Over the past years Very Long Baseline Interferometry (VLBI) data
processing in CASA has become a reality. It is now a supported
alternative to AIPS for continuum observations with the European VLBI
Network (EVN) and has established itself as one of the two official
calibration pipelines for the Event Horizon Telescope (EHT). It can
also be used for (EVN) spectral line observations, many Very Long
Baseline Array (VLBA) observations and observations by other (long
baseline) radio arrays such as LOFAR-VLBI, e-MERLIN and GMVA. A
comprehensive CASA-based VLBI pipeline that supports many of these
arrays is available in the form of rPICARD.

This presentation will give an overview of VLBI functionality in CASA,
as well as current and future developments that are needed to make
sure data processing software keeps track with other technical and
scientific developments in VLBI and future developments like the
ngVLA. It will provide some interesting examples on how basing these
developments on a packages written in "modern" languages like C++ and
Python eases improvements of existing algorithms and implementation of
new algorithms.