{
  # talk: voice notifications for scripts and AI agents.
  #
  # Usage in a NixOS / Home Manager configuration:
  #   inputs.talk.url = "git+https://code.m3ta.dev/m3tam3re/talk";
  #   environment.systemPackages = [ inputs.talk.packages.${system}.talk ];
  # or as an overlay: nixpkgs.overlays = [ inputs.talk.overlays.default ];
  #
  # In the long run this flake replaces m3ta-nixpkgs talk/crunch (bash + mpv).
  description = "talk: voice notifications for scripts and AI agents (one binary, daemon with queue)";

  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

  outputs = { self, nixpkgs }:
    let
      systems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
      forAll = f: nixpkgs.lib.genAttrs systems (system: f nixpkgs.legacyPackages.${system});
      version = if self ? shortRev then "0.0.0-${self.shortRev}" else "0.0.0-dirty";
      mkTalk = pkgs: pkgs.buildGoModule {
        pname = "talk";
        inherit version;
        src = self;
        subPackages = [ "cmd/talk" ];
        # Update after changes to go.mod/go.sum: `nix build` prints the
        # expected hash.
        vendorHash = "sha256-Cne8FiMlpsrFfntMJVtV4D3CzEWQ4Jnd+tIEHF9ecEc=";
        env.CGO_ENABLED = 0;
        ldflags = [ "-s" "-w" "-X" "main.version=${version}" "-X" "main.commit=${self.shortRev or "dirty"}" ];
        # The process-boundary tests start daemons and bind ports; not in the sandbox.
        doCheck = false;
        # Audio: oto talks to PulseAudio/PipeWire directly (pure Go) and falls
        # back to ALSA, which it loads at runtime via dlopen; on NixOS that is
        # only found if we put it on the path. OS voice: espeak-ng.
        nativeBuildInputs = pkgs.lib.optionals pkgs.stdenv.isLinux [ pkgs.makeWrapper ];
        postInstall = pkgs.lib.optionalString pkgs.stdenv.isLinux ''
          wrapProgram $out/bin/talk \
            --prefix LD_LIBRARY_PATH : ${pkgs.lib.makeLibraryPath [ pkgs.alsa-lib ]} \
            --prefix PATH : ${pkgs.lib.makeBinPath [ pkgs.espeak-ng pkgs.libnotify ]}
        '';
        meta = with pkgs.lib; {
          description = "Voice notifications for scripts and AI agents";
          homepage = "https://code.m3ta.dev/m3tam3re/talk";
          license = licenses.mit;
          mainProgram = "talk";
          platforms = platforms.unix;
        };
      };
    in
    {
      packages = forAll (pkgs: rec {
        talk = mkTalk pkgs;
        default = talk;
      });

      apps = forAll (pkgs: rec {
        talk = { type = "app"; program = "${mkTalk pkgs}/bin/talk"; };
        default = talk;
      });

      overlays.default = final: prev: { talk = mkTalk final; };

      devShells = forAll (pkgs: {
        default = pkgs.mkShell {
          packages = [ pkgs.go pkgs.gopls pkgs.gotools pkgs.espeak-ng pkgs.libnotify ];
        };
      });

      formatter = forAll (pkgs: pkgs.nixfmt-rfc-style);
    };
}