF state across a browser redirect, prefer a short-lived HttpOnly cookie scoped to the callback route. When the callback binds external credentials or mutates a workspace, do not let the cookie value be the sole authority: use a signed, expiry-bound state payload that also binds the workspace or account being connected, then require the callback cookie and query state to match before verifying that payload.

Email-Based Auth Recovery

Infrastructure admins can use Infrastructure > Auth Recovery when a manually reviewed user cannot complete normal OTP or password sign-in because of email-scoped infrastructure blocks, stale Supabase bans, or OTP counters. The support flow is:

Search the email on the Auth Recovery page and inspect diagnostics.
Create a recovery override with a support reason. Overrides default to 7 days.
Keep both normal login and recovery email enabled unless the case needs only one path.
Use Send recovery email. The platform sends the email; admins should not copy tokens or links manually.
The user can click the recovery link or enter the 6-digit code on /auth/recovery. Recovery credentials expire after 15 minutes and are single-use.
Revoke the override once the user has recovered access or the case no longer needs support access.

Normal-login overrides bypass only email-scoped infrastructure and OTP/password rate-limit blocks. They still enforce malformed request validation, suspicious user-agent checks, Turnstile, password correctness, MFA, and active IP blocks unless an admin separately clears those IP blocks. When a valid override is used, the service also attempts to clear the Supabase auth ban and confirm the email. Recovery-email sign-in stores token and code hashes in private schema tables and audits sends, consumes, rejects, creates, revokes, and Supabase unban/create attempts. The recovery session is created with the existing admin generateLink plus detached verifyOtp pattern, then normal auth cookies are set. Redirects are limited to sanitized app paths. Database objects live in:

private.auth_recovery_overrides
private.auth_recovery_tokens
private.auth_recovery_events

Use AUTH_RECOVERY_HASH_SECRET in production when available. The code falls back to existing Supabase server secrets for local development, but do not expose those values to clients or support tooling. Do not run bun sb:push for this change; apply migrations through the normal database release process.

Passkeys

Passkeys use Supabase Auth’s experimental WebAuthn APIs. Browser clients created through @tuturuuu/supabase/next/auth-browser must pass auth.experimental.passkey: true; otherwise Supabase rejects auth.signInWithPasskey(), auth.registerPasskey(), and auth.passkey.* calls. apps/web owns passkey UX:

The public login form exposes an explicit “Continue with passkey” action so users can open the browser passkey picker without relying only on autofill.
Account Security in the apps/web settings dialog owns passkey registration, rename, and delete actions. Do not add separate passkey settings pages.
Satellite apps should continue to route user authentication through apps/web cross-app auth. Passkeys are bound to the relying party domain, so the central apps/web origin remains the authority for Tuturuuu account passkeys.

Production Supabase Auth must have passkeys enabled with these relying party settings:

Relying Party Display Name: Tuturuuu
Relying Party ID: tuturuuu.com
Relying Party Origins: https://tuturuuu.com

Local Supabase Auth must also enable passkeys in apps/database/supabase/config.toml. The committed local config uses the Portless apps/web origin:

Relying Party Display Name: Tuturuuu
Relying Party ID: tuturuuu.localhost
Relying Party Origins: https://tuturuuu.localhost

Restart local Supabase after changing this config; the Auth service reads these settings on startup. Real WebAuthn ceremonies require a secure origin, so test registration and sign-in from https://tuturuuu.localhost. UI-only and unsupported-browser paths can still be exercised without registering a credential. Remote Supabase development auth is different: if a cloud Supabase project has captcha protection enabled, passkey sign-in must send a real Turnstile token. The local E2E bypass is honored only when NEXT_PUBLIC_SUPABASE_URL points at local Supabase. When testing remote Supabase from https://tuturuuu.localhost, the Turnstile site key must authorize that local hostname; Cloudflare Turnstile error 110200 means the widget cannot mint the token Supabase requires. The login UI keeps passkey sign-in blocked while that token is missing; either add the local hostname to the Cloudflare Turnstile widget used by the Supabase project, or point NEXT_PUBLIC_SUPABASE_URL at local Supabase for dev passkey testing.

