From 9eb50418034ae2e467b076c22755eb0b0b96efe4 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Fri, 15 Aug 2025 18:39:46 -0500
Subject: [PATCH 01/30] Remove support for IE conditional scripts and styles

Returns false if conditional scripts or styles are identified; updates comments; removes files that were only loaded conditionally.
---
 Gruntfile.js                                 |   1 -
 src/js/_enqueues/vendor/json2.js             | 519 -------------------
 src/wp-includes/class-wp-scripts.php         |  37 +-
 src/wp-includes/class-wp-styles.php          |  17 +-
 src/wp-includes/css/wp-embed-template-ie.css |  19 -
 src/wp-includes/embed.php                    |   1 -
 src/wp-includes/functions.wp-scripts.php     |   3 +-
 src/wp-includes/functions.wp-styles.php      |   5 +-
 src/wp-includes/script-loader.php            |  13 +-
 tests/phpunit/tests/dependencies/scripts.php |  25 +-
 tests/phpunit/tests/dependencies/styles.php  |   1 -
 11 files changed, 29 insertions(+), 612 deletions(-)
 delete mode 100644 src/js/_enqueues/vendor/json2.js
 delete mode 100644 src/wp-includes/css/wp-embed-template-ie.css

diff --git a/Gruntfile.js b/Gruntfile.js
index a577b0711dacb..1844a9574df3a 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -644,7 +644,6 @@ module.exports = function(grunt) {
 					// Exceptions.
 					'!wp-includes/css/dashicons.css',
 					'!wp-includes/css/wp-embed-template.css',
-					'!wp-includes/css/wp-embed-template-ie.css'
 				]
 			},
 			colors: {
diff --git a/src/js/_enqueues/vendor/json2.js b/src/js/_enqueues/vendor/json2.js
deleted file mode 100644
index 7f685256288f8..0000000000000
--- a/src/js/_enqueues/vendor/json2.js
+++ /dev/null
@@ -1,519 +0,0 @@
-/*
-    json2.js
-    2015-05-03
-
-    Public Domain.
-
-    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
-
-    See http://www.JSON.org/js.html
-
-
-    This code should be minified before deployment.
-    See http://javascript.crockford.com/jsmin.html
-
-    USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
-    NOT CONTROL.
-
-
-    This file creates a global JSON object containing two methods: stringify
-    and parse. This file is provides the ES5 JSON capability to ES3 systems.
-    If a project might run on IE8 or earlier, then this file should be included.
-    This file does nothing on ES5 systems.
-
-        JSON.stringify(value, replacer, space)
-            value       any JavaScript value, usually an object or array.
-
-            replacer    an optional parameter that determines how object
-                        values are stringified for objects. It can be a
-                        function or an array of strings.
-
-            space       an optional parameter that specifies the indentation
-                        of nested structures. If it is omitted, the text will
-                        be packed without extra whitespace. If it is a number,
-                        it will specify the number of spaces to indent at each
-                        level. If it is a string (such as '\t' or '&nbsp;'),
-                        it contains the characters used to indent at each level.
-
-            This method produces a JSON text from a JavaScript value.
-
-            When an object value is found, if the object contains a toJSON
-            method, its toJSON method will be called and the result will be
-            stringified. A toJSON method does not serialize: it returns the
-            value represented by the name/value pair that should be serialized,
-            or undefined if nothing should be serialized. The toJSON method
-            will be passed the key associated with the value, and this will be
-            bound to the value
-
-            For example, this would serialize Dates as ISO strings.
-
-                Date.prototype.toJSON = function (key) {
-                    function f(n) {
-                        // Format integers to have at least two digits.
-                        return n < 10 
-                            ? '0' + n 
-                            : n;
-                    }
-
-                    return this.getUTCFullYear()   + '-' +
-                         f(this.getUTCMonth() + 1) + '-' +
-                         f(this.getUTCDate())      + 'T' +
-                         f(this.getUTCHours())     + ':' +
-                         f(this.getUTCMinutes())   + ':' +
-                         f(this.getUTCSeconds())   + 'Z';
-                };
-
-            You can provide an optional replacer method. It will be passed the
-            key and value of each member, with this bound to the containing
-            object. The value that is returned from your method will be
-            serialized. If your method returns undefined, then the member will
-            be excluded from the serialization.
-
-            If the replacer parameter is an array of strings, then it will be
-            used to select the members to be serialized. It filters the results
-            such that only members with keys listed in the replacer array are
-            stringified.
-
-            Values that do not have JSON representations, such as undefined or
-            functions, will not be serialized. Such values in objects will be
-            dropped; in arrays they will be replaced with null. You can use
-            a replacer function to replace those with JSON values.
-            JSON.stringify(undefined) returns undefined.
-
-            The optional space parameter produces a stringification of the
-            value that is filled with line breaks and indentation to make it
-            easier to read.
-
-            If the space parameter is a non-empty string, then that string will
-            be used for indentation. If the space parameter is a number, then
-            the indentation will be that many spaces.
-
-            Example:
-
-            text = JSON.stringify(['e', {pluribus: 'unum'}]);
-            // text is '["e",{"pluribus":"unum"}]'
-
-
-            text = JSON.stringify(['e', {pluribus: 'unum'}], null, '\t');
-            // text is '[\n\t"e",\n\t{\n\t\t"pluribus": "unum"\n\t}\n]'
-
-            text = JSON.stringify([new Date()], function (key, value) {
-                return this[key] instanceof Date 
-                    ? 'Date(' + this[key] + ')' 
-                    : value;
-            });
-            // text is '["Date(---current time---)"]'
-
-
-        JSON.parse(text, reviver)
-            This method parses a JSON text to produce an object or array.
-            It can throw a SyntaxError exception.
-
-            The optional reviver parameter is a function that can filter and
-            transform the results. It receives each of the keys and values,
-            and its return value is used instead of the original value.
-            If it returns what it received, then the structure is not modified.
-            If it returns undefined then the member is deleted.
-
-            Example:
-
-            // Parse the text. Values that look like ISO date strings will
-            // be converted to Date objects.
-
-            myData = JSON.parse(text, function (key, value) {
-                var a;
-                if (typeof value === 'string') {
-                    a =
-/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
-                    if (a) {
-                        return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
-                            +a[5], +a[6]));
-                    }
-                }
-                return value;
-            });
-
-            myData = JSON.parse('["Date(09/09/2001)"]', function (key, value) {
-                var d;
-                if (typeof value === 'string' &&
-                        value.slice(0, 5) === 'Date(' &&
-                        value.slice(-1) === ')') {
-                    d = new Date(value.slice(5, -1));
-                    if (d) {
-                        return d;
-                    }
-                }
-                return value;
-            });
-
-
-    This is a reference implementation. You are free to copy, modify, or
-    redistribute.
-*/
-
-/*jslint 
-    eval, for, this 
-*/
-
-/*property
-    JSON, apply, call, charCodeAt, getUTCDate, getUTCFullYear, getUTCHours,
-    getUTCMinutes, getUTCMonth, getUTCSeconds, hasOwnProperty, join,
-    lastIndex, length, parse, prototype, push, replace, slice, stringify,
-    test, toJSON, toString, valueOf
-*/
-
-
-// Create a JSON object only if one does not already exist. We create the
-// methods in a closure to avoid creating global variables.
-
-if (typeof JSON !== 'object') {
-    JSON = {};
-}
-
-(function () {
-    'use strict';
-    
-    var rx_one = /^[\],:{}\s]*$/,
-        rx_two = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g,
-        rx_three = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g,
-        rx_four = /(?:^|:|,)(?:\s*\[)+/g,
-        rx_escapable = /[\\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,
-        rx_dangerous = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
-
-    function f(n) {
-        // Format integers to have at least two digits.
-        return n < 10 
-            ? '0' + n 
-            : n;
-    }
-    
-    function this_value() {
-        return this.valueOf();
-    }
-
-    if (typeof Date.prototype.toJSON !== 'function') {
-
-        Date.prototype.toJSON = function () {
-
-            return isFinite(this.valueOf())
-                ? this.getUTCFullYear() + '-' +
-                        f(this.getUTCMonth() + 1) + '-' +
-                        f(this.getUTCDate()) + 'T' +
-                        f(this.getUTCHours()) + ':' +
-                        f(this.getUTCMinutes()) + ':' +
-                        f(this.getUTCSeconds()) + 'Z'
-                : null;
-        };
-
-        Boolean.prototype.toJSON = this_value;
-        Number.prototype.toJSON = this_value;
-        String.prototype.toJSON = this_value;
-    }
-
-    var gap,
-        indent,
-        meta,
-        rep;
-
-
-    function quote(string) {
-
-// If the string contains no control characters, no quote characters, and no
-// backslash characters, then we can safely slap some quotes around it.
-// Otherwise we must also replace the offending characters with safe escape
-// sequences.
-
-        rx_escapable.lastIndex = 0;
-        return rx_escapable.test(string) 
-            ? '"' + string.replace(rx_escapable, function (a) {
-                var c = meta[a];
-                return typeof c === 'string'
-                    ? c
-                    : '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
-            }) + '"' 
-            : '"' + string + '"';
-    }
-
-
-    function str(key, holder) {
-
-// Produce a string from holder[key].
-
-        var i,          // The loop counter.
-            k,          // The member key.
-            v,          // The member value.
-            length,
-            mind = gap,
-            partial,
-            value = holder[key];
-
-// If the value has a toJSON method, call it to obtain a replacement value.
-
-        if (value && typeof value === 'object' &&
-                typeof value.toJSON === 'function') {
-            value = value.toJSON(key);
-        }
-
-// If we were called with a replacer function, then call the replacer to
-// obtain a replacement value.
-
-        if (typeof rep === 'function') {
-            value = rep.call(holder, key, value);
-        }
-
-// What happens next depends on the value's type.
-
-        switch (typeof value) {
-        case 'string':
-            return quote(value);
-
-        case 'number':
-
-// JSON numbers must be finite. Encode non-finite numbers as null.
-
-            return isFinite(value) 
-                ? String(value) 
-                : 'null';
-
-        case 'boolean':
-        case 'null':
-
-// If the value is a boolean or null, convert it to a string. Note:
-// typeof null does not produce 'null'. The case is included here in
-// the remote chance that this gets fixed someday.
-
-            return String(value);
-
-// If the type is 'object', we might be dealing with an object or an array or
-// null.
-
-        case 'object':
-
-// Due to a specification blunder in ECMAScript, typeof null is 'object',
-// so watch out for that case.
-
-            if (!value) {
-                return 'null';
-            }
-
-// Make an array to hold the partial results of stringifying this object value.
-
-            gap += indent;
-            partial = [];
-
-// Is the value an array?
-
-            if (Object.prototype.toString.apply(value) === '[object Array]') {
-
-// The value is an array. Stringify every element. Use null as a placeholder
-// for non-JSON values.
-
-                length = value.length;
-                for (i = 0; i < length; i += 1) {
-                    partial[i] = str(i, value) || 'null';
-                }
-
-// Join all of the elements together, separated with commas, and wrap them in
-// brackets.
-
-                v = partial.length === 0
-                    ? '[]'
-                    : gap
-                        ? '[\n' + gap + partial.join(',\n' + gap) + '\n' + mind + ']'
-                        : '[' + partial.join(',') + ']';
-                gap = mind;
-                return v;
-            }
-
-// If the replacer is an array, use it to select the members to be stringified.
-
-            if (rep && typeof rep === 'object') {
-                length = rep.length;
-                for (i = 0; i < length; i += 1) {
-                    if (typeof rep[i] === 'string') {
-                        k = rep[i];
-                        v = str(k, value);
-                        if (v) {
-                            partial.push(quote(k) + (
-                                gap 
-                                    ? ': ' 
-                                    : ':'
-                            ) + v);
-                        }
-                    }
-                }
-            } else {
-
-// Otherwise, iterate through all of the keys in the object.
-
-                for (k in value) {
-                    if (Object.prototype.hasOwnProperty.call(value, k)) {
-                        v = str(k, value);
-                        if (v) {
-                            partial.push(quote(k) + (
-                                gap 
-                                    ? ': ' 
-                                    : ':'
-                            ) + v);
-                        }
-                    }
-                }
-            }
-
-// Join all of the member texts together, separated with commas,
-// and wrap them in braces.
-
-            v = partial.length === 0
-                ? '{}'
-                : gap
-                    ? '{\n' + gap + partial.join(',\n' + gap) + '\n' + mind + '}'
-                    : '{' + partial.join(',') + '}';
-            gap = mind;
-            return v;
-        }
-    }
-
-// If the JSON object does not yet have a stringify method, give it one.
-
-    if (typeof JSON.stringify !== 'function') {
-        meta = {    // table of character substitutions
-            '\b': '\\b',
-            '\t': '\\t',
-            '\n': '\\n',
-            '\f': '\\f',
-            '\r': '\\r',
-            '"': '\\"',
-            '\\': '\\\\'
-        };
-        JSON.stringify = function (value, replacer, space) {
-
-// The stringify method takes a value and an optional replacer, and an optional
-// space parameter, and returns a JSON text. The replacer can be a function
-// that can replace values, or an array of strings that will select the keys.
-// A default replacer method can be provided. Use of the space parameter can
-// produce text that is more easily readable.
-
-            var i;
-            gap = '';
-            indent = '';
-
-// If the space parameter is a number, make an indent string containing that
-// many spaces.
-
-            if (typeof space === 'number') {
-                for (i = 0; i < space; i += 1) {
-                    indent += ' ';
-                }
-
-// If the space parameter is a string, it will be used as the indent string.
-
-            } else if (typeof space === 'string') {
-                indent = space;
-            }
-
-// If there is a replacer, it must be a function or an array.
-// Otherwise, throw an error.
-
-            rep = replacer;
-            if (replacer && typeof replacer !== 'function' &&
-                    (typeof replacer !== 'object' ||
-                    typeof replacer.length !== 'number')) {
-                throw new Error('JSON.stringify');
-            }
-
-// Make a fake root object containing our value under the key of ''.
-// Return the result of stringifying the value.
-
-            return str('', {'': value});
-        };
-    }
-
-
-// If the JSON object does not yet have a parse method, give it one.
-
-    if (typeof JSON.parse !== 'function') {
-        JSON.parse = function (text, reviver) {
-
-// The parse method takes a text and an optional reviver function, and returns
-// a JavaScript value if the text is a valid JSON text.
-
-            var j;
-
-            function walk(holder, key) {
-
-// The walk method is used to recursively walk the resulting structure so
-// that modifications can be made.
-
-                var k, v, value = holder[key];
-                if (value && typeof value === 'object') {
-                    for (k in value) {
-                        if (Object.prototype.hasOwnProperty.call(value, k)) {
-                            v = walk(value, k);
-                            if (v !== undefined) {
-                                value[k] = v;
-                            } else {
-                                delete value[k];
-                            }
-                        }
-                    }
-                }
-                return reviver.call(holder, key, value);
-            }
-
-
-// Parsing happens in four stages. In the first stage, we replace certain
-// Unicode characters with escape sequences. JavaScript handles many characters
-// incorrectly, either silently deleting them, or treating them as line endings.
-
-            text = String(text);
-            rx_dangerous.lastIndex = 0;
-            if (rx_dangerous.test(text)) {
-                text = text.replace(rx_dangerous, function (a) {
-                    return '\\u' +
-                            ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
-                });
-            }
-
-// In the second stage, we run the text against regular expressions that look
-// for non-JSON patterns. We are especially concerned with '()' and 'new'
-// because they can cause invocation, and '=' because it can cause mutation.
-// But just to be safe, we want to reject all unexpected forms.
-
-// We split the second stage into 4 regexp operations in order to work around
-// crippling inefficiencies in IE's and Safari's regexp engines. First we
-// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
-// replace all simple value tokens with ']' characters. Third, we delete all
-// open brackets that follow a colon or comma or that begin the text. Finally,
-// we look to see that the remaining characters are only whitespace or ']' or
-// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
-
-            if (
-                rx_one.test(
-                    text
-                        .replace(rx_two, '@')
-                        .replace(rx_three, ']')
-                        .replace(rx_four, '')
-                )
-            ) {
-
-// In the third stage we use the eval function to compile the text into a
-// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
-// in JavaScript: it can begin a block or an object literal. We wrap the text
-// in parens to eliminate the ambiguity.
-
-                j = eval('(' + text + ')');
-
-// In the optional fourth stage, we recursively walk the new structure, passing
-// each name/value pair to a reviver function for possible transformation.
-
-                return typeof reviver === 'function'
-                    ? walk({'': j}, '')
-                    : j;
-            }
-
-// If the text is not JSON parseable, then a SyntaxError is thrown.
-
-            throw new SyntaxError('JSON.parse');
-        };
-    }
-}());
\ No newline at end of file
diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index 77dff94c0497a..94801b8b220e0 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -289,12 +289,14 @@ public function do_item( $handle, $group = false ) {
 			$ver = $ver ? $ver . '&amp;' . $this->args[ $handle ] : $this->args[ $handle ];
 		}
 
