diff --git a/CHANGELOG.md b/CHANGELOG.md
index 175a1daa2..8d59cd834 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Oxide: drop invalid UTF-8 candidates ([#20389](https://github.com/tailwindlabs/tailwindcss/pull/20389))
 - `@tailwindcss/vite` no longer forces a full page reload for external files (e.g.: `.php` files) ([#20414](https://github.com/tailwindlabs/tailwindcss/issues/20414))
 - Canonicalization: don't merge utilities that reference different theme variables set to CSS-wide keywords like `unset` ([#20417](https://github.com/tailwindlabs/tailwindcss/pull/20417))
+- Don't generate utilities when a modifier is used that would otherwise be silently ignored (e.g. `rounded-sm/[5]`, `shadow-sm/foo`, `stroke-2/50`) ([#20419](https://github.com/tailwindlabs/tailwindcss/pull/20419))
 
 ## [4.3.3] - 2026-07-16
 
diff --git a/packages/tailwindcss/src/utilities.test.ts b/packages/tailwindcss/src/utilities.test.ts
index c9d4a5ff0..66b051d57 100644
--- a/packages/tailwindcss/src/utilities.test.ts
+++ b/packages/tailwindcss/src/utilities.test.ts
@@ -12154,18 +12154,28 @@ test('rounded', async () => {
     "
   `)
   expect(
-    await run([
-      '-rounded',
-      '-rounded-full',
-      '-rounded-none',
-      '-rounded-sm',
-      '-rounded-[4px]',
-      'rounded/foo',
-      'rounded-full/foo',
-      'rounded-none/foo',
-      'rounded-sm/foo',
-      'rounded-[4px]/foo',
-    ]),
+    await run(
+      [
+        '-rounded',
+        '-rounded-full',
+        '-rounded-none',
+        '-rounded-sm',
+        '-rounded-[4px]',
+        'rounded/foo',
+        'rounded-full/foo',
+        'rounded-none/foo',
+        'rounded-sm/foo',
+        'rounded-[4px]/foo',
+        'rounded-sm/[5]',
+        'rounded-sm/(--foo)',
+      ],
+      css`
+        @theme {
+          --radius-sm: 0.125rem;
+        }
+        @tailwind utilities;
+      `,
+    ),
   ).toEqual('')
 })
 
@@ -22373,6 +22383,11 @@ test('stroke', async () => {
       // Width
       '-stroke-0',
       'stroke--1',
+      'stroke-0/foo',
+      'stroke-1/50',
+      'stroke-2/[0.5]',
+      'stroke-2/(--my-opacity)',
+      'stroke-[12px]/foo',
     ]),
   ).toEqual('')
 })
@@ -24398,82 +24413,90 @@ test('filter', async () => {
     "
   `)
   expect(
-    await run([
-      '-filter',
-      '-filter-none',
-      '-filter-[var(--value)]',
-      '-blur-xl',
-      '-blur-[4px]',
-      'brightness--50',
-      '-brightness-50',
-      '-brightness-[1.23]',
-      'brightness-unknown',
-      'contrast--50',
-      '-contrast-50',
-      '-contrast-[1.23]',
-      'contrast-unknown',
-      '-grayscale',
-      '-grayscale-0',
-      'grayscale--1',
-      '-grayscale-[var(--value)]',
-      'grayscale-unknown',
-      'hue-rotate--5',
-      'hue-rotate-unknown',
-      '-invert',
-      'invert--5',
-      '-invert-0',
-      '-invert-[var(--value)]',
-      'invert-unknown',
-      '-drop-shadow-xl',
-      '-drop-shadow-[0_0_red]',
+    await run(
+      [
+        '-filter',
+        '-filter-none',
+        '-filter-[var(--value)]',
+        '-blur-xl',
+        '-blur-[4px]',
+        'brightness--50',
+        '-brightness-50',
+        '-brightness-[1.23]',
+        'brightness-unknown',
+        'contrast--50',
+        '-contrast-50',
+        '-contrast-[1.23]',
+        'contrast-unknown',
+        '-grayscale',
+        '-grayscale-0',
+        'grayscale--1',
+        '-grayscale-[var(--value)]',
+        'grayscale-unknown',
+        'hue-rotate--5',
+        'hue-rotate-unknown',
+        '-invert',
+        'invert--5',
+        '-invert-0',
+        '-invert-[var(--value)]',
+        'invert-unknown',
+        '-drop-shadow-xl',
+        '-drop-shadow-[0_0_red]',
 
