--- 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 governs the corpus: sources, permissions, and versioning. Rank retrieves candidate passages and reranks them for the question actually asked. Assemble builds the context the model may see. Inspect traces a wrong answer back to the chunk and retrieval decision behind it. Navigate keeps the index fresh: TTL policy, re-ingest, and change detection. 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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