# Brendan Cody-Kenny: Harness engineering is search-based software engineering. What did we learn the first time?

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

### 2026-10-15 published #coding-agents #harness-engineering #sbse #software-engineering
Harness engineering is search-based software engineering. What did we learn the first time?
- Local optima: stop retrying the same approach; change the search strategy.
- Fitness functions: passing tests is not enough; maintainability and future cost of change matter.
- Premature convergence and overfitting: more agents do not guarantee diversity, and passing known evals does not guarantee generalisation.
- Representation matters: some structural improvements require temporarily broken intermediate states.
- The open work is measuring architectural quality, detecting stagnation and testing which SBSE techniques actually transfer to LLM coding agents.
- https://codykenb.github.io/harness-sbse/
- https://claude.dev/blog/automating-eval-design-and-hillclimbing/

https://sub.xiliary.com/p/brendancodykenny/posts/72/harness-engineering-is-search-based-software-engineering