bun-better-auth

A Better Auth database adapter that uses Bun's built-in SQL client (Bun.sql / new SQL(...)) — no extra database drivers needed.

Supports PostgreSQL, MySQL, and SQLite out of the box.

Note: This library is actively developed. Feedback and contributions are welcome — open an issue or PR on GitHub.

Installation

bun add bun-better-auth

Quick start

import { betterAuth } from "better-auth";
import { SQL } from "bun";
import { bunSqlAdapter } from "bun-better-auth";

const sql = new SQL(process.env.DATABASE_URL!);

export const auth = betterAuth({
  database: bunSqlAdapter(sql, { provider: "pg" }),
});

That's it. Pass the adapter to database and Better Auth handles the rest.

Providers

Set provider to match your database:

| Provider | Value | |---|---| | PostgreSQL | "pg" | | MySQL | "mysql" | | SQLite | "sqlite" |

PostgreSQL

import { SQL } from "bun";
import { bunSqlAdapter } from "bun-better-auth";

const sql = new SQL("postgres://user:pass@localhost:5432/mydb");

export const auth = betterAuth({
  database: bunSqlAdapter(sql, { provider: "pg" }),
});

MySQL

import { SQL } from "bun";
import { bunSqlAdapter } from "bun-better-auth";

const sql = new SQL("mysql://user:pass@localhost:3306/mydb");

export const auth = betterAuth({
  database: bunSqlAdapter(sql, { provider: "mysql" }),
});

SQLite

import { SQL } from "bun";
import { bunSqlAdapter } from "bun-better-auth";

const sql = new SQL("sqlite://./mydb.sqlite");

export const auth = betterAuth({
  database: bunSqlAdapter(sql, { provider: "sqlite" }),
});

Configuration

bunSqlAdapter(sql, {
  provider: "pg",       // required — "pg" | "mysql" | "sqlite"
  usePlural: false,     // use plural table names (e.g. "users" instead of "user")
  transaction: true,    // wrap mutations in transactions when supported (default: true)
  debugLogs: false,     // log generated SQL queries for debugging
})

Options

| Option | Type | Default | Description | |---|---|---|---| | provider | "pg" \| "mysql" \| "sqlite" | — | Required. Your database type. | | usePlural | boolean | false | Use plural table names (users, sessions, …). | | transaction | boolean | true | Wrap mutations in a transaction via sql.begin(). Set to false if your client doesn't support it. | | debugLogs | boolean \| object | false | Enable SQL query logging. Accepts a Better Auth debug log config. |

Transactions

By default the adapter wraps write operations in a transaction using sql.begin(). If your SQL client was created without transaction support, pass transaction: false:

bunSqlAdapter(sql, {
  provider: "pg",
  transaction: false,
});

Using Bun.sql directly

If you use the global Bun.sql shorthand instead of new SQL(...), pass it in the same way:

import { bunSqlAdapter } from "bun-better-auth";

export const auth = betterAuth({
  database: bunSqlAdapter(Bun.sql, { provider: "pg" }),
});

Schema generation

bun-better-auth supports Better Auth CLI schema generation for the bun-sql adapter. Run the following command to generate your schema SQL:

bun x --bun auth@latest generate

This outputs the SQL for your tables. Apply it to your database manually — schema migration is not handled by this adapter.

Refer to the Better Auth docs for full schema guidance.

TypeScript

All exported types are available if you need them:

import type {
  BunSqlAdapterConfig,
  BunSqlAdapterInstance,
  BunSqlProvider,
} from "bun-better-auth";

License

MIT