AI Agent Architecture (Paperback)

Paperback. Every effect an agent has on the world should go through one door - and the door should keep the book.Atlas, Meridian Supply Co.'s customer-operations agent, could plan, remember, and reason by Book 3. It reached the world through function calls scattered across three books of code, and on a Tuesday a regression suite logged ninety-eight tickets in a real CRM because the mock covered the model and not the world. Nobody had a list of the places Atlas could touch the world; the whiteboard was wrong twice. This book builds the action boundary as one system, wall by wall, each justified by an incident and proved by a test.Every chapter is a lab on the companion repository - one dependency, fully offline with a scripted mock, every listing printed from a verified line range, every command paired with its expected output. Five moves per chapter: Run the demo, Read the listing, Break it with the chapter's planted failure, Fix it with the design move, Prove it with a test that turns green. You will: Every chapter carries a research lineage (purity and safety-critical surfaces, Cockburn's ports and adapters, RPC from Birrell-Nelson to MCP, Anderson's reference monitor and Saltzer-Schroeder, chroot to containers, Garcia-Molina's sagas, WebArena, master data and bank reconciliation, Meszaros's test doubles and chaos engineering), a five-item failure catalog, an applied deep-dive, and exercises in three tiers. Ten figures, a hundred and ninety tests, thirty-five decision records, one running system that grew from Book 3's graph without removing a node of it.Who it's for: engineers integrating agents with real systems - anyone who has given a model a tool and wants to know what it can do, who may call it, what happens when it is retried, and how to prove afterwards what happened. Assumes Book 2 or the equivalent; basic Python; no framework, no GPU.The AI Agent Architecture Series is the architect's track: one architectural layer per book, on one running system the reader refactors and grows by hand. This is Book 4, Tools & Environments - the action boundary, designed and audited.Tag every side effect - kind, target, reversibility, compensator - generate the catalogue, and run a lint that finds the five untagged effects in three versions of AtlasBuild a tool layer as ports and adapters: a registry the core never names, a new capability in one registration, and a schema that refuses wrong, missing, and invented arguments by nameServe and consume tools over MCP - JSON-RPC on stdio, three methods, a gateway on both ends - and draw the trust line that quarantines a carrier's injected descriptionRoute every call through one gateway with policy by principal, quotas, keys, bounded retry, and an audit line written in a finally - then attempt the bypass and watch it refused and countedSandbox the tools that execute: a jail, an allowlist, path-free flags, a clean environment, a timeout - and measure blast radius as a numberReproduce a retry storm (five refunds for one carton), fix it with idempotency keys, and undo a half-placed order with a saga whose irreversible step goes lastDrive a web shop through a text browser behind the gateway, break the plan with a page change, and write it in the page's words instead This item is printed on demand. Shipping may be from our UK warehouse or from our Australian or US warehouses, depending on stock availability.…