Theseus is a modern OS written from scratch in Rust that explores 𝐢𝐧𝐭𝐫𝐚𝐥𝐢𝐧𝐠𝐮𝐚𝐥 𝐝𝐞𝐬𝐢𝐠𝐧, novel OS structure, and state management. It strives to close the semantic gap between compiler and hardware to maximally leverage the power of language safety, and thus shift OS responsibilities like resource management into the compiler.