The current gain or "beta" of a Common Emitter (CE) amplifier is always measured with dc currents.
However, if you drive the base circuit with an ever increasing frequency, the ac current gain falls as the frequency increases. Eventually the current gain will fall to one, where the change in collector current then equals the change in base current. That is known as the "Transition Frequency", or Ft of that particular transistor.
Beyond that frequency is ceases to amplify ac signals, and becomes pretty useless.
Any modelling that assumes the transistor can amplify becomes invalid, and any circuit will fail to work as intended.