-		$src                   = $obj->src;
-		$strategy              = $this->get_eligible_loading_strategy( $handle );
-		$intended_strategy     = (string) $this->get_data( $handle, 'strategy' );
-		$ie_conditional_prefix = '';
-		$ie_conditional_suffix = '';
-		$conditional           = isset( $obj->extra['conditional'] ) ? $obj->extra['conditional'] : '';
+		$src               = $obj->src;
+		$strategy          = $this->get_eligible_loading_strategy( $handle );
+		$intended_strategy = (string) $this->get_data( $handle, 'strategy' );
+		$conditional       = isset( $obj->extra['conditional'] ) ? true : false;
+		if ( $conditional ) {
+
+			return false;
+		}
 
 		if ( ! $this->is_delayed_strategy( $intended_strategy ) ) {
 			$intended_strategy = '';
@@ -319,16 +321,11 @@ public function do_item( $handle, $group = false ) {
 			return false;
 		}
 
-		if ( $conditional ) {
-			$ie_conditional_prefix = "<!--[if {$conditional}]>\n";
-			$ie_conditional_suffix = "<![endif]-->\n";
-		}
-
 		$before_script = $this->get_inline_script_tag( $handle, 'before' );
 		$after_script  = $this->get_inline_script_tag( $handle, 'after' );
 
 		if ( $before_script || $after_script ) {
-			$inline_script_tag = $ie_conditional_prefix . $before_script . $after_script . $ie_conditional_suffix;
+			$inline_script_tag = $before_script . $after_script;
 		} else {
 			$inline_script_tag = '';
 		}
@@ -364,7 +361,7 @@ public function do_item( $handle, $group = false ) {
 				// Have to print the so-far concatenated scripts right away to maintain the right order.
 				_print_scripts();
 				$this->reset();
-			} elseif ( $this->in_default_dir( $filtered_src ) && ! $conditional ) {
+			} elseif ( $this->in_default_dir( $filtered_src ) ) {
 				$this->print_code     .= $this->print_extra_script( $handle, false );
 				$this->concat         .= "$handle,";
 				$this->concat_version .= "$handle$ver";
@@ -375,18 +372,8 @@ public function do_item( $handle, $group = false ) {
 			}
 		}
 
-		$has_conditional_data = $conditional && $this->get_data( $handle, 'data' );
-
-		if ( $has_conditional_data ) {
-			echo $ie_conditional_prefix;
-		}
-
 		$this->print_extra_script( $handle );
 
-		if ( $has_conditional_data ) {
-			echo $ie_conditional_suffix;
-		}
-
 		// A single item may alias a set of items, by having dependencies, but no source.
 		if ( ! $src ) {
 			if ( $inline_script_tag ) {
@@ -425,9 +412,9 @@ public function do_item( $handle, $group = false ) {
 		if ( $intended_strategy ) {
 			$attr['data-wp-strategy'] = $intended_strategy;
 		}
-		$tag  = $translations . $ie_conditional_prefix . $before_script;
+		$tag  = $translations . $before_script;
 		$tag .= wp_get_script_tag( $attr );
-		$tag .= $after_script . $ie_conditional_suffix;
+		$tag .= $after_script;
 
 		/**
 		 * Filters the HTML script tag of an enqueued script.
diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index e64378be5fc8d..a046260cf5b00 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -165,14 +165,11 @@ public function do_item( $handle, $group = false ) {
 			$ver = $ver ? $ver . '&amp;' . $this->args[ $handle ] : $this->args[ $handle ];
 		}
 
-		$src                   = $obj->src;
-		$ie_conditional_prefix = '';
-		$ie_conditional_suffix = '';
-		$conditional           = isset( $obj->extra['conditional'] ) ? $obj->extra['conditional'] : '';
-
+		$src         = $obj->src;
+		$conditional = isset( $obj->extra['conditional'] ) ? true : false;
 		if ( $conditional ) {
-			$ie_conditional_prefix = "<!--[if {$conditional}]>\n";
-			$ie_conditional_suffix = "<![endif]-->\n";
+
+			return false;
 		}
 
 		$inline_style = $this->print_inline_style( $handle, false );
@@ -189,7 +186,7 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		if ( $this->do_concat ) {
-			if ( $this->in_default_dir( $src ) && ! $conditional && ! isset( $obj->extra['alt'] ) ) {
+			if ( $this->in_default_dir( $src ) && ! isset( $obj->extra['alt'] ) ) {
 				$this->concat         .= "$handle,";
 				$this->concat_version .= "$handle$ver";
 
@@ -279,17 +276,13 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		if ( $this->do_concat ) {
-			$this->print_html .= $ie_conditional_prefix;
 			$this->print_html .= $tag;
 			if ( $inline_style_tag ) {
 				$this->print_html .= $inline_style_tag;
 			}
-			$this->print_html .= $ie_conditional_suffix;
 		} else {
-			echo $ie_conditional_prefix;
 			echo $tag;
 			$this->print_inline_style( $handle );
-			echo $ie_conditional_suffix;
 		}
 
 		return true;
diff --git a/src/wp-includes/css/wp-embed-template-ie.css b/src/wp-includes/css/wp-embed-template-ie.css
deleted file mode 100644
index cec05c9eeb1f8..0000000000000
--- a/src/wp-includes/css/wp-embed-template-ie.css
+++ /dev/null
@@ -1,19 +0,0 @@
-.dashicons-no {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAQAAAAngNWGAAAAcElEQVR4AdXRVxmEMBAGwJMQCUhAIhKQECmRsFJwMFfp7HfP/E8pk0173CuKpt/0R+WaBaaZqogLagBMuh+DdoKbyRCwqZ/SnM0R5oQuZ2UHS8Z6k23qPxZCTrV5UlHMi8bsfHVXP7K/GXZHaTO7S54CWLdHlN2YIwAAAABJRU5ErkJggg==);
-}
-
-.dashicons-admin-comments {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAATUlEQVR4AWMYWqCpvUcAiA8A8X9iMFStAD4DG0AKScQNVDZw1MBRAwvIMLCA5jmFlCD4AMQGlOTtBgoNwzQQ3TCKDaTcMMxYN2AYVgAAYPKsEBxN0PIAAAAASUVORK5CYII=);
-}
-
-.wp-embed-comments a:hover .dashicons-admin-comments {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAATElEQVR4AWMYYqB4lQAQHwDi/8RgqFoBfAY2gBSSiBuobOCogaMGFpBhYAEdcwrhIPgAxAaU5O0GCg3DNBDdMIoNpNwwzFg3YBhWAABG71qAFYcFqgAAAABJRU5ErkJggg==);
-}
-
-.dashicons-share {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAc0lEQVR4AWMYfqCpvccAiBcA8X8gfgDEBZQaeAFkGBoOoMR1/7HgDeQa2ECZgQiDHID4AMwAor0MCmBoQP+HBnwAskFQdgBRkQJViGk7wiAHUr21AYdhDTA1dDOQHl6mPFLokmwoT9j0z3qUFw70L77oDwAiuzCIub1XpQAAAABJRU5ErkJggg==);
-}
-
-.wp-embed-share-dialog-open:hover .dashicons-share {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAc0lEQVR4AWMYhqB4lQEQLwDi/0D8AIgLKDXwAsgwNBxAiev+Y8EbyDWwgTIDEQY5APEBmAFEexkUwNCA/g8N+ABkg6DsAKIiBaoQ03aEQQ6kemsDDsMaYEroZiA9vEx5pNAl2VCesOmf9SgvHOhffNEfAAAMqPR5IEZH5wAAAABJRU5ErkJggg==);
-}
diff --git a/src/wp-includes/embed.php b/src/wp-includes/embed.php
index 6ef190d0ea600..9d66a4abd85d4 100644
--- a/src/wp-includes/embed.php
+++ b/src/wp-includes/embed.php
@@ -1055,7 +1055,6 @@ function wp_embed_excerpt_attachment( $content ) {
  * @since 4.4.0
  */
 function enqueue_embed_scripts() {
-	wp_enqueue_style( 'wp-embed-template-ie' );
 
