Client

Setup

Create an auth client with mutation hooks:

src/lib/convex/auth-client.ts

import { inferAdditionalFields } from 'better-auth/client/plugins';
import { createAuthClient } from 'better-auth/react';
import { convexClient } from 'kitcn/auth/client';
import { createAuthMutations } from 'kitcn/react';

import type { Auth } from '@convex/auth-shared';

export const authClient = createAuthClient({
  baseURL: process.env.NEXT_PUBLIC_SITE_URL!,
  plugins: [inferAdditionalFields<Auth>(), convexClient()],
});

export const {
  useSignInMutationOptions,
  useSignInSocialMutationOptions,
  useSignOutMutationOptions,
  useSignUpMutationOptions,
} = createAuthMutations(authClient);

On Next.js, the scaffolded auth route lives on the same origin as the page, so the client does not need an explicit baseURL. Add one only when your auth handler lives on a different origin.

src/components/login-form.tsx

'use client';

import { useMutation } from '@tanstack/react-query';
import { useSignInSocialMutationOptions } from '@/lib/convex/auth-client';

function LoginForm() {
  const signInSocial = useMutation(useSignInSocialMutationOptions());

  const handleGoogleSignIn = () => {
    signInSocial.mutate({
      callbackURL: window.location.origin,
      provider: 'google',
    });
  };

  const handleGithubSignIn = () => {
    signInSocial.mutate({
      callbackURL: window.location.origin,
      provider: 'github',
    });
  };

  return (
    <div>
      <button disabled={signInSocial.isPending} onClick={handleGoogleSignIn}>
        Continue with Google
      </button>
      <button disabled={signInSocial.isPending} onClick={handleGithubSignIn}>
        Continue with GitHub
      </button>
    </div>
  );
}

Email/Password

First enable email/password in your Convex auth config:

convex/functions/auth.ts

import { defineAuth } from './generated/auth';

export default defineAuth((ctx) => ({
  emailAndPassword: {
    enabled: true,
  },
  // ... rest of config
}));

Then use the sign in/up hooks:

src/components/login-form.tsx

'use client';

import { useMutation } from '@tanstack/react-query';
import { useRouter } from 'next/navigation';
import { useState } from 'react';
import {
  useSignInMutationOptions,
  useSignUpMutationOptions,
} from '@/lib/convex/auth-client';

function EmailLoginForm() {
  const [mode, setMode] = useState<'signin' | 'signup'>('signin');
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [name, setName] = useState('');
  const router = useRouter();

  const signIn = useMutation(
    useSignInMutationOptions({
      onSuccess: () => router.push('/'),
    })
  );
  const signUp = useMutation(
    useSignUpMutationOptions({
      onSuccess: () => router.push('/'),
    })
  );

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();

    if (mode === 'signup') {
      signUp.mutate({
        callbackURL: window.location.origin,
        email,
        name,
        password,
      });
    } else {
      signIn.mutate({
        callbackURL: window.location.origin,
        email,
        password,
      });
    }
  };

  const isPending = signIn.isPending || signUp.isPending;

  return (
    <form onSubmit={handleSubmit}>
      {mode === 'signup' && (
        <input
          type="text"
          placeholder="Name"
          value={name}
          onChange={(e) => setName(e.target.value)}
          required
        />
      )}
      <input
        type="email"
        placeholder="Email"
        value={email}
        onChange={(e) => setEmail(e.target.value)}
        required
      />
      <input
        type="password"
        placeholder="Password"
        value={password}
        onChange={(e) => setPassword(e.target.value)}
        required
        minLength={8}
      />
      <button type="submit" disabled={isPending}>
        {mode === 'signup' ? 'Sign Up' : 'Sign In'}
      </button>
      <button type="button" onClick={() => setMode(mode === 'signin' ? 'signup' : 'signin')}>
        {mode === 'signin' ? "Don't have an account? Sign up" : 'Already have an account? Sign in'}
      </button>
    </form>
  );
}

Unlike OAuth (which redirects server-side), email/password auth requires a client-side redirect via onSuccess.

Sign Out

src/components/logout-button.tsx

'use client';

import { useMutation } from '@tanstack/react-query';
import { useRouter } from 'next/navigation';
import { toast } from 'sonner';
import { useSignOutMutationOptions } from '@/lib/convex/auth-client';

function LogoutButton() {
  const router = useRouter();
  const signOut = useMutation(
    useSignOutMutationOptions({
      onSuccess: () => router.push('/login'),
      onError: () => toast.error('Failed to sign out'),
    })
  );

  return (
    <button disabled={signOut.isPending} onClick={() => signOut.mutate()}>
      {signOut.isPending ? 'Signing out...' : 'Sign out'}
    </button>
  );
}

Why createAuthMutations?

