While performing a security assessment on a React Native Android application, I encountered a non-standard asset structure. After decompressing the initial APK with apktool, I located a bundle file named FilenameBundle.js.hbc.spk.xz.

I successfully decompressed the .xz layer, resulting in FilenameBundle.js.hbc.spk. However, I am hitting a wall with the .spk extension. I’ve attempted to treat it as a standard ZIP archive by renaming it, but the headers do not match.

Given the .hbc (Hermes Bytecode) middle extension, my ultimate goal is to reach the bytecode or the original JavaScript source. Does anyone have experience unpacking this specific .spk wrapper or identifying the tool used to generate it?