diff --git a/assets/wallpapers/topography-dark.jpg b/assets/wallpapers/topography-dark.jpg
deleted file mode 100644
index 9f24489..0000000
Binary files a/assets/wallpapers/topography-dark.jpg and /dev/null differ
diff --git a/assets/wallpapers/topography-dark.png b/assets/wallpapers/topography-dark.png
new file mode 100644
index 0000000..8da49a8
Binary files /dev/null and b/assets/wallpapers/topography-dark.png differ
diff --git a/assets/wallpapers/topography-light.jpg b/assets/wallpapers/topography-light.jpg
deleted file mode 100644
index ba106b4..0000000
Binary files a/assets/wallpapers/topography-light.jpg and /dev/null differ
diff --git a/assets/wallpapers/topography-light.png b/assets/wallpapers/topography-light.png
new file mode 100644
index 0000000..cfb04c5
Binary files /dev/null and b/assets/wallpapers/topography-light.png differ
diff --git a/lib/theme.nix b/lib/theme.nix
index cb452ec..aae0e9c 100644
--- a/lib/theme.nix
+++ b/lib/theme.nix
@@ -62,11 +62,11 @@ let
     };
   wallpapers = {
     dir = "${config.home.homeDirectory}/Pictures/Screensavers";
-    dark = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper-dark.jpg";
-    light = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper-light.jpg";
-    current = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper.jpg";
-    staticDark = ../assets/wallpapers/topography-dark.jpg;
-    staticLight = ../assets/wallpapers/topography-light.jpg;
+    dark = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper-dark.png";
+    light = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper-light.png";
+    current = "${config.home.homeDirectory}/Pictures/Screensavers/wallpaper.png";
+    staticDark = ../assets/wallpapers/topography-dark.png;
+    staticLight = ../assets/wallpapers/topography-light.png;
     generation = wallpaperGeneration;
   };
   paths = {
diff --git a/scripts/theme.sh b/scripts/theme.sh
index c2b6f3f..0429b4c 100644
--- a/scripts/theme.sh
+++ b/scripts/theme.sh
@@ -23,8 +23,8 @@ set_wallpaper() {
       # macOS caches wallpaper data by file path - copy to a unique temp path
       # so macOS is forced to read the new image data
       wp_dir=$(dirname "$wp_resolved")
-      wp_tmp="${wp_dir}/.wallpaper-active-$$.jpg"
-      rm -f "${wp_dir}"/.wallpaper-active-*.jpg 2>/dev/null || true
+      wp_tmp="${wp_dir}/.wallpaper-active-$$.png"
+      rm -f "${wp_dir}"/.wallpaper-active-*.png 2>/dev/null || true
       cp "$wp_resolved" "$wp_tmp"
       osascript -e "tell application \"System Events\" to tell every desktop to set picture to \"${wp_tmp}\"" >/dev/null 2>&1 || true
     fi
diff --git a/scripts/wallpaper-gen.py b/scripts/wallpaper-gen.py
index 3640152..2a90465 100644
--- a/scripts/wallpaper-gen.py
+++ b/scripts/wallpaper-gen.py
@@ -77,8 +77,8 @@ CONTOUR_LEVELS: int = max(1, int(CONTOURS.get("levels", 20)))
 # cozybox palette - matches lib/theme.nix
 THEMES: dict[str, dict[str, Rgb]] = {
     "dark": {
-        "bg": (0x18, 0x18, 0x18),
-        "line": (0x2d, 0x2d, 0x2d),
+        "bg": (0x00, 0x00, 0x00),
+        "line": (0x1a, 0x1a, 0x1a),
         "label": (0xFF, 0xFF, 0xFF),
     },
     "light": {
@@ -451,14 +451,16 @@ def gen() -> None:
         if LABEL_ENABLED and font is not None:
             draw = ImageDraw.Draw(img)
             draw.text((LABEL_MARGIN_X, H - LABEL_MARGIN_BOTTOM), label, fill=colors["label"], font=font)
-        out_path = os.path.join(DIR, f"wallpaper-{theme_name}.jpg")
-        img.save(out_path, quality=95)
+        out_path = os.path.join(DIR, f"wallpaper-{theme_name}.png")
+        if os.path.exists(out_path):
+            os.remove(out_path)
+        img.save(out_path)
         log(f"wrote theme={theme_name} path={out_path}")
 
-    link = os.path.join(DIR, "wallpaper.jpg")
+    link = os.path.join(DIR, "wallpaper.png")
     if os.path.lexists(link):
         os.unlink(link)
-    target = os.path.join(DIR, f"wallpaper-{theme}.jpg")
+    target = os.path.join(DIR, f"wallpaper-{theme}.png")
     os.symlink(target, link)
     log(f"finish status=ok target={target} link={link}")