agents that store reusable experience as raw instances stay brittle under reworded tasks. ArchOR organizes skills by archetype, retrieves them by structural signature (weighted Jaccard overlap, bounded semantic re-ranking), and arbitrates when the structural route should override the default selector; on the same backbone and skill library it reaches 65.00% Micro-Avg. Pass@1 across five optimization-modeling benchmarks, +1.64pp over its OptSkills predecessor. A small margin, but the retrieval-and-arbitration design maps straight onto a fleet skill library.