The Silent Merge Queue Corruption That Hit 658 GitHub Repos
A silent bug in GitHub's merge queue affected 658 repositories, causing incorrect commits to be created. The issue arose from an incomplete feature flag that allowed a new code path to run unexpectedly, leading to the reversion of prior changes in multi-PR squash merges. GitHub identified the problem after customer reports and implemented a fix within hours, but the incident highlighted vulnerabilities in their automated monitoring system.
- ▪The bug affected 658 repositories and 2,092 pull requests.
- ▪An incomplete feature flag allowed a new code path to run, causing incorrect commits.
- ▪GitHub's automated monitoring did not detect the issue for over three hours.
Hacker News (Newest) files mainly under programming. We currently carry 5,257 of its stories.
Opening excerpt (first ~120 words) tap to expand
~/library/FM-029FM-029GitHub2026-04-23impact 4h38mSEV-1A silent merge queue bug corrupted 658 GitHub reposGitHub's merge queue is supposed to protect the default branch. An incomplete feature-flag gate let an unreleased merge-base path run inside squash merge groups, producing valid-looking commits that silently reverted prior work while availability monitoring stayed green.merge-queuefeature-flagsquash-mergegit-correctnesssilent-failuresummary#The merge queue's job is to protect the last dangerous step before code reaches the default branch. It takes pull requests that have passed review and CI, groups them, retests the combined state, and lands them in order. That contract depends on one quiet guarantee: the commit the queue writes must contain exactly what was validated.
…
Excerpt limited to ~120 words for fair-use compliance. The full article is at Failure-modes.
Discussion
0 commentsMore from Failure-modes