 	/**
 	 * Fires when scripts and styles are enqueued for the embed iframe.
diff --git a/src/wp-includes/functions.wp-scripts.php b/src/wp-includes/functions.wp-scripts.php
index 1be1822aa7c3d..bda3e05e8db13 100644
--- a/src/wp-includes/functions.wp-scripts.php
+++ b/src/wp-includes/functions.wp-scripts.php
@@ -425,9 +425,10 @@ function wp_script_is( $handle, $status = 'enqueued' ) {
  * Works only if the script has already been registered.
  *
  * Possible values for $key and $value:
- * 'conditional' string Comments for IE 6, lte IE 7, etc.
+ * 'strategy' string 'defer' or 'async'.
  *
  * @since 4.2.0
+ * @since 6.9.0 Updated possible values to remove reference to 'conditional' and add 'strategy'.
  *
  * @see WP_Dependencies::add_data()
  *
diff --git a/src/wp-includes/functions.wp-styles.php b/src/wp-includes/functions.wp-styles.php
index ad5f574dd84c0..f84b931866818 100644
--- a/src/wp-includes/functions.wp-styles.php
+++ b/src/wp-includes/functions.wp-styles.php
@@ -220,7 +220,6 @@ function wp_style_is( $handle, $status = 'enqueued' ) {
  * Works only if the stylesheet has already been registered.
  *
  * Possible values for $key and $value:
- * 'conditional' string      Comments for IE 6, lte IE 7 etc.
  * 'rtl'         bool|string To declare an RTL stylesheet.
  * 'suffix'      string      Optional suffix, used in combination with RTL.
  * 'alt'         bool        For rel="alternate stylesheet".
@@ -233,10 +232,12 @@ function wp_style_is( $handle, $status = 'enqueued' ) {
  * @since 3.6.0
  * @since 5.8.0 Added 'path' as an official value for $key.
  *              See {@see wp_maybe_inline_styles()}.
+ * @since 6.9.0 'conditional' value changed. If the 'conditional' parameter is present
+ *              the stylesheet will be ignored.
  *
  * @param string $handle Name of the stylesheet.
  * @param string $key    Name of data point for which we're storing a value.
- *                       Accepts 'conditional', 'rtl' and 'suffix', 'alt', 'title' and 'path'.
+ *                       Accepts 'rtl' and 'suffix', 'alt', 'title' and 'path'.
  * @param mixed  $value  String containing the CSS data to be added.
  * @return bool True on success, false on failure.
  */
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 54193c841c7c3..e34a13f017829 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -1041,15 +1041,12 @@ function wp_default_scripts( $scripts ) {
 	$scripts->add( 'plupload-handlers', "/wp-includes/js/plupload/handlers$suffix.js", array( 'clipboard', 'jquery', 'plupload', 'underscore', 'wp-a11y', 'wp-i18n' ) );
 	did_action( 'init' ) && $scripts->localize( 'plupload-handlers', 'pluploadL10n', $uploader_l10n );
 
-	$scripts->add( 'wp-plupload', "/wp-includes/js/plupload/wp-plupload$suffix.js", array( 'plupload', 'jquery', 'json2', 'media-models' ), false, 1 );
+	$scripts->add( 'wp-plupload', "/wp-includes/js/plupload/wp-plupload$suffix.js", array( 'plupload', 'jquery', 'media-models' ), false, 1 );
 	did_action( 'init' ) && $scripts->localize( 'wp-plupload', 'pluploadL10n', $uploader_l10n );
 
 	$scripts->add( 'comment-reply', "/wp-includes/js/comment-reply$suffix.js", array(), false, 1 );
 	did_action( 'init' ) && $scripts->add_data( 'comment-reply', 'strategy', 'async' );
 
-	$scripts->add( 'json2', "/wp-includes/js/json2$suffix.js", array(), '2015-05-03' );
-	did_action( 'init' ) && $scripts->add_data( 'json2', 'conditional', 'lt IE 8' );
-
 	$scripts->add( 'underscore', "/wp-includes/js/underscore$dev_suffix.js", array(), '1.13.7', 1 );
 	$scripts->add( 'backbone', "/wp-includes/js/backbone$dev_suffix.js", array( 'underscore', 'jquery' ), '1.6.0', 1 );
 
@@ -1278,7 +1275,7 @@ function wp_default_scripts( $scripts ) {
 	// JS-only version of hoverintent (no dependencies).
 	$scripts->add( 'hoverintent-js', '/wp-includes/js/hoverintent-js.min.js', array(), '2.2.1', 1 );
 
-	$scripts->add( 'customize-base', "/wp-includes/js/customize-base$suffix.js", array( 'jquery', 'json2', 'underscore' ), false, 1 );
+	$scripts->add( 'customize-base', "/wp-includes/js/customize-base$suffix.js", array( 'jquery', 'underscore' ), false, 1 );
 	$scripts->add( 'customize-loader', "/wp-includes/js/customize-loader$suffix.js", array( 'customize-base' ), false, 1 );
 	$scripts->add( 'customize-preview', "/wp-includes/js/customize-preview$suffix.js", array( 'wp-a11y', 'customize-base' ), false, 1 );
 	$scripts->add( 'customize-models', '/wp-includes/js/customize-models.js', array( 'underscore', 'backbone' ), false, 1 );
@@ -1498,7 +1495,7 @@ function wp_default_scripts( $scripts ) {
 		$scripts->add( 'media', "/wp-admin/js/media$suffix.js", array( 'jquery', 'clipboard', 'wp-i18n', 'wp-a11y' ), false, 1 );
 		$scripts->set_translations( 'media' );
 
-		$scripts->add( 'image-edit', "/wp-admin/js/image-edit$suffix.js", array( 'jquery', 'jquery-ui-core', 'json2', 'imgareaselect', 'wp-a11y' ), false, 1 );
+		$scripts->add( 'image-edit', "/wp-admin/js/image-edit$suffix.js", array( 'jquery', 'jquery-ui-core', 'imgareaselect', 'wp-a11y' ), false, 1 );
 		$scripts->set_translations( 'image-edit' );
 
 		$scripts->add( 'set-post-thumbnail', "/wp-admin/js/set-post-thumbnail$suffix.js", array( 'jquery' ), false, 1 );
@@ -1508,7 +1505,7 @@ function wp_default_scripts( $scripts ) {
 		 * Navigation Menus: Adding underscore as a dependency to utilize _.debounce
 		 * see https://core.trac.wordpress.org/ticket/42321
 		 */
-		$scripts->add( 'nav-menu', "/wp-admin/js/nav-menu$suffix.js", array( 'jquery-ui-sortable', 'jquery-ui-draggable', 'jquery-ui-droppable', 'wp-lists', 'postbox', 'json2', 'underscore' ) );
+		$scripts->add( 'nav-menu', "/wp-admin/js/nav-menu$suffix.js", array( 'jquery-ui-sortable', 'jquery-ui-draggable', 'jquery-ui-droppable', 'wp-lists', 'postbox', 'underscore' ) );
 		$scripts->set_translations( 'nav-menu' );
 
 		$scripts->add( 'custom-header', '/wp-admin/js/custom-header.js', array( 'jquery-masonry' ), false, 1 );
@@ -1640,9 +1637,7 @@ function wp_default_styles( $styles ) {
 	$styles->add( 'media-views', "/wp-includes/css/media-views$suffix.css", array( 'buttons', 'dashicons', 'wp-mediaelement' ) );
 	$styles->add( 'wp-pointer', "/wp-includes/css/wp-pointer$suffix.css", array( 'dashicons' ) );
 	$styles->add( 'customize-preview', "/wp-includes/css/customize-preview$suffix.css", array( 'dashicons' ) );
-	$styles->add( 'wp-embed-template-ie', "/wp-includes/css/wp-embed-template-ie$suffix.css" );
 	$styles->add( 'wp-empty-template-alert', "/wp-includes/css/wp-empty-template-alert$suffix.css" );
-	$styles->add_data( 'wp-embed-template-ie', 'conditional', 'lte IE 8' );
 
 	// External libraries and friends.
 	$styles->add( 'imgareaselect', '/wp-includes/js/imgareaselect/imgareaselect.css', array(), '0.9.8' );
diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index d00c77b5a1f6c..c2f22a2d771e7 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1630,6 +1630,8 @@ public function test_wp_script_add_data_with_data_key() {
 
 	/**
 	 * Testing `wp_script_add_data` with the conditional key.
+	 * 
+	 * @since 6.9.0 Conditional comments should now return an empty string.
 	 *
 	 * @ticket 16024
 	 */
@@ -1637,28 +1639,7 @@ public function test_wp_script_add_data_with_conditional_key() {
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
-		$expected = "<!--[if gt IE 7]>\n<script type=\"text/javascript\" src=\"http://example.com\" id=\"test-only-conditional-js\"></script>\n<![endif]-->\n";
-
-		// Go!
-		$this->assertEqualHTML( $expected, get_echo( 'wp_print_scripts' ) );
-
-		// No scripts left to print.
-		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );
-	}
-
-	/**
-	 * Testing `wp_script_add_data` with both the data & conditional keys.
-	 *
-	 * @ticket 16024
-	 */
-	public function test_wp_script_add_data_with_data_and_conditional_keys() {
-		// Enqueue and add data plus conditional comments for both.
-		wp_enqueue_script( 'test-conditional-with-data', 'example.com', array(), null );
-		wp_script_add_data( 'test-conditional-with-data', 'data', 'testing' );
-		wp_script_add_data( 'test-conditional-with-data', 'conditional', 'lt IE 9' );
-		$expected  = "<!--[if lt IE 9]>\n<script type='text/javascript' id='test-conditional-with-data-js-extra'>\n/* <![CDATA[ */\ntesting\n/* ]]> */\n</script>\n<![endif]-->\n";
-		$expected .= "<!--[if lt IE 9]>\n<script type='text/javascript' src='http://example.com' id='test-conditional-with-data-js'></script>\n<![endif]-->\n";
-		$expected  = str_replace( "'", '"', $expected );
+		$expected = '';
 
 		// Go!
 		$this->assertEqualHTML( $expected, get_echo( 'wp_print_scripts' ) );
diff --git a/tests/phpunit/tests/dependencies/styles.php b/tests/phpunit/tests/dependencies/styles.php
index 9cb6283c488d5..1a1757b88a050 100644
--- a/tests/phpunit/tests/dependencies/styles.php
+++ b/tests/phpunit/tests/dependencies/styles.php
@@ -337,7 +337,6 @@ public function test_conditional_inline_styles_are_also_conditional() {
 
 CSS;
 		wp_enqueue_style( 'handle', 'http://example.com', array(), 1 );
-		wp_style_add_data( 'handle', 'conditional', 'IE' );
 		wp_add_inline_style( 'handle', 'a { color: blue; }' );
 
 		$this->assertSameIgnoreEOL( $expected, get_echo( 'wp_print_styles' ) );

From caf0887fa068bd441d11c94af7f9ec6155a41e6b Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Fri, 15 Aug 2025 18:42:10 -0500
Subject: [PATCH 02/30] Update scripts.php

---
 tests/phpunit/tests/dependencies/scripts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index c2f22a2d771e7..4d7c3253494d5 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1630,7 +1630,7 @@ public function test_wp_script_add_data_with_data_key() {
 
 	/**
 	 * Testing `wp_script_add_data` with the conditional key.
-	 * 
+	 *
 	 * @since 6.9.0 Conditional comments should now return an empty string.
 	 *
 	 * @ticket 16024

From 1bd20aea1bc19578fb510bbf598d2c0e66b0b8f5 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 18 Aug 2025 10:12:27 -0500
Subject: [PATCH 03/30] Update tests to expect empty results for conditional
 scripts and their dependencies.

---
 tests/phpunit/tests/dependencies/scripts.php | 33 ++++++--------------
 1 file changed, 10 insertions(+), 23 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 4d7c3253494d5..91e8212242b64 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -2055,6 +2055,7 @@ public function test_wp_add_inline_script_after_with_concat() {
 
 	/**
 	 * @ticket 14853
+	 * @ticket 63821
 	 */
 	public function test_wp_add_inline_script_after_and_before_with_concat_and_conditional() {
 		global $wp_scripts;
@@ -2062,17 +2063,9 @@ public function test_wp_add_inline_script_after_and_before_with_concat_and_condi
 		$wp_scripts->do_concat    = true;
 		$wp_scripts->default_dirs = array( '/wp-admin/js/', '/wp-includes/js/' ); // Default dirs as in wp-includes/script-loader.php.
 
