Do you have any technical blog post how the filesystem is intercepting and caching build steps? This seems like a non-obvious development. The blog alludes to a sandbox step which I’m assuming is for establishing the graph somehow but it’s not obvious to understand where the pitfalls are (eg what if I install some system library - does this interception recognize when system libraries or tools have changed, what if the build description changes slightly, how does the invalidation work etc). Basically, it’s a bold claim to be able to deliver Blaze-like features without requiring any changes to the build system.