Specialization for file formats is not novel (e.g. 7-Zip uses BCJ2 prefiltering to convert x86 opcodes from absolute to relative JMP instructions), nor is embedding specialized decoder bytecode in the archive (e.g. ZPAQ did this and won a lot of Matt Mahoney's benchmarks) but i think OpenZL's execution here, along with the data description and training system, is really fantastic.
Thanks, I've enjoyed reading more about ZPAQ but their main focus seems to be versioning (which is quite a useful feature too, will try it later) but they don't include specialized compression per context.
Like you mention, the expandability is quite something. In a few years we might see a very capable compressor.
