From 13db1adcb846fe192dd0e50eefe64bdc46114122 Mon Sep 17 00:00:00 2001
From: Robin Malfait <malfait.robin@gmail.com>
Date: Mon, 28 Apr 2025 19:17:09 +0200
Subject: [PATCH 1/3] add failing test

---
 packages/tailwindcss/src/utilities.test.ts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/packages/tailwindcss/src/utilities.test.ts b/packages/tailwindcss/src/utilities.test.ts
index 1b7cf00edd16..419e6373a27d 100644
--- a/packages/tailwindcss/src/utilities.test.ts
+++ b/packages/tailwindcss/src/utilities.test.ts
@@ -10695,6 +10695,8 @@ test('bg', async () => {
         'bg-red-500/2.75',
         'bg-red-500/[0.5]',
         'bg-red-500/[50%]',
+        'bg-red-500/100',
+        'bg-red-500/[100%]',
         'bg-blue-500',
         'bg-current',
         'bg-current/50',
@@ -10992,6 +10994,10 @@ test('bg', async () => {
       }
     }
 
+    .bg-red-500\\/100 {
+      background-color: var(--color-red-500);
+    }
+
     .bg-red-500\\/\\[0\\.5\\] {
       background-color: #ef444480;
     }
@@ -11012,6 +11018,10 @@ test('bg', async () => {
       }
     }
 
+    .bg-red-500\\/\\[100\\%\\] {
+      background-color: var(--color-red-500);
+    }
+
     .bg-transparent {
       background-color: #0000;
     }

From cd452e3993fc3fc500cf9afe35132737c79285e7 Mon Sep 17 00:00:00 2001
From: Robin Malfait <malfait.robin@gmail.com>
Date: Sun, 27 Apr 2025 12:23:51 +0200
Subject: [PATCH 2/3] alpha of 100% is the default

---
 packages/tailwindcss/src/utilities.ts | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/packages/tailwindcss/src/utilities.ts b/packages/tailwindcss/src/utilities.ts
index 40050cfd2ab1..3c9a189c1af2 100644
--- a/packages/tailwindcss/src/utilities.ts
+++ b/packages/tailwindcss/src/utilities.ts
@@ -173,6 +173,11 @@ export function withAlpha(value: string, alpha: string): string {
     alpha = `${alphaAsNumber * 100}%`
   }
 
+  // No need for `color-mix` if the alpha is `100%`
+  if (alpha === '100%') {
+    return value
+  }
+
   return `color-mix(in oklab, ${value} ${alpha}, transparent)`
 }
 

From c788f42ca82aa724357604d8fca1beaec667914d Mon Sep 17 00:00:00 2001
From: Robin Malfait <malfait.robin@gmail.com>
Date: Mon, 28 Apr 2025 19:21:31 +0200
Subject: [PATCH 3/3] update changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71822866829c..2bed1490d0fa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Replace `_` with `.` in theme suggestions for `@utility` if surrounded by digits ([#17743](https://github.com/tailwindlabs/tailwindcss/pull/17743))
 - Upgrade: Bump all Tailwind CSS related dependencies during upgrade ([#17763](https://github.com/tailwindlabs/tailwindcss/pull/17763))
 - PostCSS: Ensure that errors in stylesheet dependencies are recoverable ([#17754](https://github.com/tailwindlabs/tailwindcss/pull/17754))
+- Skip `color-mix(…)` when opacity is `100%` ([#17815](https://github.com/tailwindlabs/tailwindcss/pull/17815))
 
 ## [4.1.4] - 2025-04-14