Working on Aqueous [1], a next-generation compressed archive format. I've just finished a long refactoring session that enables streamed processing instead of keeping intermediate results into the memory or spill file, and am now working on formats that were big enough that required this support (e.g. disk images). Meanwhile sparse file handling and in-place move and delete operation of archive members have been implemented.

[1] https://lifthrasiir.github.io/aqueous/