diff --git a/CHANGELOG.md b/CHANGELOG.md
index 82c7add42a23..ceba3010700c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix `order-first` and `order-last` for Firefox ([#16266](https://github.com/tailwindlabs/tailwindcss/pull/16266))
 - Ensure `NODE_PATH` is respected when resolving JavaScript and CSS files ([#16274](https://github.com/tailwindlabs/tailwindcss/pull/16274))
 - Ensure Node addons are packaged correctly with FreeBSD builds ([#16277](https://github.com/tailwindlabs/tailwindcss/pull/16277))
+- Fix an issue where `@variant` inside a referenced stylesheet could cause a stack overflow ([#16300](https://github.com/tailwindlabs/tailwindcss/pull/16300))
 
 ## [4.0.3] - 2025-02-01
 
diff --git a/packages/tailwindcss/src/ast.test.ts b/packages/tailwindcss/src/ast.test.ts
index 142fd6312ccf..8bd2004ace73 100644
--- a/packages/tailwindcss/src/ast.test.ts
+++ b/packages/tailwindcss/src/ast.test.ts
@@ -1,5 +1,15 @@
 import { expect, it } from 'vitest'
-import { context, decl, optimizeAst, styleRule, toCss, walk, WalkAction } from './ast'
+import {
+  atRule,
+  context,
+  decl,
+  optimizeAst,
+  styleRule,
+  toCss,
+  walk,
+  WalkAction,
+  type AstNode,
+} from './ast'
 import * as CSS from './css-parser'
 
 const css = String.raw
@@ -188,3 +198,310 @@ it('should not emit empty rules once optimized', () => {
     "
   `)
 })
+
+it('should only visit children once when calling `replaceWith` with single element array', () => {
+  let visited = new Set()
+
+  let ast = [
+    atRule('@media', '', [styleRule('.foo', [decl('color', 'blue')])]),
+    styleRule('.bar', [decl('color', 'blue')]),
+  ]
+
+  walk(ast, (node, { replaceWith }) => {
+    if (visited.has(node)) {
+      throw new Error('Visited node twice')
+    }
+    visited.add(node)
+
+    if (node.kind === 'at-rule') replaceWith(node.nodes)
+  })
+})
+
+it('should only visit children once when calling `replaceWith` with multi-element array', () => {
+  let visited = new Set()
+
+  let ast = [
+    atRule('@media', '', [
+      context({}, [
+        styleRule('.foo', [decl('color', 'red')]),
+        styleRule('.baz', [decl('color', 'blue')]),
+      ]),
+    ]),
+    styleRule('.bar', [decl('color', 'green')]),
+  ]
+
+  walk(ast, (node, { replaceWith }) => {
+    let key = id(node)
+    if (visited.has(key)) {
+      throw new Error('Visited node twice')
+    }
+    visited.add(key)
+
+    if (node.kind === 'at-rule') replaceWith(node.nodes)
+  })
+
+  expect(visited).toMatchInlineSnapshot(`
+    Set {
+      "@media ",
+      ".foo",
+      "color: red",
+      ".baz",
+      "color: blue",
+      ".bar",
+      "color: green",
+    }
+  `)
+})
+
+it('should never visit children when calling `replaceWith` with `WalkAction.Skip`', () => {
+  let visited = new Set()
+
+  let inner = styleRule('.foo', [decl('color', 'blue')])
+
+  let ast = [atRule('@media', '', [inner]), styleRule('.bar', [decl('color', 'blue')])]
+
+  walk(ast, (node, { replaceWith }) => {
+    visited.add(node)
+
+    if (node.kind === 'at-rule') {
+      replaceWith(node.nodes)
+      return WalkAction.Skip
+    }
+  })
+
+  expect(visited).not.toContain(inner)
+  expect(visited).toMatchInlineSnapshot(`
+    Set {
+      {
+        "kind": "at-rule",
+        "name": "@media",
+        "nodes": [
+          {
+            "kind": "rule",
+            "nodes": [
+              {
+                "important": false,
+                "kind": "declaration",
+                "property": "color",
+                "value": "blue",
+              },
+            ],
+            "selector": ".foo",
+          },
+        ],
+        "params": "",
+      },
+      {
+        "kind": "rule",
+        "nodes": [
+          {
+            "important": false,
+            "kind": "declaration",
+            "property": "color",
+            "value": "blue",
+          },
+        ],
+        "selector": ".bar",
+      },
+      {
+        "important": false,
+        "kind": "declaration",
+        "property": "color",
+        "value": "blue",
+      },
+    }
+  `)
+})
+
+it('should skip the correct number of children based on the the replaced children nodes', () => {
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([])
+        return WalkAction.Skip
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([])
+        return WalkAction.Continue
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([decl('--index', '2.1')])
+        return WalkAction.Skip
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([decl('--index', '2.1')])
+        return WalkAction.Continue
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 2.1",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([decl('--index', '2.1'), decl('--index', '2.2')])
+        return WalkAction.Skip
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+
+  {
+    let ast = [
+      decl('--index', '0'),
+      decl('--index', '1'),
+      decl('--index', '2'),
+      decl('--index', '3'),
+      decl('--index', '4'),
+    ]
+    let visited: string[] = []
+    walk(ast, (node, { replaceWith }) => {
+      visited.push(id(node))
+      if (node.kind === 'declaration' && node.value === '2') {
+        replaceWith([decl('--index', '2.1'), decl('--index', '2.2')])
+        return WalkAction.Continue
+      }
+    })
+
+    expect(visited).toMatchInlineSnapshot(`
+      [
+        "--index: 0",
+        "--index: 1",
+        "--index: 2",
+        "--index: 2.1",
+        "--index: 2.2",
+        "--index: 3",
+        "--index: 4",
+      ]
+    `)
+  }
+})
+
+function id(node: AstNode) {
+  switch (node.kind) {
+    case 'at-rule':
+      return `${node.name} ${node.params}`
+    case 'rule':
+      return node.selector
+    case 'context':
+      return '<context>'
+    case 'at-root':
+      return '<at-root>'
+    case 'declaration':
+      return `${node.property}: ${node.value}`
+    case 'comment':
+      return `// ${node.value}`
+    default:
+      node satisfies never
+      throw new Error('Unknown node kind')
+  }
+}
diff --git a/packages/tailwindcss/src/ast.ts b/packages/tailwindcss/src/ast.ts
index ac4529e87000..0e9215bbec0f 100644
--- a/packages/tailwindcss/src/ast.ts
+++ b/packages/tailwindcss/src/ast.ts
@@ -137,39 +137,54 @@ export function walk(
     }
 