-		$expected_localized  = "<!--[if gte IE 9]>\n";
-		$expected_localized .= "<script type='text/javascript' id='test-example-js-extra'>\n/* <![CDATA[ */\nvar testExample = {\"foo\":\"bar\"};\n/* ]]> */\n</script>\n";
-		$expected_localized .= "<![endif]-->\n";
-		$expected_localized  = str_replace( "'", '"', $expected_localized );
-
-		$expected  = "<!--[if gte IE 9]>\n";
-		$expected .= "<script type='text/javascript' id='test-example-js-before'>\n/* <![CDATA[ */\nconsole.log(\"before\");\n/* ]]> */\n</script>\n";
-		$expected .= "<script type='text/javascript' src='http://example.com' id='test-example-js'></script>\n";
-		$expected .= "<script type='text/javascript' id='test-example-js-after'>\n/* <![CDATA[ */\nconsole.log(\"after\");\n/* ]]> */\n</script>\n";
-		$expected .= "<![endif]-->\n";
-		$expected  = str_replace( "'", '"', $expected );
+		// Conditional scripts should not output.
+		$expected_localized = '';
+		$expected           = '';
 
 		wp_enqueue_script( 'test-example', 'example.com', array(), null );
 		wp_localize_script( 'test-example', 'testExample', array( 'foo' => 'bar' ) );
@@ -2111,20 +2104,16 @@ public function test_wp_add_inline_script_after_with_concat_and_core_dependency(
 
 	/**
 	 * @ticket 36392
+	 * @ticket 63821
 	 */
 	public function test_wp_add_inline_script_after_with_concat_and_conditional_and_core_dependency() {
-		global $wp_scripts, $wp_version;
+		global $wp_scripts;
 
 		wp_default_scripts( $wp_scripts );
 
 		$wp_scripts->base_url  = '';
 		$wp_scripts->do_concat = true;
-
-		$expected  = "<script type='text/javascript' src='/wp-admin/load-scripts.php?c=0&amp;load%5Bchunk_0%5D=jquery-core,jquery-migrate&amp;ver={$wp_version}'></script>\n";
-		$expected .= "<!--[if gte IE 9]>\n";
-		$expected .= "<script type=\"text/javascript\" src=\"http://example.com\" id=\"test-example-js\"></script>\n";
-		$expected .= "<script type=\"text/javascript\" id=\"test-example-js-after\">\n/* <![CDATA[ */\nconsole.log(\"after\");\n/* ]]> */\n</script>\n";
-		$expected .= "<![endif]-->\n";
+		$expected              = '';
 
 		wp_enqueue_script( 'test-example', 'http://example.com', array( 'jquery' ), null );
 		wp_add_inline_script( 'test-example', 'console.log("after");' );
@@ -2138,19 +2127,17 @@ public function test_wp_add_inline_script_after_with_concat_and_conditional_and_
 
 	/**
 	 * @ticket 36392
+	 * @ticket 63821
 	 */
 	public function test_wp_add_inline_script_before_with_concat_and_core_dependency() {
-		global $wp_scripts, $wp_version;
+		global $wp_scripts;
 
 		wp_default_scripts( $wp_scripts );
 		wp_default_packages( $wp_scripts );
 
 		$wp_scripts->base_url  = '';
 		$wp_scripts->do_concat = true;
-
-		$expected  = "<script type='text/javascript' src='/wp-admin/load-scripts.php?c=0&amp;load%5Bchunk_0%5D=jquery-core,jquery-migrate&amp;ver={$wp_version}'></script>\n";
-		$expected .= "<script type='text/javascript' id='test-example-js-before'>\n/* <![CDATA[ */\nconsole.log(\"before\");\n/* ]]> */\n</script>\n";
-		$expected .= "<script type='text/javascript' src='http://example.com' id='test-example-js'></script>\n";
+		$expected              = '';
 
 		wp_enqueue_script( 'test-example', 'http://example.com', array( 'jquery' ), null );
 		wp_add_inline_script( 'test-example', 'console.log("before");', 'before' );

From e4d171790fad2b2628187c081f311a10e3496899 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 18 Aug 2025 13:55:50 -0500
Subject: [PATCH 04/30] Update conditional inline styles test

---
 tests/phpunit/tests/dependencies/styles.php | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/styles.php b/tests/phpunit/tests/dependencies/styles.php
index 1a1757b88a050..33696991f0d03 100644
--- a/tests/phpunit/tests/dependencies/styles.php
+++ b/tests/phpunit/tests/dependencies/styles.php
@@ -327,16 +327,9 @@ public function test_unnecessary_style_tags() {
 	 * stylesheets are also conditional.
 	 */
 	public function test_conditional_inline_styles_are_also_conditional() {
-		$expected = <<<CSS
-<!--[if IE]>
-<link rel='stylesheet' id='handle-css' href='http://example.com?ver=1' type='text/css' media='all' />
-<style id='handle-inline-css' type='text/css'>
-a { color: blue; }
-</style>
-<![endif]-->
-
-CSS;
+		$expected = '';
 		wp_enqueue_style( 'handle', 'http://example.com', array(), 1 );
+		wp_style_add_data( 'handle', 'conditional', 'IE' );
 		wp_add_inline_style( 'handle', 'a { color: blue; }' );
 
 		$this->assertSameIgnoreEOL( $expected, get_echo( 'wp_print_styles' ) );

From 5fb72b7ebbe51698908ff81f0af58932f946cfa5 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 18 Aug 2025 14:34:49 -0500
Subject: [PATCH 05/30] Unset dependencies for conditional scripts.

Prevent dependencies from being added when only required by a conditional script or style.
---
 src/wp-includes/class-wp-scripts.php |  4 ++++
 src/wp-includes/class-wp-styles.php  | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index 94801b8b220e0..46e8b62ca0bcf 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -792,6 +792,10 @@ public function add_data( $handle, $key, $value ) {
 			return false;
 		}
 
+		if ( 'conditional' === $key ) {
+			$this->registered[ $handle ]->deps = array();
+		}
+
 		if ( 'strategy' === $key ) {
 			if ( ! empty( $value ) && ! $this->is_delayed_strategy( $value ) ) {
 				_doing_it_wrong(
diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index a046260cf5b00..6a3e179ecce7b 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -346,6 +346,28 @@ public function print_inline_style( $handle, $display = true ) {
 		return true;
 	}
 
+	/**
+	 * Overrides the add_data method from WP_Dependencies, to allow unsetting dependencies for conditional styles.
+	 *
+	 * @since 6.9.0
+	 *
+	 * @param string $handle Name of the item. Should be unique.
+	 * @param string $key    The data key.
+	 * @param mixed  $value  The data value.
+	 * @return bool True on success, false on failure.
+	 */
+	public function add_data( $handle, $key, $value ) {
+		if ( ! isset( $this->registered[ $handle ] ) ) {
+			return false;
+		}
+
+		if ( 'conditional' === $key ) {
+			$this->registered[ $handle ]->deps = array();
+		}
+
+		return $this->registered[ $handle ]->add_data( $key, $value );
+	}
+
 	/**
 	 * Determines style dependencies.
 	 *

From 22fe20cfeddd3ef9494281840dbf046952fe58b4 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Tue, 19 Aug 2025 18:41:09 -0500
Subject: [PATCH 06/30] Restore concat_and_core_dependency test

Accidentally changed this one, but it's not a conditional test.
---
 tests/phpunit/tests/dependencies/scripts.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 91e8212242b64..29076cb4dd925 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -2130,14 +2130,17 @@ public function test_wp_add_inline_script_after_with_concat_and_conditional_and_
 	 * @ticket 63821
 	 */
 	public function test_wp_add_inline_script_before_with_concat_and_core_dependency() {
-		global $wp_scripts;
+		global $wp_scripts, $wp_version;
 
 		wp_default_scripts( $wp_scripts );
 		wp_default_packages( $wp_scripts );
 
 		$wp_scripts->base_url  = '';
 		$wp_scripts->do_concat = true;
-		$expected              = '';
+
+		$expected  = "<script type='text/javascript' src='/wp-admin/load-scripts.php?c=0&amp;load%5Bchunk_0%5D=jquery-core,jquery-migrate&amp;ver={$wp_version}'></script>\n";
+		$expected .= "<script type='text/javascript' id='test-example-js-before'>\n/* <![CDATA[ */\nconsole.log(\"before\");\n/* ]]> */\n</script>\n";
+		$expected .= "<script type='text/javascript' src='http://example.com' id='test-example-js'></script>\n";
 
 		wp_enqueue_script( 'test-example', 'http://example.com', array( 'jquery' ), null );
 		wp_add_inline_script( 'test-example', 'console.log("before");', 'before' );

From f2011cdc95a9369a5e6e865e2e004b8593a97ff3 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Tue, 19 Aug 2025 18:41:43 -0500
Subject: [PATCH 07/30] Remove ticket ref

---
 tests/phpunit/tests/dependencies/scripts.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 29076cb4dd925..541d028518f92 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -2127,7 +2127,6 @@ public function test_wp_add_inline_script_after_with_concat_and_conditional_and_
 
 	/**
 	 * @ticket 36392
-	 * @ticket 63821
 	 */
 	public function test_wp_add_inline_script_before_with_concat_and_core_dependency() {
 		global $wp_scripts, $wp_version;

From f4b1ccb7f6b2396743693d111976da1035ab46d9 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 21 Aug 2025 17:57:19 -0500
Subject: [PATCH 08/30] Update src/wp-includes/class-wp-scripts.php

Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>
---
 src/wp-includes/class-wp-scripts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index 46e8b62ca0bcf..c42c0255d0960 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -292,7 +292,7 @@ public function do_item( $handle, $group = false ) {
 		$src               = $obj->src;
 		$strategy          = $this->get_eligible_loading_strategy( $handle );
 		$intended_strategy = (string) $this->get_data( $handle, 'strategy' );
-		$conditional       = isset( $obj->extra['conditional'] ) ? true : false;
+		$conditional       = (bool) ( $obj->extra['conditional'] ?? false );
 		if ( $conditional ) {
 
 			return false;

From 69b243aed724afe8dfd78c5a13b12bf3c4f2bf77 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 21 Aug 2025 17:57:26 -0500
Subject: [PATCH 09/30] Update src/wp-includes/class-wp-styles.php

Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>
---
 src/wp-includes/class-wp-styles.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index 6a3e179ecce7b..72645d6a3e89d 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -166,7 +166,7 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		$src         = $obj->src;
-		$conditional = isset( $obj->extra['conditional'] ) ? true : false;
+		$conditional = (bool) ( $obj->extra['conditional'] ?? false );
 		if ( $conditional ) {
 
 			return false;

From b0cfbc8846450472affd8aa385f9382b8cfe85fd Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 21 Aug 2025 17:57:34 -0500
Subject: [PATCH 10/30] Update tests/phpunit/tests/dependencies/scripts.php

Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>
---
 tests/phpunit/tests/dependencies/scripts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 541d028518f92..5c0b0e4a788cb 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1638,7 +1638,7 @@ public function test_wp_script_add_data_with_data_key() {
 	public function test_wp_script_add_data_with_conditional_key() {
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
-		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
+		$this->assertFalse( wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' ) );
 		$expected = '';
 
 		// Go!

From 9d5da03276a0220cd2d123225195e09156efc7d6 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 21 Aug 2025 17:57:41 -0500
Subject: [PATCH 11/30] Update tests/phpunit/tests/dependencies/scripts.php

Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>
---
 tests/phpunit/tests/dependencies/scripts.php | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 5c0b0e4a788cb..d1e37939e0546 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1639,10 +1639,9 @@ public function test_wp_script_add_data_with_conditional_key() {
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		$this->assertFalse( wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' ) );
-		$expected = '';
 
-		// Go!
-		$this->assertEqualHTML( $expected, get_echo( 'wp_print_scripts' ) );
+// Go!
+$this->assertEqualHTML( '', get_echo( 'wp_print_scripts' ) );
 
 		// No scripts left to print.
 		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );

From 141b5bc63dd936a9077e72ea2077f053ce459e73 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 21 Aug 2025 18:03:58 -0500
Subject: [PATCH 12/30] Move dependency exits earlier per suggestion

---
 src/wp-includes/class-wp-scripts.php |  8 ++++----
 src/wp-includes/class-wp-styles.php  | 11 ++++-------
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index c42c0255d0960..5e776baf7c13e 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -278,6 +278,10 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		$obj = $this->registered[ $handle ];
+		if ( $obj->extra['conditional'] ?? false ) {
+
+			return false;
+		}
 
 		if ( null === $obj->ver ) {
 			$ver = '';
@@ -292,11 +296,7 @@ public function do_item( $handle, $group = false ) {
 		$src               = $obj->src;
 		$strategy          = $this->get_eligible_loading_strategy( $handle );
 		$intended_strategy = (string) $this->get_data( $handle, 'strategy' );
-		$conditional       = (bool) ( $obj->extra['conditional'] ?? false );
-		if ( $conditional ) {
 
-			return false;
-		}
 
 		if ( ! $this->is_delayed_strategy( $intended_strategy ) ) {
 			$intended_strategy = '';
diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index 72645d6a3e89d..8d247072bcc0d 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -154,7 +154,10 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		$obj = $this->registered[ $handle ];
+		if ( $obj->extra['conditional'] ?? false ) {
 
+			return false;
+		}
 		if ( null === $obj->ver ) {
 			$ver = '';
 		} else {
@@ -165,13 +168,7 @@ public function do_item( $handle, $group = false ) {
 			$ver = $ver ? $ver . '&amp;' . $this->args[ $handle ] : $this->args[ $handle ];
 		}
 
-		$src         = $obj->src;
-		$conditional = (bool) ( $obj->extra['conditional'] ?? false );
-		if ( $conditional ) {
-
-			return false;
-		}
-
+		$src          = $obj->src;
 		$inline_style = $this->print_inline_style( $handle, false );
 
 		if ( $inline_style ) {

From 0df6ba1d2c2987caa668584846a4b4d3f8c28ee9 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Fri, 22 Aug 2025 18:54:20 -0500
Subject: [PATCH 13/30] Code style

