better-auth-effect

A Better Auth database adapter for @effect/sql.

Use any Effect SQL provider (PostgreSQL, MySQL, SQLite) with Better Auth.

Installation

``bash
npm install better-auth-effect


or


pnpm add better-auth-effect
`

$3

`bash
npm install better-auth effect @effect/sql
`

And one of the database drivers:

`bash


PostgreSQL

npm install @effect/sql-pg

MySQL

npm install @effect/sql-mysql2

SQLite

npm install @effect/sql-sqlite-node
`

Usage

`typescript
import { ManagedRuntime } from "effect"
import { PgClient } from "@effect/sql-pg"
import { effectSqlAdapter } from "better-auth-effect"
import { betterAuth } from "better-auth"

// 1. Create your database Layer
const SqlLive = PgClient.layer({
url: "postgresql://postgres:password@localhost:5432/myapp"
})

// Or with individual options:
// const SqlLive = PgClient.layer({
// host: "localhost",
// database: "myapp",
// username: "postgres",
// password: "password",
// })

// 2. Create a ManagedRuntime
const runtime = ManagedRuntime.make(SqlLive)

// 3. Use the adapter with Better Auth
export const auth = betterAuth({
database: effectSqlAdapter({
runtime,
dialect: "pg",
}),
// ... other Better Auth options
})
`

Configuration

`typescript
interface EffectSqlAdapterConfig {
/**
* ManagedRuntime that provides SqlClient.
* Create with ManagedRuntime.make(YourSqlLayer)
*/
runtime: ManagedRuntime.ManagedRuntime

/**
* Database dialect for SQL differences (RETURNING clause, etc.)
* - "pg": PostgreSQL
* - "mysql": MySQL
* - "sqlite": SQLite
*/
dialect: "pg" | "mysql" | "sqlite"

/**
* Enable debug logging for adapter operations.
* @default false
*/
debugLogs?: boolean
}
`

Why ManagedRuntime?

Using ManagedRuntime allows you to share the same connection pool between Better Auth and your Effect application code:

`typescript
import { Effect, ManagedRuntime } from "effect"
import { SqlClient } from "@effect/sql"
import { PgClient } from "@effect/sql-pg"

// Single Layer for your entire app
const SqlLive = PgClient.layer({ database: "myapp" })

// Single Runtime - shared connection pool
const runtime = ManagedRuntime.make(SqlLive)

// Better Auth uses the same pool
const auth = betterAuth({
database: effectSqlAdapter({ runtime, dialect: "pg" }),
})

// Your app code uses the same pool
const getUsers = Effect.gen(function* () {
const sql = yield* SqlClient.SqlClient
return yield sqlSELECT FROM users
})

// Run with the same runtime
runtime.runPromise(getUsers)
`

Database Support

| Database | Dialect | RETURNING Support |
|------------|------------|-------------------|
| PostgreSQL | "pg" | Native |
| SQLite | "sqlite" | Native (3.35+) |
| MySQL | "mysql" | Emulated* |

\* MySQL doesn't support RETURNING. The adapter uses LAST_INSERT_ID() + SELECT as a fallback. Tables must have an id column as primary key. This is not a problem for Better Auth, which always uses id.

Column Naming (snake_case / camelCase)

Better Auth uses camelCase field names (emailVerified, accessToken). If your database uses snake_case columns (email_verified, access_token), configure transformation in PgClient.layer:

`typescript
import { PgClient } from "@effect/sql-pg"

const snakeToCamel = (str: string) =>
str.replace(/_([a-z])/g, (_, letter) => letter.toUpperCase())

const camelToSnake = (str: string) =>
str.replace(/[A-Z]/g, (letter) => _${letter.toLowerCase()})

const SqlLive = PgClient.layer({
database: "myapp",
// Transform column names automatically
transformResultNames: snakeToCamel, // DB → JS (snake_case → camelCase)
transformQueryNames: camelToSnake, // JS → DB (camelCase → snake_case)
})
`

This is configured once at the client level and applies to all queries automatically.

Supported Operations

All Better Auth adapter methods are implemented:

- create - Insert with RETURNING
- findOne - SELECT with WHERE, LIMIT 1
- findMany - SELECT with WHERE, ORDER BY, LIMIT, OFFSET
- update - UPDATE with RETURNING
- updateMany - UPDATE multiple rows
- delete - DELETE single row
- deleteMany - DELETE multiple rows
- count - SELECT COUNT(*)

Error Handling

The adapter maps SQL errors to typed errors:

`typescript
import {
AdapterError,
ConstraintViolationError,
ConnectionError
} from "better-auth-effect"
``

- ConstraintViolationError - Unique/foreign key violations
- ConnectionError - Database connection issues
- AdapterError - Other SQL errors

License

MIT