Better Auth

better-auth - D1 Adapter & Error Prevention Guide

Package: better-auth@1.4.16 (Jan 21, 2026) Breaking Changes: ESM-only (v1.4.0), Admin impersonation prevention default (v1.4.6), Multi-team table changes (v1.3), D1 requires Drizzle/Kysely (no direct adapter)

⚠️ CRITICAL: D1 Adapter Requirement

better-auth DOES NOT have d1Adapter(). You MUST use:

• Drizzle ORM (recommended): drizzleAdapter(db, { provider: "sqlite" })
• Kysely: new Kysely({ dialect: new D1Dialect({ database: env.DB }) })

See Issue #1 below for details.

What's New in v1.4.10 (Dec 31, 2025)

Major Features:

• OAuth 2.1 Provider plugin - Build your own OAuth provider (replaces MCP plugin)
• Patreon OAuth provider - Social sign-in with Patreon
• Kick OAuth provider - With refresh token support
• Vercel OAuth provider - Sign in with Vercel
• Global backgroundTasks config - Deferred actions for better performance
• Form data support - Email authentication with fetch metadata fallback
• Stripe enhancements - Flexible subscription lifecycle, disableRedirect option

Admin Plugin Updates:

• ⚠️ Breaking: Impersonation of admins disabled by default (v1.4.6)
• Support role with permission-based user updates
• Role type inference improvements

Security Fixes:

• SAML XML parser hardening with configurable size constraints
• SAML assertion timestamp validation with per-provider clock skew
• SSO domain-verified provider trust
• Deprecated algorithm rejection
• Line nonce enforcement

📚 Docs: https://www.better-auth.com/changelogs

What's New in v1.4.0 (Nov 22, 2025)

Major Features:

• Stateless session management - Sessions without database storage
• ESM-only package ⚠️ Breaking: CommonJS no longer supported
• JWT key rotation - Automatic key rotation for enhanced security
• SCIM provisioning - Enterprise user provisioning protocol
• @standard-schema/spec - Replaces ZodType for validation
• CaptchaFox integration - Built-in CAPTCHA support
• Automatic server-side IP detection
• Cookie-based account data storage
• Multiple passkey origins support
• RP-Initiated Logout endpoint (OIDC)

📚 Docs: https://www.better-auth.com/changelogs

What's New in v1.3 (July 2025)

Major Features:

• SSO with SAML 2.0 - Enterprise single sign-on (moved to separate @better-auth/sso package)
• Multi-team support ⚠️ Breaking: teamId removed from member table, new teamMembers table required
• Additional fields - Custom fields for organization/member/invitation models
• Performance improvements and bug fixes

📚 Docs: https://www.better-auth.com/blog/1-3

Alternative: Kysely Adapter Pattern

If you prefer Kysely over Drizzle:

File: src/auth.ts

import { betterAuth } from "better-auth";
import { Kysely, CamelCasePlugin } from "kysely";
import { D1Dialect } from "kysely-d1";

type Env = {
  DB: D1Database;
  BETTER_AUTH_SECRET: string;
  // ... other env vars
};

export function createAuth(env: Env) {
  return betterAuth({
    secret: env.BETTER_AUTH_SECRET,

    // Kysely with D1Dialect
    database: {
      db: new Kysely({
        dialect: new D1Dialect({
          database: env.DB,
        }),
        plugins: [
          // CRITICAL: Required if using Drizzle schema with snake_case
          new CamelCasePlugin(),
        ],
      }),
      type: "sqlite",
    },

    emailAndPassword: {
      enabled: true,
    },

    // ... other config
  });
}

Why CamelCasePlugin?

If your Drizzle schema uses snake_case column names (e.g., email_verified), but better-auth expects camelCase (e.g., emailVerified), the CamelCasePlugin automatically converts between the two.

⚠️ Cloudflare Workers Note: D1 database bindings are only available inside the request handler (the fetch() function). You cannot initialize better-auth outside the request context. Use a factory function pattern:

// ❌ WRONG - DB binding not available outside request
const db = drizzle(env.DB, { schema }) // env.DB doesn't exist here
export const auth = betterAuth({ database: drizzleAdapter(db, { provider: "sqlite" }) })

// ✅ CORRECT - Create auth instance per-request
export default {
  fetch(request, env, ctx) {
    const db = drizzle(env.DB, { schema })
    const auth = betterAuth({ database: drizzleAdapter(db, { provider: "sqlite" }) })
    return auth.handler(request)
  }
}

Community Validation: Multiple production implementations confirm this pattern (Medium, AnswerOverflow, official Hono examples).