The hooks provide two key features:

Feature	Description
Auth query cleanup	`useSignOutMutationOptions` automatically calls `unsubscribeAuthQueries()` before `signOut()` to prevent `UNAUTHORIZED` errors from subscribed queries during logout
Proper loading state	The mutation's `isPending` stays `true` until the auth token is actually cleared (not just when the API call completes), preventing UI flicker

Client Hooks

useAuth

Get comprehensive auth state:

src/components/auth-status.tsx

import { useAuth } from 'kitcn/react';

function AuthStatus() {
  const { hasSession, isAuthenticated, isLoading } = useAuth();

  if (isLoading) return <Spinner />;

  return (
    <div>
      {isAuthenticated ? 'Logged in' : 'Logged out'}
    </div>
  );
}

Property	Description
`hasSession`	Has a session token (may not be verified)
`isAuthenticated`	Token exists AND Convex auth verified
`isLoading`	Convex auth is still loading

useMaybeAuth

Check if user maybe has auth (optimistic, has token):

import { useMaybeAuth } from 'kitcn/react';

function Component() {
  const isAuth = useMaybeAuth();
  return isAuth ? <LoggedInUI /> : <LoginButton />;
}

useIsAuth

Check if user is authenticated (server-verified):

import { useIsAuth } from 'kitcn/react';

function SecureComponent() {
  const isAuth = useIsAuth();
  return isAuth ? <SensitiveData /> : <Loading />;
}

useAuthGuard

Guard mutations that require authentication:

src/components/create-post.tsx

import { useAuthGuard } from 'kitcn/react';
import { useMutation } from '@tanstack/react-query';

function CreatePostButton() {
  const guard = useAuthGuard();
  const createPost = useMutation(crpc.post.create.mutationOptions());

  const handleClick = () => {
    // Returns true if blocked (not authenticated)
    if (guard()) return;

    // User is authenticated, safe to mutate
    createPost.mutate({ title: 'New Post' });
  };

  return <button onClick={handleClick}>Create Post</button>;
}

With callback:

const handleClick = () => {
  guard(async () => {
    // Only runs if authenticated
    await createPost.mutateAsync({ title: 'New Post' });
    toast.success('Post created!');
  });
};

Conditional Rendering

MaybeAuthenticated

Render children only when has session (optimistic):

import { MaybeAuthenticated } from 'kitcn/react';

function App() {
  return (
    <MaybeAuthenticated>
      <Dashboard />
    </MaybeAuthenticated>
  );
}

Authenticated

Render children only when server-verified:

import { Authenticated } from 'kitcn/react';

function App() {
  return (
    <Authenticated>
      <SensitiveData />
    </Authenticated>
  );
}

MaybeUnauthenticated

Render children only when no session (optimistic):

import { MaybeAuthenticated, MaybeUnauthenticated } from 'kitcn/react';

function App() {
  return (
    <>
      <MaybeAuthenticated>
        <Dashboard />
      </MaybeAuthenticated>
      <MaybeUnauthenticated>
        <LoginPage />
      </MaybeUnauthenticated>
    </>
  );
}

Unauthenticated

Render children only when not server-verified (waits for loading):

import { Unauthenticated } from 'kitcn/react';

function App() {
  return (
    <Unauthenticated>
      <LoginPage />
    </Unauthenticated>
  );
}

Provider Configuration

Configure auth callbacks in the provider:

src/app.tsx

import { ConvexAuthProvider } from 'kitcn/auth/client';

function App() {
  return (
    <ConvexAuthProvider
      client={convexClient}
      authClient={authClient}
      initialToken={serverToken}
      onMutationUnauthorized={() => {
        // Custom handler for unauthorized mutations
        openLoginModal();
      }}
      onQueryUnauthorized={({ queryName }) => {
        // Custom handler for unauthorized queries
        console.log(`Unauthorized query: ${queryName}`);
      }}
    >
      {children}
    </ConvexAuthProvider>
  );
}

Props

Prop	Type	Description
`client`	`ConvexReactClient`	Convex client instance
`authClient`	`AuthClient`	Better Auth client instance
`initialToken`	`string?`	Initial session token (from SSR)
`onMutationUnauthorized`	`() => void`	Called when mutation is blocked
`onQueryUnauthorized`	`({ queryName }) => void`	Called when query is blocked

SSR → client hydration: getToken() reads cookie → prefetch queries with token → pass initialToken to client → ConvexAuthProvider mounts with token → Convex validates JWT → AuthStateSync updates isAuthenticated → HydrationBoundary hydrates prefetched data.

Concept	Detail
Token flows server → client	Via `initialToken` prop
Instant hydration	Prefetched queries hydrate immediately — no loading spinner
Defensive isLoading	Prevents `UNAUTHORIZED` errors during hydration race
Two sources sync	Better Auth (cookie-based) and Convex (WebSocket-based)

React Native / @convex-dev/auth Users

If you're using @convex-dev/auth (common in React Native) instead of better-auth, import ConvexProviderWithAuth from kitcn/react:

App.tsx

import { ConvexProviderWithAuth } from 'kitcn/react';

function App() {
  return (
    <ConvexProviderWithAuth client={convex} useAuth={useAuthFromConvexDev}>
      <YourApp />
    </ConvexProviderWithAuth>
  );
}

This enables skipUnauth queries, useAuth, and conditional rendering components to work with @convex-dev/auth.