ReGreet background doesn't work with WebP

[TymekDev]

I just set up regreet with greetd and Hyprland on NixOS and noticed that if I use a .webp image as the background the background doesn't show at all.

I checked the config at /etc/greetd/regreet.toml and the path under background points to an existing .webp file. I can open that file by other means (e.g. via Firefox).

Logs at /var/log/regreet/log show no signs of errors—it just fails silently.

/var/log/regreet/log

2025-10-15T09:55:05.872881658+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::gui::model: Creating session for user: tymek
2025-10-15T09:55:05.872895448+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::client: Creating session for username: tymek
2025-10-15T09:55:05.914737392+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::gui::model: greetd asks for a secret auth input: Password: 
2025-10-15T09:55:09.129873172+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::client: Sending password to greetd
2025-10-15T09:55:09.16705328+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::gui::model: Successfully logged in; starting session
2025-10-15T09:55:09.16707206+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::gui::model: Saving cache to disk
2025-10-15T09:55:09.1670802+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::cache: Saving cache to disk
2025-10-15T09:55:09.167211969+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::client: Starting greetd session with command: ["/nix/store/n165k1rj8i97kxls08zwc759v47n8gxi-uwsm-0.21.4/bin/uwsm", "start", "-S", "-F", "/run/current-system/sw/bin/Hyprland"]
2025-10-15T09:55:09.167339499+02:00  INFO update_with_view{input=Login { info: UserSessInfo { user_id: Some("tymek"), user_text: "", sess_id: Some("Hyprland (UWSM)"), sess_text: "" } } component="regreet::gui::model::Greeter" id="0x7ffd7c0f4c98"}:login_click_handler: regreet::gui::model: Session successfully started

/etc/greetd/regreet.toml

[GTK]
cursor_theme_name = "Adwaita"
font_name = "Cantarell 16"
icon_theme_name = "Adwaita"
theme_name = "Adwaita"

[background]
fit = "Cover"
path = "/nix/store/fb68gys4p9myrpmdyk1h0dh38qi1g4v4-wallpaper_squoosh.webp"

greeter.nix

  programs.regreet = {
    enable = true;

    settings.background = {
      path = ../../local/share/wallpaper_squoosh.webp;
      fit = "Cover";
    };
  };

  services.greetd = { 
    enable = true;

    settings = {
      default_session = {
        command = "${pkgs.hyprland}/bin/Hyprland --config ${pkgs.writeText "greetd-hyprland-config" ''
          monitor = DP-2, preferred, auto, 1
          monitor = , disable

          misc {
            disable_hyprland_logo = true
            disable_splash_rendering = true
            disable_hyprland_qtutils_check = true
          }

          animations {
            animation = global, 0
          }

          exec-once = ${pkgs.greetd.regreet}/bin/regreet; hyprctl dispatch exit
        ''}";
        user = "greeter";
      };
    };
  };