The Last Harness Youll Ever Build arXiv

I'm Matt Wood, and this is For Your Information. A live list of riffs and links for you and your agent, drawn from what I'm reading, noticing, questioning, concluding, and revising.

Title: The Last Harness You'll Ever Build
Authors: Haebin Seong, Li Yin, Haoran Zhang, Zhan Shi
Submitted: April 22, 2026 (v1), revised May 1, 2026 (v3)
Subject: Artificial Intelligence (cs.AI)

arxiv.org →

Connections

Harness engineering: leveraging Codex in an agent-first world | OpenAI OpenAI's Codex harness-engineering piece and the arXiv 'Last Harness' paper both argue that the scaffolding around a model is the key lasting artifact in agentic coding.
The Shape of Things to Come, Part 1: The Continuous Thunderdome Both directly address the design philosophy of AI agent harnesses; Yegge's Wheelhouse and 'The Last Harness' both tackle the core problem of orchestrating autonomous coding agents through loops and structured execution frameworks
Pi, Minimal and Performant Both directly address the design philosophy of AI coding harnesses; Pi's minimalist 4-tool approach is a concrete instantiation of the 'ideal harness' concept explored in that piece

Supported by

Schema: Frontier Models with the Right Harness Achieve ~99% on ARC-AGI-3 Public ARC-AGI-3's finding that harness quality (not just model capability) drives near-99% performance backs the paper's thesis that a well-built harness is the durable investment.
Formal Methods at Jane Street: Agentic Coding Changes the Calculus Jane Street's account of agents helping with formal proofs illustrates how domain-specific verification harnesses multiply agent usefulness, echoing the paper's core claim.

Type:	link
First published:	Saturday, 23 May 2026 at 12:00 UTC
Location:	https://arxiv.org/abs/2604.21003
URL:	https://mattwood.fyi/i/258c733e