both the Hous and Senate will be holding pro forma sessions starting Monday, so technically, in session.
https://www.congress.gov/congressional-record/2019/12/19
Next Meeting of the
SENATE
10 a.m., Monday, December 23
Senate Chamber
Program for Monday: Senate will meet in a pro forma session.
Next Meeting of the
HOUSE OF REPRESENTATIVES
11 a.m., Monday, December 23
House Chamber
Program for Monday: House will meet in Pro Forma session at 11 a.m.
I believe they started this so that Trump could NOT make recess appointments. Not any president, but targeted Trump.