     path.push(node)
+    let replacedNode = false
+    let replacedNodeOffset = 0
     let status =
       visit(node, {
         parent,
         context,
         path,
         replaceWith(newNode) {
+          replacedNode = true
+
           if (Array.isArray(newNode)) {
             if (newNode.length === 0) {
               ast.splice(i, 1)
+              replacedNodeOffset = 0
             } else if (newNode.length === 1) {
               ast[i] = newNode[0]
+              replacedNodeOffset = 1
             } else {
               ast.splice(i, 1, ...newNode)
+              replacedNodeOffset = newNode.length
             }
           } else {
             ast[i] = newNode
+            replacedNodeOffset = 1
           }
-
-          // We want to visit the newly replaced node(s), which start at the
-          // current index (i). By decrementing the index here, the next loop
-          // will process this position (containing the replaced node) again.
-          i--
         },
       }) ?? WalkAction.Continue
     path.pop()
 
+    // We want to visit or skip the newly replaced node(s), which start at the
+    // current index (i). By decrementing the index here, the next loop will
+    // process this position (containing the replaced node) again.
+    if (replacedNode) {
+      if (status === WalkAction.Continue) {
+        i--
+      } else {
+        i += replacedNodeOffset - 1
+      }
+      continue
+    }
+
     // Stop the walk entirely
     if (status === WalkAction.Stop) return WalkAction.Stop
 
     // Skip visiting the children of this node
     if (status === WalkAction.Skip) continue
 
