MikroORM Better Auth Adapter

1.1.1 · active · verified Wed Apr 22

mikro-orm-better-auth is an adapter for the 'better-auth' authentication library, specifically designed to integrate with MikroORM. It provides a robust database layer for better-auth, abstracting common CRUD operations and transactional support through MikroORM's `EntityManager`. A key differentiator is its `createSchema` implementation, which leverages `ts-morph` to generate MikroORM entity files automatically. These generated entities are intelligently patched in-place on regeneration, preserving user-owned code like custom imports, decorators, methods, and comments, while only updating generator-managed fields and decorators. The current stable version is 1.1.1, released in March 2026, indicating active development with a focus on stability and feature enhancements. It is primarily SQL-oriented, utilizing MikroORM's SQL entity manager, and defers native join support for future development.

Common errors

```
Error: Cannot find module 'better-auth' or its corresponding type declarations.
```
cause The `better-auth` package is a peer dependency and was not installed in the project.

fix Run `pnpm add better-auth` (or `npm install better-auth`, `yarn add better-auth`) to install the missing peer dependency.
```
TypeError: mikroOrmAdapter is not a function or is undefined
```
cause Incorrect import statement for `mikroOrmAdapter`, or trying to use it with CommonJS `require()` in an ESM context.

fix Ensure you are using `import { mikroOrmAdapter } from 'mikro-orm-better-auth';` and your project is configured for ESM if appropriate.
```
Argument of type 'EntityManager<IDatabaseDriver<Connection>>' is not assignable to parameter of type '() => EntityManager<IDatabaseDriver<Connection>>'.
```
cause Attempting to pass the `EntityManager` instance directly to `mikroOrmAdapter` instead of a function that returns it (since v1.1.0).

fix Wrap the `EntityManager` in an arrow function: `mikroOrmAdapter(() => orm.em)`.

Warnings

breaking Starting from v1.1.1, `@mikro-orm/core`, `@mikro-orm/knex`, `better-auth`, `prettier`, and `ts-morph` were moved from direct dependencies to peer dependencies. This means these packages are no longer automatically installed and must be explicitly added to your project's `dependencies`.
Fix: Manually install all required peer dependencies: `pnpm add better-auth @mikro-orm/core @mikro-orm/knex prettier ts-morph`.
gotcha The `mikroOrmAdapter` now accepts a closure that returns the `EntityManager` (e.g., `() => orm.em` or `() => RequestContext.getEntityManager()`). Direct passing of the `EntityManager` instance is no longer supported.
Fix: Wrap your `EntityManager` access in a function: `mikroOrmAdapter(() => orm.em)` or `mikroOrmAdapter(() => RequestContext.getEntityManager()! as SqlEntityManager)`.
gotcha When using entity generation, ensure the output directory for generated entities (`generateEntity.outputDir`) is correctly configured and included in your MikroORM `entities` array during `MikroORM.init` (or handled by an entity discovery mechanism).
Fix: Add the generated entity path to your MikroORM configuration, e.g., `entities: ['./dist/auth/entities/**/*.entity.js']` or `entities: ['./src/auth/entities/**/*.entity.ts']` for ts-node environments.
gotcha Direct edits to generator-owned field definitions or MikroORM decorator arguments within generated entities may be overwritten during subsequent regeneration. The patching mechanism preserves user-owned code but not modifications to managed elements.
Fix: Place custom logic (imports, methods, properties, decorators) outside of the generator-owned blocks. Avoid modifying the `@Entity`, `@PrimaryKey`, and `@Property` decorators or the fields they manage.

Install

npm install mikro-orm-better-auth npm
yarn add mikro-orm-better-auth yarn
pnpm add mikro-orm-better-auth pnpm

Imports

mikroOrmAdapter
wrong:
```
const { mikroOrmAdapter } = require('mikro-orm-better-auth');
```
correct:
```
import { mikroOrmAdapter } from 'mikro-orm-better-auth';
```
This library is primarily ESM-first, common in modern TypeScript projects. Avoid CommonJS `require`.
betterAuth
wrong:
```
import betterAuth from 'better-auth';
```
correct:
```
import { betterAuth } from 'better-auth';
```
While `better-auth` is a peer dependency, it's a named export, not a default one. Incorrectly importing as a default is a common mistake.
RequestContext
wrong:
```
import RequestContext from '@mikro-orm/core';
```
correct:
```
import { RequestContext } from '@mikro-orm/core';
```
Used for per-request EntityManager isolation in MikroORM. It's a named export from @mikro-orm/core.

Quickstart

Demonstrates the basic setup of `mikro-orm-better-auth` with MikroORM, including `RequestContext` for per-request EntityManager isolation and configuring entity generation.

import { betterAuth } from 'better-auth';
import { mikroOrmAdapter } from 'mikro-orm-better-auth';
import { MikroORM, RequestContext } from '@mikro-orm/core';
import { SqliteDriver, SqlEntityManager } from '@mikro-orm/sqlite';

async function bootstrap() {
  const orm = await MikroORM.init<SqliteDriver>({
    driver: SqliteDriver,
    dbName: 'app.sqlite',
    entities: [], // Mikro-orm-better-auth generates entities, so leave this empty initially or add manually
  });

  // For per-request EntityManager isolation (recommended in web servers)
  const auth = betterAuth({
    database: mikroOrmAdapter(() => RequestContext.getEntityManager()! as SqlEntityManager),
  });

  // Example of generating entities
  const adapter = mikroOrmAdapter(() => orm.em, {
    generateEntity: {
      outputDir: 'src/auth/entities', // Output directory for generated MikroORM entities
    },
  });

  // In a real application, you would pass the adapter to betterAuth and then call auth methods.
  // This snippet focuses on setup and entity generation.
  console.log('MikroORM initialized and adapter configured. Entities will be generated to src/auth/entities.');
}

bootstrap().catch(console.error);

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