-      'drop-shadow/foo',
-      '-drop-shadow/foo',
-      '-drop-shadow/25',
-      '-drop-shadow-red-500',
-      'drop-shadow-red-500/foo',
-      '-drop-shadow-red-500/foo',
-      '-drop-shadow-red-500/50',
+        'drop-shadow/foo',
+        '-drop-shadow/foo',
+        '-drop-shadow/25',
+        '-drop-shadow-red-500',
+        'drop-shadow-red-500/foo',
+        '-drop-shadow-red-500/foo',
+        '-drop-shadow-red-500/50',
 
-      '-saturate-0',
-      'saturate--5',
-      '-saturate-[1.75]',
-      '-saturate-[var(--value)]',
-      'saturate-saturate',
-      '-sepia',
-      'sepia--50',
-      '-sepia-0',
-      '-sepia-[50%]',
-      '-sepia-[var(--value)]',
-      'sepia-unknown',
-      'filter/foo',
-      'filter-none/foo',
-      'filter-[var(--value)]/foo',
-      'blur-xl/foo',
-      'blur-none/foo',
-      'blur-[4px]/foo',
-      'brightness-50/foo',
-      'brightness-[1.23]/foo',
-      'contrast-50/foo',
-      'contrast-[1.23]/foo',
-      'grayscale/foo',
-      'grayscale-0/foo',
-      'grayscale-[var(--value)]/foo',
-      'hue-rotate-15/foo',
-      'hue-rotate-[45deg]/foo',
-      'invert/foo',
-      'invert-0/foo',
-      'invert-[var(--value)]/foo',
-      'drop-shadow-xl/foo',
-      'drop-shadow-[0_0_red]/foo',
-      'saturate-0/foo',
-      'saturate-[1.75]/foo',
-      'saturate-[var(--value)]/foo',
-      'sepia/foo',
-      'sepia-0/foo',
-      'sepia-[50%]/foo',
-      'sepia-[var(--value)]/foo',
-    ]),
+        '-saturate-0',
+        'saturate--5',
+        '-saturate-[1.75]',
+        '-saturate-[var(--value)]',
+        'saturate-saturate',
+        '-sepia',
+        'sepia--50',
+        '-sepia-0',
+        '-sepia-[50%]',
+        '-sepia-[var(--value)]',
+        'sepia-unknown',
+        'filter/foo',
+        'filter-none/foo',
+        'filter-[var(--value)]/foo',
+        'blur-xl/foo',
+        'blur-none/foo',
+        'blur-[4px]/foo',
+        'brightness-50/foo',
+        'brightness-[1.23]/foo',
+        'contrast-50/foo',
+        'contrast-[1.23]/foo',
+        'grayscale/foo',
+        'grayscale-0/foo',
+        'grayscale-[var(--value)]/foo',
+        'hue-rotate-15/foo',
+        'hue-rotate-[45deg]/foo',
+        'invert/foo',
+        'invert-0/foo',
+        'invert-[var(--value)]/foo',
+        'drop-shadow-xl/foo',
+        'drop-shadow-[0_0_red]/foo',
+        'saturate-0/foo',
+        'saturate-[1.75]/foo',
+        'saturate-[var(--value)]/foo',
+        'sepia/foo',
+        'sepia-0/foo',
+        'sepia-[50%]/foo',
+        'sepia-[var(--value)]/foo',
+      ],
+      css`
+        @theme {
+          --drop-shadow: 0 1px 1px rgb(0 0 0 / 0.05);
+        }
+        @tailwind utilities;
+      `,
+    ),
   ).toEqual('')
 
   expect(
@@ -27243,25 +27266,36 @@ test('text-shadow', async () => {
     "
   `)
   expect(
-    await run([
-      '-shadow-xl',
-      '-shadow-none',
-      '-shadow-red-500',
-      '-shadow-red-500/50',
-      '-shadow-red-500/[0.5]',
-      '-shadow-red-500/[50%]',
-      '-shadow-current',
-      '-shadow-current/50',
-      '-shadow-current/[0.5]',
-      '-shadow-current/[50%]',
-      '-shadow-inherit',
-      '-shadow-transparent',
-      '-shadow-[#0088cc]',
-      '-shadow-[#0088cc]/50',
-      '-shadow-[#0088cc]/[0.5]',
-      '-shadow-[#0088cc]/[50%]',
-      '-shadow-[var(--value)]',
-    ]),
+    await run(
+      [
+        '-text-shadow-sm',
+        '-text-shadow-none',
+        '-text-shadow-red-500',
+        '-text-shadow-red-500/50',
+        '-text-shadow-red-500/[0.5]',
+        '-text-shadow-red-500/[50%]',
+        '-text-shadow-current',
+        '-text-shadow-current/50',
+        '-text-shadow-current/[0.5]',
+        '-text-shadow-current/[50%]',
+        '-text-shadow-inherit',
+        '-text-shadow-transparent',
+        '-text-shadow-[#0088cc]',
+        '-text-shadow-[#0088cc]/50',
+        '-text-shadow-[#0088cc]/[0.5]',
+        '-text-shadow-[#0088cc]/[50%]',
+        '-text-shadow-[var(--value)]',
+        'text-shadow/foo',
+        'text-shadow-sm/foo',
+      ],
+      css`
+        @theme {
+          --text-shadow: 0 1px 1px rgb(0 0 0 / 0.05);
+          --text-shadow-sm: 0 1px 2px rgb(0 0 0 / 0.06);
+        }
+        @tailwind utilities;
+      `,
+    ),
   ).toEqual('')
 })
 