Framework Integrations

TanStack Start

⚠️ CRITICAL: TanStack Start requires the reactStartCookies plugin to handle cookie setting properly.

import { betterAuth } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
import { reactStartCookies } from "better-auth/react-start";

export const auth = betterAuth({
  database: drizzleAdapter(db, { provider: "sqlite" }),
  plugins: [
    twoFactor(),
    organization(),
    reactStartCookies(), // ⚠️ MUST be LAST plugin
  ],
});

Why it's needed: TanStack Start uses a special cookie handling system. Without this plugin, auth functions like signInEmail() and signUpEmail() won't set cookies properly, causing authentication to fail.

Important: The reactStartCookies plugin must be the last plugin in the array.

Session Nullability Pattern: When using useSession() in TanStack Start, the session object always exists, but session.user and session.session are null when not logged in:

const { data: session } = authClient.useSession()

// When NOT logged in:
console.log(session) // { user: null, session: null }
console.log(!!session) // true (unexpected!)

// Correct check:
if (session?.user) {
  // User is logged in
}

Always check session?.user or session?.session, not just session. This is expected behavior (session object container always exists).

API Route Setup (/src/routes/api/auth/$.ts):

import { auth } from '@/lib/auth'
import { createFileRoute } from '@tanstack/react-router'

export const Route = createFileRoute('/api/auth/$')({
  server: {
    handlers: {
      GET: ({ request }) => auth.handler(request),
      POST: ({ request }) => auth.handler(request),
    },
  },
})

📚 Official Docs: https://www.better-auth.com/docs/integrations/tanstack

Available Plugins (v1.4+)

Better Auth provides plugins for advanced authentication features:

OAuth 2.1 Provider Plugin (New in v1.4.9)

Build your own OAuth provider for MCP servers, third-party apps, or API access:

import { betterAuth } from "better-auth";
import { oauthProvider } from "better-auth/plugins";
import { jwt } from "better-auth/plugins";

export const auth = betterAuth({
  plugins: [
    jwt(), // Required for token signing
    oauthProvider({
      // Token expiration (seconds)
      accessTokenExpiresIn: 3600,      // 1 hour
      refreshTokenExpiresIn: 2592000,  // 30 days
      authorizationCodeExpiresIn: 600, // 10 minutes
    }),
  ],
});

Key Features:

• OAuth 2.1 compliant - PKCE mandatory, S256 only, no implicit flow
• Three grant types: authorization_code, refresh_token, client_credentials
• JWT or opaque tokens - Configurable token format
• Dynamic client registration - RFC 7591 compliant
• Consent management - Skip consent for trusted clients
• OIDC UserInfo endpoint - /oauth2/userinfo with scope-based claims

Required Well-Known Endpoints:

// app/api/.well-known/oauth-authorization-server/route.ts
export async function GET() {
  return Response.json({
    issuer: process.env.BETTER_AUTH_URL,
    authorization_endpoint: `${process.env.BETTER_AUTH_URL}/api/auth/oauth2/authorize`,
    token_endpoint: `${process.env.BETTER_AUTH_URL}/api/auth/oauth2/token`,
    // ... other metadata
  });
}

Create OAuth Client:

const client = await auth.api.createOAuthClient({
  body: {
    name: "My MCP Server",
    redirectURLs: ["https://claude.ai/callback"],
    type: "public", // or "confidential"
  },
});
// Returns: { clientId, clientSecret (if confidential) }

📚 Full Docs: https://www.better-auth.com/docs/plugins/oauth-provider

⚠️ Note: This plugin is in active development and may not be suitable for production use yet.

