Serverless Function Size grows between 14.2.16 -> 14.2.23 on Vercel

[derjogi]

Link to the code that reproduces this issue

harmonicabot/harmonica-web-app@17757ce

To Reproduce

In a project using llamaindex and some other dependencies, when you change the next.js version from 14.2.16 to 14.2.23 and deploy it on Vercel, it will fail to build because it will be over the max function size of 250mb.
Note: building locally does not show any apparent differences; I suspect the next.js version might be wrongly including cache or other modules in the server function that should normally not be included.

Current vs. Expected behavior

Current behaviour: Server Function is above 250mb (~800mb in my case). Expected: It should only be ~13mb, which is what the contents of .next are without the .next/cache folder.

Provide environment information

Operating System: 
  [Not relevant, as it happens on vercel servers]
Binaries:
  Node: 23.6.0
  npm: 10.9.2
  Yarn: N/A
  pnpm: 9.15.3
Relevant Packages:
  next: 14.2.23 // An outdated version detected (latest is 15.1.6), upgrade is highly recommended!
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.6.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Not sure, Instrumentation, Output, Package Managers, Webpack

Which stage(s) are affected? (Select all that apply)

Vercel (Deployed)

Additional context

No response

[samcx]

@derjogi Not sure if this is related to Next.js or how we're bundling Functions on Vercel.

Can you share Deployment URLs between the two versions?

[derjogi]

@samcx Not sure whether these work, they're preview URLs:

With next.js 14.2.16 (✅): https://harmonica-web-app-git-fix-build-harmonicas-projects.vercel.app/
With next.js 14.2.23 (❌): https://harmonica-web-app-git-fix-build-harmonicas-projects.vercel.app/