Minified React error #418 in production

[MasterProvider]

Summary

In development

In production

Is this fine? It's so annoying to have hydration errors in production, especially when there are no errors in development.
This occurred only in console log

Additional information

"dependencies": {
    "@emotion/react": "^11.14.0",
    "@emotion/styled": "^11.14.0",
    "next": "^15.1.2",
    "react": "^19.0.0",
    "react-dom": "^19.0.0",
     ...
  },
  "devDependencies": {
    "@eslint/eslintrc": "^3",
    "eslint": "^9",
    "eslint-config-next": "^15.1.2"
  }

Example

No response

[MasterProvider]

Is this problem in Next.js, or is it in React 19 itself?

[icyJoseph]

These are React hydration issues. Any party that manipulates JSX to produce the first server HTML, and even those that pre-process it in the browser can be at fault.

With that being said, there is a new experimental, Next.js config, experimental.allowDevelopmentBuild, to help you debug this kind of issue, #65463

So you'd need to add that to your next.config.js experimental:

const config: NextConfig = {
  experimental: {
      allowDevelopmentBuild: true
  }
};

And then run NODE_ENV=development npm run build, on your terminal, does it give you more information?

[icyJoseph]

Another reason to see this kind of issue, is code that uses certain conditionals, such as timestamps and such, or takes different codepaths during dev and prod builds...

[MasterProvider]

This issue was resolved by not initializing real-time timestamps.