prisma-7-driver-adapter

name	prisma-7-driver-adapter
description	Fix Prisma 7 "engine type client requires adapter" error after upgrading from Prisma 6. Use when: (1) Error "Using engine type 'client' requires either 'adapter' or 'accelerateUrl' to be provided to PrismaClient constructor", (2) PrismaClientConstructorValidationError after Prisma 7 upgrade, (3) Setting engineType = "library" doesn't fix the error, (4) Next.js build fails after upgrading Prisma to v7.x.
author	Claude Code
user-invocable	false

Prisma 7 Driver Adapter Requirement

Problem

Prisma 7 introduced a breaking change where the old Rust-based query engine is no longer the default. The new "client" engine type requires a driver adapter for all database connections. Simply setting engineType = "library" in the schema generator block does NOT work - this is a common misconception during the upgrade.

This is non-obvious because:

1. The error message mentions "adapter" but doesn't explain what changed
2. Setting engineType = "library" seems like it should revert to the old behavior
3. The old new PrismaClient() pattern compiled fine but fails at runtime
4. Cache clearing and regeneration don't help

Context / Trigger Conditions

This skill applies when you see:

Primary error (exact match):

Error [PrismaClientConstructorValidationError]: Using engine type "client" requires either "adapter" or "accelerateUrl" to be provided to PrismaClient constructor.

Related symptoms:

• Upgrading from Prisma 6.x to Prisma 7.x
• Next.js build fails with PrismaClientConstructorValidationError
• engineType = "library" in schema.prisma doesn't resolve the error
• Clearing .next, node_modules/.prisma, and regenerating doesn't help
• npx prisma generate succeeds but application fails at runtime

Environment indicators:

• Prisma version 7.0.0 or higher
• PostgreSQL, MySQL, SQLite, or other supported database
• Any framework (Next.js, Express, Fastify, etc.)

Solution

Step 1: Install Driver Adapter Package

For PostgreSQL:

npm install @prisma/adapter-pg pg

For MySQL:

npm install @prisma/adapter-mysql mysql2

For SQLite:

npm install @prisma/adapter-libsql @libsql/client

For PlanetScale:

npm install @prisma/adapter-planetscale @planetscale/database

Step 2: Update Prisma Client Initialization

Replace the old pattern with the adapter pattern.

For PostgreSQL:

// lib/prisma.ts
import { PrismaClient } from '@prisma/client'
import { PrismaPg } from '@prisma/adapter-pg'

const connectionString = process.env.DATABASE_URL!

// Create adapter with connection string
const adapter = new PrismaPg({ connectionString })

// Global singleton pattern for development
const globalForPrisma = globalThis as unknown as {
  prisma: PrismaClient | undefined
}

export const prisma = globalForPrisma.prisma ?? new PrismaClient({ adapter })

if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma

For MySQL:

// lib/prisma.ts
import { PrismaClient } from '@prisma/client'
import { PrismaMySql } from '@prisma/adapter-mysql'
import mysql from 'mysql2/promise'

const connectionString = process.env.DATABASE_URL!

const pool = mysql.createPool(connectionString)
const adapter = new PrismaMySql(pool)

const globalForPrisma = globalThis as unknown as {
  prisma: PrismaClient | undefined
}

export const prisma = globalForPrisma.prisma ?? new PrismaClient({ adapter })

if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma

Step 3: Update Schema (Optional but Recommended)

You can remove or keep the generator config. The adapter in code takes precedence:

generator client {
  provider = "prisma-client-js"
  // engineType is optional when using adapter in code
}

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

Step 4: Regenerate and Clear Cache

# Clear all caches
rm -rf .next node_modules/.prisma

# Regenerate Prisma client
npx prisma generate

# Rebuild application
npm run build

Verification

After applying fixes:

1. Run npx prisma generate - should complete without errors
2. Run npm run build - should complete without PrismaClientConstructorValidationError
3. Run npm run dev and test a database query - should work
4. Check application logs for any connection errors

Example

Scenario: Upgrading a Next.js app from Prisma 6.5.0 to Prisma 7.3.0

Before (failing code):

// lib/prisma.ts - OLD PATTERN (broken in Prisma 7)
import { PrismaClient } from '@prisma/client'

const globalForPrisma = globalThis as unknown as {
  prisma: PrismaClient | undefined
}

export const prisma = globalForPrisma.prisma ?? new PrismaClient()

if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma

Error:

Error [PrismaClientConstructorValidationError]: Using engine type "client"
requires either "adapter" or "accelerateUrl" to be provided to PrismaClient constructor.

After (working code):

// lib/prisma.ts - NEW PATTERN (Prisma 7+)
import { PrismaClient } from '@prisma/client'
import { PrismaPg } from '@prisma/adapter-pg'

const connectionString = process.env.DATABASE_URL!
const adapter = new PrismaPg({ connectionString })

const globalForPrisma = globalThis as unknown as {
  prisma: PrismaClient | undefined
}

export const prisma = globalForPrisma.prisma ?? new PrismaClient({ adapter })

if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma

Notes

• Do NOT rely on engineType = "library" - This setting alone does not work in Prisma 7. The adapter is required regardless of engine type configuration.

• Prisma Accelerate alternative: If using Prisma Accelerate, you can provide accelerateUrl instead of an adapter:

  const prisma = new PrismaClient({
    accelerateUrl: process.env.PRISMA_ACCELERATE_URL
  })
  

• Connection pooling: The driver adapters handle connection pooling differently than the old engine. For PostgreSQL with pg, you can configure pooling:

  import { Pool } from 'pg'
  const pool = new Pool({ connectionString, max: 10 })
  const adapter = new PrismaPg(pool)
  

• TypeScript types: Ensure @types/pg is installed for PostgreSQL type definitions:

  npm install -D @types/pg
  

• Migration from Prisma 6: This is a one-way migration. The new adapter pattern is the only supported method in Prisma 7+.

• Serverless environments: The adapter pattern works well with serverless. Each cold start creates a new adapter instance, similar to the old singleton pattern.

• Related issue: If you also see connection pool exhaustion errors, see the prisma-connection-pool-exhaustion skill for additional configuration.