--- title: "STACK | The Agentic Codebase" description: "STACK is a five-layer architecture for repositories where humans and agents share work: Structure, Toolchain, Agent configuration, Connection, Knowledge and…" image: "https://lenvanderhof.com/photos/len-portrait-1.jpg" --- Framework # STACK The Agentic Codebase STACK is a five-layer architecture for repositories where humans and agents share work: Structure, Toolchain, Agent configuration, Connection, Knowledge and quality. The agent OS is versioned like the app. The moves 5 ## When to use it Use STACK 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. ## The moves 1. 01 ### Structure Layout, entry points, workspaces, and boundaries an agent can navigate on its first minute in the repo. 2. 02 ### Toolchain The shells, commands, and CLI contracts an agent is allowed to run, written down instead of remembered. 3. 03 ### Agent configuration AGENTS.md, CLAUDE.md, rules, skills, and subagent charters as versioned standing context. 4. 04 ### Connection MCP servers, tool contracts, hooks, and guardrails with least privilege and a real failure story. 5. 05 ### Knowledge and quality Memory tiers, context budgets, evals, and CI, so a model upgrade does not silently lower the bar. ## The book Available now ### The Agentic Codebase The Five-Layer Architecture That Makes Agent Work Survive Production Open the bookThe articleThe series ## Related frameworks CHORUS ### The Multi-Agent Organization CHORUS is a six-skill coordination protocol for teams of 2 to 15 people who share work with specialised AI workers: Charter, Handoff, Orchestrate, Review, Update, Sync. Org charts name reporting lines. CHORUS names coordination lines. SENSE ### AI Agents for Startup Strategy SENSE is a five-move strategic intelligence layer: Scan, Evaluate, Navigate, Simulate, Execute. It turns agent work from a productivity shortcut into a sourced claim that changes a watchlist, an assumption register, or a Monday decision. BooksOS ### The Agentic Author BooksOS is a gated production system for serious nonfiction: Brief, Bible, Map, Draft, Edit, Package, Launch. Agents do specialist work inside the gates. Judgment, voice, and accountability stay human. GRAIN ### The RAG Engineer GRAIN is a retrieval loop: Gather, Rank, Assemble, Inspect, Navigate. Gather collects candidate passages. Rank orders them for the question actually asked. Assemble builds the context the model may see. Inspect checks that the cited chunk is the one used. Navigate decides the next lookup or the refusal. If you cannot point at the passage, you do not have retrieval. You have a fluent guess. ## Essays on this site - [What is an AI agent?](https://lenvanderhof.com/en/blog/what-is-an-ai-agent/) - [MCP explained for founders](https://lenvanderhof.com/en/blog/mcp-explained-for-founders/) - [The Agentic Codebase: introduction](https://lenvanderhof.com/en/blog/the-agentic-codebase-introduction/) - [Version the agent OS](https://lenvanderhof.com/en/blog/stack-version-the-agent-os/) - [An agentic workflow is not an automation](https://lenvanderhof.com/en/blog/agentic-workflow-vs-automation/) - [LLM integration is an operating-design problem](https://lenvanderhof.com/en/blog/llm-integration-is-operating-design/) - [MCP meaning: Model Context Protocol, not a product](https://lenvanderhof.com/en/blog/mcp-meaning/) - [What is STACK? Five layers, not a vendor diagram](https://lenvanderhof.com/en/blog/what-is-stack/) ## Terminology - [STACK](https://lenvanderhof.com/glossary/stack/) - [CHORUS](https://lenvanderhof.com/glossary/chorus/) - [SENSE](https://lenvanderhof.com/glossary/sense/) - [BooksOS](https://lenvanderhof.com/glossary/booksos/) - [GRAIN](https://lenvanderhof.com/glossary/grain/) - [AI agent](https://lenvanderhof.com/glossary/ai-agent/) - [Human in the loop](https://lenvanderhof.com/glossary/human-in-the-loop/) - [Override doctrine](https://lenvanderhof.com/glossary/override-doctrine/) STACK is the five-layer model in The Agentic Codebase. It is not a vendor "AI stack" diagram, not an AGENTS.md file by itself, and not a vertical-slice tutorial. A repo that only has a markdown instruction sheet still has agentic debt. ## Citation STACK (The Agentic Codebase). 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