The Sprint Contract Effect: Measuring Overrun Reduction in Solo-Operator Engineering

1. Introduction

Estimation accuracy is a long-studied problem in software engineering — the median project ships at roughly 1.7× its original estimate, with variance dominated by the long right tail of severely overrun projects (Jørgensen & Shepperd 2007 [3]). The reasons are well documented: planning fallacy [4], optimism bias, scope inflation, the inability to enumerate failure modes ex ante.

Solo operators running agent-mediated engineering work have all of these problems plus several novel ones. The agent reads vague briefs as license to scope expansively. “Done” without an explicit definition becomes whatever the agent renders. Mid-session detours into research that turn into multi-day rabbit holes are routine. Without explicit pre-work contracts, individual sessions ship reasonable artifacts, but the artifact is rarely the one originally requested.

We present an empirical study of one operator across three ventures, measuring the effect of adopting a structured sprint-contract discipline on contract overrun rates. The study is small (n=48 contracts, single operator, 16 weeks), but the within-subject design — same operator, same ventures, same agent stack, before vs after a single intervention — produces an unusually clean signal: median overrun fell from 78% pre-discipline to 12% post-discipline, with the largest reduction in contracts whose original definition of done was vague.