Git Bisect: Finding Bugs Fast

Binary search over history beats scanning diffs manually.

1. Identify Good & Bad Commits

Find a recent bad commit (failing) and an older good commit (working).

2. Start Bisect

git bisect start
git bisect bad <bad-hash>
git bisect good <good-hash>
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3. Test Each Step

Git checks out midpoint. Run your failing test or manual repro script. Mark result:

git bisect good   # if pass
git bisect bad    # if fail
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4. Automate (Optional)

If you have a deterministic script returning 0/1:

git bisect run ./scripts/repro.sh
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5. Finish

When bisect ends, it prints the first bad commit.

6. Patch & Validate

Create a fix branch from that commit or latest main, patch, and confirm test passes.

7. Add Regression Test

Prevent recurrence by encoding the failure in a test.

8. Reset State

git bisect reset
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9. Tips

• Skip flaky commits: git bisect skip
• Tag releases to speed future hunts.

10. Summary Template

Issue:
Range:
Root cause commit:
Fix commit:
Regression test:
Lessons:
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Bisect turns mysteries into certainty.