The Agent Engineering Stack

A trail from prompt to fleet. Each layer owns a different question.

flowchart LR
    P[Prompt Engineering] --> C[Context Engineering]
    C --> H[Harness Engineering]
    H --> L[Loop Engineering]
    L --> F[Fleet Engineering]

Layer Summary

Layer	Question	Unit	Canonical reference
Prompt	What do we say?	One turn	—
Context	What does the model see?	One inference	Cobus — Context Engineering
Harness	How does one run execute?	One agent run	Cobus — Harness Engineering · awesome-harness-engineering
Loop	What keeps working over time?	One autonomous system	loop-engineering
Fleet	How do many systems govern together?	Population	This repo

When to graduate

Signal	Graduate to
Context window fills or rots	Context engineering
Single runs are flaky	Harness engineering
You are still typing prompts daily	Loop engineering
3+ loops or 5+ agents; compliance questions	Fleet engineering

Cross-links

• Loop repo → Fleet: loop-engineering multi-loop is the seed of fleet coordination
• Fleet repo → Loop: every registered agent should reference which loop pattern it runs

Vendor products on the stack

Product	Layer
Claude Code, Codex, Grok CLI	Harness + Loop
LangGraph	Harness + Loop (orchestration)
LangSmith	Harness observability
LangSmith Fleet	Fleet (enterprise workspace)

Fleet engineering as a discipline is bigger than any one product. Use the stack doc to place tools without conflating them.