Idempotent Redundancy

When you're building fallback paths or redundant systems, you need them to be safe to run multiple times without causing loops or corruption. This pattern is about making those safety nets idempotent. Check if a value exists before writing it in your fallback, use atomic operations for files, pass flags like `_is_merge: true` when updating data stores. The alternative is repair actions that trigger more repairs, or multiple code paths stomping on each other's writes. It's one of those things that seems obvious after you've debugged a reconciliation loop at 2am, but easy to miss when you're just trying to add redundancy.