Post-Mortem: How a "Performance" PR Introduced 28 New Regressions

Analyzing Jellyfin PR #16062 with GauntletCI Jellyfin PR #16062 is titled "Query Performance Improvements." It was a massive architectural shift: 126 files, 27,810 lines of code. It was reviewed, approved, and merged on May 3, 2026. By May 7, the community was already reporting 90-second query hangs (Issue #16279). We ran GauntletCI: a deterministic, rules-based Behavioral Change Risk (BCR) detector: against the merged diff. It took exactly 660 ms to find exactly why the "Performance Improvement