Recently upgraded a NextJS app to version 14.2.5 from version 14.2.4, and during the process, I ran npm update and got some stuff messed up, and the NextJS app was not running well, eg: logging in did not work.

This took me a while to solve so I figured to document it here, and to be honest I still did not know the root cause, but I guess it had something to do with package-lock.json. Here is how I fixed it.

I was on the dev branch with the troubling NextJS app. I git checkout to main (which was still on next@14.2.4) and noticed that if I ran npm ci then npm run dev, the app worked as expected.

Then, I copied main’s package.json and package-lock.json to a different folder, then I git checkout to dev, and pasted the 2 files to dev.

Next, I ran npm ci to do a clean install, then I ran npm rm next to uninstall next@14.2.4, and npm i next@latest to install next@14.2.5.

And, voila it worked again!