January 2026 performance summary focused on stability and correctness of Android core rules defaults by reverting a prior change that set content-based paths as the default. Work spanned two repos (facebook/buck2 and facebook/buck2-prelude) and involved targeted revert commits, restoring the prior configuration to avoid unintended user impact while preserving expected behavior. The changes were coordinated across repos to ensure consistency and minimize user disruption for Android builds.

Month: 2025-12. This month focused on stabilizing Android rule behavior in Buck2 by reverting the content-based paths change, ensuring compatibility and preventing regressions. The team closed a pair of Android-specific reversions in Buck2 and Buck2 Prelude, aligning behavior with established expectations and enabling informed future re-evaluation of path handling.

Month: 2025-09. Focused on stabilizing Buck2 prelude (facebook/buck2-prelude) by addressing a regression in Postprocess_jar category formatting. No new user-facing features were delivered this month; the primary effort was a critical bug fix that reverts a prior change and restores correct formatting and behavior in post-processing.

In August 2025, stabilized Buck2 prelude behavior by reverting an experimental content-based path hashing feature for prebuilt_jar symlinks, restoring the prior stable hashing behavior and ensuring consistent builds across environments. The change involved removing uses_experimental_content_based_path_hashing = True from declare_output, effectively disabling the experimental hashing for symlinks generated by prebuilt_jar targets. Implemented in facebook/buck2-prelude with commit b89e5300ec732297dba6d3d914643112547b43fe (Revert D79556774: Use content-based path hashing for prebuilt_jar symlink).

July 2025: Focused on stabilizing JavaCD path handling by reverting the experimental content-based path hashing feature and cleaning up artifact declarations, resulting in improved build reliability and maintainability.