/p/2026-10-21 · explainer
Paper explainer · 2610.25899 · Li, Liu, Xu, Yang, Yang, Zhang, Wang, Shan and Ngai

It inherited the work and the mistake.

Coding-agent benchmarks start from a clean checkout. Production hands an agent a retry, a resumed session, or another agent’s branch. This paper rebuilt 198 starting points from 111 tasks — each the state an agent left after declaring the task done while hidden tests still failed — and gave a fresh agent only the original request and that state, with no hint the attempt had failed. Every one of five frontier agents fell 20.6 to 53.5 points below its clean-start score, and the ranking inverted. The failure is not weaker coding: agents read the inherited diff as the definition of the task, keep 86–98% of its lines, and submit with exactly the tests that were already failing.

01 · The problem

how the starting state was built

02 · The mechanism

pick an agent, then switch where it starts

03 · The evidence

read one symptom of acceptance bias at a time

04 · Why I care

05 · Apply it

Your handoff pipeline illustrative

Results

What the paper actually measured

What it does not show

In practice