Event-Sourcing State

Use this skill when an app keeps adding mutable fields to track lifecycle, phase, status, or UI state that could instead be derived from an event log.

Core idea

Do not store the answer when you can store the evidence.

Coding agents overproduce state. Every bug looks like it wants one more flag, one more cached answer, one more special case. Every field feels locally justified. Globally you are building a machine nobody can hold in their head.

Every boolean you add: