From d6d904b048ba780a774c929c08643be49955cbf4 Mon Sep 17 00:00:00 2001
From: Romain Menke <romainmenke@gmail.com>
Date: Sat, 29 Nov 2025 09:14:16 +0100
Subject: [PATCH 1/2] css-syntax-patches-for-csstree: patch overflow-*

---
 .../CHANGELOG.md                              |  5 ++
 .../dist/index.json                           |  4 ++
 .../webref-over-csstree-properties.json       | 72 +++++++++++++++++++
 .../webref-over-csstree-properties.json       | 24 +++++++
 .../raw-data/webref-properties.json           |  8 +--
 .../scripts/generate-webref-sets.mjs          |  9 +++
 6 files changed, 118 insertions(+), 4 deletions(-)

diff --git a/packages/css-syntax-patches-for-csstree/CHANGELOG.md b/packages/css-syntax-patches-for-csstree/CHANGELOG.md
index 0ea390f059..d705a53816 100644
--- a/packages/css-syntax-patches-for-csstree/CHANGELOG.md
+++ b/packages/css-syntax-patches-for-csstree/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changes to CSS Syntax Patches For CSSTree
 
+### Unreleased (patch)
+
+- Patch `overflow-*` to include `<-non-standard-overflow>`
+
+
 ### 1.0.19
 