---
 src/wp-includes/class-wp-scripts.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index 5e776baf7c13e..337c98004ce0f 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -297,7 +297,6 @@ public function do_item( $handle, $group = false ) {
 		$strategy          = $this->get_eligible_loading_strategy( $handle );
 		$intended_strategy = (string) $this->get_data( $handle, 'strategy' );
 
-
 		if ( ! $this->is_delayed_strategy( $intended_strategy ) ) {
 			$intended_strategy = '';
 		}

From 64f11e10c0437ebab628c7e92b17ae9798c7ee8b Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Fri, 22 Aug 2025 18:54:34 -0500
Subject: [PATCH 14/30] Fix test_wp_script_add_data_with_conditional_key

---
 tests/phpunit/tests/dependencies/scripts.php | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index d1e37939e0546..5b3c9ad96169a 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1638,11 +1638,8 @@ public function test_wp_script_add_data_with_data_key() {
 	public function test_wp_script_add_data_with_conditional_key() {
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
-		$this->assertFalse( wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' ) );
-
-// Go!
-$this->assertEqualHTML( '', get_echo( 'wp_print_scripts' ) );
-
+		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
+		
 		// No scripts left to print.
 		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );
 	}

From ede759b106ebf3049168921f0c0fcb78e9246d41 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 1 Sep 2025 15:00:28 -0500
Subject: [PATCH 15/30] Remove space

---
 tests/phpunit/tests/dependencies/scripts.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 5b3c9ad96169a..f18ae5106cd6a 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1639,7 +1639,6 @@ public function test_wp_script_add_data_with_conditional_key() {
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
-		
 		// No scripts left to print.
 		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );
 	}

From 383493413bea7cd7b6034797c6c8dbb2b1d3bee3 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 1 Sep 2025 15:04:26 -0500
Subject: [PATCH 16/30] Add comment about removal of conditional dependencies

---
 src/wp-includes/class-wp-scripts.php | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index 337c98004ce0f..fd45fb9e8bda9 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -792,6 +792,7 @@ public function add_data( $handle, $key, $value ) {
 		}
 
 		if ( 'conditional' === $key ) {
+			// If a dependency is declared by a conditional script, remove it.
 			$this->registered[ $handle ]->deps = array();
 		}
 

From 1b5181a499295e49dbd768abd145f2be06de9fb1 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 1 Sep 2025 15:07:40 -0500
Subject: [PATCH 17/30] Add a deprecated argument for conditional keys

---
 src/wp-includes/class-wp-dependencies.php | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/wp-includes/class-wp-dependencies.php b/src/wp-includes/class-wp-dependencies.php
index ef9dfa7d5fd49..05b3d6d69ebd0 100644
--- a/src/wp-includes/class-wp-dependencies.php
+++ b/src/wp-includes/class-wp-dependencies.php
@@ -289,6 +289,14 @@ public function add_data( $handle, $key, $value ) {
 		if ( ! isset( $this->registered[ $handle ] ) ) {
 			return false;
 		}
+		if ( 'conditional' === $key ) {
+			_deprecated_argument(
+				'WP_Dependencies->add_data()',
+				'6.9.0',
+				/* translators: 1: WPLANG, 2: wp-config.php */
+				sprintf( __( 'The %1$s argument is no longer supported for inline scripts or styles.' ), 'conditional' )
+			);
+		}
 
 		return $this->registered[ $handle ]->add_data( $key, $value );
 	}

From d083a48e36abd1fa7075f09ac4fb871ed4934616 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 1 Sep 2025 15:47:32 -0500
Subject: [PATCH 18/30] Add expect deprecation to tests.

---
 tests/phpunit/tests/dependencies/scripts.php | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index f18ae5106cd6a..cd91d32548753 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1636,6 +1636,9 @@ public function test_wp_script_add_data_with_data_key() {
 	 * @ticket 16024
 	 */
 	public function test_wp_script_add_data_with_conditional_key() {
+		$this->expectDeprecation();
+		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
+
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
@@ -2058,6 +2061,9 @@ public function test_wp_add_inline_script_after_and_before_with_concat_and_condi
 		$wp_scripts->do_concat    = true;
 		$wp_scripts->default_dirs = array( '/wp-admin/js/', '/wp-includes/js/' ); // Default dirs as in wp-includes/script-loader.php.
 
+		$this->expectDeprecation();
+		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
+
 		// Conditional scripts should not output.
 		$expected_localized = '';
 		$expected           = '';
@@ -2103,6 +2109,8 @@ public function test_wp_add_inline_script_after_with_concat_and_core_dependency(
 	 */
 	public function test_wp_add_inline_script_after_with_concat_and_conditional_and_core_dependency() {
 		global $wp_scripts;
+		$this->expectDeprecation();
+		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
 
 		wp_default_scripts( $wp_scripts );
 

From ab365f1a753b3085b34861de95d3c0bf72541614 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Wed, 3 Sep 2025 21:58:43 -0500
Subject: [PATCH 19/30] expectDeprecation is not the appropriate method.

---
 tests/phpunit/tests/dependencies/scripts.php | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index cd91d32548753..ceb5e5dbe4d68 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1636,14 +1636,11 @@ public function test_wp_script_add_data_with_data_key() {
 	 * @ticket 16024
 	 */
 	public function test_wp_script_add_data_with_conditional_key() {
-		$this->expectDeprecation();
-		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
-
 		// Enqueue and add conditional comments.
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
 		// No scripts left to print.
-		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );
+		$this->assertSame( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.', get_echo( 'wp_print_scripts' ) );
 	}
 
 	/**
@@ -2061,12 +2058,9 @@ public function test_wp_add_inline_script_after_and_before_with_concat_and_condi
 		$wp_scripts->do_concat    = true;
 		$wp_scripts->default_dirs = array( '/wp-admin/js/', '/wp-includes/js/' ); // Default dirs as in wp-includes/script-loader.php.
 
-		$this->expectDeprecation();
-		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
-
 		// Conditional scripts should not output.
-		$expected_localized = '';
-		$expected           = '';
+		$expected_localized = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
+		$expected           = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
 
 		wp_enqueue_script( 'test-example', 'example.com', array(), null );
 		wp_localize_script( 'test-example', 'testExample', array( 'foo' => 'bar' ) );
@@ -2109,14 +2103,11 @@ public function test_wp_add_inline_script_after_with_concat_and_core_dependency(
 	 */
 	public function test_wp_add_inline_script_after_with_concat_and_conditional_and_core_dependency() {
 		global $wp_scripts;
-		$this->expectDeprecation();
-		$this->expectDeprecationMessageMatches( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.' );
-
 		wp_default_scripts( $wp_scripts );
 
 		$wp_scripts->base_url  = '';
 		$wp_scripts->do_concat = true;
-		$expected              = '';
+		$expected              = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
 
 		wp_enqueue_script( 'test-example', 'http://example.com', array( 'jquery' ), null );
 		wp_add_inline_script( 'test-example', 'console.log("after");' );

From 63dd8a7b23490fa2d4925c66a8eb63faf1d4e358 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Wed, 3 Sep 2025 22:04:37 -0500
Subject: [PATCH 20/30] Remove translator comment; this string does not require
 arguments.

---
 src/wp-includes/class-wp-dependencies.php | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/wp-includes/class-wp-dependencies.php b/src/wp-includes/class-wp-dependencies.php
index 05b3d6d69ebd0..4c8adf6041396 100644
--- a/src/wp-includes/class-wp-dependencies.php
+++ b/src/wp-includes/class-wp-dependencies.php
@@ -293,8 +293,7 @@ public function add_data( $handle, $key, $value ) {
 			_deprecated_argument(
 				'WP_Dependencies->add_data()',
 				'6.9.0',
-				/* translators: 1: WPLANG, 2: wp-config.php */
-				sprintf( __( 'The %1$s argument is no longer supported for inline scripts or styles.' ), 'conditional' )
+				__( 'The conditional argument is no longer supported for inline scripts or styles.' )
 			);
 		}
 

From 21934fd8bbc55e97a3420211e2fffa9f5c427d0a Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Wed, 3 Sep 2025 22:08:17 -0500
Subject: [PATCH 21/30] Update src/wp-includes/class-wp-styles.php

Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>
---
 src/wp-includes/class-wp-styles.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index 8d247072bcc0d..16889d2bc1abb 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -362,7 +362,7 @@ public function add_data( $handle, $key, $value ) {
 			$this->registered[ $handle ]->deps = array();
 		}
 
-		return $this->registered[ $handle ]->add_data( $key, $value );
+		return parent::add_data( $handle, $key, $value ); 
 	}
 
 	/**

From bf35196e27dd303be998e17d6042b65969808e17 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Wed, 3 Sep 2025 22:08:55 -0500
Subject: [PATCH 22/30] Update class-wp-styles.php

---
 src/wp-includes/class-wp-styles.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-styles.php b/src/wp-includes/class-wp-styles.php
index 16889d2bc1abb..65b2d4df386be 100644
--- a/src/wp-includes/class-wp-styles.php
+++ b/src/wp-includes/class-wp-styles.php
@@ -362,7 +362,7 @@ public function add_data( $handle, $key, $value ) {
 			$this->registered[ $handle ]->deps = array();
 		}
 
-		return parent::add_data( $handle, $key, $value ); 
+		return parent::add_data( $handle, $key, $value );
 	}
 
 	/**

From bcc89177b361cd47e954a64172cca04c2c4e684a Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Wed, 3 Sep 2025 22:30:07 -0500
Subject: [PATCH 23/30] Remove that.

Interestingly, this failed in a completely different way than it did before.
---
 tests/phpunit/tests/dependencies/scripts.php | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index 4be0fa75c2bec..ef7c787611f5c 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1773,7 +1773,7 @@ public function test_wp_script_add_data_with_conditional_key() {
 		wp_enqueue_script( 'test-only-conditional', 'example.com', array(), null );
 		wp_script_add_data( 'test-only-conditional', 'conditional', 'gt IE 7' );
 		// No scripts left to print.
-		$this->assertSame( 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.', get_echo( 'wp_print_scripts' ) );
+		$this->assertSame( '', get_echo( 'wp_print_scripts' ) );
 	}
 
 	/**
@@ -2192,8 +2192,8 @@ public function test_wp_add_inline_script_after_and_before_with_concat_and_condi
 		$wp_scripts->default_dirs = array( '/wp-admin/js/', '/wp-includes/js/' ); // Default dirs as in wp-includes/script-loader.php.
 
 		// Conditional scripts should not output.
-		$expected_localized = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
-		$expected           = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
+		$expected_localized = '';
+		$expected           = '';
 
 		wp_enqueue_script( 'test-example', 'example.com', array(), null );
 		wp_localize_script( 'test-example', 'testExample', array( 'foo' => 'bar' ) );
@@ -2240,7 +2240,7 @@ public function test_wp_add_inline_script_after_with_concat_and_conditional_and_
 
 		$wp_scripts->base_url  = '';
 		$wp_scripts->do_concat = true;
-		$expected              = 'Function WP_Dependencies->add_data() was called with an argument that is deprecated since version 6.9.0! The conditional argument is no longer supported for inline scripts or styles.';
+		$expected              = '';
 
 		wp_enqueue_script( 'test-example', 'http://example.com', array( 'jquery' ), null );
 		wp_add_inline_script( 'test-example', 'console.log("after");' );

From cae85c8371b000e69a974c36984100390f914264 Mon Sep 17 00:00:00 2001
From: Jon Surrell <sirreal@users.noreply.github.com>
Date: Fri, 5 Sep 2025 16:04:47 +0200
Subject: [PATCH 24/30] Add @expectedDeprecated annotation to tests

---
 tests/phpunit/tests/dependencies/scripts.php | 6 ++++++
 tests/phpunit/tests/dependencies/styles.php  | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index ef7c787611f5c..79a8fe2da6573 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1764,6 +1764,8 @@ public function test_wp_script_add_data_with_data_key() {
 	/**
 	 * Testing `wp_script_add_data` with the conditional key.
 	 *
+	 * @expectedDeprecated WP_Dependencies->add_data()
+	 *
 	 * @since 6.9.0 Conditional comments should now return an empty string.
 	 *
 	 * @ticket 16024
@@ -2182,6 +2184,8 @@ public function test_wp_add_inline_script_after_with_concat() {
 	}
 
 	/**
+	 * @expectedDeprecated WP_Dependencies->add_data()
+	 *
 	 * @ticket 14853
 	 * @ticket 63821
 	 */
@@ -2231,6 +2235,8 @@ public function test_wp_add_inline_script_after_with_concat_and_core_dependency(
 	}
 
 	/**
+	 * @expectedDeprecated WP_Dependencies->add_data()
+	 *
 	 * @ticket 36392
 	 * @ticket 63821
 	 */
diff --git a/tests/phpunit/tests/dependencies/styles.php b/tests/phpunit/tests/dependencies/styles.php
index 33696991f0d03..34a45c8b9fd5c 100644
--- a/tests/phpunit/tests/dependencies/styles.php
+++ b/tests/phpunit/tests/dependencies/styles.php
@@ -325,6 +325,8 @@ public function test_unnecessary_style_tags() {
 	/**
 	 * Test to make sure that inline styles attached to conditional
 	 * stylesheets are also conditional.
+	 *
+	 * @expectedDeprecated WP_Dependencies->add_data()
 	 */
 	public function test_conditional_inline_styles_are_also_conditional() {
 		$expected = '';

From 7e9191180ecf84f6ff57c41481b4438ec6209cda Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 29 Sep 2025 10:26:50 -0500
Subject: [PATCH 25/30] Update deprecation notice text

---
 src/wp-includes/class-wp-dependencies.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-dependencies.php b/src/wp-includes/class-wp-dependencies.php
index 4c8adf6041396..59a5b4b41b90c 100644
--- a/src/wp-includes/class-wp-dependencies.php
+++ b/src/wp-includes/class-wp-dependencies.php
@@ -293,7 +293,7 @@ public function add_data( $handle, $key, $value ) {
 			_deprecated_argument(
 				'WP_Dependencies->add_data()',
 				'6.9.0',
-				__( 'The conditional argument is no longer supported for inline scripts or styles.' )
+				__( 'IE conditional comments are ignored by all supported browsers.' )
 			);
 		}
 

From 9541e3c6f529163e076f34e648f20df95d30c518 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Mon, 29 Sep 2025 10:35:30 -0500
Subject: [PATCH 26/30] Restore json2.js, register with backward compatibility
 comment.

