D001 - Rust as the implementation language

Status: decided Date: 2026-08-19

orbistoun is written in Rust, one crate per subsystem.

Why: guest threads call into host code from threads no runtime created, so the host needs no garbage collector and no managed runtime. Foreign-function boundaries are explicit rather than ambient, which suits implementing someone else's ABI. Host-side bookkeeping is most of the code, and that is where Rust removes whole classes of defect.

Rejected:

• C++: the same control, without the memory-safety guarantees on the bookkeeping.
• C#: a managed runtime contends with guest threads it never created.