@@ -302,7 +302,7 @@ export const DIFF_SURFACE_THEME_UNSAFE_CSS = `
   /* Pierre resolves emphasis on the host, before the diff's overrides can inherit. */
   /* Light emphasis stays above t3-light's readable syntax luminance floor. */
   --diffs-bg-addition-emphasis: light-dark(
-    rgb(from var(--diffs-addition-base) r g b / calc(15% + var(--appearance-contrast-boost, 0%) / 50)),
+    rgb(from var(--diffs-addition-base) r g b / 15%),
     rgb(from var(--diffs-addition-base) r g b / calc(20% + var(--appearance-contrast-boost, 0%) / 4))
   );
 
@@ -320,7 +320,7 @@ export const DIFF_SURFACE_THEME_UNSAFE_CSS = `
     var(--diff-deletion)
   );
   --diffs-bg-deletion-emphasis: light-dark(
-    rgb(from var(--diffs-deletion-base) r g b / calc(15% + var(--appearance-contrast-boost, 0%) / 50)),
+    rgb(from var(--diffs-deletion-base) r g b / 15%),
     rgb(from var(--diffs-deletion-base) r g b / calc(20% + var(--appearance-contrast-boost, 0%) / 4))
   );