I Broke 50 PRs With One Config Change. Here's How I Built a Time Machine to Prevent It.

We've all been there. You decide it's time to improve code quality. "No more console.log in production code," you declare. You add a simple ESLint rule, push the config, and merge. Ten minutes later, your Slack blows up. "Why is the build failing on my PR?" "I can't deploy the hotfix!" "Who turned on the fun police?" You just broke 50 open pull requests because you didn't know how widespread the "violation" was. You revert the change, apologize, and the codebase remains messy. This fear of "Policy Shock" —the disruption caused by enforcing new rules—is why many teams are afraid to tighten their governance. But what if you could time-travel? What if you could test your new rule against the last 100 PRs in your repo before you merged it? That's exactly what we built. Here is the technical deep dive into how we created a Policy Impact Simulator for GitHub. The Problem: Governance is a Guessing Game Most CI/CD pipelines are binary: pass or fail. When you introduce a new check, it applies t