Model layer
The model layer produces reasoning or structured decisions. Keeping it replaceable avoids making one model provider the architecture.
Control layer
A control layer coordinates bounded work, applies product policy and determines when more evidence or human input is needed.
Execution layer
The execution layer exposes approved machine capabilities behind explicit permission and audit boundaries.
Why separation helps
A model can change without redefining file access. A new computer capability can be introduced without giving it authority over the whole workflow. Verification policy can evolve without rebuilding every tool.
Do not confuse a public pattern with a private implementation
This layered pattern is general engineering guidance. ARKTOR uses modular separation, but its exact internal state, routing, recovery and trust contracts are proprietary and intentionally not documented here.