Web QR Session Handoff

QR-based session handoff must never be a public login bootstrap. An unauthenticated browser cannot prove that it belongs to the account scanning the QR code, so public challenge creation would allow QR phishing where an attacker polls a victim-approved challenge and receives the victim’s session. The QR challenge endpoints are therefore constrained to authenticated, same-account handoff:

POST /api/v1/auth/qr-login/challenges validates the request origin and the request-scoped Supabase session before inserting a qr_login_challenges row. The row stores a hashed secret, request metadata, creatorUserId, and a two-minute expiry.
The client renders a tuturuuu://auth/qr-login payload that contains the challenge id, one-time secret, and web origin.
The signed-in mobile app scans the code from Settings > Session. Mobile must have app lock enabled, then performs local authentication before approving.
POST /api/v1/auth/qr-login/challenges/:id/approve validates the mobile Bearer session, challenge secret, and creatorUserId. The approver must be the same user that created the challenge.
The creator polls GET /api/v1/auth/qr-login/challenges/:id?secret=.... Once approved, the server consumes the challenge and creates a fresh detached Supabase session via admin generateLink plus detached verifyOtp.

QR challenge rows never store access or refresh tokens. The table is RLS-enabled without anon/authenticated grants; API routes use the service role for challenge state and the request-scoped client to validate both the challenge creator and the mobile approver.

Sign Out

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";
import { redirect } from "next/navigation";

export async function signOut() {
  const supabase = await createClient();
  await supabase.auth.signOut();
  redirect("/login");
}

Server-side Auth Resolution (`getClaims` first)

For server-side route and helper authorization checks, prefer a claims-first flow:

Call supabase.auth.getClaims() first.
Use claims.sub as the authenticated user id when available.
Fall back to supabase.auth.getUser() when claims are unavailable or insufficient.

This reduces auth latency on hot API paths while preserving correctness for call sites that still need canonical user resolution.

async function resolveCurrentUserId(supabase: TypedSupabaseClient) {
  const getClaims = (supabase.auth as { getClaims?: () => Promise<unknown> })
    .getClaims;

  if (typeof getClaims === "function") {
    const { data, error } = (await getClaims.call(supabase.auth)) as {
      data?: { claims?: { sub?: string } };
      error?: unknown;
    };

    if (!error && data?.claims?.sub) {
      return data.claims.sub;
    }
  }

  const {
    data: { user },
  } = await supabase.auth.getUser();

  return user?.id ?? null;
}

When implementing this pattern, feature-detect getClaims first. Some tests and older stubs only mock getUser, and unconditional getClaims calls will break those environments.

Multi-Factor Authentication (MFA)

Enable TOTP MFA

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function enableMFA() {
  const supabase = await createClient();

  // Enroll in MFA
  const { data, error } = await supabase.auth.mfa.enroll({
    factorType: "totp",
  });

  if (error) throw error;

  return {
    qrCode: data.totp.qr_code, // Display to user
    secret: data.totp.secret, // For manual entry
    factorId: data.id,
  };
}

Verify MFA Enrollment

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function verifyMFAEnrollment(factorId: string, code: string) {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.mfa.challengeAndVerify({
    factorId,
    code,
  });

  if (error) throw error;
  return { success: true };
}

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function signInWithMFA(email: string, password: string) {
  const supabase = await createClient();

  // Initial sign in
  const { data: signInData, error: signInError } =
    await supabase.auth.signInWithPassword({
      email,
      password,
    });

  if (signInError) throw signInError;

  // Check if MFA is required
  const { data: factors } = await supabase.auth.mfa.listFactors();

  if (factors && factors.totp.length > 0) {
    const factorId = factors.totp[0].id;

    // Create MFA challenge
    const { data: challengeData, error: challengeError } =
      await supabase.auth.mfa.challenge({ factorId });

    if (challengeError) throw challengeError;

    return {
      requiresMFA: true,
      challengeId: challengeData.id,
      factorId,
    };
  }

  return { requiresMFA: false };
}

Verify MFA Code

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function verifyMFACode(
  factorId: string,
  challengeId: string,
  code: string,
) {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.mfa.verify({
    factorId,
    challengeId,
    code,
  });

  if (error) throw error;
  return { success: true };
}

Mobile MFA Approval Cookies

Mobile approval for web MFA is scoped to the Supabase login session that created and consumed the approval challenge. When the web browser polls an approved mobile MFA challenge, store the current JWT session_id in the challenge approval metadata. The auth proxy must compare that stored session id with the current request claims before using ttr_mfa_mobile_approval to bypass the MFA redirect. Do not treat the approval cookie as a user-scoped remember-me token. A valid cookie only proves that one challenge secret was approved; it must also match the current Supabase session. Central logout responses should expire the approval cookie, and MFA redirects should clear stale approval cookies that do not satisfy the current-session binding.

