How are the comp cors computed in fmriprep?

Specifically, are the components calculated for each run and session separately, or is their some concatenation at the session level?

Since the confounds file is produced for each run, I suppose there is no concatenation. The slightly odd thing about this approach is that done this way the components are not “matched” across runs - a_comp_cor_XX in run N and a_comp_cor_XX in run M could reflect different noise sources. In this case, removal of the top 5 (for example) comps in run 1 and run 2 actually removes different noise sources. I feel that estimating the components across sessions rather then runs may be a bit better fit for multi session experiments (like my own).

Any insight appreciated.