What 1k Harness Experiments Taught Me About Self-Improving Agents

I recently wanted to see whether an AI agent could self-improve a harness to solve terminal bench tasks. It’s possible for an AI agent to propose a meaningful one-time change to the harness, but after experimenting with this for a couple of weeks, I think the continuous self-improvement is mostly an experiment-systems problem. The system needs a way to decide what kind of improvements can safely compound.

Turns out there's a lot of parallels to coding-agent customization (e.g. SKILLS.md etc..) too.

I wrote my experience of building such system here, including the successful and failure attempts during the process, and how I approached the self-improvement loop. It's not intended as a benchmark claim but more of a systems/research writeup.

https://www.henrypan.com/blog/2026-05-25-self-improvement-ha...