The Complete Claude Code Harness Engineering Guide (5 Layers, 8 Deep-Dives)

Harness engineering is everything around your AI agent except the model: memory, tools, permissions, hooks, observability. LangChain gained 13.7 benchmark points changing only the harness. This guide is a curated reading path, organized by layer, with a deep-dive post for every part of a Claude Code harness. Layer 1 only (what most devs have) → Advice the model may ignore All 5 layers (Memory → Tools → → Enforcement the model Permissions → Hooks → Observability) cannot bypass LangChain jumped fr