flakes

Shared Nix flake infrastructure for systemic-engineering projects. Provides reusable devShells, Rust toolchains, BEAM environments, and NIF support so individual projects don't each re-roll their own.

What's in here

File	What it provides
flake.nix	Top-level: exports lib.{beam,rust,nif,conversation,crate} + devShells
rust.nix	Pinned Rust toolchain (1.94.0 via rust-overlay) + persistent CARGO_HOME
beam.nix	Elixir 1.18 / OTP 27 + Gleam, worktree guard, glue connect
nif.nix	Rustler NIF build tools (for fragmentation, etc.)
conversation.nix	.conv package development environment
crate.nix	Cargo.toml materialization DSL
ci.nix	Typed OBC pipeline module (observable, budget, cascade)
actor.nix	NixOS module for actor services

How to consume

In your project's flake.nix:

{
  inputs = {
    nixpkgs.url     = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    flakes.url      = "github:systemic-engineering/flakes";
  };

  outputs = { self, nixpkgs, flake-utils, flakes }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        rust = flakes.lib.rust.${system};
      in {
        devShells.default = pkgs.mkShell {
          buildInputs = rust.rustTools;
          shellHook   = rust.rustHook;
        };
      });
}

Or grab a ready-made devShell directly:

nix develop github:systemic-engineering/flakes#rust

Available devShells: default, rust, elixir, gleam, beam, gleam-rust, elixir-nif, conversation.

Pinned toolchain — why

The Rust toolchain is pinned via rust-overlay at 1.94.0. This is deliberate: when consuming projects update nixpkgs, the rustc store path does not change. Cargo fingerprints stay stable, which means CI caches (e.g. Swatinem/rust-cache) actually hit on subsequent runs instead of invalidating on every nixpkgs bump.

CARGO_HOME points at ~/.cargo (persistent, shared across projects) rather than per-project, so the registry index and crate sources are downloaded once and reused everywhere. CARGO_TARGET_DIR is left to the consumer's ~/.cargo/config.toml.

Updating Rust is now an explicit edit to rust.nix, not a side effect of nix flake update.

License

Apache-2.0 — Copyright 2026 Alex Wolf / systemic.engineering.