What causes CI rebuilding Docker images from scratch every run?

Docker images are rebuilt with no layer cache, so every CI run reinstalls dependencies and rebuilds layers that did not change.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Cache Docker Layers to Speed Up CI Builds

Quick answer: Cache and reuse Docker layers across CI runs, ordering the Dockerfile so volatile steps come last, so unchanged layers are reused.

Rebuilding every Docker layer each run wastes minutes. Layer caching reuses what did not change. Here is how.

How to fix it

1. Order layers by volatility

Put stable steps (dependencies) early and volatile steps (source) late so caching is effective.

2. Cache layers across runs

Persist and restore the layer cache in CI so unchanged layers are reused.

3. Use build cache mounts

Use cache mounts for package managers so downloads are not repeated.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.