Additional Plugins Reference

Bearer Token Plugin

For API-only authentication (mobile apps, CLI tools, third-party integrations):

import { bearer } from "better-auth/plugins";
import { bearerClient } from "better-auth/client/plugins";

// Server
export const auth = betterAuth({
  plugins: [bearer()],
});

// Client - Store token after sign-in
const { token } = await authClient.signIn.email({ email, password });
localStorage.setItem("auth_token", token);

// Client - Configure fetch to include token
const authClient = createAuthClient({
  plugins: [bearerClient()],
  fetchOptions: {
    auth: { type: "Bearer", token: () => localStorage.getItem("auth_token") },
  },
});

Google One Tap Plugin

Frictionless single-tap sign-in for users already signed into Google:

import { oneTap } from "better-auth/plugins";
import { oneTapClient } from "better-auth/client/plugins";

// Server
export const auth = betterAuth({
  plugins: [oneTap()],
});

// Client
authClient.oneTap({
  onSuccess: (session) => {
    window.location.href = "/dashboard";
  },
});

Requirement: Configure authorized JavaScript origins in Google Cloud Console.

Anonymous Plugin

Guest access without requiring email/password:

import { anonymous } from "better-auth/plugins";

// Server
export const auth = betterAuth({
  plugins: [
    anonymous({
      emailDomainName: "anon.example.com", // temp@{id}.anon.example.com
      onLinkAccount: async ({ anonymousUser, newUser }) => {
        // Migrate anonymous user data to linked account
        await migrateUserData(anonymousUser.id, newUser.id);
      },
    }),
  ],
});

// Client
await authClient.signIn.anonymous();
// Later: user can link to real account via signIn.social/email

Generic OAuth Plugin

Add custom OAuth providers not in the built-in list:

import { genericOAuth } from "better-auth/plugins";

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        {
          providerId: "linear",
          clientId: env.LINEAR_CLIENT_ID,
          clientSecret: env.LINEAR_CLIENT_SECRET,
          discoveryUrl: "https://linear.app/.well-known/openid-configuration",
          scopes: ["openid", "email", "profile"],
          pkce: true, // Recommended
        },
      ],
    }),
  ],
});

Callback URL pattern: {baseURL}/api/auth/oauth2/callback/{providerId}

Rate Limiting

Built-in rate limiting with customizable rules:

export const auth = betterAuth({
  rateLimit: {
    window: 60,  // seconds (default: 60)
    max: 100,    // requests per window (default: 100)

    // Custom rules for sensitive endpoints
    customRules: {
      "/sign-in/email": { window: 10, max: 3 },
      "/two-factor/*": { window: 10, max: 3 },
      "/forget-password": { window: 60, max: 5 },
    },

    // Use Redis/KV for distributed systems
    storage: "secondary-storage", // or "database"
  },

  // Secondary storage for rate limiting
  secondaryStorage: {
    get: async (key) => env.KV.get(key),
    set: async (key, value, ttl) => env.KV.put(key, value, { expirationTtl: ttl }),
    delete: async (key) => env.KV.delete(key),
  },
});

Note: Server-side calls via auth.api.* bypass rate limiting.

Stateless Sessions (v1.4.0+)

Store sessions entirely in signed cookies without database storage:

export const auth = betterAuth({
  session: {
    // Stateless: No database storage, session lives in cookie only
    storage: undefined, // or omit entirely

    // Cookie configuration
    cookieCache: {
      enabled: true,
      maxAge: 60 * 60 * 24 * 7, // 7 days
      encoding: "jwt", // Use JWT for stateless (not "compact")
    },

    // Session expiration
    expiresIn: 60 * 60 * 24 * 7, // 7 days
  },
});

When to Use:

Key Points:

• Stateless sessions can't be revoked (user must wait for expiry)
• Cookie size limit ~4KB (limits session data)
• Use encoding: "jwt" for interoperability, "jwe" for encrypted
• Server must have consistent BETTER_AUTH_SECRET across all instances

JWT Key Rotation (v1.4.0+)

Automatically rotate JWT signing keys for enhanced security:

import { jwt } from "better-auth/plugins";

export const auth = betterAuth({
  plugins: [
    jwt({
      // Key rotation (optional, enterprise security)
      keyRotation: {
        enabled: true,
        rotationInterval: 60 * 60 * 24 * 30, // Rotate every 30 days
        keepPreviousKeys: 3, // Keep 3 old keys for validation
      },

      // Custom signing algorithm (default: HS256)
      algorithm: "RS256", // Requires asymmetric keys

