diff --git a/CHANGELOG.md b/CHANGELOG.md
index 86205ef4e..22d88df1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Discard matched variants with non-string values ([#18799](https://github.com/tailwindlabs/tailwindcss/pull/18799))
 - Show suggestions for known `matchVariant` values ([#18798](https://github.com/tailwindlabs/tailwindcss/pull/18798))
 - Replace deprecated `clip` with `clip-path` in `sr-only` ([#18769](https://github.com/tailwindlabs/tailwindcss/pull/18769))
+- Hide internal fields from completions in `matchUtilities` ([#18820](https://github.com/tailwindlabs/tailwindcss/pull/18820))
 - Upgrade: Migrate `aria` theme keys to `@custom-variant` ([#18815](https://github.com/tailwindlabs/tailwindcss/pull/18815))
 - Upgrade: Migrate `data` theme keys to `@custom-variant` ([#18816](https://github.com/tailwindlabs/tailwindcss/pull/18816))
 - Upgrade: Migrate `supports` theme keys to `@custom-variant` ([#18817](https://github.com/tailwindlabs/tailwindcss/pull/18817))
diff --git a/packages/tailwindcss/src/compat/plugin-api.ts b/packages/tailwindcss/src/compat/plugin-api.ts
index c52693ef0..42b1c6176 100644
--- a/packages/tailwindcss/src/compat/plugin-api.ts
+++ b/packages/tailwindcss/src/compat/plugin-api.ts
@@ -472,6 +472,10 @@ export function buildPluginApi({
           // work even with legacy configs and plugins
           valueKeys.delete('__BARE_VALUE__')
 
+          // The `__CSS_VALUES__` key is a special key used by the theme function
+          // to transport `@theme` metadata about values from CSS
+          valueKeys.delete('__CSS_VALUES__')
+
           // The `DEFAULT` key is represented as `null` in the utility API
           if (valueKeys.has('DEFAULT')) {
             valueKeys.delete('DEFAULT')
diff --git a/packages/tailwindcss/src/intellisense.test.ts b/packages/tailwindcss/src/intellisense.test.ts
index f9aca65ce..32893b1a0 100644
--- a/packages/tailwindcss/src/intellisense.test.ts
+++ b/packages/tailwindcss/src/intellisense.test.ts
@@ -712,3 +712,38 @@ test('matchVariant', async () => {
   expect(v1.name).toEqual('foo')
   expect(v1.values).toEqual(['a', 'b'])
 })
+
+test('matchUtilities discards internal only helpers from suggestions when using the theme function', async () => {
+  let input = css`
+    @import 'tailwindcss/utilities';
+    @plugin "./plugin.js";
+
+    @theme {
+      --color-red: red;
+    }
+  `
+
+  let design = await __unstable__loadDesignSystem(input, {
+    loadStylesheet: async (_, base) => ({
+      path: '',
+      base,
+      content: '@tailwind utilities;',
+    }),
+    loadModule: async () => ({
+      path: '',
+      base: '',
+      module: plugin(({ matchUtilities, theme }) => {
+        matchUtilities({ foo: (val) => ({ color: val }) }, { values: theme('colors') })
+        matchUtilities({ bar: (val) => ({ color: val }) }, { values: theme('transitionDuration') })
+      }),
+    }),
+  })
+
+  let classNames = design.getClassList().map((e) => e[0])
+
+  expect(classNames).not.toContain('foo-__BARE_VALUE__')
+  expect(classNames).not.toContain('bar-__BARE_VALUE__')
+
+  expect(classNames).not.toContain('foo-__CSS_VALUES__')
+  expect(classNames).not.toContain('bar-__CSS_VALUES__')
+})