git bisect: Usage, Options & Common CI Errors

git bisect runs a binary search through your history to pinpoint the commit that broke something.

Bisect turns "somewhere in 500 commits" into ~9 checks. With git bisect run it is fully automatable in CI.

What it does

git bisect checks out commits between a known-good and known-bad point, asking you (or a script) to mark each as good or bad, halving the search range until it finds the first bad commit.

Common usage

Terminal

git bisect start
git bisect bad                    # current commit is broken
git bisect good v1.0.0            # this tag was fine
# ... test each checkout, mark good/bad ...
git bisect run ./test.sh          # fully automated
git bisect reset                  # return to original HEAD

Options

Subcommand	What it does
start	Begin a bisect session
good <rev> / bad <rev>	Mark a commit as working / broken
run <cmd>	Auto-bisect using a test script exit code
skip	Skip an untestable commit
reset	End bisect and restore HEAD

Common errors in CI

For git bisect run, the test script must exit 0 for good, 1-124/126/127 for bad, and 125 to skip an untestable commit; a non-conforming exit code derails the search. Always finish with git bisect reset, and ensure full history is present (no shallow clone).

Related guides

git log: Usage, Options & Common CI Errorsgit log shows commit history with flexible formatting. Reference for --oneline, --graph, --pretty, ranges, an… git reflog: Usage, Options & Common CI Errorsgit reflog records where HEAD and branches have been, so you can recover lost commits. Reference for show, ex… git checkout: Usage, Options & Common CI Errorsgit checkout switches branches and restores files. Reference for -b, --detach, and pathspecs, plus the detach… git revert: Usage, Options & Common CI Errorsgit revert undoes a commit by creating a new inverse commit, keeping history intact. Reference for -m, --no-c…