Most of the code is in Rust. More than 75% of the entire stack. One component in the stack, the bt-host driver, is currently still in C++ as the oldest component. This part of the code only deals with low level connection management and speaking HCI with the hardware as well as hosting the GATT implementation, but everything is handed off to other components that are all written in Rust. Parts that remaining component itself of it have already been migrated to rust over time as well including GAP. All of the profiles and upper layers are entirely in Rust as well.