A label with no official definition - which is exactly why every lab slaps it on itself.
The term started with the companies themselves, not scientists or law. OpenAI, Anthropic and Google DeepMind (Google's big artificial intelligence lab) came up with a label for 'models at the leading edge' together - systems so new that nobody outside has a counter-measure to check their claims. A convenient move: you slap your own sign that says 'we're ahead' before someone else does it for you.
Except the word doesn't measure ability - it measures posture. One model can be strong at language and weak at code. Another can be frontier only because it came out a month ago - and already stop being so, because a competitor shipped a better one on a Thursday afternoon. That's why the label ages faster than the systems themselves.
Regulators don't fall for marketing - they grabbed the number behind it. The EU AI Act (the European Union's AI law) sets an automatic presumption of 'systemic risk' on every model trained with over 10 to the 25th power FLOPs - computing operations burned during training. Cross the threshold and the burden of proof falls on the company - it's the one that has to prove the model isn't dangerous.
Crossing the threshold isn't abstract - it leads to concrete obligations. Adversarial tests (deliberate attempts to break the model before someone outside does), a systemic risk report, reporting serious incidents to the European AI office. In other words - the 'frontier' label on paper means more responsibility, not more bragging, even if companies sell it back the other way.
Wait a minute
I'm allergic to words that sound impressive and mean nothing concrete. 'Frontier' is exactly that - it works as advertising precisely because it has no fixed boundary. Anyone can stand in front of it and say 'we're here', without anyone easily disputing it. It's a trick - the word sells confidence while the actual measure (how much compute, how much data, what the model really does differently) stays hidden behind it.
The distinction I keep for myself: I don't watch who calls themselves frontier, I watch who crosses the threshold the regulator measures in numbers - and then what they do with that crossing. The rest is noise at the leading edge of the wave, gone by next Thursday.