Nestor G Pestelos Jr · Writing · Print
A Legacy Rails Upgrade With Agents Under a Human Gate
A production Rails commerce platform was upgraded with agents in the loop and a human merge gate. The engagement started in February 2025. The upgrade branch ran from April to October 2025. The shipped line continued to May 2026.
From the fork to the upgrade-branch tip: 4,349 commits, 13,305 files, +1,116,726 / −274,987. The "1M+ line" figure is that diff, not the size of the tree.
The pre-commit hook is an 8-check gate: RuboCop, ESLint with Stimulus 1.1.0 rules, Stimulus template validation, Simple Popup compliance, JS.ERB syntax, BigDecimal safety, factory usage, and integration-test setup (warning-only).
Git history names the agents in that loop: code-reviewer, gap-analyzer, baseline-fidelity-guardian, feature-gap-analyzer, feature-restoration-engineer, historian, quality-architect, reality-checker, restoration-engineer, scribe, and test-debugger.
The human gate is the commit log. All 4,349 upgrade-branch commits carry the author's name. Git cannot separate agent-written lines from hand-written ones.