Project-scoped users (email unique per project) — possible?

Hey 👋
I’m building a multi-tenant platform where each project is a standalone website (Shopify-style).

For project users (customers / blog members) I need:

Separate accounts per project

Same email usable on multiple projects

Credentials, sessions, password resets fully isolated per project

Email uniqueness = (project_id, email), not global


I understand Better Auth assumes a global user identity and that Organizations are for roles/membership, not credential isolation.

Questions:

Is this possible with Better Auth at all?

Would it require a custom adapter, or is it fundamentally incompatible?

Can plugins influence user lookup/uniqueness, or is that adapter-level only?

If unsupported, is the recommended approach to use Better Auth only for platform users and handle project auth separately?


Thanks!
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