Getting this error when attempting to join singleplayer world. Only mods installed are Cold Sweat (2.3.9 on 1.21), and an addon mod I'm working on. The addon mod doesn't modify your configs, only accessing them (for min temp, max temp, etc..).

disconnect-2024-11-29_22.19.25-client.txt

This issue will be solved in the next version. Thank you for your report

I may have figured out the culprit. Inside the item.toml config, "Insulation Ingredients" array contains 255 entries of this:

["minecraft:white_wool,minecraft:orange_wool,minecraft:magenta_wool,minecraft:light_blue_wool,minecraft:yellow_wool,minecraft:lime_wool,minecraft:pink_wool,minecraft:gray_wool,minecraft:light_gray_wool,minecraft:cyan_wool,minecraft:purple_wool,minecraft:blue_wool,minecraft:brown_wool,minecraft:green_wool,minecraft:red_wool,minecraft:black_wool", 1.5, 0.0, "static", "{}"]

I am unsure how this happened, but I'm assuming this is the cause for the NBT serialization of the configs being synced being too big.

Having it generate a brand new config and joining the world shows 16 entries of the wool colors.
Having it generate a brand new config and immediately exiting the game shows ["#minecraft:wool", 1.5, 0] as an entry without the wool array.

I am assuming you're breaking down the item tag into a list of items and then overwriting the config with the broken down list during config sync. Somehow this list is causing it to save as a new entry multiple times causing the config file to balloon in size.
This eventually leads to the config file becoming too large to send in a packet to sync with the integrated server's config.