lean-bisect

To find a Lean toolchain regression, you provide a self-contained test file and two endpoint versions. The bisect process automatically compares toolchain versions to pinpoint the exact commit that changed behavior.

Yes, you can bisect Lean nightly builds using a #guard_msgs test file. The toolchain bisecting process supports #guard_msgs workflows and includes --nightly-only and --ignore-messages flags to tailor the search.

Before bisecting Lean toolchain versions, you need a self-contained Lean test file isolating the regression and access to the targeted toolchain environment. The test file must reproduce the behavior change across the specified commit or nightly range.

The best way to isolate a behavior change across Lean nightly versions is automated bisecting across the toolchain range. This process compares nightly endpoints to identify the exact commit or nightly change that altered behavior.

Lean toolchain bisecting works with custom timeout and message filtering flags. It supports --timeout to manage execution limits and --ignore-messages to filter message-specific behavior during the regression search.

After locating the responsible commit, you report a Lean regression by producing a Zettelkasten note or upstream report. The process guides users to generate these reports via @lean-zettelkasten or @lean-pr for upstream submission.