---
 src/js/_enqueues/vendor/json2.js  | 519 ++++++++++++++++++++++++++++++
 src/wp-includes/script-loader.php |   3 +
 2 files changed, 522 insertions(+)
 create mode 100644 src/js/_enqueues/vendor/json2.js

diff --git a/src/js/_enqueues/vendor/json2.js b/src/js/_enqueues/vendor/json2.js
new file mode 100644
index 0000000000000..7f685256288f8
--- /dev/null
+++ b/src/js/_enqueues/vendor/json2.js
@@ -0,0 +1,519 @@
+/*
+    json2.js
+    2015-05-03
+
+    Public Domain.
+
+    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
+
+    See http://www.JSON.org/js.html
+
+
+    This code should be minified before deployment.
+    See http://javascript.crockford.com/jsmin.html
+
+    USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
+    NOT CONTROL.
+
+
+    This file creates a global JSON object containing two methods: stringify
+    and parse. This file is provides the ES5 JSON capability to ES3 systems.
+    If a project might run on IE8 or earlier, then this file should be included.
+    This file does nothing on ES5 systems.
+
+        JSON.stringify(value, replacer, space)
+            value       any JavaScript value, usually an object or array.
+
+            replacer    an optional parameter that determines how object
+                        values are stringified for objects. It can be a
+                        function or an array of strings.
+
+            space       an optional parameter that specifies the indentation
+                        of nested structures. If it is omitted, the text will
+                        be packed without extra whitespace. If it is a number,
+                        it will specify the number of spaces to indent at each
+                        level. If it is a string (such as '\t' or '&nbsp;'),
+                        it contains the characters used to indent at each level.
+
+            This method produces a JSON text from a JavaScript value.
+
+            When an object value is found, if the object contains a toJSON
+            method, its toJSON method will be called and the result will be
+            stringified. A toJSON method does not serialize: it returns the
+            value represented by the name/value pair that should be serialized,
+            or undefined if nothing should be serialized. The toJSON method
+            will be passed the key associated with the value, and this will be
+            bound to the value
+
+            For example, this would serialize Dates as ISO strings.
+
+                Date.prototype.toJSON = function (key) {
+                    function f(n) {
+                        // Format integers to have at least two digits.
+                        return n < 10 
+                            ? '0' + n 
+                            : n;
+                    }
+
+                    return this.getUTCFullYear()   + '-' +
+                         f(this.getUTCMonth() + 1) + '-' +
+                         f(this.getUTCDate())      + 'T' +
+                         f(this.getUTCHours())     + ':' +
+                         f(this.getUTCMinutes())   + ':' +
+                         f(this.getUTCSeconds())   + 'Z';
+                };
+
+            You can provide an optional replacer method. It will be passed the
+            key and value of each member, with this bound to the containing
+            object. The value that is returned from your method will be
+            serialized. If your method returns undefined, then the member will
+            be excluded from the serialization.
+
+            If the replacer parameter is an array of strings, then it will be
+            used to select the members to be serialized. It filters the results
+            such that only members with keys listed in the replacer array are
+            stringified.
+
+            Values that do not have JSON representations, such as undefined or
+            functions, will not be serialized. Such values in objects will be
+            dropped; in arrays they will be replaced with null. You can use
+            a replacer function to replace those with JSON values.
+            JSON.stringify(undefined) returns undefined.
+
+            The optional space parameter produces a stringification of the
+            value that is filled with line breaks and indentation to make it
+            easier to read.
+
+            If the space parameter is a non-empty string, then that string will
+            be used for indentation. If the space parameter is a number, then
+            the indentation will be that many spaces.
+
+            Example:
+
+            text = JSON.stringify(['e', {pluribus: 'unum'}]);
+            // text is '["e",{"pluribus":"unum"}]'
+
+
+            text = JSON.stringify(['e', {pluribus: 'unum'}], null, '\t');
+            // text is '[\n\t"e",\n\t{\n\t\t"pluribus": "unum"\n\t}\n]'
+
+            text = JSON.stringify([new Date()], function (key, value) {
+                return this[key] instanceof Date 
+                    ? 'Date(' + this[key] + ')' 
+                    : value;
+            });
+            // text is '["Date(---current time---)"]'
+
+
+        JSON.parse(text, reviver)
+            This method parses a JSON text to produce an object or array.
+            It can throw a SyntaxError exception.
+
+            The optional reviver parameter is a function that can filter and
+            transform the results. It receives each of the keys and values,
+            and its return value is used instead of the original value.
+            If it returns what it received, then the structure is not modified.
+            If it returns undefined then the member is deleted.
+
+            Example:
+
+            // Parse the text. Values that look like ISO date strings will
+            // be converted to Date objects.
+
+            myData = JSON.parse(text, function (key, value) {
+                var a;
+                if (typeof value === 'string') {
+                    a =
+/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
+                    if (a) {
+                        return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
+                            +a[5], +a[6]));
+                    }
+                }
+                return value;
+            });
+
+            myData = JSON.parse('["Date(09/09/2001)"]', function (key, value) {
+                var d;
+                if (typeof value === 'string' &&
+                        value.slice(0, 5) === 'Date(' &&
+                        value.slice(-1) === ')') {
+                    d = new Date(value.slice(5, -1));
+                    if (d) {
+                        return d;
+                    }
+                }
+                return value;
+            });
+
+
+    This is a reference implementation. You are free to copy, modify, or
+    redistribute.
+*/
+
+/*jslint 
+    eval, for, this 
+*/
+
+/*property
+    JSON, apply, call, charCodeAt, getUTCDate, getUTCFullYear, getUTCHours,
+    getUTCMinutes, getUTCMonth, getUTCSeconds, hasOwnProperty, join,
+    lastIndex, length, parse, prototype, push, replace, slice, stringify,
+    test, toJSON, toString, valueOf
+*/
+
+
+// Create a JSON object only if one does not already exist. We create the
+// methods in a closure to avoid creating global variables.
+
+if (typeof JSON !== 'object') {
+    JSON = {};
+}
+
+(function () {
+    'use strict';
+    
+    var rx_one = /^[\],:{}\s]*$/,
+        rx_two = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g,
+        rx_three = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g,
+        rx_four = /(?:^|:|,)(?:\s*\[)+/g,
+        rx_escapable = /[\\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,
+        rx_dangerous = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
+
+    function f(n) {
+        // Format integers to have at least two digits.
+        return n < 10 
+            ? '0' + n 
+            : n;
+    }
+    
+    function this_value() {
+        return this.valueOf();
+    }
+
+    if (typeof Date.prototype.toJSON !== 'function') {
+
+        Date.prototype.toJSON = function () {
+
+            return isFinite(this.valueOf())
+                ? this.getUTCFullYear() + '-' +
+                        f(this.getUTCMonth() + 1) + '-' +
+                        f(this.getUTCDate()) + 'T' +
+                        f(this.getUTCHours()) + ':' +
+                        f(this.getUTCMinutes()) + ':' +
+                        f(this.getUTCSeconds()) + 'Z'
+                : null;
+        };
+
+        Boolean.prototype.toJSON = this_value;
+        Number.prototype.toJSON = this_value;
+        String.prototype.toJSON = this_value;
+    }
+
+    var gap,
+        indent,
+        meta,
+        rep;
+
+
+    function quote(string) {
+
+// If the string contains no control characters, no quote characters, and no
+// backslash characters, then we can safely slap some quotes around it.
+// Otherwise we must also replace the offending characters with safe escape
+// sequences.
+
+        rx_escapable.lastIndex = 0;
+        return rx_escapable.test(string) 
+            ? '"' + string.replace(rx_escapable, function (a) {
+                var c = meta[a];
+                return typeof c === 'string'
+                    ? c
+                    : '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
+            }) + '"' 
+            : '"' + string + '"';
+    }
+
+
+    function str(key, holder) {
+
+// Produce a string from holder[key].
+
+        var i,          // The loop counter.
+            k,          // The member key.
+            v,          // The member value.
+            length,
+            mind = gap,
+            partial,
+            value = holder[key];
+
+// If the value has a toJSON method, call it to obtain a replacement value.
+
+        if (value && typeof value === 'object' &&
+                typeof value.toJSON === 'function') {
+            value = value.toJSON(key);
+        }
+
+// If we were called with a replacer function, then call the replacer to
+// obtain a replacement value.
+
+        if (typeof rep === 'function') {
+            value = rep.call(holder, key, value);
+        }
+
+// What happens next depends on the value's type.
+
+        switch (typeof value) {
+        case 'string':
+            return quote(value);
+
+        case 'number':
+
+// JSON numbers must be finite. Encode non-finite numbers as null.
+
+            return isFinite(value) 
+                ? String(value) 
+                : 'null';
+
+        case 'boolean':
+        case 'null':
+
+// If the value is a boolean or null, convert it to a string. Note:
+// typeof null does not produce 'null'. The case is included here in
+// the remote chance that this gets fixed someday.
+
+            return String(value);
+
+// If the type is 'object', we might be dealing with an object or an array or
+// null.
+
+        case 'object':
+
+// Due to a specification blunder in ECMAScript, typeof null is 'object',
+// so watch out for that case.
+
+            if (!value) {
+                return 'null';
+            }
+
+// Make an array to hold the partial results of stringifying this object value.
+
+            gap += indent;
+            partial = [];
+
+// Is the value an array?
+
+            if (Object.prototype.toString.apply(value) === '[object Array]') {
+
+// The value is an array. Stringify every element. Use null as a placeholder
+// for non-JSON values.
+
+                length = value.length;
+                for (i = 0; i < length; i += 1) {
+                    partial[i] = str(i, value) || 'null';
+                }
+
+// Join all of the elements together, separated with commas, and wrap them in
+// brackets.
+
+                v = partial.length === 0
+                    ? '[]'
+                    : gap
+                        ? '[\n' + gap + partial.join(',\n' + gap) + '\n' + mind + ']'
+                        : '[' + partial.join(',') + ']';
+                gap = mind;
+                return v;
+            }
+
+// If the replacer is an array, use it to select the members to be stringified.
+
+            if (rep && typeof rep === 'object') {
+                length = rep.length;
+                for (i = 0; i < length; i += 1) {
+                    if (typeof rep[i] === 'string') {
+                        k = rep[i];
+                        v = str(k, value);
+                        if (v) {
+                            partial.push(quote(k) + (
+                                gap 
+                                    ? ': ' 
+                                    : ':'
+                            ) + v);
+                        }
+                    }
+                }
+            } else {
+
+// Otherwise, iterate through all of the keys in the object.
+
+                for (k in value) {
+                    if (Object.prototype.hasOwnProperty.call(value, k)) {
+                        v = str(k, value);
+                        if (v) {
+                            partial.push(quote(k) + (
+                                gap 
+                                    ? ': ' 
+                                    : ':'
+                            ) + v);
+                        }
+                    }
+                }
+            }
+
+// Join all of the member texts together, separated with commas,
+// and wrap them in braces.
+
+            v = partial.length === 0
+                ? '{}'
+                : gap
+                    ? '{\n' + gap + partial.join(',\n' + gap) + '\n' + mind + '}'
+                    : '{' + partial.join(',') + '}';
+            gap = mind;
+            return v;
+        }
+    }
+
+// If the JSON object does not yet have a stringify method, give it one.
+
+    if (typeof JSON.stringify !== 'function') {
+        meta = {    // table of character substitutions
+            '\b': '\\b',
+            '\t': '\\t',
+            '\n': '\\n',
+            '\f': '\\f',
+            '\r': '\\r',
+            '"': '\\"',
+            '\\': '\\\\'
+        };
+        JSON.stringify = function (value, replacer, space) {
+
+// The stringify method takes a value and an optional replacer, and an optional
+// space parameter, and returns a JSON text. The replacer can be a function
+// that can replace values, or an array of strings that will select the keys.
+// A default replacer method can be provided. Use of the space parameter can
+// produce text that is more easily readable.
+
+            var i;
+            gap = '';
+            indent = '';
+
+// If the space parameter is a number, make an indent string containing that
+// many spaces.
+
+            if (typeof space === 'number') {
+                for (i = 0; i < space; i += 1) {
+                    indent += ' ';
+                }
+
+// If the space parameter is a string, it will be used as the indent string.
+
+            } else if (typeof space === 'string') {
+                indent = space;
+            }
+
+// If there is a replacer, it must be a function or an array.
+// Otherwise, throw an error.
+
+            rep = replacer;
+            if (replacer && typeof replacer !== 'function' &&
+                    (typeof replacer !== 'object' ||
+                    typeof replacer.length !== 'number')) {
+                throw new Error('JSON.stringify');
+            }
+
+// Make a fake root object containing our value under the key of ''.
+// Return the result of stringifying the value.
+
+            return str('', {'': value});
+        };
+    }
+
+
+// If the JSON object does not yet have a parse method, give it one.
+
+    if (typeof JSON.parse !== 'function') {
+        JSON.parse = function (text, reviver) {
+
+// The parse method takes a text and an optional reviver function, and returns
+// a JavaScript value if the text is a valid JSON text.
+
+            var j;
+
+            function walk(holder, key) {
+
+// The walk method is used to recursively walk the resulting structure so
+// that modifications can be made.
+
+                var k, v, value = holder[key];
+                if (value && typeof value === 'object') {
+                    for (k in value) {
+                        if (Object.prototype.hasOwnProperty.call(value, k)) {
+                            v = walk(value, k);
+                            if (v !== undefined) {
+                                value[k] = v;
+                            } else {
+                                delete value[k];
+                            }
+                        }
+                    }
+                }
+                return reviver.call(holder, key, value);
+            }
+
+
+// Parsing happens in four stages. In the first stage, we replace certain
+// Unicode characters with escape sequences. JavaScript handles many characters
+// incorrectly, either silently deleting them, or treating them as line endings.
+
+            text = String(text);
+            rx_dangerous.lastIndex = 0;
+            if (rx_dangerous.test(text)) {
+                text = text.replace(rx_dangerous, function (a) {
+                    return '\\u' +
+                            ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
+                });
+            }
+
+// In the second stage, we run the text against regular expressions that look
+// for non-JSON patterns. We are especially concerned with '()' and 'new'
+// because they can cause invocation, and '=' because it can cause mutation.
+// But just to be safe, we want to reject all unexpected forms.
+
+// We split the second stage into 4 regexp operations in order to work around
+// crippling inefficiencies in IE's and Safari's regexp engines. First we
+// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
+// replace all simple value tokens with ']' characters. Third, we delete all
+// open brackets that follow a colon or comma or that begin the text. Finally,
+// we look to see that the remaining characters are only whitespace or ']' or
+// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
+
+            if (
+                rx_one.test(
+                    text
+                        .replace(rx_two, '@')
+                        .replace(rx_three, ']')
+                        .replace(rx_four, '')
+                )
+            ) {
+
+// In the third stage we use the eval function to compile the text into a
+// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
+// in JavaScript: it can begin a block or an object literal. We wrap the text
+// in parens to eliminate the ambiguity.
+
+                j = eval('(' + text + ')');
+
+// In the optional fourth stage, we recursively walk the new structure, passing
+// each name/value pair to a reviver function for possible transformation.
+
+                return typeof reviver === 'function'
+                    ? walk({'': j}, '')
+                    : j;
+            }
+
+// If the text is not JSON parseable, then a SyntaxError is thrown.
+
+            throw new SyntaxError('JSON.parse');
+        };
+    }
+}());
\ No newline at end of file
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 12923186ea5ed..f2d826d832e06 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -1052,6 +1052,9 @@ function wp_default_scripts( $scripts ) {
 		$scripts->add_data( 'comment-reply', 'fetchpriority', 'low' ); // In Chrome this is automatically low due to the async strategy, but in Firefox and Safari the priority is normal/medium.
 	}
 
