Our #neatHack submission We built Wincheck: an agent that takes a Windows-only Python bug report, reproduces it on a real Windows machine, fixes it, and proves the fix with the maintainers' own tests. Built with @arithecfo @EntireHQ @neatlogs The problem: most Python maintainers don't run Windows, so Windows-only bugs can sit open for months. Nobody on the team can even see them fail. How it works. Three phases, and the harness enforces each one, not the prompt: 1. Read: the agent reads the issue and the code 2. Reproduce: it can only write test files, and every test it submits must fail 3. Fix: tests are frozen, and the fix only counts if the reproduction passes and nothing that passed before breaks No failing test, no code change. Results, all on GitHub's Windows runners: • 6 real upstream bugs from click, tox, pytest and build • 4 fixed, including 3 of 4 held-out bugs the agent never saw while I tuned it • Scored with the maintainers' own tests from their fix commits • Run again for consistency: 3/3 on the held-out pytest bug, 2/3 on click • 27 harness tests on Windows and Linux CI. Disable any gate and a test fails • The misses are logged with the reason, not hidden How the partner tools fit in: @neatlogs: every run is one trace, with setup, baseline, the agent's three phases, every Claude and tool call, and the score. It surfaced three incidents while I built: • Each run was split into 4 traces. One missing parent span, fixed • "Slow Project Preparation" on every run. Switched installs to uv, and time outside the agent went from ~50s to ~34s • "Execution Failed" on runs where the gates refused out-of-phase writes. The refusals worked Zero open incidents now. @EntireHQ: 9 public checkpoints, so you can see the agent sessions behind the commits. Emails and phone numbers are redacted before anything is published. @arithecfo: a 12-month plan built from measured run costs. $49 per successful fix or $199/month for 10 fixes per repo. Both clear a 70% margin, and 23 paying repos cover a founder's salary. Try it yourself: fork the repo and run it on GitHub's Windows runners, or add it to Claude as an MCP server. Repo: github.com/nftkingiii/winche… Every claim links to a run you can open: docs/evidence.md Demo below 👇 #neatHack