Function slot_file_name 

pub fn slot_file_name(model_id: u32, session_id: &str) -> String

Filename for a model+session slot cache file: {model_id}__{session_id}.bin.

This is both the on-disk name (directly under slot_dir) and the filename value sent to llama-server’s save/restore endpoint — they must match, and both must be free of path separators (see the module docs).