It is stuff like this that fills it up:

Autosaved puzzles/0000996813/0000108474/default/autosave.ir_solution.

and

core.scoring.CartesianBondedEnergy: Creating new peptide-bonded energy container (129)

and

core.pack.pack_rotamers: built 247 rotamers at 10 positions.

Thousands and thousands of lines of useless debug info.

Alright. Seriously. Foldit should be using a rotating log system so that the latest log is only 100 kb. We pretty much only look at these when it crashes, right?

Even better, it should use debug, info, warn and fatal log levels and only warn and fatal in the players logfiles.

The rotating log approach fails if you have multiple clients running. Each client should open its individual log file. And indeed, the logs should include only severe errors. That way you do not have to worry about deleting them either. If there is a log file, there is trouble.

Just to reassure you, this complaint isn't falling on deaf ears. This will be corrected. The reason it's coming up is that Foldit uses many of the core components of Rosetta, the automated structure prediction and design software developed in the Baker lab. The NewChapter update brought much of the new functionality added to Rosetta recently into Foldit -- but that meant some additional output messages that were added recently to these core components now need to be turned off (and some of these were evidently overlooked). The developers are busily troubleshooting now, and this will be one of the issues that they'll address soon, I'm sure. (It should be one of the easier ones to fix.)

@ v_mulligan

I think you either missed or didn't address one of the big issues with log files -

When you run multiple clients from the same folder, each client should have its own log file. Can you make this happen ?

Would the preferred solution be a rotated logfile for each running client?

For now I've reduced the verbosity of Rosetta's output. You should see a lot less spam from running actions.