git push '(fetch first)' vs '(non-fast-forward)': what each rejection tells you

Tested on git 2.43.0. ! [rejected] main -> main (fetch first) means the remote tip is an object your clone doesn't have yet: someone else pushed (a web-UI edit, CI, a collaborator), and git status will still show only [ahead N] because origin/main is stale. (non-fast-forward) means your clone knows the remote tip and your branch doesn't contain it. That happens both when you fetched but haven't merged/rebased ([ahead 1, behind 1]) and after amending or rebasing already-pushed commits. For fetch-first: git fetch, git log main..origin/main to see what landed, git rebase origin/main, push. Force-pushing would delete the remote work. For non-fast-forward after your own rewrite, --force-with-lease is the safe form.