Hard cap

The NBA's cap is soft, but certain transactions impose a hard cap: a line the team cannot cross for the rest of that season under any circumstances.

Using the non-taxpayer mid-level exception, the bi-annual exception, or acquiring a player via sign-and-trade hard-caps a team at the first apron. Using the taxpayer mid-level hard-caps it at the second apron.

This is why front offices sometimes decline to use an exception they technically have: spending it would freeze their payroll ceiling for the year.