Res judicata
a matter that has been judged
Where the phrase comes from
The doctrine that a final judgment between the same parties on the same claim stops that claim being tried again. Related rules cover a specific issue that was actually decided.
What lawyers are pointing at
Claim preclusion needs a final judgment, the same parties or their privies, and the same claim. A new party, a claim that could not have been brought the first time, or a decision that was not final is not the same thing. Issue preclusion is narrower: an issue that was actually litigated and necessary to the result. The Latin is not a way to shut down a different dispute because it reminds you of an old one.
The same shape in code
A migration framework records the versions it has applied. Running the same migration again as if the judgment did not exist double-writes the data. The applied-version table is the judgment. Refuse the replay. A new migration, with a new version, is a new claim.
A concrete picture
A court enters final judgment that a debt was paid. The same creditor cannot sue the same debtor again for that same debt. A different invoice is a different claim.