{
  description = "Gleam compiler (wasm / Zed extension support fork)";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    systems.url = "github:nix-systems/default";
    fenix.url = "github:nix-community/fenix";
    fenix.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs =
    {
      self,
      nixpkgs,
      systems,
      fenix,
      ...
    }:
    let
      forEachSystem = nixpkgs.lib.genAttrs (import systems);
    in
    {
      packages = forEachSystem (
        system:
        let
          pkgs = nixpkgs.legacyPackages.${system};
          inherit (pkgs) lib;

          # Recent stable for edition 2024 workspace.
          rustToolchain =
            fenix.packages.${system}.stable.toolchain
              or fenix.packages.${system}.complete.toolchain;

          rustPlatform = pkgs.makeRustPlatform {
            cargo = rustToolchain;
            rustc = rustToolchain;
          };

          gleam = rustPlatform.buildRustPackage {
            pname = "gleam";
            version = "1.18.0-rc2";
            src = lib.cleanSourceWith {
              src = ./.;
              filter =
                path: type:
                let
                  base = baseNameOf path;
                in
                lib.cleanSourceFilter path type
                && base != "target"
                && base != "result"
                && !(lib.hasSuffix ".wasm" base)
                && !(lib.hasSuffix ".cwasm" base);
            };

            cargoLock = {
              lockFile = ./Cargo.lock;
            };

            nativeBuildInputs = [
              pkgs.capnproto
              pkgs.pkg-config
            ];

            # Workspace: only build/install the CLI crate.
            buildAndTestSubdir = "gleam-bin";

            # Full test suite is heavy and needs network / many backends.
            doCheck = false;

            meta = {
              description = "Gleam compiler with Wasm / Zed extension export";
              mainProgram = "gleam";
              homepage = "https://tangled.org/nandi.uk/gleam";
              license = lib.licenses.asl20;
            };
          };
        in
        {
          default = gleam;
          inherit gleam;
        }
      );

      apps = forEachSystem (system: {
        default = {
          type = "app";
          program = "${self.packages.${system}.gleam}/bin/gleam";
        };
      });

      devShells = forEachSystem (
        system:
        let
          pkgs = nixpkgs.legacyPackages.${system};
          rustToolchain =
            fenix.packages.${system}.stable.toolchain
              or fenix.packages.${system}.complete.toolchain;
        in
        {
          default = pkgs.mkShell {
            packages = [
              rustToolchain
              pkgs.capnproto
              pkgs.pkg-config
              self.packages.${system}.gleam
            ];
            shellHook = ''
              echo "gleam wasm fork dev shell"
              echo "  gleam --version  # store build when packages.gleam is built"
              echo "  cargo build -p gleam"
            '';
          };
        }
      );

      checks = forEachSystem (system: {
        package = self.packages.${system}.gleam;
      });

      formatter = forEachSystem (system: nixpkgs.legacyPackages.${system}.nixfmt-rfc-style);
    };
}