Troubleshooting · Oct 2026 · 2 min read

When the build only fails in CI

A build that passes on your computer and fails in continuous integration is telling you something about your setup.

Remember that CI starts from a clean machine every time. Anything your computer has that the repository does not, such as a cached dependency, a local configuration file or a globally installed tool, is missing in CI.

Check that the lock file is committed and that CI installs from it. If CI resolves dependencies fresh, it may pick up a newer version that breaks the build.

Compare runtime versions. CI images often use a different version of Node.js, PHP, Python or Java than your computer. Pin the version in the CI configuration so it matches what you develop with.

Look for missing secrets and environment variables. CI hides secrets from logs, so a missing value can look like an unrelated error further down.

Tests that depend on time, order, network access or a particular machine are often fine locally and fail in CI. If a test fails only sometimes, treat it as a real bug in the test.

The fastest way to the cause is often to reproduce CI locally: make a fresh clone of the repository, or run the same container image your CI uses, and run the same commands in the same order.