      // JWKS endpoint (auto-generated at /api/auth/jwks)
      exposeJWKS: true,
    }),
  ],
});

Key Points:

• Key rotation prevents compromised key from having indefinite validity
• Old keys are kept temporarily to validate existing tokens
• JWKS endpoint at /api/auth/jwks for external services
• Use RS256 for public key verification (microservices)
• HS256 (default) for single-service apps

Provider Scopes Reference

Common OAuth providers and the scopes needed for user data:

Configuration Example:

socialProviders: {
  google: {
    clientId: env.GOOGLE_CLIENT_ID,
    clientSecret: env.GOOGLE_CLIENT_SECRET,
    scope: ["openid", "email", "profile"], // All user data
  },
  github: {
    clientId: env.GITHUB_CLIENT_ID,
    clientSecret: env.GITHUB_CLIENT_SECRET,
    scope: ["user:email", "read:user"], // Email + full profile
  },
  microsoft: {
    clientId: env.MS_CLIENT_ID,
    clientSecret: env.MS_CLIENT_SECRET,
    scope: ["openid", "email", "profile", "User.Read"],
  },
}

Session Cookie Caching

Three encoding strategies for session cookies:

export const auth = betterAuth({
  session: {
    cookieCache: {
      enabled: true,
      maxAge: 300, // 5 minutes
      encoding: "compact", // or "jwt" or "jwe"
    },
    freshAge: 60 * 60 * 24, // 1 day - operations requiring fresh session
  },
});

Fresh sessions: Some sensitive operations require recently created sessions. Configure freshAge to control this window.

New Social Providers (v1.4.9+)

socialProviders: {
  // Patreon - Creator economy
  patreon: {
    clientId: env.PATREON_CLIENT_ID,
    clientSecret: env.PATREON_CLIENT_SECRET,
    scope: ["identity", "identity[email]"],
  },

  // Kick - Streaming platform (with refresh tokens)
  kick: {
    clientId: env.KICK_CLIENT_ID,
    clientSecret: env.KICK_CLIENT_SECRET,
  },

  // Vercel - Developer platform
  vercel: {
    clientId: env.VERCEL_CLIENT_ID,
    clientSecret: env.VERCEL_CLIENT_SECRET,
  },
}

Cloudflare Workers Requirements

⚠️ CRITICAL: Cloudflare Workers require AsyncLocalStorage support:

# wrangler.toml
compatibility_flags = ["nodejs_compat"]
# or for older Workers:
# compatibility_flags = ["nodejs_als"]

Without this flag, better-auth will fail with context-related errors.

Database Hooks

Execute custom logic during database operations:

export const auth = betterAuth({
  databaseHooks: {
    user: {
      create: {
        before: async (user, ctx) => {
          // Validate or modify before creation
          if (user.email?.endsWith("@blocked.com")) {
            throw new APIError("BAD_REQUEST", { message: "Email domain not allowed" });
          }
          return { data: { ...user, role: "member" } };
        },
        after: async (user, ctx) => {
          // Send welcome email, create related records, etc.
          await sendWelcomeEmail(user.email);
          await createDefaultWorkspace(user.id);
        },
      },
    },
    session: {
      create: {
        after: async (session, ctx) => {
          // Audit logging
          await auditLog.create({ action: "session_created", userId: session.userId });
        },
      },
    },
  },
});

Available hooks: create, update for user, session, account, verification tables.

Expo/React Native Integration

Complete mobile integration pattern:

// Client setup with secure storage
import { expoClient } from "@better-auth/expo";
import * as SecureStore from "expo-secure-store";

const authClient = createAuthClient({
  baseURL: "https://api.example.com",
  plugins: [expoClient({ storage: SecureStore })],
});

// OAuth with deep linking
await authClient.signIn.social({
  provider: "google",
  callbackURL: "myapp://auth/callback", // Deep link
});

// Or use ID token verification (no redirect)
await authClient.signIn.social({
  provider: "google",
  idToken: {
    token: googleIdToken,
    nonce: generatedNonce,
  },
});

// Authenticated requests
const cookie = await authClient.getCookie();
await fetch("https://api.example.com/data", {
  headers: { Cookie: cookie },
  credentials: "omit",
});

app.json deep link setup:

{
  "expo": {
    "scheme": "myapp"
  }
}

Server trustedOrigins (development):

trustedOrigins: ["exp://**", "myapp://"]

API Reference

Overview: What You Get For Free

When you call auth.handler(), better-auth automatically exposes 80+ production-ready REST endpoints at /api/auth/*. Every endpoint is also available as a server-side method via auth.api.* for programmatic use.