+	// Not used in core, obsolete. Registered for backward compatibility.
+	$scripts->add( 'json2', "/wp-includes/js/json2$suffix.js", array(), '2015-05-03' );
+
 	$scripts->add( 'underscore', "/wp-includes/js/underscore$dev_suffix.js", array(), '1.13.7', 1 );
 	$scripts->add( 'backbone', "/wp-includes/js/backbone$dev_suffix.js", array( 'underscore', 'jquery' ), '1.6.0', 1 );
 

From 56682c325c96171bd0ef2082cc2cb8bd615efa84 Mon Sep 17 00:00:00 2001
From: Jon Surrell <sirreal@users.noreply.github.com>
Date: Thu, 2 Oct 2025 15:49:37 +0200
Subject: [PATCH 27/30] Remove extra empty line

---
 src/wp-includes/class-wp-scripts.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/wp-includes/class-wp-scripts.php b/src/wp-includes/class-wp-scripts.php
index e37592048d834..a42928d9aa262 100644
--- a/src/wp-includes/class-wp-scripts.php
+++ b/src/wp-includes/class-wp-scripts.php
@@ -293,7 +293,6 @@ public function do_item( $handle, $group = false ) {
 
 		$obj = $this->registered[ $handle ];
 		if ( $obj->extra['conditional'] ?? false ) {
-
 			return false;
 		}
 

From 681b3b6a1e9bb8f81093e8de2ff3a577442b2722 Mon Sep 17 00:00:00 2001
From: Jon Surrell <sirreal@users.noreply.github.com>
Date: Thu, 2 Oct 2025 15:54:46 +0200
Subject: [PATCH 28/30] Add bypass mechanism for doing it wrong

---
 src/wp-includes/class-wp-dependencies.php | 2 +-
 src/wp-includes/script-loader.php         | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/class-wp-dependencies.php b/src/wp-includes/class-wp-dependencies.php
index 59a5b4b41b90c..f0c1aaa371ed0 100644
--- a/src/wp-includes/class-wp-dependencies.php
+++ b/src/wp-includes/class-wp-dependencies.php
@@ -289,7 +289,7 @@ public function add_data( $handle, $key, $value ) {
 		if ( ! isset( $this->registered[ $handle ] ) ) {
 			return false;
 		}
-		if ( 'conditional' === $key ) {
+		if ( 'conditional' === $key && '_required-conditional-dependency_' !== $value ) {
 			_deprecated_argument(
 				'WP_Dependencies->add_data()',
 				'6.9.0',
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index b76fbc019d27b..040325935f3c9 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -1054,6 +1054,7 @@ function wp_default_scripts( $scripts ) {
 
 	// Not used in core, obsolete. Registered for backward compatibility.
 	$scripts->add( 'json2', "/wp-includes/js/json2$suffix.js", array(), '2015-05-03' );
+	did_action( 'init' ) && $scripts->add_data( 'json2', 'conditional', '_required-conditional-dependency_' );
 
 	$scripts->add( 'underscore', "/wp-includes/js/underscore$dev_suffix.js", array(), '1.13.7', 1 );
 	$scripts->add( 'backbone', "/wp-includes/js/backbone$dev_suffix.js", array( 'underscore', 'jquery' ), '1.6.0', 1 );

From 104c0769c6a01695554c4735a134b795e701c064 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 2 Oct 2025 17:01:01 -0500
Subject: [PATCH 29/30] Empty json2

---
 src/js/_enqueues/vendor/json2.js | 520 +------------------------------
 1 file changed, 1 insertion(+), 519 deletions(-)

