The Day the CI Pipeline Turned Into a Pumpkin

This is a story about how a simple dependency bump
caused my CI pipeline to collapse at 2 AM like a fairy-tale carriage at midnight.

Incident

A minor patch upgrade triggered:

• 247 failing build jobs
• rising container times
• runners backing up
• and a Slack channel full of “is anyone awake?”

Diagnosis

It wasn’t obvious at first.

Builds were intermittently failing with checksum mismatches—
yet the packages were correct locally.

After digging:

• The dependency graph changed
• A transitive package switched mirrors
• The CI cache contained stale tarballs
• The new mirror required updated checksums

Classic “it only breaks in CI” energy.

Fix

• Purged the CI cache
• Rebuilt the lockfile
• Added deterministic registry URLs
• Enforced checksum pinning

Lesson

CI isn’t just a build system.
It’s a distributed state machine.
If you don’t treat it like one, you’ll eventually get pumpkins.