@@ -27725,25 +27759,38 @@ test('shadow', async () => {
     "
   `)
   expect(
-    await run([
-      '-shadow-xl',
-      '-shadow-none',
-      '-shadow-red-500',
-      '-shadow-red-500/50',
-      '-shadow-red-500/[0.5]',
-      '-shadow-red-500/[50%]',
-      '-shadow-current',
-      '-shadow-current/50',
-      '-shadow-current/[0.5]',
-      '-shadow-current/[50%]',
-      '-shadow-inherit',
-      '-shadow-transparent',
-      '-shadow-[#0088cc]',
-      '-shadow-[#0088cc]/50',
-      '-shadow-[#0088cc]/[0.5]',
-      '-shadow-[#0088cc]/[50%]',
-      '-shadow-[var(--value)]',
-    ]),
+    await run(
+      [
+        '-shadow-sm',
+        '-shadow-none',
+        '-shadow-red-500',
+        '-shadow-red-500/50',
+        '-shadow-red-500/[0.5]',
+        '-shadow-red-500/[50%]',
+        '-shadow-current',
+        '-shadow-current/50',
+        '-shadow-current/[0.5]',
+        '-shadow-current/[50%]',
+        '-shadow-inherit',
+        '-shadow-transparent',
+        '-shadow-[#0088cc]',
+        '-shadow-[#0088cc]/50',
+        '-shadow-[#0088cc]/[0.5]',
+        '-shadow-[#0088cc]/[50%]',
+        '-shadow-[var(--value)]',
+        'shadow/foo',
+        'shadow-sm/foo',
+        'shadow-[10px_10px]/foo',
+        'shadow-[#0088cc]/foo',
+      ],
+      css`
+        @theme {
+          --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
+          --shadow-sm: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
+        }
+        @tailwind utilities;
+      `,
+    ),
   ).toEqual('')
 })
 
@@ -28216,25 +28263,37 @@ test('inset-shadow', async () => {
     "
   `)
   expect(
-    await run([
-      '-inset-shadow-sm',
-      '-inset-shadow-none',
-      '-inset-shadow-red-500',
-      '-inset-shadow-red-500/50',
-      '-inset-shadow-red-500/[0.5]',
-      '-inset-shadow-red-500/[50%]',
-      '-inset-shadow-current',
-      '-inset-shadow-current/50',
-      '-inset-shadow-current/[0.5]',
-      '-inset-shadow-current/[50%]',
-      '-inset-shadow-inherit',
-      '-inset-shadow-transparent',
-      '-inset-shadow-[#0088cc]',
-      '-inset-shadow-[#0088cc]/50',
-      '-inset-shadow-[#0088cc]/[0.5]',
-      '-inset-shadow-[#0088cc]/[50%]',
-      '-inset-shadow-[var(--value)]',
-    ]),
+    await run(
+      [
+        '-inset-shadow-sm',
+        '-inset-shadow-none',
+        '-inset-shadow-red-500',
+        '-inset-shadow-red-500/50',
+        '-inset-shadow-red-500/[0.5]',
+        '-inset-shadow-red-500/[50%]',
+        '-inset-shadow-current',
+        '-inset-shadow-current/50',
+        '-inset-shadow-current/[0.5]',
+        '-inset-shadow-current/[50%]',
+        '-inset-shadow-inherit',
+        '-inset-shadow-transparent',
+        '-inset-shadow-[#0088cc]',
+        '-inset-shadow-[#0088cc]/50',
+        '-inset-shadow-[#0088cc]/[0.5]',
+        '-inset-shadow-[#0088cc]/[50%]',
+        '-inset-shadow-[var(--value)]',
+        'inset-shadow/foo',
+        'inset-shadow-sm/foo',
+        'inset-shadow-[10px_10px]/foo',
+      ],
+      css`
+        @theme {
+          --inset-shadow: inset 0 1px 3px 0 rgb(0 0 0 / 0.1);
+          --inset-shadow-sm: inset 0 1px 1px rgb(0 0 0 / 0.05);
+        }
+        @tailwind utilities;
+      `,
+    ),
   ).toEqual('')
 })
 
