225,000 Lines of Tests, Written and Merged by Agents - Kush Agrawal, Duolingo

Duolingo's iOS app has nearly 2 million lines of code, and its unit test coverage lagged far behind. Kush Agrawal walks through the autonomous pipeline that fixed it: scheduled workflows pick untested code, coding agents open pull requests, and a lifecycle manager monitors CI, fixes failures, runs AI review and merges, with engineers as the final reviewers. Since March it has merged more than 700 PRs and 225,000 lines of tests, raising overall app coverage from 11% to 24%. He covers the architecture, the guardrails, the failure modes, and how they're reusing the same loop for other migrations. Kush Agrawal, Duolingo: https://www.duolingo.com