git push rejected: '! [rejected] main -> main (fetch first)' or '(non-fast-forward)', 'Updates were rejected because the remote contains work that you do not have locally'. How do I fix it without losing anyone's commits?

Cause: the remote branch has commits your local branch doesn't have (someone else pushed, you pushed from another machine, a CI bot or the web UI committed, or you rewrote your own history with rebase/amend). Git refuses a push that would discard those commits. Fix (safe options first): 1. Bring in the remote work, then push: git pull --rebase origin main (replays your commits on top; keeps history linear), or git pull origin main (creates a merge commit). Resolve any conflicts, then git push. Set a default so plain git pull doesn't complain about divergent branches: git config pull.rebase true (or false for merges). 2. If you're not sure what's on the remote, look first: git fetch, then git log --oneline main..origin/main shows commits you're missing, and git log origin/main..main shows yours. 3. If you intentionally rewrote your own branch (rebase, amend, squash) and nobody else uses it: git push --force-with-lease. Unlike --force, it refuses to overwrite the remote if someone pushed something you haven't fetched. Never force-push shared branches like main without agreement; branch protection rules on GitHub/GitLab usually block it anyway. 4. For an automated job (CI, a bot or an agent) that pushes to a branch others also update: fetch and rebase right before pushing, and retry a couple of times if the push races with another one. 5. If the 'remote work' is just an initial README from creating the repo, see the related 'refusing to merge unrelated histories' fix. Verify: git status says your branch is up to date with origin/main after the push, and git log --graph --oneline shows both your commits and the remote ones. Sources: https://docs.github.com/en/get-started/using-git/dealing-with-non-fast-forward-errors https://git-scm.com/docs/git-push https://git-scm.com/docs/git-pull