 _November 26, 2025_
diff --git a/packages/css-syntax-patches-for-csstree/dist/index.json b/packages/css-syntax-patches-for-csstree/dist/index.json
index 82f478eb0d..bfb9e9dea5 100644
--- a/packages/css-syntax-patches-for-csstree/dist/index.json
+++ b/packages/css-syntax-patches-for-csstree/dist/index.json
@@ -339,6 +339,7 @@
 			"outline-color": "auto | <'border-top-color'>",
 			"outline-style": "auto | none | dotted | dashed | solid | double | groove | ridge | inset | outset",
 			"overflow": "<'overflow-block'>{1,2} | <-non-standard-overflow>",
+			"overflow-block": "| <-non-standard-overflow>",
 			"overflow-clip-margin-block": "<visual-box> || <length [0,∞]>",
 			"overflow-clip-margin-block-end": "<visual-box> || <length [0,∞]>",
 			"overflow-clip-margin-block-start": "<visual-box> || <length [0,∞]>",
@@ -349,6 +350,9 @@
 			"overflow-clip-margin-left": "<visual-box> || <length [0,∞]>",
 			"overflow-clip-margin-right": "<visual-box> || <length [0,∞]>",
 			"overflow-clip-margin-top": "<visual-box> || <length [0,∞]>",
+			"overflow-inline": "| <-non-standard-overflow>",
+			"overflow-x": "| <-non-standard-overflow>",
+			"overflow-y": "| <-non-standard-overflow>",
 			"padding": "<'padding-top'>{1,4}",
 			"padding-block": "<'padding-top'>{1,2}",
 			"padding-block-end": "<'padding-top'>",
diff --git a/packages/css-syntax-patches-for-csstree/patches/webref-over-csstree-properties.json b/packages/css-syntax-patches-for-csstree/patches/webref-over-csstree-properties.json
index 306b0f9880..e1baf5e9ce 100644
--- a/packages/css-syntax-patches-for-csstree/patches/webref-over-csstree-properties.json
+++ b/packages/css-syntax-patches-for-csstree/patches/webref-over-csstree-properties.json
@@ -4027,6 +4027,24 @@
 			"failing": []
 		}
 	},
+	"overflow-block": {
+		"type": "modified",
+		"comment": "",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"syntax-m": "| <-non-standard-overflow>",
+		"tests": {
+			"passing": [
+				{
+					"value": "visible"
+				},
+				{
+					"value": "overlay"
+				}
+			],
+			"failing": []
+		}
+	},
 	"overflow-clip-margin-block": {
 		"type": "added",
 		"comment": "",
@@ -4137,6 +4155,60 @@
 			"failing": []
 		}
 	},
+	"overflow-inline": {
+		"type": "modified",
+		"comment": "",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"syntax-m": "| <-non-standard-overflow>",
+		"tests": {
+			"passing": [
+				{
+					"value": "visible"
+				},
+				{
+					"value": "overlay"
+				}
+			],
+			"failing": []
+		}
+	},
+	"overflow-x": {
+		"type": "modified",
+		"comment": "",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"syntax-m": "| <-non-standard-overflow>",
+		"tests": {
+			"passing": [
+				{
+					"value": "visible"
+				},
+				{
+					"value": "overlay"
+				}
+			],
+			"failing": []
+		}
+	},
+	"overflow-y": {
+		"type": "modified",
+		"comment": "",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"syntax-m": "| <-non-standard-overflow>",
+		"tests": {
+			"passing": [
+				{
+					"value": "visible"
+				},
+				{
+					"value": "overlay"
+				}
+			],
+			"failing": []
+		}
+	},
 	"padding": {
 		"type": "modified",
 		"comment": "",
diff --git a/packages/css-syntax-patches-for-csstree/raw-data/webref-over-csstree-properties.json b/packages/css-syntax-patches-for-csstree/raw-data/webref-over-csstree-properties.json
index ff9063afe7..970a044b5f 100644
--- a/packages/css-syntax-patches-for-csstree/raw-data/webref-over-csstree-properties.json
+++ b/packages/css-syntax-patches-for-csstree/raw-data/webref-over-csstree-properties.json
@@ -1751,6 +1751,12 @@
 		"syntax-a": "<'overflow-block'>{1,2}",
 		"comment": ""
 	},
+	"overflow-block": {
+		"type": "modified",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"comment": ""
+	},
 	"overflow-clip-margin-block": {
 		"type": "added",
 		"syntax-b": "",
@@ -1811,6 +1817,24 @@
 		"syntax-a": "<visual-box> || <length [0,∞]>",
 		"comment": ""
 	},
+	"overflow-inline": {
+		"type": "modified",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"comment": ""
+	},
+	"overflow-x": {
+		"type": "modified",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"comment": ""
+	},
+	"overflow-y": {
+		"type": "modified",
+		"syntax-b": "visible | hidden | clip | scroll | auto",
+		"syntax-a": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>",
+		"comment": ""
+	},
 	"padding": {
 		"type": "modified",
 		"syntax-b": "[ <length> | <percentage> ]{1,4}",
diff --git a/packages/css-syntax-patches-for-csstree/raw-data/webref-properties.json b/packages/css-syntax-patches-for-csstree/raw-data/webref-properties.json
index 2821d4751e..d2902de72c 100644
--- a/packages/css-syntax-patches-for-csstree/raw-data/webref-properties.json
+++ b/packages/css-syntax-patches-for-csstree/raw-data/webref-properties.json
@@ -1650,7 +1650,7 @@
 		"syntax": "auto | none"
 	},
 	"overflow-block": {
-		"syntax": "visible | hidden | clip | scroll | auto"
+		"syntax": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>"
 	},
 	"overflow-clip-box": {
 		"syntax": "padding-box | content-box"
@@ -1689,7 +1689,7 @@
 		"syntax": "<visual-box> || <length [0,∞]>"
 	},
 	"overflow-inline": {
-		"syntax": "visible | hidden | clip | scroll | auto"
+		"syntax": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>"
 	},
 	"-webkit-overflow-scrolling": {
 		"syntax": "auto | touch"
@@ -1701,10 +1701,10 @@
 		"syntax": "normal | break-word | anywhere"
 	},
 	"overflow-x": {
-		"syntax": "visible | hidden | clip | scroll | auto"
+		"syntax": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>"
 	},
 	"overflow-y": {
-		"syntax": "visible | hidden | clip | scroll | auto"
+		"syntax": "visible | hidden | clip | scroll | auto | <-non-standard-overflow>"
 	},
 	"overlay": {
 		"syntax": "none | auto"
diff --git a/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs b/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
index 9b659ad94d..2936ea2ad3 100644
--- a/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
+++ b/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
@@ -112,6 +112,15 @@ export async function generate_webref_sets() {
 			property.syntax = 'rect( <top> , <right> , <bottom> , <left> ) | rect( <top> <right> <bottom> <left> ) | auto';
 		}
 
+		if ((
+			property.name === 'overflow-x' ||
+			property.name === 'overflow-y' ||
+			property.name === 'overflow-inline' ||
+			property.name === 'overflow-block'
+		) && property.syntax === 'visible | hidden | clip | scroll | auto') {
+			property.syntax = '| <-non-standard-overflow>';
+		}
+
 		if (!property.syntax) {
 			continue;
 		}

From 83899c7fa64aad9d26da3e489a143c507bdb0373 Mon Sep 17 00:00:00 2001
From: Romain Menke <romainmenke@gmail.com>
Date: Sat, 29 Nov 2025 09:21:55 +0100
Subject: [PATCH 2/2] docs

---
 .../scripts/generate-webref-sets.mjs                             | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs b/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
index 2936ea2ad3..55d57bed1e 100644
--- a/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
+++ b/packages/css-syntax-patches-for-csstree/scripts/generate-webref-sets.mjs
@@ -112,6 +112,7 @@ export async function generate_webref_sets() {
 			property.syntax = 'rect( <top> , <right> , <bottom> , <left> ) | rect( <top> <right> <bottom> <left> ) | auto';
 		}
 
+		// https://github.com/csstree/csstree/pull/354
 		if ((
 			property.name === 'overflow-x' ||
 			property.name === 'overflow-y' ||