Next.js (App Router + API routes) failing on Nginx Unit – appendHeader error

[Cartitarul]

Hello,
I’m trying to run a Next.js application (App Router) on a server using DirectAdmin + Nginx Unit, and I’m running into what looks like a compatibility issue.

My setup​

• DirectAdmin with Nginx Unit
• Node.js (tested Node 24, also tried downgrading)
• Next.js (App Router, using /app)
• The app includes API routes (e.g. /app/api/projects, /app/api/admin/session)
• Previously worked locally using npm run dev and npm run start

What I tried​

• Created a Unit Node application with a proper server.js
• Installed dependencies and ran npm run build
• Confirmed .next/ build output exists
• Ensured Unit working directory is correct
• Cleaned up workspace/lockfile issues
• Tried static export (output: "export") but it fails due to API routes (expected)

The error​

When running the app via Unit, it crashes during SSR with:

TypeError: b.appendHeader is not a function

This happens consistently inside .next/server/chunks/ssr/....

From debugging, it appears that Next.js expects a standard Node http.ServerResponse, but Unit’s Node HTTP adapter provides a response object that doesn’t fully match Node’s API, causing Next SSR to fail.

My question​

Is modern Next.js (App Router + SSR + API routes) officially supported on Nginx Unit?
If not:

• Is there a recommended workaround?
• Or is the expected approach to run Next.js outside Unit (Node + pm2) and reverse-proxy with nginx?

I want to make sure I’m not fighting a known limitation.

Thanks in advance for any clarification.

 

[zEitEr]

Hello,

Nginx Unit

NGINX Unit no longer receives new features or enhancements from the project maintainers.
The latest version is 1.34.2, released on Feb 26, 2025. As of October 2025, NGINX Unit is archived and unmaintained.

NGINX Unit: Universal web app server

unit.nginx.org

 

[Cartitarul]

Thank you for the response, any alternatives plugins or ideeas on how I can host this type of applications ?

 

[zEitEr]

You might try PM2 for Next.js and configure an installed webserver to reverse proxy requests to Next.JS.

 

[johannes]

DA is falling behind. Wasnt there an announcement about another implementation upcoming?

 

[zEitEr]

DA is falling behind. Wasnt there an announcement about another implementation upcoming?

Post in thread 'Nginx Unit: PHP application?'

Jan 29, 2026

No, it will not be added there.
Currently UNIT tool is not under developing anymore (as it is 3-rd party tool) and we are looking for the replacement.
But there is no any ETA when it will be replaced.

• romans

• 

 

[DrWizzle]

DA is falling behind. Wasnt there an announcement about another implementation upcoming?

I'm currently having a look at OpenResty. Word on the street is it's faster and possibly better than NGINX, while staying compatible with NGINX. I'll be having another look at it later tonight after work.

 

[Ohm J]

Yep, I still find the workaround on nodejs app for my customer too.

This is just my idea, create systemd service and run
"/bin/jailshell -c 'pm2-runtime ${HOME}/pm2.econsystem.config.js".


Like

systemctl start "[email protected]"
systemctl start "[email protected]"

Is this safe enought ?

I'm using pm2 for my own App and working well, but I don't know when give some one to running this is secure enought or not.