From 8a4a60d9fc8af71a7c7205ef839def1b6d69d51a Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Mon, 14 Apr 2025 13:54:34 -0400
Subject: [PATCH 1/3] Add failing test

---
 packages/tailwindcss/src/intellisense.test.ts | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/packages/tailwindcss/src/intellisense.test.ts b/packages/tailwindcss/src/intellisense.test.ts
index 04a6ed7961b9..f5902a2613df 100644
--- a/packages/tailwindcss/src/intellisense.test.ts
+++ b/packages/tailwindcss/src/intellisense.test.ts
@@ -653,3 +653,25 @@ test('shadow utility default suggestions', async () => {
   expect(classNames).toContain('inset-shadow')
   expect(classNames).toContain('text-shadow')
 })
+
+test('Custom @utility and existing utility with names matching theme keys dont give duplicate results', async () => {
+  let input = css`
+    @theme reference {
+      --leading-sm: 0.25rem;
+      --text-header: 1.5rem;
+    }
+
+    @utility text-header {
+      text-transform: uppercase;
+    }
+  `
+
+  let design = await __unstable__loadDesignSystem(input)
+
+  let classList = design.getClassList()
+  let classMap = new Map(classList)
+  let matches = classList.filter(([className]) => className === 'text-header')
+
+  expect(matches).toHaveLength(1)
+  expect(classMap.get('text-header')?.modifiers).toEqual(['sm'])
+})

From 2e5e1f9a964c4e8dc7dd3a341011366b341a957c Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Mon, 14 Apr 2025 14:04:11 -0400
Subject: [PATCH 2/3] Ensure class suggestions are unique

---
 packages/tailwindcss/src/intellisense.ts | 39 ++++++++++++------------
 1 file changed, 19 insertions(+), 20 deletions(-)

diff --git a/packages/tailwindcss/src/intellisense.ts b/packages/tailwindcss/src/intellisense.ts
index ca9c1a386099..27db3a540bc3 100644
--- a/packages/tailwindcss/src/intellisense.ts
+++ b/packages/tailwindcss/src/intellisense.ts
@@ -20,16 +20,18 @@ export type ClassEntry = [string, ClassMetadata]
 const IS_FRACTION = /^\d+\/\d+$/
 
 export function getClassList(design: DesignSystem): ClassEntry[] {
-  let list: ClassItem[] = []
+  let items = new DefaultMap<string, ClassItem>((utility) => ({
+    name: utility,
+    utility,
+    fraction: false,
+    modifiers: [],
+  }))
 
   // Static utilities only work as-is
   for (let utility of design.utilities.keys('static')) {
-    list.push({
-      name: utility,
-      utility,
-      fraction: false,
-      modifiers: [],
-    })
+    let item = items.get(utility)
+    item.fraction = false
+    item.modifiers = []
   }
 
   // Functional utilities have their own list of completions
@@ -42,28 +44,25 @@ export function getClassList(design: DesignSystem): ClassEntry[] {
 
         let name = value === null ? utility : `${utility}-${value}`
 
-        list.push({
-          name,
-          utility,
-          fraction,
-          modifiers: group.modifiers,
-        })
+        let item = items.get(name)
+        item.utility = utility
+        item.fraction ||= fraction
+        item.modifiers.push(...group.modifiers)
 
         if (group.supportsNegative) {
-          list.push({
-            name: `-${name}`,
-            utility: `-${utility}`,
-            fraction,
-            modifiers: group.modifiers,
-          })
+          let item = items.get(`-${name}`)
+          item.utility = `-${utility}`
+          item.fraction ||= fraction
+          item.modifiers.push(...group.modifiers)
         }
       }
     }
   }
 
-  if (list.length === 0) return []
+  if (items.size === 0) return []
 
   // Sort utilities by their class name
+  let list = Array.from(items.values())
   list.sort((a, b) => compare(a.name, b.name))
 
   let entries = sortFractionsLast(list)

From 57300d572ec01560b17cf833a27543e43e9fb873 Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Fri, 9 May 2025 13:37:48 -0400
Subject: [PATCH 3/3] Update changelog

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

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d76daf0fb56..9f146b04446b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Allow `_` before numbers during candidate extraction ([#17961](https://github.com/tailwindlabs/tailwindcss/pull/17961))
+- Prevent duplicate suggestions when using `@theme` and `@utility` together ([#17675](https://github.com/tailwindlabs/tailwindcss/pull/17675))
 
 ## [4.1.6] - 2025-05-09