PrismaClientConstructorValidationError: Using engine type "client" requires either "adapter" or "accelerateUrl"

npm install @prisma/adapter-pg      # Postgres
# SQLite: @prisma/adapter-better-sqlite3   MySQL/MariaDB: @prisma/adapter-mariadb

Before:

import { PrismaClient } from '@prisma/client'
export const prisma = new PrismaClient({ datasourceUrl: process.env.DATABASE_URL })

After:

import 'dotenv/config'
import { PrismaClient } from './generated/prisma/client'
import { PrismaPg } from '@prisma/adapter-pg'

const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL })
export const prisma = new PrismaClient({ adapter })

SQLite:

import { PrismaBetterSqlite3 } from '@prisma/adapter-better-sqlite3'
const adapter = new PrismaBetterSqlite3({ url: process.env.DATABASE_URL || 'file:./dev.db' })

Every new PrismaClient() needs this — including seed scripts and tests; create the client in one module and import it.

Note: adapters use the Node driver's pool defaults, which differ from v6 (e.g. pg has no connection timeout by default; v6 used 5 s). Configure pool/timeout on the adapter if you depended on the old behavior. MongoDB is not supported in Prisma 7 — stay on v6 for Mongo.