I wonder what the longest single space mission ever was/is. This question doesn't ask for the longest single spaceflight of a human (this are Valery Polyakov's 437 d 18 h on Mir who launched with Soyuz TM-18 and landed with Soyuz TM-20) but for the longest space mission or one could say for the longest flight of a (crewed) spacecraft. This is something that isn't mentioned on Wikipedia. This isn't about space stations either unless the crew (or most of it) on the space station returned in the same spacecraft they launched from Earth with (and the spacecraft remained docked as long as the crew was on the station).
The longest U.S. space mission was Skylab 4 (~ 84 d) and the longest Chinese one was Shenzhou 11 (~ 32.5 d). While these missions look record-suspicious, the longest single mission must have been a Russian one because the Russian Soyuz spacecraft remain docked to Mir and to the ISS very long. As per this list the longest single Russian space mission seems to have been Soyuz TMA-9 at ~ 215 days. Is this the longest space mission ever?