A portable agent definition has a subtle design choice: should it name a model? My thesis is that model: inherit is the better default for an APC agent unless a particular model is genuinely part of the project's contract. It keeps the role portable while letting the runtime make an operational choice. APC is the repository-owned context layer: AGENTS.md and .apc/ describe what a contributor or agent needs to know about a project. APX is the daily-use runtime and tooling layer that read...