Critical Compatibility Issue - Prisma Client v6 Support

[JacoT1989-dotcom]

Dear Lucia Development Team,

I'm writing to express my concern about a significant compatibility issue that's blocking development and deployment for many users.

Issue Summary:
The current version of @lucia-auth/adapter-prisma@4.0.1 only supports Prisma Client versions ^4.2.0 || ^5.0.0, while the latest Prisma Client is now at v6.13.0. This creates a dependency conflict that prevents:

Installing dependencies without --legacy-peer-deps
Deploying applications on platforms like Vercel
Using the latest Prisma features and security updates

Impact:
Developers are forced to use outdated Prisma versions
Build processes fail in CI/CD environments
New projects cannot easily integrate Lucia with modern Prisma setups
Development teams lose access to Prisma v6 improvements and bug fixes

Current Workarounds:
Downgrading to Prisma v5 (losing access to newer features)
Using --legacy-peer-deps (which can mask other dependency issues)
These are temporary solutions that shouldn't be necessary

Request:
Could you please prioritize updating the Prisma adapter to support Prisma Client v6? This would greatly improve the developer experience and allow teams to use Lucia with modern Prisma installations.
If there are technical blockers preventing this update, please consider:

Publishing a timeline for v6 support
Documenting the specific compatibility requirements
Providing migration guidance for teams wanting to upgrade

Thank you for your time and for maintaining this valuable authentication library. I look forward to a resolution that allows seamless integration with current Prisma versions.
Best regards

Jaco Thiart

[wesleysmyth]

Lucia v3 uses the Prisma Client v4/v5 API for its @lucia-auth/adapter-prisma adapter. Prisma v6 introduced breaking changes to the client API that affect the adapter.

Workaround: Use @prisma/client v6 with compatibility mode

Prisma v6 includes a compatibility layer for v5 APIs. In your schema.prisma:

generator client {
  provider        = "prisma-client-js"
  // No changes needed here — the adapter issue is at the API level
}

If the adapter crashes, the issue is likely with how Prisma v6 changed PrismaClient method signatures. You can pin the adapter to use the v5-compatible API:

// Workaround: Wrap Prisma v6 client for Lucia
import { PrismaClient } from "@prisma/client";
import { PrismaAdapter } from "@lucia-auth/adapter-prisma";

const prisma = new PrismaClient();

// This should work if Prisma v6 maintains v5 API compatibility
const adapter = new PrismaAdapter(prisma.session, prisma.user);

If the adapter still fails

The most common Prisma v6 breaking change that affects Lucia is the removal of the $transaction interactive mode default and changes to findUnique/findFirst return types.

Option 1: Pin Prisma to v5

npm install @prisma/client@5 prisma@5

This is the safest path until Lucia officially supports v6.

Option 2: Use the Drizzle adapter instead

If you want to stay on Prisma v6, consider switching to Lucia's Drizzle adapter which doesn't have this compatibility issue:

npm install @lucia-auth/adapter-drizzle drizzle-orm

import { DrizzlePostgreSQLAdapter } from "@lucia-auth/adapter-drizzle";
import { db } from "./db"; // Your Drizzle instance
import { userTable, sessionTable } from "./schema";

const adapter = new DrizzlePostgreSQLAdapter(db, sessionTable, userTable);

Option 3: Write a custom adapter

Lucia's adapter interface is minimal — just 6 methods:

import { Adapter } from "lucia";
import { PrismaClient } from "@prisma/client";

const prisma = new PrismaClient();

export const prismaV6Adapter: Adapter = {
  async deleteSession(sessionId: string) {
    await prisma.session.delete({ where: { id: sessionId } });
  },
  async deleteUserSessions(userId: string) {
    await prisma.session.deleteMany({ where: { userId } });
  },
  async getSessionAndUser(sessionId: string) {
    const session = await prisma.session.findUnique({
      where: { id: sessionId },
      include: { user: true },
    });
    if (!session) return [null, null];
    const { user, ...sessionData } = session;
    return [
      { id: sessionData.id, userId: sessionData.userId, expiresAt: sessionData.expiresAt },
      { id: user.id, ...user },
    ];
  },
  async getUserSessions(userId: string) {
    const sessions = await prisma.session.findMany({ where: { userId } });
    return sessions.map((s) => ({
      id: s.id,
      userId: s.userId,
      expiresAt: s.expiresAt,
    }));
  },
  async setSession(session) {
    await prisma.session.create({
      data: {
        id: session.id,
        userId: session.userId,
        expiresAt: session.expiresAt,
      },
    });
  },
  async updateSessionExpiration(sessionId: string, expiresAt: Date) {
    await prisma.session.update({
      where: { id: sessionId },
      data: { expiresAt },
    });
  },
};

This gives you full control over the Prisma v6 API calls without depending on the adapter package.

Status

As of now, there's no official Prisma v6 support in @lucia-auth/adapter-prisma. Given that Lucia v3 is in maintenance mode (the author has shifted focus), a community PR or custom adapter may be the fastest path forward.

[JacoT1989-dotcom]

Thanks Wesley, I will check it out when I start a new project again.