-    if (node.kind === 'rule' || node.kind === 'at-rule') {
+    if ('nodes' in node) {
       path.push(node)
       let result = walk(node.nodes, visit, path, context)
       path.pop()
diff --git a/packages/tailwindcss/src/at-import.test.ts b/packages/tailwindcss/src/at-import.test.ts
index 108498216d9a..07922e83a44a 100644
--- a/packages/tailwindcss/src/at-import.test.ts
+++ b/packages/tailwindcss/src/at-import.test.ts
@@ -586,3 +586,35 @@ test('resolves @reference as `@import "…" reference`', async () => {
     "
   `)
 })
+
+test('resolves `@variant` used as `@custom-variant` inside `@reference`', async () => {
+  let loadStylesheet = async (id: string, base: string) => {
+    expect(base).toBe('/root')
+    expect(id).toBe('./foo/bar.css')
+    return {
+      content: css`
+        @variant dark {
+          &:where([data-theme='dark'] *) {
+            @slot;
+          }
+        }
+      `,
+      base: '/root/foo',
+    }
+  }
+
+  await expect(
+    run(
+      css`
+        @reference './foo/bar.css';
+        @tailwind utilities;
+      `,
+      { loadStylesheet, candidates: ['dark:flex'] },
+    ),
+  ).resolves.toMatchInlineSnapshot(`
+    ".dark\\:flex:where([data-theme="dark"] *) {
+      display: flex;
+    }
+    "
+  `)
+})
diff --git a/packages/tailwindcss/src/compat/selector-parser.ts b/packages/tailwindcss/src/compat/selector-parser.ts
index f62e0aed4cec..341f9b581379 100644
--- a/packages/tailwindcss/src/compat/selector-parser.ts
+++ b/packages/tailwindcss/src/compat/selector-parser.ts
@@ -92,29 +92,44 @@ export function walk(
 ) {
   for (let i = 0; i < ast.length; i++) {
     let node = ast[i]
+    let replacedNode = false
+    let replacedNodeOffset = 0
     let status =
       visit(node, {
         parent,
         replaceWith(newNode) {
+          replacedNode = true
+
           if (Array.isArray(newNode)) {
             if (newNode.length === 0) {
               ast.splice(i, 1)
+              replacedNodeOffset = 0
             } else if (newNode.length === 1) {
               ast[i] = newNode[0]
+              replacedNodeOffset = 1
             } else {
               ast.splice(i, 1, ...newNode)
+              replacedNodeOffset = newNode.length
             }
           } else {
             ast[i] = newNode
+            replacedNodeOffset = 1
           }
-
-          // We want to visit the newly replaced node(s), which start at the
-          // current index (i). By decrementing the index here, the next loop
-          // will process this position (containing the replaced node) again.
-          i--
         },
       }) ?? SelectorWalkAction.Continue
 
+    // We want to visit or skip the newly replaced node(s), which start at the
+    // current index (i). By decrementing the index here, the next loop will
+    // process this position (containing the replaced node) again.
+    if (replacedNode) {
+      if (status === SelectorWalkAction.Continue) {
+        i--
+      } else {
+        i += replacedNodeOffset - 1
+      }
+      continue
+    }
+
     // Stop the walk entirely
     if (status === SelectorWalkAction.Stop) return SelectorWalkAction.Stop
 
diff --git a/packages/tailwindcss/src/index.ts b/packages/tailwindcss/src/index.ts
index 37c19a3f3edf..14bcee2fe104 100644
--- a/packages/tailwindcss/src/index.ts
+++ b/packages/tailwindcss/src/index.ts
@@ -433,15 +433,6 @@ async function parseCss(
       } else if (params.length > 0) {
         replaceWith(node.nodes)
       }
-
-      walk(node.nodes, (node) => {
-        if (node.kind !== 'at-rule') return
-        if (node.name !== '@variant') return
-
-        variantNodes.push(node)
-      })
-
-      return WalkAction.Skip
     }
 
     // Handle `@theme`
diff --git a/packages/tailwindcss/src/value-parser.ts b/packages/tailwindcss/src/value-parser.ts
index 80a7827b2e8a..dda1a7d80ab7 100644
--- a/packages/tailwindcss/src/value-parser.ts
+++ b/packages/tailwindcss/src/value-parser.ts
@@ -63,29 +63,43 @@ export function walk(
 ) {
   for (let i = 0; i < ast.length; i++) {
     let node = ast[i]
+    let replacedNode = false
+    let replacedNodeOffset = 0
     let status =
       visit(node, {
         parent,
         replaceWith(newNode) {
+          replacedNode = true
+
           if (Array.isArray(newNode)) {
             if (newNode.length === 0) {
               ast.splice(i, 1)
+              replacedNodeOffset = 0
             } else if (newNode.length === 1) {
               ast[i] = newNode[0]
+              replacedNodeOffset = 1
             } else {
               ast.splice(i, 1, ...newNode)
+              replacedNodeOffset = newNode.length
             }
           } else {
             ast[i] = newNode
           }
-
-          // We want to visit the newly replaced node(s), which start at the
-          // current index (i). By decrementing the index here, the next loop
-          // will process this position (containing the replaced node) again.
-          i--
         },
       }) ?? ValueWalkAction.Continue
 
+    // We want to visit or skip the newly replaced node(s), which start at the
+    // current index (i). By decrementing the index here, the next loop will
+    // process this position (containing the replaced node) again.
+    if (replacedNode) {
+      if (status === ValueWalkAction.Continue) {
+        i--
+      } else {
+        i += replacedNodeOffset - 1
+      }
+      continue
+    }
+
     // Stop the walk entirely
     if (status === ValueWalkAction.Stop) return ValueWalkAction.Stop