In the network coding framework, given a prime power q and the vector space
Fqn, a constant type flag code is a set of nested sequences of
Fq-subspaces (flags) with the same increasing sequence of
dimensions (the type of the flag). If a flag code arises as the orbit under the
action of a cyclic subgroup of the general linear group over a flag, we say
that it is a cyclic orbit flag code. Among the parameters of such a family of
codes, we have its best friend, that is the largest field over which all the
subspaces in the generating flag are vector spaces. This object permits to
compute the cardinality of the code and estimate its minimum distance. However,
as it occurs with other absolute parameters of a flag code, the information
given by the best friend is not complete in many cases due to the fact that it
can be obtained in different ways. In this work, we present a new invariant,
the best friend vector, that captures the specific way the best friend can be
unfolded. Furthermore, throughout the paper we analyze the strong underlying
interaction between this invariant and other parameters such as the
cardinality, the flag distance, or the type vector, and how it conditions them.
Finally, we investigate the realizability of a prescribed best friend vector in
a vector space