Session Management

Get Current Session

import { createClient } from "@tuturuuu/supabase/next/server";

export async function getSession() {
  const supabase = await createClient();

  const {
    data: { session },
    error,
  } = await supabase.auth.getSession();

  if (error) throw error;
  return session;
}

Get Current User

import { createClient } from "@tuturuuu/supabase/next/server";

export async function getCurrentUser() {
  const supabase = await createClient();

  const {
    data: { user },
    error,
  } = await supabase.auth.getUser();

  if (error || !user) {
    return null;
  }

  return user;
}

Refresh Session

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function refreshSession() {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.refreshSession();

  if (error) throw error;
  return data.session;
}

Password Reset

Request Password Reset

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function requestPasswordReset(email: string) {
  const supabase = await createClient();

  const { error } = await supabase.auth.resetPasswordForEmail(email, {
    redirectTo: `${process.env.NEXT_PUBLIC_APP_URL}/auth/reset-password`,
  });

  if (error) throw error;
  return { success: true };
}

Reset Password

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function resetPassword(newPassword: string) {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.updateUser({
    password: newPassword,
  });

  if (error) throw error;
  return { success: true };
}

Email Verification

Resend Verification Email

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function resendVerificationEmail() {
  const supabase = await createClient();

  const {
    data: { user },
  } = await supabase.auth.getUser();

  if (!user?.email) {
    throw new Error("No user email found");
  }

  const { error } = await supabase.auth.resend({
    type: "signup",
    email: user.email,
  });

  if (error) throw error;
  return { success: true };
}

Cross-App Authentication

The platform supports token-based authentication across different apps using @tuturuuu/auth/cross-app. When a new satellite app participates in centralized login, wire both sides in the same patch:

Register the app URL in packages/utils/src/internal-domains.ts so mapUrlToApp(...) can recognize its returnUrl.
Add apps/<app>/src/app/api/auth/verify-app-token/route.ts so /verify-token can exchange the cross-app token for a host-only tuturuuu_app_session cookie. When the satellite requires rewritten apps/web API access, use createPOST('<app>', { verificationBaseUrl: WEB_APP_URL }) so the handoff also stores the Web-issued app-session cookie.
Keep generate_cross_app_token(...) bound to the authenticated caller (p_user_id = auth.uid()) so verify endpoints cannot mint sessions for arbitrary users.
Do not call supabase.auth.setSession() in registered internal apps. The verifier route sets the HttpOnly app-session cookie, and satellite UI should fetch user/profile data by forwarding that cookie to central internal APIs.
Registered internal app source must not call supabase.auth.* directly. Use @tuturuuu/auth/app-session server helpers and @tuturuuu/internal-api profile/default-workspace helpers instead; bun check runs the static guard across all registered app src directories.
App-session auth is read/update oriented for satellite apps. Destructive workspace operations such as DELETE /api/workspaces/[wsId] require a full Supabase session (cookie or bearer) and manage_workspace_settings; they do not opt into allowAppSessionAuth because the app-session path uses an admin-backed client that would bypass workspace delete RLS.

If either piece is missing, centralized login can stall on the web login spinner or land on /verify-token with no token-verification endpoint to finish the handoff.

Generate Cross-App Token

generateCrossAppToken(supabase, targetApp, originApp, expirySeconds?) is the real signature. It reads the authenticated user from the passed Supabase client, calls the generate_cross_app_token RPC, and returns the token string (or null on failure). The origin app ('web') mints the token; the target app ('shortener', 'nova', 'rewise', etc.) verifies it.

import { generateCrossAppToken } from "@tuturuuu/auth/cross-app";
import { createClient } from "@tuturuuu/supabase/next/server";

export async function createShortenerLink() {
  const supabase = await createClient();

  // Generate a token the shortener app can verify (default expiry: 300s).
  const token = await generateCrossAppToken(
    supabase,
    "shortener", // targetApp
    "web", // originApp
    3600, // expirySeconds (optional)
  );

  if (!token) {
    throw new Error("Failed to generate cross-app token");
  }

  return {
    url: `${process.env.SHORTENER_APP_URL}/create?token=${token}`,
  };
}

