NestJS

NestJS 12: CI runs it on @nestjs/platform-express, its default platform, and @nestjs/platform-fastify works the same way. Follow Setup, with two changes: the preload goes through the Nest CLI, and the Prisma client is a provider.

The dev command

The Nest CLI starts Node itself: give it the preload with --exec.

{
  "scripts": {
    "start:dev": "nest start --watch --exec \"node --import query-profiler/register\"",
    "start:prod": "node dist/main"
  }
}

When --watch restarts the app, the profiler comes back on the same port.

The Prisma client, as a provider

A Nest app compiles to CommonJS, where the await at the top of Setup’s db.ts does not compile. Load the profiler in a provider’s factory instead:

src/prisma.provider.ts

import type { Provider } from "@nestjs/common";
import { PrismaPg } from "@prisma/adapter-pg";
import { PrismaClient } from "./generated/prisma/client";

export const prismaProvider: Provider = {
  provide: PrismaClient,
  useFactory: async () => {
    const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL });
    // A dev dependency: a production install leaves it out, and the client stays plain.
    const profiler = await import("query-profiler/prisma").catch(() => undefined);
    return profiler
      ? profiler.profilePrisma(new PrismaClient(profiler.withProfiler({ adapter })))
      : new PrismaClient({ adapter });
  },
};

Put it in a module’s providers (and its exports, to share it), and inject the client as usual: constructor(private readonly prisma: PrismaClient) {}. It takes the place of a PrismaService that extends PrismaClient: profilePrisma() returns a new client, which a subclass cannot be.

CORS

app.enableCors() hands its options to Express’s cors or to @fastify/cors. A page on another origin can read X-Debug-Token: the preload exposes it. If you set exposedHeaders, your list replaces it, so add the token there:

app.enableCors({ origin: "http://localhost:5173", exposedHeaders: ["X-Debug-Token"] });

In production no response carries it, so the extra name does nothing.