Merge Conflict

A merge conflict arises when two identities are merged and a property has conflicting values on each side, forcing a decision about which value survives.

Identity merging is often necessary — for instance when an anonymous visitor logs in and their history must attach to a known user. But merging is not painless: if the anonymous profile recorded the city as 'Tehran' and the known profile as 'Mashhad', the system must pick one. Common approaches are 'last write wins', 'first value stays' or a rule based on trust in the source, and none is always right. The real danger is when a wrong merge unifies two different people; then the merge conflict is not just a broken property but two contaminated identities. So identity merging should be conservative and reversible, and conflict-resolution rules defined in advance and transparently, not on the fly.