Term
STACK
STACK is a five-layer architecture for repositories where humans and agents share work: Structure, Toolchain, Agent configuration, Connection, Knowledge and quality. Structure is the map an agent can navigate on minute one. Toolchain is the commands it may run. Agent configuration is versioned standing context. Connection is MCP with contracts and least privilege. Knowledge and quality is memory, evals, and CI, so a model upgrade does not silently lower the bar. The agent OS is versioned like the app.
When to use it
Use it when agents demo well and then rot the repo: rules in five tools, MCP without contracts, skills nobody owns. The disease is agentic repo debt, not a weak model.
Do not confuse with
Not a vendor “AI stack” diagram, not AGENTS.md alone, and not a vertical-slice tutorial. It is the five-layer model in The Agentic Codebase.