This dual-layer API system means:

• Clients (React, Vue, mobile apps) call HTTP endpoints directly
• Server-side code (middleware, background jobs) uses auth.api.* methods
• Zero boilerplate - no need to write auth endpoints manually

Time savings: Building this from scratch = ~220 hours. With better-auth = ~4-8 hours. 97% reduction.

Auto-Generated HTTP Endpoints

All endpoints are automatically exposed at /api/auth/* when using auth.handler().

Core Authentication Endpoints

Social OAuth Endpoints

Example OAuth flow:

// Client initiates
await authClient.signIn.social({
  provider: "google",
  callbackURL: "/dashboard",
});

// better-auth handles redirect to Google
// Google redirects back to /api/auth/callback/google
// better-auth creates session automatically

Plugin Endpoints

Two-Factor Authentication (2FA Plugin)

import { twoFactor } from "better-auth/plugins";

📚 Docs: https://www.better-auth.com/docs/plugins/2fa

Organization Plugin (Multi-Tenant SaaS)

import { organization } from "better-auth/plugins";

Organizations (10 endpoints):

Members (8 endpoints):

Invitations (7 endpoints):

Teams (8 endpoints):

Permissions & Roles (6 endpoints):

📚 Docs: https://www.better-auth.com/docs/plugins/organization

Admin Plugin

import { admin } from "better-auth/plugins";

// v1.4.10 configuration options
admin({
  defaultRole: "user",
  adminRoles: ["admin"],
  adminUserIds: ["user_abc123"], // Always grant admin to specific users
  impersonationSessionDuration: 3600, // 1 hour (seconds)
  allowImpersonatingAdmins: false, // ⚠️ Default changed in v1.4.6
  defaultBanReason: "Violation of Terms of Service",
  bannedUserMessage: "Your account has been suspended",
})

⚠️ Breaking Change (v1.4.6): allowImpersonatingAdmins now defaults to false. Set to true explicitly if you need admin-on-admin impersonation.

Custom Roles with Permissions (v1.4.10):

import { createAccessControl } from "better-auth/plugins/access";

// Define resources and permissions
const ac = createAccessControl({
  user: ["create", "read", "update", "delete", "ban", "impersonate"],
  project: ["create", "read", "update", "delete", "share"],
} as const);

// Create custom roles
const supportRole = ac.newRole({
  user: ["read", "ban"],      // Can view and ban users
  project: ["read"],          // Can view projects
});

const managerRole = ac.newRole({
  user: ["read", "update"],
  project: ["create", "read", "update", "delete"],
});

// Use in plugin
admin({
  ac,
  roles: {
    support: supportRole,
    manager: managerRole,
  },
})

📚 Docs: https://www.better-auth.com/docs/plugins/admin

Other Plugin Endpoints

Passkey Plugin (5 endpoints) - Docs:

• /passkey/add, /sign-in/passkey, /passkey/list, /passkey/delete, /passkey/update

Magic Link Plugin (2 endpoints) - Docs:

• /sign-in/magic-link, /magic-link/verify

Username Plugin (2 endpoints) - Docs:

• /sign-in/username, /username/is-available

Phone Number Plugin (5 endpoints) - Docs:

• /sign-in/phone-number, /phone-number/send-otp, /phone-number/verify, /phone-number/request-password-reset, /phone-number/reset-password

Email OTP Plugin (6 endpoints) - Docs:

• /email-otp/send-verification-otp, /email-otp/check-verification-otp, /sign-in/email-otp, /email-otp/verify-email, /forget-password/email-otp, /email-otp/reset-password

Anonymous Plugin (1 endpoint) - Docs:

• /sign-in/anonymous

JWT Plugin (2 endpoints) - Docs:

• /token (get JWT), /jwks (public key for verification)

OpenAPI Plugin (2 endpoints) - Docs:

