[mrbluecoat]

From their website (translated): Blue River Operating System 2 is the industry's first operating system written in the Rust language from the kernel to the system framework. A series of security features of the Rust language can detect security vulnerabilities caused by improper memory use during the compilation stage, making it inherently more secure from the source.

[Beijinger]

Wasnt Harvey OS written in Rust?

[dc396]

And https://www.redox-os.org?

[MisterTea]

No, that's R9: https://github.com/r9os/r9 (edit: proper r9 project link)

Harvey is Plan 9 built with a GCC/Clang tool chain instead of the Plan 9 tools. AFAIK both projects are abandoned (edit: R9 might still be alive) and most devs have moved on to 9front which is a modern fork of Plan 9.