When putting a compostable item into an empty composter by hand or via a hopper, it has a 100% chance to increase the fill level to 1 regardless of the item type. The item specific probabilities are only applied when the composter is not empty.

Expected behavior:
When interacting with a composter using Fabric Transfer API, it should behave the same way as it does when interacting with the composter using a vanilla hopper.

Observed behavior:
Inserting items into an empty composter via Transfer API has a chance to leave the composter at level 0, which is inconsistent with vanilla behavior.

While I found this issue testing with a 1.19.2 build, the Git history of ComposterWrapper suggests this inconsistency is present in all versions since that class was added in a 1.17 changeset in August 2021.

Ah, I hadn't noticed that when writing the ComposterWrapper. Thank you for the report, I'll propose a fix soon.