Next.js build fails on Windows with TypeError: Cannot read properties of null (reading 'useContext') - works fine on Vercel

[arjunresha]

Summary

Hey all,

I’ve run into a frustrating issue where my Next.js app runs perfectly in dev mode and deploys fine to Vercel, but fails only when running next build locally on Windows.

Error log:

Creating an optimized production build ...
Compiled successfully
Collecting page data
TypeError: Cannot read properties of null (reading 'useContext')
    at p (C:\path\to\project\.next\server\pages\_error.js:8:45448)
Error occurred prerendering page "/404".
Export encountered an error on /_error: /404, exiting the build.

What makes this odd:

• Happens only on Windows, not on macOS/Linux (Vercel builds pass fine)
• Happens in production build, not next dev
• No custom _error.js or 404.js pages
• Project uses several @radix-ui/react-* packages that rely heavily on useContext
• Error originates from compiled .next/server/pages/_error.js, not my own code directly

What I’ve tried so far:

• Deleted node_modules, .next/, package-lock.json and reinstalled
• git clean -xfd
• Verified no peer dependency warnings
• Tried both React 19 + Next.js 15, and React 18 + Next.js 14
• Replaced Radix components with placeholders — build still fails

Environment:

• OS: Windows 10 (x64)
• Next.js: 15.4.6
• React: 19.1.1 (also tested 18.2.0)
• React-DOM: same as React

Question:
Could this be a Windows-specific SSR edge case in Next.js 15 where certain dependencies (like Radix UI) break during _error page prerendering?
Has anyone else seen useContext returning null only during production build?

Any leads or workarounds would be greatly appreciated. I can prepare a minimal reproduction repo if that would help.

Additional information

• OS: Windows 10 (x64)
• Next.js: 15.4.6
• React: 19.1.1 (also tested 18.2.0)
• React-DOM: same as React

Example

Creating an optimized production build ...
Compiled successfully
Collecting page data
TypeError: Cannot read properties of null (reading 'useContext')
    at p (C:\path\to\project\.next\server\pages\_error.js:8:45448)
Error occurred prerendering page "/404".
Export encountered an error on /_error: /404, exiting the build.

[Anipaleja]

Hey @adiranawal,
I ran into a very similar issue when building on Windows, and in my case it turned out to be a combination of Next.js prerendering the _error page and a dependency (Radix UI in particular) importing useContext in a non-client context.

A few things that fixed it for me:

Ensure client components have "use client"

Next.js 15+ is stricter about when hooks like useContext can run.
If any of your components (or a dependency’s wrapper) calls hooks but is being rendered on the server, you’ll get this error.

Check:

// Add this to the top of components that must run on the client
"use client";

For Radix UI components, you may need to wrap them in your own "use client" file, then import from that instead.

Force consistent React & React-DOM versions

On Windows, I found that multiple versions of React were being resolved in node_modules due to peer deps.
Run:

npm ls react

If you see more than one, align them:

npm install [email protected] [email protected]

(or whatever single version you’re targeting)

Check for stale .next cache on Windows

Sometimes the .next build cache stores server-side compiled versions of components from an older React version.
Delete it and rebuild:

rd /s /q .next
npm run build

Test with next.config.mjs set to output standalone

This can help narrow down dependency inclusion issues:

export default {
  output: "standalone",
}

Why Vercel builds work but Windows doesn’t:
Vercel runs on Linux, where the dependency tree may resolve differently and cached .next builds are isolated per build. On Windows, Next.js sometimes picks up cached, server-compiled artifacts or resolves different dependency entry points — causing SSR to break when useContext is called in a non-client render path.

After I marked my Radix imports as "use client" and ensured a single React version, the error disappeared both locally and on Vercel.