• /reference (interactive API docs with Scalar UI)
• /generate-openapi-schema (get OpenAPI spec as JSON)

Server-Side API Methods (auth.api.*)

Every HTTP endpoint has a corresponding server-side method. Use these for:

• Server-side middleware (protecting routes)
• Background jobs (user cleanup, notifications)
• Admin operations (bulk user management)
• Custom auth flows (programmatic session creation)

Core API Methods

// Authentication
await auth.api.signUpEmail({
  body: { email, password, name },
  headers: request.headers,
});

await auth.api.signInEmail({
  body: { email, password, rememberMe: true },
  headers: request.headers,
});

await auth.api.signOut({ headers: request.headers });

// Session Management
const session = await auth.api.getSession({ headers: request.headers });

await auth.api.listSessions({ headers: request.headers });

await auth.api.revokeSession({
  body: { token: "session_token_here" },
  headers: request.headers,
});

// User Management
await auth.api.updateUser({
  body: { name: "New Name", image: "https://..." },
  headers: request.headers,
});

await auth.api.changeEmail({
  body: { newEmail: "newemail@example.com" },
  headers: request.headers,
});

await auth.api.deleteUser({
  body: { password: "current_password" },
  headers: request.headers,
});

// Account Linking
await auth.api.linkSocialAccount({
  body: { provider: "google" },
  headers: request.headers,
});

await auth.api.unlinkAccount({
  body: { providerId: "google", accountId: "google_123" },
  headers: request.headers,
});

Plugin API Methods

2FA Plugin:

// Enable 2FA
const { totpUri, backupCodes } = await auth.api.enableTwoFactor({
  body: { issuer: "MyApp" },
  headers: request.headers,
});

// Verify TOTP code
await auth.api.verifyTOTP({
  body: { code: "123456", trustDevice: true },
  headers: request.headers,
});

// Generate backup codes
const { backupCodes } = await auth.api.generateBackupCodes({
  headers: request.headers,
});

Organization Plugin:

// Create organization
const org = await auth.api.createOrganization({
  body: { name: "Acme Corp", slug: "acme" },
  headers: request.headers,
});

// Add member
await auth.api.addMember({
  body: {
    userId: "user_123",
    role: "admin",
    organizationId: org.id,
  },
  headers: request.headers,
});

// Check permissions
const hasPermission = await auth.api.hasPermission({
  body: {
    organizationId: org.id,
    permission: "users:delete",
  },
  headers: request.headers,
});

Admin Plugin:

// List users with pagination
const users = await auth.api.listUsers({
  query: {
    search: "john",
    limit: 10,
    offset: 0,
    sortBy: "createdAt",
    sortOrder: "desc",
  },
  headers: request.headers,
});

// Ban user
await auth.api.banUser({
  body: {
    userId: "user_123",
    reason: "Violation of ToS",
    expiresAt: new Date("2025-12-31"),
  },
  headers: request.headers,
});

// Impersonate user (for admin support)
const impersonationSession = await auth.api.impersonateUser({
  body: {
    userId: "user_123",
    expiresIn: 3600, // 1 hour
  },
  headers: request.headers,
});

When to Use Which

Example: Protected Route Middleware

import { Hono } from "hono";
import { createAuth } from "./auth";
import { createDatabase } from "./db";

const app = new Hono<{ Bindings: Env }>();

// Middleware using server-side API
app.use("/api/protected/*", async (c, next) => {
  const db = createDatabase(c.env.DB);
  const auth = createAuth(db, c.env);

  // Use server-side method
  const session = await auth.api.getSession({
    headers: c.req.raw.headers,
  });

  if (!session) {
    return c.json({ error: "Unauthorized" }, 401);
  }

  // Attach to context
  c.set("user", session.user);
  c.set("session", session.session);

  await next();
});

// Protected route
app.get("/api/protected/profile", async (c) => {
  const user = c.get("user");
  return c.json({ user });
});

Discovering Available Endpoints

Use the OpenAPI plugin to see all endpoints in your configuration:

import { betterAuth } from "better-auth";
import { openAPI } from "better-auth/plugins";

export const auth = betterAuth({
  database: /* ... */,
  plugins: [
    openAPI(), // Adds /api/auth/reference endpoint
  ],
});

