7 Infra Improvement Strategies to Prevent Next.js Deployment Build Failures in 2026

Recently, our team's deployment pipeline started showing serious instability. Specifically, we encountered recurring build failures related to the chat build. As a result, the entire development team was preoccupied with battling these build failures.

Attempts and Pitfalls

Initially, I thought the --preload detection logic was the problem. I modified it to detect only specific lines, but this ended up causing issues in other areas. The recurring chat build failures were actually caused by the next.config file not properly recognizing file extensions. I modified it to allow extensions like .mjs, .js, .ts, and .cjs, but even that didn't work correctly at first, leading to some wasted effort.

# .github/workflows/deploy.yml (Excerpt from initial version)
- name: Run Preload Detection
  run: |
    # ... existing logic ...
    if [[ "$LINE" == *"some_pattern"* ]]; then
      echo "Preload detected"
      # ...
    fi

I modified it to detect only specific lines like the above, which led to unintended behavior.

// next.config.js (Initial configuration)
module.exports = {
  // ...
  experimental: {
    // ...
  },
  // ...
};

Regarding extensions, I initially allowed only a few types, and only after experiencing chat build failures did I modify it to support more extensions.

Root Causes

In the end, it was a combination of several complex issues. There were flaws in the --preload detection logic, and the range of supported extensions in the next.config file was too narrow, which was the direct cause of the chat build failures. Additionally, there was confusion arising from the chat server builds being inconsistent between P1/P2 and P0 stages. Problems also occurred because the .next directory was not preserved, and the smoke gate was too lenient, failing to catch build failures. Finally, there was an unexpected side effect where the next/font/google library caused GCE outbound connection errors.

Solutions

To address these issues, I implemented several measures.

First, I improved the --preload detection logic in the deployment pipeline to make it more accurate.

# .github/workflows/deploy.yml (Excerpt from improved version)
- name: Run Preload Detection
  run: |
    # ... improved logic ...
    # Changed to more flexible and accurate pattern matching
    if grep -q "preload" "$FILE"; then
      echo "Preload detected"
      # ...
    fi

I expanded the extension support in the next.config file to include .mjs, .js, .ts, and .cjs, which prevented recurring chat build failures.

// next.config.js (Final configuration)
module.exports = {
  // ...
  experimental: {
    // ...
  },
  // Expanded extension support
  pageExtensions: ['tsx', 'ts', 'js', 'jsx', 'mjs', 'cjs'],
  // ...
};

I standardized the chat server builds for P1/P2 and P0 stages and configured it to preserve the .next directory. I also strengthened the smoke gate to ensure build failures are detected more reliably.

# Example of preserving the .next directory (in CI/CD settings)
cp -R .next ../previous_build/.next

Finally, I removed the next/font/google library, which blocked GCE outbound connection errors.

Results

Thanks to these improvements, the stability of our deployment pipeline has significantly increased, and the recurring chat build failure issue has been resolved. GCE outbound connection errors no longer occur.

Deployment pipeline stability improved by over 90%
0 recurring chat build failures recorded
GCE outbound connection error frequency 0%

Summary — How to Avoid the Same Pitfalls

To prevent similar issues in the future, I've created a checklist:

[ ] Always verify that detailed logic within the deployment pipeline, such as --preload detection, does not cause unintended side effects.
[ ] Set a broad default range of supported extensions in the next.config file to ensure build flexibility.
[ ] Always keep in mind that external libraries (especially font-related ones) can affect network connections.
[ ] Unify build configurations across environments (like P1/P2 and P0) to minimize confusion.
[ ] Include settings in the CI/CD pipeline to preserve the .next directory to maintain compatibility with previous builds.
[ ] Strengthen smoke gates to create a system that can immediately detect build failures and roll back.
[ ] Add dotfile guards during sibling builds to prevent unexpected build conflicts.