What were the first Soviet spacecraft to use an internal docking tunnel?

Question

The first crew transfer between space vehicles was from Soyuz 5 to Soyuz 4. It was done outside the spacecraft by Aleksei Yeliseyev and Yevgeny Khrunov.

The first U.S. crew transfer was during Apollo 9, between the command module and the lunar module. It was done both internally through the docking tunnel, and outside the spacecraft with a spacewalk by Rusty Schweickart.

Docking tunnels are now the standard method to transfer crew between vehicles.

What was the first (pair) of Soviet spacecraft to use a docking tunnel to transfer crew?

Answer 1

I believe that would be Soyuz 11 and Salyut 1.

After the EVA transfer of Soyuz 4/5, Soyuz 6, 7, and 8 flew together, with the plan apparently being for 7 and 8 to dock and transfer crew while 6 filmed, but some sort of hardware problem prevented the attempt.

Soyuz 9 was a long-duration flight of a single spacecraft.

Soyuz 10 was supposed to dock with (then uncrewed) Salyut space station, but was unable to hard-dock and the crew did not enter the station.

Soyuz 11 repeated the attempt, this time successfully, and stayed three weeks on Salyut. Their mission ended in tragedy when a valve opened during reentry and depressurized the spacecraft cabin, killing all three crew members.