I ran Claude Code with TDD quality gates for 3 months — here are the actual before/after metrics

Three months ago I started running Claude Code with TDD quality gates — not as a prompt trick, but as a real CI/CD layer that enforces test coverage and lint standards before code is committed. Here's what actually changed, what surprised me, and what I'd do differently. What the setup looks like The core loop: Write a failing test Claude Code implements the code to make it pass A separate quality layer ( Tribunal — more on this below) runs lint, type checks, and coverage thresholds If quality gates fail, the agent iterates without human intervention This is different from just telling Claude Code "write tests" — the quality gates are enforced, not suggested . If coverage drops below 80%, it doesn't proceed. If lint errors appear, it fixes them. The numbers (before/after, same codebase, 3-month window) Metric Before After Bug reports filed by QA 23 7 Mean time to merge a PR 4.2 hours 2.1 hours Test coverage 61% 89% Lint violations in main branch (per week) ~12 ~0.3 Developer confidence