diff --git a/src/js/_enqueues/vendor/json2.js b/src/js/_enqueues/vendor/json2.js
index 7f685256288f8..708252bd5915a 100644
--- a/src/js/_enqueues/vendor/json2.js
+++ b/src/js/_enqueues/vendor/json2.js
@@ -1,519 +1 @@
-/*
-    json2.js
-    2015-05-03
-
-    Public Domain.
-
-    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
-
-    See http://www.JSON.org/js.html
-
-
-    This code should be minified before deployment.
-    See http://javascript.crockford.com/jsmin.html
-
-    USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
-    NOT CONTROL.
-
-
-    This file creates a global JSON object containing two methods: stringify
-    and parse. This file is provides the ES5 JSON capability to ES3 systems.
-    If a project might run on IE8 or earlier, then this file should be included.
-    This file does nothing on ES5 systems.
-
-        JSON.stringify(value, replacer, space)
-            value       any JavaScript value, usually an object or array.
-
-            replacer    an optional parameter that determines how object
-                        values are stringified for objects. It can be a
-                        function or an array of strings.
-
-            space       an optional parameter that specifies the indentation
-                        of nested structures. If it is omitted, the text will
-                        be packed without extra whitespace. If it is a number,
-                        it will specify the number of spaces to indent at each
-                        level. If it is a string (such as '\t' or '&nbsp;'),
-                        it contains the characters used to indent at each level.
-
-            This method produces a JSON text from a JavaScript value.
-
-            When an object value is found, if the object contains a toJSON
-            method, its toJSON method will be called and the result will be
-            stringified. A toJSON method does not serialize: it returns the
-            value represented by the name/value pair that should be serialized,
-            or undefined if nothing should be serialized. The toJSON method
-            will be passed the key associated with the value, and this will be
-            bound to the value
-
-            For example, this would serialize Dates as ISO strings.
-
-                Date.prototype.toJSON = function (key) {
-                    function f(n) {
-                        // Format integers to have at least two digits.
-                        return n < 10 
-                            ? '0' + n 
-                            : n;
-                    }
-
-                    return this.getUTCFullYear()   + '-' +
-                         f(this.getUTCMonth() + 1) + '-' +
-                         f(this.getUTCDate())      + 'T' +
-                         f(this.getUTCHours())     + ':' +
-                         f(this.getUTCMinutes())   + ':' +
-                         f(this.getUTCSeconds())   + 'Z';
-                };
-
-            You can provide an optional replacer method. It will be passed the
-            key and value of each member, with this bound to the containing
-            object. The value that is returned from your method will be
-            serialized. If your method returns undefined, then the member will
-            be excluded from the serialization.
-
-            If the replacer parameter is an array of strings, then it will be
-            used to select the members to be serialized. It filters the results
-            such that only members with keys listed in the replacer array are
-            stringified.
-
-            Values that do not have JSON representations, such as undefined or
-            functions, will not be serialized. Such values in objects will be
-            dropped; in arrays they will be replaced with null. You can use
-            a replacer function to replace those with JSON values.
-            JSON.stringify(undefined) returns undefined.
-
-            The optional space parameter produces a stringification of the
-            value that is filled with line breaks and indentation to make it
-            easier to read.
-
-            If the space parameter is a non-empty string, then that string will
-            be used for indentation. If the space parameter is a number, then
-            the indentation will be that many spaces.
-
-            Example:
-
-            text = JSON.stringify(['e', {pluribus: 'unum'}]);
-            // text is '["e",{"pluribus":"unum"}]'
-
-
-            text = JSON.stringify(['e', {pluribus: 'unum'}], null, '\t');
-            // text is '[\n\t"e",\n\t{\n\t\t"pluribus": "unum"\n\t}\n]'
-
-            text = JSON.stringify([new Date()], function (key, value) {
-                return this[key] instanceof Date 
-                    ? 'Date(' + this[key] + ')' 
-                    : value;
-            });
-            // text is '["Date(---current time---)"]'
-
-
-        JSON.parse(text, reviver)
-            This method parses a JSON text to produce an object or array.
-            It can throw a SyntaxError exception.
-
-            The optional reviver parameter is a function that can filter and
-            transform the results. It receives each of the keys and values,
-            and its return value is used instead of the original value.
-            If it returns what it received, then the structure is not modified.
-            If it returns undefined then the member is deleted.
-
-            Example:
-
-            // Parse the text. Values that look like ISO date strings will
-            // be converted to Date objects.
-
-            myData = JSON.parse(text, function (key, value) {
-                var a;
-                if (typeof value === 'string') {
-                    a =
-/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
-                    if (a) {
-                        return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
-                            +a[5], +a[6]));
-                    }
-                }
-                return value;
-            });
-
-            myData = JSON.parse('["Date(09/09/2001)"]', function (key, value) {
-                var d;
-                if (typeof value === 'string' &&
-                        value.slice(0, 5) === 'Date(' &&
-                        value.slice(-1) === ')') {
-                    d = new Date(value.slice(5, -1));
-                    if (d) {
-                        return d;
-                    }
-                }
-                return value;
-            });
-
-
-    This is a reference implementation. You are free to copy, modify, or
-    redistribute.
-*/
-
-/*jslint 
-    eval, for, this 
-*/
-
-/*property
-    JSON, apply, call, charCodeAt, getUTCDate, getUTCFullYear, getUTCHours,
-    getUTCMinutes, getUTCMonth, getUTCSeconds, hasOwnProperty, join,
-    lastIndex, length, parse, prototype, push, replace, slice, stringify,
-    test, toJSON, toString, valueOf
-*/
-
-
-// Create a JSON object only if one does not already exist. We create the
-// methods in a closure to avoid creating global variables.
-
-if (typeof JSON !== 'object') {
-    JSON = {};
-}
-
-(function () {
-    'use strict';
-    
-    var rx_one = /^[\],:{}\s]*$/,
-        rx_two = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g,
-        rx_three = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g,
-        rx_four = /(?:^|:|,)(?:\s*\[)+/g,
-        rx_escapable = /[\\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,
-        rx_dangerous = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
-
-    function f(n) {
-        // Format integers to have at least two digits.
-        return n < 10 
-            ? '0' + n 
-            : n;
-    }
-    
-    function this_value() {
-        return this.valueOf();
-    }
-
-    if (typeof Date.prototype.toJSON !== 'function') {
-
-        Date.prototype.toJSON = function () {
-
-            return isFinite(this.valueOf())
-                ? this.getUTCFullYear() + '-' +
-                        f(this.getUTCMonth() + 1) + '-' +
-                        f(this.getUTCDate()) + 'T' +
-                        f(this.getUTCHours()) + ':' +
-                        f(this.getUTCMinutes()) + ':' +
-                        f(this.getUTCSeconds()) + 'Z'
-                : null;
-        };
-
-        Boolean.prototype.toJSON = this_value;
-        Number.prototype.toJSON = this_value;
-        String.prototype.toJSON = this_value;
-    }
-
-    var gap,
-        indent,
-        meta,
-        rep;
-
-
-    function quote(string) {
-
-// If the string contains no control characters, no quote characters, and no
-// backslash characters, then we can safely slap some quotes around it.
-// Otherwise we must also replace the offending characters with safe escape
-// sequences.
-
-        rx_escapable.lastIndex = 0;
-        return rx_escapable.test(string) 
-            ? '"' + string.replace(rx_escapable, function (a) {
-                var c = meta[a];
-                return typeof c === 'string'
-                    ? c
-                    : '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
-            }) + '"' 
-            : '"' + string + '"';
-    }
-
-
-    function str(key, holder) {
-
-// Produce a string from holder[key].
-
-        var i,          // The loop counter.
-            k,          // The member key.
-            v,          // The member value.
-            length,
-            mind = gap,
-            partial,
-            value = holder[key];
-
-// If the value has a toJSON method, call it to obtain a replacement value.
-
-        if (value && typeof value === 'object' &&
-                typeof value.toJSON === 'function') {
-            value = value.toJSON(key);
-        }
-
-// If we were called with a replacer function, then call the replacer to
-// obtain a replacement value.
-
-        if (typeof rep === 'function') {
-            value = rep.call(holder, key, value);
-        }
-
-// What happens next depends on the value's type.
-
-        switch (typeof value) {
-        case 'string':
-            return quote(value);
-
-        case 'number':
-
-// JSON numbers must be finite. Encode non-finite numbers as null.
-
-            return isFinite(value) 
-                ? String(value) 
-                : 'null';
-
-        case 'boolean':
-        case 'null':
-
-// If the value is a boolean or null, convert it to a string. Note:
-// typeof null does not produce 'null'. The case is included here in
-// the remote chance that this gets fixed someday.
-
-            return String(value);
-
-// If the type is 'object', we might be dealing with an object or an array or
-// null.
-
-        case 'object':
-
-// Due to a specification blunder in ECMAScript, typeof null is 'object',
-// so watch out for that case.
-
-            if (!value) {
-                return 'null';
-            }
-
-// Make an array to hold the partial results of stringifying this object value.
-
-            gap += indent;
-            partial = [];
-
-// Is the value an array?
-
-            if (Object.prototype.toString.apply(value) === '[object Array]') {
-
-// The value is an array. Stringify every element. Use null as a placeholder
-// for non-JSON values.
-
-                length = value.length;
-                for (i = 0; i < length; i += 1) {
-                    partial[i] = str(i, value) || 'null';
-                }
-
-// Join all of the elements together, separated with commas, and wrap them in
-// brackets.
-
-                v = partial.length === 0
-                    ? '[]'
-                    : gap
-                        ? '[\n' + gap + partial.join(',\n' + gap) + '\n' + mind + ']'
-                        : '[' + partial.join(',') + ']';
-                gap = mind;
-                return v;
-            }
-
-// If the replacer is an array, use it to select the members to be stringified.
-
-            if (rep && typeof rep === 'object') {
-                length = rep.length;
-                for (i = 0; i < length; i += 1) {
-                    if (typeof rep[i] === 'string') {
-                        k = rep[i];
-                        v = str(k, value);
-                        if (v) {
-                            partial.push(quote(k) + (
-                                gap 
-                                    ? ': ' 
-                                    : ':'
-                            ) + v);
-                        }
-                    }
-                }
-            } else {
-
-// Otherwise, iterate through all of the keys in the object.
-
-                for (k in value) {
-                    if (Object.prototype.hasOwnProperty.call(value, k)) {
-                        v = str(k, value);
-                        if (v) {
-                            partial.push(quote(k) + (
-                                gap 
-                                    ? ': ' 
-                                    : ':'
-                            ) + v);
-                        }
-                    }
-                }
-            }
-
-// Join all of the member texts together, separated with commas,
-// and wrap them in braces.
-
-            v = partial.length === 0
-                ? '{}'
-                : gap
-                    ? '{\n' + gap + partial.join(',\n' + gap) + '\n' + mind + '}'
-                    : '{' + partial.join(',') + '}';
-            gap = mind;
-            return v;
-        }
-    }
-
-// If the JSON object does not yet have a stringify method, give it one.
-
-    if (typeof JSON.stringify !== 'function') {
-        meta = {    // table of character substitutions
-            '\b': '\\b',
-            '\t': '\\t',
-            '\n': '\\n',
-            '\f': '\\f',
-            '\r': '\\r',
-            '"': '\\"',
-            '\\': '\\\\'
-        };
-        JSON.stringify = function (value, replacer, space) {
-
-// The stringify method takes a value and an optional replacer, and an optional
-// space parameter, and returns a JSON text. The replacer can be a function
-// that can replace values, or an array of strings that will select the keys.
-// A default replacer method can be provided. Use of the space parameter can
-// produce text that is more easily readable.
-
-            var i;
-            gap = '';
-            indent = '';
-
-// If the space parameter is a number, make an indent string containing that
-// many spaces.
-
-            if (typeof space === 'number') {
-                for (i = 0; i < space; i += 1) {
-                    indent += ' ';
-                }
-
-// If the space parameter is a string, it will be used as the indent string.
-
-            } else if (typeof space === 'string') {
-                indent = space;
-            }
-
-// If there is a replacer, it must be a function or an array.
-// Otherwise, throw an error.
-
-            rep = replacer;
-            if (replacer && typeof replacer !== 'function' &&
-                    (typeof replacer !== 'object' ||
-                    typeof replacer.length !== 'number')) {
-                throw new Error('JSON.stringify');
-            }
-
-// Make a fake root object containing our value under the key of ''.
-// Return the result of stringifying the value.
-
-            return str('', {'': value});
-        };
-    }
-
-
-// If the JSON object does not yet have a parse method, give it one.
-
-    if (typeof JSON.parse !== 'function') {
-        JSON.parse = function (text, reviver) {
-
-// The parse method takes a text and an optional reviver function, and returns
-// a JavaScript value if the text is a valid JSON text.
-
-            var j;
-
-            function walk(holder, key) {
-
-// The walk method is used to recursively walk the resulting structure so
-// that modifications can be made.
-
-                var k, v, value = holder[key];
-                if (value && typeof value === 'object') {
-                    for (k in value) {
-                        if (Object.prototype.hasOwnProperty.call(value, k)) {
-                            v = walk(value, k);
-                            if (v !== undefined) {
-                                value[k] = v;
-                            } else {
-                                delete value[k];
-                            }
-                        }
-                    }
-                }
-                return reviver.call(holder, key, value);
-            }
-
-
-// Parsing happens in four stages. In the first stage, we replace certain
-// Unicode characters with escape sequences. JavaScript handles many characters
-// incorrectly, either silently deleting them, or treating them as line endings.
-
-            text = String(text);
-            rx_dangerous.lastIndex = 0;
-            if (rx_dangerous.test(text)) {
-                text = text.replace(rx_dangerous, function (a) {
-                    return '\\u' +
-                            ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
-                });
-            }
-
-// In the second stage, we run the text against regular expressions that look
-// for non-JSON patterns. We are especially concerned with '()' and 'new'
-// because they can cause invocation, and '=' because it can cause mutation.
-// But just to be safe, we want to reject all unexpected forms.
-
-// We split the second stage into 4 regexp operations in order to work around
-// crippling inefficiencies in IE's and Safari's regexp engines. First we
-// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
-// replace all simple value tokens with ']' characters. Third, we delete all
-// open brackets that follow a colon or comma or that begin the text. Finally,
-// we look to see that the remaining characters are only whitespace or ']' or
-// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
-
-            if (
-                rx_one.test(
-                    text
-                        .replace(rx_two, '@')
-                        .replace(rx_three, ']')
-                        .replace(rx_four, '')
-                )
-            ) {
-
-// In the third stage we use the eval function to compile the text into a
-// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
-// in JavaScript: it can begin a block or an object literal. We wrap the text
-// in parens to eliminate the ambiguity.
-
-                j = eval('(' + text + ')');
-
-// In the optional fourth stage, we recursively walk the new structure, passing
-// each name/value pair to a reviver function for possible transformation.
-
-                return typeof reviver === 'function'
-                    ? walk({'': j}, '')
-                    : j;
-            }
-
-// If the text is not JSON parseable, then a SyntaxError is thrown.
-
-            throw new SyntaxError('JSON.parse');
-        };
-    }
-}());
\ No newline at end of file
+// Deprecated in WordPress 6.9.
\ No newline at end of file

From 14c196bbc3e4b27a72ae4e058b6b64c70361bf28 Mon Sep 17 00:00:00 2001
From: Joe Dolson <design@joedolson.com>
Date: Thu, 2 Oct 2025 17:06:40 -0500
Subject: [PATCH 30/30] Restore empty wp-embed-template-ie.css and enqueue with
 exempted conditional

---
 Gruntfile.js                                 | 1 +
 src/wp-includes/css/wp-embed-template-ie.css | 1 +
 src/wp-includes/script-loader.php            | 2 ++
 3 files changed, 4 insertions(+)
 create mode 100644 src/wp-includes/css/wp-embed-template-ie.css

diff --git a/Gruntfile.js b/Gruntfile.js
index 2c4942f56642a..729f1117522e4 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -644,6 +644,7 @@ module.exports = function(grunt) {
 					// Exceptions.
 					'!wp-includes/css/dashicons.css',
 					'!wp-includes/css/wp-embed-template.css',
+					'!wp-includes/css/wp-embed-template-ie.css'
 				]
 			},
 			colors: {
diff --git a/src/wp-includes/css/wp-embed-template-ie.css b/src/wp-includes/css/wp-embed-template-ie.css
new file mode 100644
index 0000000000000..5a9bad3da03ab
--- /dev/null
+++ b/src/wp-includes/css/wp-embed-template-ie.css
@@ -0,0 +1 @@
+/* Deprecated in WordPress 6.9 */
\ No newline at end of file
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 040325935f3c9..aca0363cba800 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -1663,6 +1663,8 @@ function wp_default_styles( $styles ) {
 	$styles->add( 'jcrop', '/wp-includes/js/jcrop/jquery.Jcrop.min.css', array(), '0.9.15' );
 	$styles->add( 'colors-fresh', false, array( 'wp-admin', 'buttons' ) ); // Old handle.
 	$styles->add( 'open-sans', $open_sans_font_url ); // No longer used in core as of 4.6.
+	$styles->add( 'wp-embed-template-ie', false );
+	$styles->add_data( 'wp-embed-template-ie', 'conditional', '_required-conditional-dependency_' );
 
 	// Noto Serif is no longer used by core, but may be relied upon by themes and plugins.
 	$fonts_url = '';