one can use direnv, nix-direnv and flake.nix to get an immutable and reproducible build toolchain protected from nix garbage collection, while keeping the llama.cpp branches and/or compiled binaries mutable on the local filesystem. https://github.com/nix-community/nix-direnv

for agentic execution sandboxing, preventing 'rm -rf /home' nix or nix-direnv doesn't help, podman could be used next to nix. https://discourse.nixos.org/t/what-is-sandboxing-and-what-do...