cssbundling-rails 1.4.3 introduced a regression in PR #165 that causes Yarn-based Rails apps to be misidentified as Bun projects. The bug occurs when yarn.lock was added to the Bun lockfile detection list, and Bun happens to be present on PATH (e.g., in Docker base images or CI environments). This causes asset precompilation to fail with a misleading 'ensure bun is installed' error. The fix (PR #172, commit 466cd57) was merged to main in July 2025 but has not been released. The workaround is to pin the gem directly to that commit in the Gemfile using a git reference, with a comment explaining when it's safe to remove the pin.
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The Short VersionHow We Ran Into ItWhat’s Actually HappeningWhere the Regression Came FromMerged Is Not Yet ReleasedConclusion59 Impressions