"OMG it's a 25GB game patch, must be tons of amazing new content that they're keeping quiet about."

*Could* be, sure, and stealth launches are a thing sometimes, but generally speaking, if it's a big patch for no discernible reason not attached to anything upcoming that's already been announced, the actual reason is probably something very boring and usually non-game-related

(Very) incomplete list of reasons for big patches that are completely unrelated to new content, from personal experience:

- Somebody added an extra field to some header somewhere, so everything that comes after the header moves and has slightly different context, plus content chunking puts chunk boundaries in different places now, so all the compressed data after changes
- We updated compilers and our assets are built using fast math, YOLO

- Sound assets use Opus in float (not fixed-point) mode which uses RCPSS/RSQRTSS during encode, and we switched our build machines between Intel and AMD, so presto, new audio for everyone
- we changed audio codecs
- we changed lossless data codecs for some or all data
- we changed _something_ and don't know for sure what or why it's a 15GB patch but we only noticed 4 days before cert and it was too scary to figure out and fix before then, so here's hoping it's fine
- this one simple bugfix in our vector math library had bigger ripple effects than we thought
- this one simple bugfix in the platform libm had bigger ripple effects than we thought
- this one simple bugfix in our compiled asset caching had bigger ripple effects than we thought
- who are we kidding, past a certain scale there's really no such thing as a simple bugfix
- given all of the above, reproducible asset builds are Actually Hard, therefore we use content-addressed storage and just cache build artifacts... unfortunately something went wrong and corrupted that store so we had to rebuild everything and this is what happened
(TFW what you thought was just a transient local cache is actually a load-bearing persistent data store that it was never designed to be)
@rygorous In a totally different context I recently spent hours to keep a cache that was no longer just a cache from getting cleared. Ah, the beautiful, elegant, exact science of computing! 😭