We characterize several stability properties, such as inverse or composition closedness, for
ultraholomorphic function classes of Roumieu type defined in terms of a weight matrix. In
this way we transfer and extend known results from J. Siddiqi and M. Ider, from the weight
sequence setting and in sectors not wider than a half-plane, to the weight matrix framework
and for sectors in the Riemann surface of the logarithm with arbitrary opening. The key
argument rests on the construction, under suitable hypotheses, of characteristic functions in
these classes for unrestricted sectors. As a by-product, we obtain new stability results when
the growth control in these classes is expressed in terms of a weight sequence, or of a weight
function in the sense of Braun–Meise–Taylor.
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