How to Fix a Crash from R8 / ProGuard Stripping on Android

An R8/ProGuard crash is code the shrinker removed because it could not see it used. Keep rules fix it. Here is how.

How to fix it

1. Add keep rules

Classes and members accessed by reflection, from native (JNI), or by name (serialization) are invisible to the shrinker and get removed or renamed. Add keep rules so R8 preserves them in the release build.

2. Test the minified build

These crashes only appear in the shrunk release build, not debug. Build and test with minification enabled so stripping issues surface before release, not in player crash reports.

3. Read the crash for the symbol

A stripping crash usually names a missing class or a no-such-method. That tells you exactly what to keep. Trace the symbol back to its keep rule and add it.

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 mobile 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.