diff --git a/.browserslistrc b/.browserslistrc
index 7acddfb1beab..a48650abf804 100644
--- a/.browserslistrc
+++ b/.browserslistrc
@@ -2,9 +2,12 @@
 
 last 2 major versions
 not dead
-Chrome >= 120
+# Floors set to the first versions with native CSS `light-dark()` (and nesting),
+# so Lightning CSS no longer lowers them to the brittle custom-property polyfill
+# that broke `data-bs-theme` dark mode.
+Chrome >= 123
+Edge >= 123
 Firefox >= 121
-iOS >= 15.6
-Safari >= 15.6
-not Explorer <= 11
+iOS >= 17.5
+Safari >= 17.5
 not kaios <= 2.5 # fix floating label issues in Firefox (see https://github.com/postcss/autoprefixer/issues/1533)
diff --git a/build/css-minify.mjs b/build/css-minify.mjs
index 6f1d112aa326..19082d61fc62 100644
--- a/build/css-minify.mjs
+++ b/build/css-minify.mjs
@@ -9,7 +9,7 @@
 
 import fs from 'node:fs'
 import path from 'node:path'
-import { transform, browserslistToTargets } from 'lightningcss'
+import { transform, browserslistToTargets, Features } from 'lightningcss'
 
 const distDir = path.join(process.cwd(), 'dist/css')
 
@@ -48,7 +48,11 @@ for (const file of cssFiles) {
       minify: true,
       sourceMap: true,
       inputSourceMap: inputMap ? JSON.stringify(inputMap) : undefined,
-      targets
+      targets,
+      // Never lower `light-dark()`: its custom-property polyfill breaks our
+      // `data-bs-theme` dark mode. We bumped browser support to versions with
+      // native support to fix this, but this guards against a regression.
+      exclude: Features.LightDark
     })
 
     // Write minified CSS with source map reference