Luminous loop representing harness engineering for long-running coding agents

Harness Engineering: Loops for Long-Running Coding Agents

LangChain tuned only the harness and lifted a coding agent from Top 30 to Top 5 on Terminal Bench 2.0 — no model change required. Here are the loop patterns that make it possible.

June 14, 2026 · 12 min · Agents' Codex