Validate Cross-App Token

The target app validates the token with validateCrossAppToken(supabase, token, targetApp), which calls the validate_cross_app_token_with_session RPC and returns { userId } (or null). The target app is responsible for establishing its own session/app-session from that userId; the token never carries access or refresh tokens.

import { validateCrossAppToken } from "@tuturuuu/auth/cross-app";
import { createClient } from "@tuturuuu/supabase/next/server";

export async function handleCrossAppRequest(token: string) {
  const supabase = await createClient();

  const result = await validateCrossAppToken(supabase, token, "shortener");

  if (!result) {
    throw new Error("Invalid token");
  }

  // result contains: { userId }
  return result;
}

@tuturuuu/auth/cross-app does not export a verifyCrossAppToken function. For the browser-side handoff on /verify-token, use the exported verifyRouteToken({ searchParams, token, router }) helper, which POSTs the token to /api/auth/verify-app-token and lets the verifier route set the HttpOnly app-session cookie. revokeAllCrossAppTokens(supabase) invalidates a user’s outstanding tokens.

Proxy (Edge Middleware) Authentication

In apps/web the edge entry point that protects routes lives in apps/web/src/proxy.ts (not a middleware.ts file). It exports an async proxy(req) function plus a config.matcher, and Next.js is configured to use this file as the request middleware. The real implementation delegates the heavy lifting to createCentralizedAuthProxy from @tuturuuu/auth/proxy, then layers on onboarding checks, workspace-slug normalization, guest-route guards, and locale handling. See Routing for how the proxy coordinates those concerns. The simplified example below shows the core shape: resolve the user from a request-scoped Supabase client and redirect when unauthenticated. Note that createDynamicClient() is async and must be awaited.

// apps/web/src/proxy.ts (simplified)
import { createClient } from "@tuturuuu/supabase/next/server";
import { type NextRequest, NextResponse } from "next/server";

export async function proxy(request: NextRequest) {
  const supabase = await createClient();

  const {
    data: { user },
  } = await supabase.auth.getUser();

  // Protect dashboard routes
  if (request.nextUrl.pathname.startsWith("/dashboard") && !user) {
    return NextResponse.redirect(new URL("/login", request.url));
  }

  // Redirect authenticated users from auth pages
  if (request.nextUrl.pathname.startsWith("/login") && user) {
    return NextResponse.redirect(new URL("/dashboard", request.url));
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/dashboard/:path*", "/login", "/signup"],
};

The production proxy resolves the user with resolveAuthenticatedSessionUser(supabase) and propagates refreshed auth cookies onto every redirect via propagateAuthCookies(authRes, response). Reuse those helpers instead of re-implementing session resolution and cookie forwarding when you extend the proxy.

Protected Server Component

import { createClient } from '@tuturuuu/supabase/next/server';
import { redirect } from 'next/navigation';

export default async function ProtectedPage() {
  const supabase = await createClient();

  const { data: { user } } = await supabase.auth.getUser();

  if (!user) {
    redirect('/login');
  }

  return (
    <div>
      <h1>Welcome, {user.email}</h1>
    </div>
  );
}

Client-Side Authentication

@tuturuuu/supabase/next/client is deprecated for CRUD/storage and may throw unless a compatibility flag is set. For browser data access, use @tuturuuu/internal-api. For the narrow case where the browser genuinely needs an auth client (reacting to live auth-state changes), use createAuthClient() from @tuturuuu/supabase/next/auth-browser. Do not fetch product data on the client through raw Supabase clients, and prefer TanStack Query over useEffect for any data fetching.

useUser Hook (auth-state subscription)

Subscribing to Supabase auth-state changes is a legitimate exception to the “no useEffect for data fetching” guidance: this hook does not fetch product data, it mirrors the live session into React state. Use createAuthClient and subscribe once.

"use client";

import type { User } from "@supabase/supabase-js";
import { createAuthClient } from "@tuturuuu/supabase/next/auth-browser";
import { useEffect, useMemo, useState } from "react";

export function useUser() {
  const [user, setUser] = useState<User | null>(null);
  const [loading, setLoading] = useState(true);
  const supabase = useMemo(() => createAuthClient(), []);

  useEffect(() => {
    // Resolve the current user once on mount.
    supabase.auth.getUser().then(({ data: { user } }) => {
      setUser(user ?? null);
      setLoading(false);
    });

    // Then keep it in sync with live auth-state changes.
    const {
      data: { subscription },
    } = supabase.auth.onAuthStateChange((_event, session) => {
      setUser(session?.user ?? null);
    });

    return () => subscription.unsubscribe();
  }, [supabase]);

  return { user, loading };
}

For authorization decisions, always re-verify the user server-side (await supabase.auth.getUser() or the getClaims-first pattern above). Client auth state is for UX only — never trust it as the sole gate for protected data.

