Sorin Sbarnea no one has been able to work out a solution that works for both (after spending a week on it), so it may not be possible at this time. Or bigger brains than mine are required... (highly likely)
Background doc on how complex this all is based on early jenkins design decisions: https://docs.google.com/document/d/1wIBYfU734c4CU45l_EZMwKAqoVeQL3SsbzQhESoYWI4/edit#heading=h.4kdft5qo8ksb
Perhaps if ansicolor would not strip the codes - it could work in both, but the classic view would need to know to strip them somewhere else (just thinking aloud) - if you were only interested in ANSI working in both? (or are there other notes?)... perhaps...
**Maybe some bigger brains than mine can find a solution? But jenkins logging was never designer other than for the original view of the log (server side rendering with fixed markup, log mutation via plugins that can't be uninstalled or the log data looks broken). If ANSI color is most of it though... perhaps there is hope? It's a tought place to be in.. more brains needed.