Midori (Microsoft's post-Windows research OS)
loreprogrammingops culture
Microsoft's incubation project, running from around 2008 until it was wound down in 2015, to build an operating system from scratch in managed code - kernel, drivers and applications all memory-safe - as a commercial descendant of the Singularity research OS, designed for concurrency and capability-based isolation.
It never shipped, and it is studied anyway because its team published unusually candid retrospectives, chiefly Joe Duffy's series, describing what a language-enforced safe operating system actually costs and what it buys. Ideas from it surfaced later in mainstream work on safe systems programming, async and error handling. Read alongside the memory-safety argument now driving Rust adoption in kernels, Midori reads as an experiment that answered the question a decade before the industry asked it. Note: the name is reused - there is also a lightweight web browser called Midori, unrelated to this project.
Also known as: singularity os, managed code operating system, joe duffy midori, m#