{
  description = "Vertical-tab terminal built on libghostty-vt";

  inputs = {
    # Ghostty tracks nixpkgs-unstable to get GTK 4.20 / GNOME 49. We follow
    # suit so that our zig-gobject bindings (shared with Ghostty) match the
    # GObject introspection data of the GTK we link against.
    nixpkgs.url = "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";

    flake-compat = {
      url = "github:edolstra/flake-compat";
      flake = false;
    };

    systems = {
      url = "github:nix-systems/default";
      flake = false;
    };

    # Zig 0.16.0 is not in nixpkgs yet; libghostty-vt requires it.
    zig = {
      url = "github:mitchellh/zig-overlay";
      inputs = {
        nixpkgs.follows = "nixpkgs";
        flake-compat.follows = "flake-compat";
        systems.follows = "systems";
      };
    };
  };

  outputs = {
    self,
    nixpkgs,
    zig,
    systems,
    ...
  }: let
    inherit (nixpkgs) lib legacyPackages;

    forAllSystems = f:
      lib.genAttrs (import systems) (system: f legacyPackages.${system} system);
  in {
    devShells = forAllSystems (pkgs: system: {
      default = pkgs.mkShell {
        name = "vtabs";

        nativeBuildInputs = [
          zig.packages.${system}."0.16.0"
          pkgs.pkg-config
          pkgs.gdb

          # Used by ./shot.sh to run the app inside a throwaway headless
          # compositor and screenshot it, so UI can be checked without
          # touching the developer's real session.
          pkgs.sway
          pkgs.grim
          pkgs.wtype
        ];

        buildInputs = with pkgs; [
          # GTK4 + libadwaita, the same native UI stack Ghostty uses on Linux.
          gtk4
          libadwaita
          glib
          gobject-introspection
          pango
          cairo
          harfbuzz
          gdk-pixbuf
          graphene

          # Windowing backends GTK links against.
          wayland
          libxkbcommon
          libx11

          # Font stack used by Pango for glyph rasterization.
          fontconfig
          freetype

          # Icon themes so the app doesn't render missing-image icons.
          adwaita-icon-theme
          hicolor-icon-theme
        ];

        shellHook = ''
          # The runtime data GTK needs to find at startup: its own GSettings
          # schemas and the icon themes our widgets pull symbolic icons from.
          #
          # These are exported under their own names, rather than only folded
          # into XDG_DATA_DIRS, because `mise run install` reads them back out
          # to bake into the installed launcher. The built binary already has
          # an RPATH into the Nix store and runs fine outside this shell, but
          # it still has to be pointed at this data or GTK aborts on a missing
          # schema and falls back to broken-image icons.
          export VTABS_GSETTINGS_SCHEMA_DIR="${pkgs.gtk4}/share/gsettings-schemas/${pkgs.gtk4.name}/glib-2.0/schemas"
          export VTABS_RUNTIME_DATA_DIRS="${pkgs.gtk4}/share/gsettings-schemas/${pkgs.gtk4.name}:${pkgs.adwaita-icon-theme}/share:${pkgs.hicolor-icon-theme}/share"

          export GSETTINGS_SCHEMA_DIR="$VTABS_GSETTINGS_SCHEMA_DIR"
          export XDG_DATA_DIRS="$VTABS_RUNTIME_DATA_DIRS:$XDG_DATA_DIRS"
        '';
      };
    });

    formatter = forAllSystems (pkgs: _: pkgs.alejandra);
  };
}