src/instrumentation.js not loading in production mode

[bigdefect]

Summary

Hey folks, I'm fairly new to this node stack. In trying to set up Sentry's Next.js integration, it worked fine in development (next dev), but not in production mode (next start).

src/instrumentation.js
export async function register() {
  if (process.env.NEXT_RUNTIME === "nodejs") {
    await import("./sentry.server.config");
  }
  ...
}

If I move the file to the project root, next start does load it. Any ideas why?

Additional information

https://nextjs.org/docs/app/api-reference/file-conventions/instrumentation

Based on this, I did confirm that the instrumentationHook experiment is indeed showing enabled.

> npx next build && npx next start
  ▲ Next.js 14.2.1
  - Environments: .env.local, .env
  - Experiments (use with caution):
    · instrumentationHook
...

[lforst]

In what way did it not work in production mode?

[bigdefect]

It wasn't being loaded, as evidenced by the startup log snippet I shared of it being loaded.

[nikolayemrikh]

instrumentation.ts placed in project root doesn't execute in 15.2.4 and 15.3.1 in production build. But executes if placed in src

[estevao-fay-deel]

What if you're not using a src directory in your project?

[Chimochikhin]

I can say more - instrumentation-client.ts - does not run in SRC folder.
Only if it inside root folder!

[ruisilva450]

I found out that instrumentation[-client].ts only runs on next start if they are placed on the same level as pages and app

|                                       Root directory structure
├── src                                 <-- The source code for your service.
    └── pages                           <-- The source code for Next.js [pages](https://nextjs.org/docs/basic-features/pages) routing.
    └── instrumentation[-client].ts     <-- Instrumentation hooks for client-side and server-side.

|                                   Root directory structure
├── src                             <-- The source code for your service.
|── pages                           <-- The source code for Next.js [pages](https://nextjs.org/docs/basic-features/pages) routing.
|── instrumentation[-client].ts     <-- Instrumentation hooks for client-side and server-side.

[robinkarlberg]

Incredible how it still works in dev but not in prod. And there is no clear message stating this if I'm not mistaken.

But thanks for the solution!