# Brendan Cody-Kenny: Learnings from harness engineering

Technical Due Diligence for Software M&A https://sub.xiliary.com/p/brendancodykenny

### 2026-10-15 offering #coding-agents #harness-engineering #local-optima #sbse
Learnings from harness engineering
- My coding harness gets stuck in local optima, and that creates long lead times. Each task is a small change that merges only if every test passes. Agents patch around the existing structure.
- When a feature needs a structural change, progress slows because the required breakage does not fit inside one passing task.
- I pause the harness and make the larger structural change myself, or ask for it directly.
- It breaks many things at once. Then I run the harness again and use small tasks to clean up the failures until every test passes.
- When a task fails repeatedly, I get better results by rewriting the task than by retrying the same instruction. Rewriting the task keeps the harness useful after I've made the larger change possible.
- https://codykenb.github.io/learnings/

https://sub.xiliary.com/p/brendancodykenny/posts/70/learnings-from-harness-engineering