--- title: "What if the harness mattered more than the model? - Aditya Bhargava, Etsy" url: https://daily.dev/posts/what-if-the-harness-mattered-more-than-the-model---aditya-bhargava-etsy-crmcqyynk source_url: https://www.youtube.com/watch?v=2e9ANoOEn28 type: video:youtube source: "AI Engineer" published: 2026-07-07T23:46:40.512Z updated: 2026-07-08T02:21:53.252Z tags: ["llm", "ai-agents"] reading_time: 32 upvotes: 1 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # What if the harness mattered more than the model? - Aditya Bhargava, Etsy **[AI Engineer](https://daily.dev/sources/aidotengineer)** · 32 min read · 1 upvotes · 0 comments ## Summary A staff engineer at Etsy argues that the agent harness matters more than the underlying model, especially for weaker or local open-source models. Drawing on HarnessBench research showing 20+ point performance differences from harness changes alone, the talk walks through building a coding agent using a new language called Agency. Seven progressive examples demonstrate key harness improvements: adding tools, safety via interrupts and handlers, partial function application for constrained autonomy, ReAct-style feedback loops, sub-agents for parallel task execution, and self-optimizing prompts. The core thesis is that investing in harness quality can reduce dependence on expensive proprietary models. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: --- Tags: [#llm](https://daily.dev/tags/llm), [#ai-agents](https://daily.dev/tags/ai-agents) [View this post on daily.dev](https://daily.dev/posts/what-if-the-harness-mattered-more-than-the-model---aditya-bhargava-etsy-crmcqyynk)