---
title: "Migrate from Better Auth"
description: "Move Better Auth server and client sign-in calls onto the MainSDK auth interface, keeping your users until you choose to move them."
section: "guides"
status: "Planned for 0.7"
spec: "migration-guides"
canonical: "https://mainsdk.dev/docs/guides/migrate-from-better-auth"
updated: "2026-10-28"
---

# Migrate from Better Auth

> Move Better Auth server and client sign-in calls onto the MainSDK auth interface, keeping your users until you choose to move them.

Status: Planned for 0.7 · Canonical: https://mainsdk.dev/docs/guides/migrate-from-better-auth · Updated: 2026-10-28

Move Better Auth server and client sign-in calls onto the MainSDK auth interface, keeping your users until you choose to move them. Your Better Auth account stays; nothing here deletes it.

**Before you start:**

- A git repository with a clean working tree. `mainsdk migrate` works on a branch and never touches yours.
- Node 22 and `npx mainsdk`. No `main.yaml` yet? `migrate` writes one; or start with [Adopt an existing app](https://mainsdk.dev/docs/getting-started/existing-app).
- Your Better Auth keys stay where they are. Move them to `secret:` references when the driver is chosen (see [Secrets](https://mainsdk.dev/docs/interfaces/secrets)).

## 1. Read the report

```text
npx mainsdk migrate better-auth --report-only
```

The report writes no file. It sorts every Better Auth call in your code into three lists: **mapped** (an interface call replaces it), **raw** (it stays behind `raw()`, with the reason) and **needs a person** (a policy, a rule file or a call with no interface). Add `--json` for a machine-readable report.

For the sample app of this guide (`packages/cli/test/fixtures/migrate/better-auth`), the report finds 2 mapped, 0 raw and 1 for a person.

## 2. What the codemod changes

| Where | Before | After |
| --- | --- | --- |
| `app/api/me/route.ts:4` | `const session = await auth.api.getSession({ headers: req.headers })` | `auth.require(req)` |
| `lib/client.ts:6` | `authClient.signIn.email({ email, password })` | `auth.signIn()` |

Each rewrite is mechanical and one line at a time. Imports of Better Auth go when no call needs them, and `mainsdk` is added to `package.json`.

## 3. What stays behind raw()

- Nothing in the sample stays behind raw().

A call behind `raw()` keeps working through the `Better Auth` host on your network allow list, and `mainsdk check` still sees it. Each one has a marker comment, `// mainsdk migrate: ...`, so you can find it later.

## 4. What needs a person

- `lib/auth.ts:3`: no interface call for betterAuth(; a person decides

The codemod leaves these lines alone and marks them. No tool should guess a policy.

## 5. Stateful moves are guided jobs

Data does not move with the code. Each stateful move is a job with steps and a rollback, listed in the pull request and never run by the codemod.

### users: Keep Better Auth as the auth driver; move nothing

1. Set auth.driver: better-auth in main.yaml; it reads the same tables.
2. Replace calls one module at a time and run mainsdk check after each.

Rollback: Revert the pull request; no data moved.

## 6. Open the pull request

```text
npx mainsdk migrate better-auth
```

This records your sign-in and checkout flows as locked flows first, then creates the branch `migrate/better-auth`, applies the codemods, adds `.github/workflows/mainsdk-migrate.yml`, runs `mainsdk check` and the locked flows, commits, pushes and opens one pull request with `gh`. If a gate fails, the branch is kept and no pull request opens (`MAIN-MIGRATE-0001`). `--no-pr` stops after the commit.

Locked flows run again in CI: `npx mainsdk migrate flows`.

## Where you end

You end at the reference architecture [`mainsdk/saas-web`](https://mainsdk.dev/docs/guides/reference-saas-web): the same shape, with its tests, benchmark and chaos drills.

```text
npx mainsdk init --template mainsdk/saas-web
```