diff --git a/packages/tailwindcss/src/utilities.ts b/packages/tailwindcss/src/utilities.ts
index 6c4a20cbc..477559d7e 100644
--- a/packages/tailwindcss/src/utilities.ts
+++ b/packages/tailwindcss/src/utilities.ts
@@ -421,6 +421,13 @@ export function createUtilities(theme: Theme) {
             desc.themeKeys ?? [],
           )
 
+          // If the theme value resolved without consuming the modifier, then
+          // the modifier would be silently ignored and `w-4` and `w-4/foo`
+          // would generate the same CSS.
+          //
+          // The modifier would be consumed if it's a fraction, e.g.: `w-1/2`
+          if (value !== null && candidate.modifier && !candidate.value.fraction) return
+
           // Automatically handle things like `w-1/2` without requiring `1/2` to
           // exist as a theme value.
           if (value === null && desc.supportsFractions && candidate.value.fraction) {
@@ -3888,6 +3895,10 @@ export function createUtilities(theme: Theme) {
     }
 
     {
+      // A modifier is only valid as the opacity of a stroke color. The value
+      // did not resolve to a color, so a modifier would be silently ignored.
+      if (candidate.modifier) return
+
       let value = theme.resolve(candidate.value.value, ['--stroke-width'])
       if (value) {
         return [decl('stroke-width', value)]
@@ -4628,6 +4639,7 @@ export function createUtilities(theme: Theme) {
         let value = theme.get(['--drop-shadow'])
         let resolved = theme.resolve(null, ['--drop-shadow'])
         if (value === null || resolved === null) return
+        if (candidate.modifier && !alpha) return
 
         return [
           filterProperties(),
@@ -5436,6 +5448,7 @@ export function createUtilities(theme: Theme) {
     if (!candidate.value) {
       let value = theme.get(['--text-shadow'])
       if (value === null) return
+      if (candidate.modifier && !alpha) return
 
       return [
         textShadowProperties(),
@@ -5463,6 +5476,8 @@ export function createUtilities(theme: Theme) {
           ]
         }
         default: {
+          if (candidate.modifier && !alpha) return
+
           return [
             textShadowProperties(),
             decl('--tw-text-shadow-alpha', alpha),
@@ -5491,6 +5506,8 @@ export function createUtilities(theme: Theme) {
     {
       let value = theme.get([`--text-shadow-${candidate.value.value}`])
       if (value) {
+        if (candidate.modifier && !alpha) return
+
         return [
           textShadowProperties(),
           decl('--tw-text-shadow-alpha', alpha),
@@ -5582,6 +5599,7 @@ export function createUtilities(theme: Theme) {
       if (!candidate.value) {
         let value = theme.get(['--shadow'])
         if (value === null) return
+        if (candidate.modifier && !alpha) return
 
         return [
           boxShadowProperties(),
@@ -5611,6 +5629,8 @@ export function createUtilities(theme: Theme) {
             ]
           }
           default: {
+            if (candidate.modifier && !alpha) return
+
             return [
               boxShadowProperties(),
               decl('--tw-shadow-alpha', alpha),
@@ -5644,6 +5664,8 @@ export function createUtilities(theme: Theme) {
       {
         let value = theme.get([`--shadow-${candidate.value.value}`])
         if (value) {
+          if (candidate.modifier && !alpha) return
+
           return [
             boxShadowProperties(),
             decl('--tw-shadow-alpha', alpha),
@@ -5708,6 +5730,7 @@ export function createUtilities(theme: Theme) {
       if (!candidate.value) {
         let value = theme.get(['--inset-shadow'])
         if (value === null) return
+        if (candidate.modifier && !alpha) return
 
         return [
           boxShadowProperties(),
@@ -5737,6 +5760,8 @@ export function createUtilities(theme: Theme) {
             ]
           }
           default: {
+            if (candidate.modifier && !alpha) return
+
             return [
               boxShadowProperties(),
               decl('--tw-inset-shadow-alpha', alpha),
@@ -5772,6 +5797,8 @@ export function createUtilities(theme: Theme) {
         let value = theme.get([`--inset-shadow-${candidate.value.value}`])
 
         if (value) {
+          if (candidate.modifier && !alpha) return
+
           return [
             boxShadowProperties(),
             decl('--tw-inset-shadow-alpha', alpha),