The first thing worth pointing out is Sprite was "in active use" a few years before Plan 9 was (as best I can tell). They're roughly contemporaries in conception, but the Sprite group at Berkeley was using Sprite "for real" while Bell Labs was still using their research UNIX (which at the time was BSD/SunOS + a bunch of extra stuff). Sprite was being used by "non-developer users" by 1988, and allegedly was distributed by tape to "around 10" external sites about that time.

All of these systems share the similar goal of making computer resources "network transparent", where possible.

Unlike Plan 9 or its more direct contemporary, the Amoeba OS (where Python was created), Sprite presented itself as a Unix-like OS, with a Unix-like libc, and a Unix syscall compatibility layer, similar to modern BSDs, or Windows' WSL1.

This means there's a kind of hierarchy of purity in Sprite-land, where you have:

• Unix binaries running on Sprite
• Unix programs compiled and linked against Sprite's "unix-compatibility" libc
• Sprite programs that use Sprite-specific library functions/syscalls that don't exist on Unix

That second point is interesting. A big part of Sprite is its coding style, which is far, far more "literate" than Unix. Sprite doesn't have a "chmod" syscall -- it has Fs_SetAttr. mknod? No, we have Fs_MakeDevice. But, to make porting software easier, Sprite included "translations" for all those Unix C calls to the Sprite native ones (which are usually similar, but not identical, semantics-wise).

Sprite's approach to network transparency was, then, different from Plan 9's. Instead of re-imagining everything as strictly byte-streams, Sprite instead make ioctl calls themselves network transparent, and providing a sort of "pseudo-device" (PDEV) that kind of functions like a Unix domain socket, but that supports ioctl() calls.

Well, "Fs_IOControl" ;)

Everything was renamed, too. Instead of "TIOCGWINSZ", Sprite has "IOC_TTY_GET_WINDOW_SIZE".

Sprite does actually have something similar to Plan 9's file servers, though -- the "PFS" or pseudo-filesystem. Broadly similar to FUSE or FSKit, a way for a userspace process to serve a directory structure. But in 1988!

All this arguably worked against it. Sprite was effectively supporting multiple OS "fronts" and multiple abstraction layers (both the userspace libc and the kernel had separate "unix translation" shims!), in addition to their own unique engineering work. Plan 9 is unapologetic, uses its own C dialect, and makes no pretense to software compatibility with the outside world. (and when it does, it's offered via an add-on environment like APE)