HARNESSTAX: HOW MUCH DOES THE HARNESS MATTER FOR CODING AGENTS?

Summary from the TLDR DevOps newsletter

Coding-agent harnesses such as Claude Code, Codex CLI, and Pi can produce similar task success rates while using dramatically different amounts of tokens and money. Across 21 model–harness combinations on SWE-bench Lite and Terminal-Bench 2.0, harness choice changed cost by as much as 5×, and the model provider's own harness was not consistently the most efficient option.