Building LLVM as a shared library is routine on Unix, where symbols are exported by default. Windows works the other way: nothing crosses the library boundary unless you say so, and its 64K limit on a DLL's public ABI forces a deliberate decision about what belongs in the public surface. Trimming the rest carries over to the other platforms — fewer exported symbols mean fewer relocations for the loader to resolve and faster loads on macOS and Linux, alongside smaller distributions and faster Windows builds. This talk covers the boundary work, the tooling that maintains it, and the cross-platform wins.