Usage

"use client";

import { useUser } from "@/hooks/useUser";

export function UserProfile() {
  const { user, loading } = useUser();

  if (loading) return <div>Loading...</div>;
  if (!user) return <div>Not authenticated</div>;

  return <div>Logged in as {user.email}</div>;
}

Identity Linking

Link multiple auth providers to same account:

"use server";

import { createClient } from "@tuturuuu/supabase/next/server";

export async function linkIdentity(provider: "google" | "github") {
  const supabase = await createClient();

  const { data, error } = await supabase.auth.linkIdentity({
    provider,
  });

  if (error) throw error;
  return { url: data.url };
}

Best Practices

✅ DO

Always check authentication server-side

const {
  data: { user },
} = await supabase.auth.getUser();
if (!user) throw new Error("Unauthorized");

Redirect after authentication

redirect("/dashboard"); // Don't return sensitive data

Handle errors gracefully

if (error) return { error: error.message };

Implement MFA for sensitive operations

const mfaRequired = await checkMFAEnabled(userId);

❌ DON’T

Don’t trust client-side auth state alone

// ❌ Bad
if (localStorage.getItem("user")) {
  /* ... */
}

Don’t expose sensitive data in auth redirects

// ❌ Bad
redirect(`/dashboard?apiKey=${apiKey}`);

Don’t store passwords

// ❌ Bad: Let Supabase handle password storage

Don’t use createAdminClient() for auth operations

// ❌ Bad: Use regular client
const sbAdmin = await createAdminClient();
await sbAdmin.auth.signUp({ ... });

Authorization - Permission system
Supabase Client - Client creation patterns
RLS Policies - Database security

​Authentication Flow

​Cross-App Supabase Cookies

​Web Multi-Account Sessions

​Keeping stored sessions usable

​Sign Up

​Basic Email/Password Sign Up

​Client Component

​Sign In

​Email/Password Sign In

​OAuth Sign In

​OAuth Callback State

​Email-Based Auth Recovery

​Passkeys

​Web QR Session Handoff

​Sign Out

​Server-side Auth Resolution (getClaims first)

​Multi-Factor Authentication (MFA)

​Enable TOTP MFA

​Verify MFA Enrollment

​MFA Challenge During Sign In

​Verify MFA Code

​Mobile MFA Approval Cookies

​Session Management

​Get Current Session

​Get Current User

​Refresh Session

​Password Reset

​Request Password Reset

​Reset Password

​Email Verification

​Resend Verification Email

​Cross-App Authentication

​Generate Cross-App Token

​Validate Cross-App Token

​Proxy (Edge Middleware) Authentication

​Protected Server Component

​Client-Side Authentication

​useUser Hook (auth-state subscription)

​Usage

​Identity Linking

​Best Practices

​✅ DO

​❌ DON’T

​Related Documentation

​External Resources

Authentication Flow

Cross-App Supabase Cookies

Web Multi-Account Sessions

Keeping stored sessions usable

Sign Up

Basic Email/Password Sign Up

Client Component

Sign In

Email/Password Sign In

OAuth Sign In

OAuth Callback State

Email-Based Auth Recovery

Passkeys

Web QR Session Handoff

Sign Out

Server-side Auth Resolution (`getClaims` first)

Multi-Factor Authentication (MFA)

Enable TOTP MFA

Verify MFA Enrollment

MFA Challenge During Sign In

Verify MFA Code

Mobile MFA Approval Cookies

Session Management

Get Current Session

Get Current User

Refresh Session

Password Reset

Request Password Reset

Reset Password

Email Verification

Resend Verification Email

Cross-App Authentication

Generate Cross-App Token

Validate Cross-App Token

Proxy (Edge Middleware) Authentication

Protected Server Component

Client-Side Authentication

useUser Hook (auth-state subscription)

Usage

Identity Linking

Best Practices

✅ DO

❌ DON’T

Related Documentation

External Resources