Interactive documentation: Visit http://localhost:8787/api/auth/reference

This shows a Scalar UI with:

• ✅ All available endpoints grouped by feature
• ✅ Request/response schemas with types
• ✅ Try-it-out functionality (test endpoints in browser)
• ✅ Authentication requirements
• ✅ Code examples in multiple languages

Programmatic access:

const schema = await auth.api.generateOpenAPISchema();
console.log(JSON.stringify(schema, null, 2));
// Returns full OpenAPI 3.0 spec

Quantified Time Savings

Building from scratch (manual implementation):

• Core auth endpoints (sign-up, sign-in, OAuth, sessions): 40 hours
• Email verification & password reset: 10 hours
• 2FA system (TOTP, backup codes, email OTP): 20 hours
• Organizations (teams, invitations, RBAC): 60 hours
• Admin panel (user management, impersonation): 30 hours
• Testing & debugging: 50 hours
• Security hardening: 20 hours

Total manual effort: ~220 hours (5.5 weeks full-time)

With better-auth:

• Initial setup: 2-4 hours
• Customization & styling: 2-4 hours

Total with better-auth: 4-8 hours

Savings: ~97% development time

Key Takeaway

better-auth provides 80+ production-ready endpoints covering:

• ✅ Core authentication (20 endpoints)
• ✅ 2FA & passwordless (15 endpoints)
• ✅ Organizations & teams (35 endpoints)
• ✅ Admin & user management (15 endpoints)
• ✅ Social OAuth (auto-configured callbacks)
• ✅ OpenAPI documentation (interactive UI)

You write zero endpoint code. Just configure features and call auth.handler().

Known Issues & Solutions

Issue 1: "d1Adapter is not exported" Error

Problem: Code shows import { d1Adapter } from 'better-auth/adapters/d1' but this doesn't exist.

Symptoms: TypeScript error or runtime error about missing export.

Solution: Use Drizzle or Kysely instead:

// ❌ WRONG - This doesn't exist
import { d1Adapter } from 'better-auth/adapters/d1'
database: d1Adapter(env.DB)

// ✅ CORRECT - Use Drizzle
import { drizzleAdapter } from 'better-auth/adapters/drizzle'
import { drizzle } from 'drizzle-orm/d1'
const db = drizzle(env.DB, { schema })
database: drizzleAdapter(db, { provider: "sqlite" })

// ✅ CORRECT - Use Kysely
import { Kysely } from 'kysely'
import { D1Dialect } from 'kysely-d1'
database: {
  db: new Kysely({ dialect: new D1Dialect({ database: env.DB }) }),
  type: "sqlite"
}

Source: Verified from 4 production repositories using better-auth + D1

Issue 2: Schema Generation Fails

Problem: npx better-auth migrate doesn't create D1-compatible schema.

Symptoms: Migration SQL has wrong syntax or doesn't work with D1.

Solution: Use Drizzle Kit to generate migrations:

# Generate migration from Drizzle schema
npx drizzle-kit generate

# Apply to D1
wrangler d1 migrations apply my-app-db --remote

Why: Drizzle Kit generates SQLite-compatible SQL that works with D1.

Issue 3: "CamelCase" vs "snake_case" Column Mismatch

Problem: Database has email_verified but better-auth expects emailVerified.

Symptoms: Session reads fail, user data missing fields.

⚠️ CRITICAL (v1.4.10+): Using Kysely's CamelCasePlugin breaks join parsing in better-auth adapter. The plugin converts join keys like _joined_user_user_id to _joinedUserUserId, causing user data to be null in session queries.

Solution for Drizzle: Define schema with camelCase from the start (as shown in examples).

Solution for Kysely with CamelCasePlugin: Use separate Kysely instance without CamelCasePlugin for better-auth:

// DB for better-auth (no CamelCasePlugin)
const authDb = new Kysely({
  dialect: new D1Dialect({ database: env.DB }),
})

// DB for app queries (with CamelCasePlugin)
const appDb = new Kysely({
  dialect: new D1Dialect({ database: env.DB }),
  plugins: [new CamelCasePlugin()],
})

export const auth = betterAuth({
  database: { db: authDb, type: "sqlite" },
})

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