diff --git a/src/wp-includes/html-api/class-wp-html-template.php b/src/wp-includes/html-api/class-wp-html-template.php
new file mode 100644
index 0000000000000..c3161a4d3895b
--- /dev/null
+++ b/src/wp-includes/html-api/class-wp-html-template.php
@@ -0,0 +1,228 @@
+<?php
+
+class WP_HTML_Template {
+	/**
+	 * Wraps HTML in a class indicating that it was generated from within
+	 * the HTML API. Used for safely merging HTML of varying provenance,
+	 * where miscoordination could otherwise result in double-encoding.
+	 *
+	 * @since 7.0
+	 * @access private
+	 */
+	private static $sentinel_class = null;
+
+	/**
+	 * @param string     $template
+	 * @param array|null $args
+	 * @return object Rendered and wrapped HTML.
+	 */
+	public static function compile( string $template, ?array $args = null ) {
+		self::ensure_sentinel();
+
+		$builder = new class ( '', WP_HTML_Processor::CONSTRUCTOR_UNLOCK_CODE ) extends WP_HTML_Processor {
+			public $deferred_updates = array();
+
+			public function get_raw_attribute( $name ) {
+				$lexical_updates = $this->lexical_updates;
+				$this->remove_attribute( $name );
+				$span = $this->lexical_updates[ strtolower( $name ) ];
+				$this->lexical_updates = $lexical_updates;
+				$span->text = substr( $this->html, $span->start, $span->length );
+				return $span;
+			}
+
+			public function raw_replace_token( $content ) {
+				$this->set_bookmark( 'here' );
+				$here = $this->bookmarks['_here'];
+				$this->deferred_updates[] = new WP_HTML_Text_Replacement(
+					$here->start,
+					$here->length,
+					$content
+				);
+			}
+
+			public function set_attribute( $name, $value ): bool {
+				if ( ! parent::set_attribute( $name, $value ) ) {
+					return false;
+				}
+				$lower_name = strtolower( $name );
+				$this->deferred_updates[ $lower_name ] = $this->lexical_updates[ $lower_name ];
+				return true;
+			}
+
+			public function remove_attribute( $name ): bool {
+				if ( ! parent::remove_attribute( $name ) ) {
+					return false;
+				}
+
+				$lower_name = strtolower( $name );
+				$this->deferred_updates[ $lower_name ] = $this->lexical_updates[ $lower_name ];
+				return true;
+			}
+		};
+
+		$processor   = $builder::create_fragment( $template );
+		$bit_pattern = '%(?P<VAR>[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*)';
+
+		$refers_to = function ( $input ) use ( $args, $bit_pattern ){
+			if ( 1 === preg_match( "~^</{$bit_pattern}>$~", $input, $matches ) ) {
+				return isset( $args[ $matches['VAR'] ] ) ? $matches['VAR'] : null;
+			}
+
+			return false;
+		};
+
+		while ( $processor->next_token() ) {
+			$token_type = $processor->get_token_type();
+
+			// Skip over entire elements when instructed.
+			if ( '#tag' === $token_type ) {
+				if ( is_string( $processor->get_attribute( 'data-wp-if' ) ) ) {
+					$ignorable = $processor->get_raw_attribute( 'data-wp-if' )->text;
+					$quote     = $ignorable[ strlen( $ignorable ) - 1 ];
+					$ignorable = substr(
+						$ignorable,
+						strcspn( $ignorable, $quote ) + 1,
+						-1
+					);
+					$processor->remove_attribute( 'data-wp-if' );
+					$condition = $refers_to( $ignorable );
+
+					if ( isset( $condition, $args[ $condition ] ) && in_array( $args[ $condition ], array( false, null, '' ), true ) ) {
+						$depth = $processor->get_current_depth();
+						while ( $processor->next_token() && $processor->get_current_depth() > $depth ) {
+							continue;
+						}
+
+						continue;
+					}
+				}
+
+				// Replace Bits in attributes and spread attributes.
+				foreach ( $processor->get_attribute_names_with_prefix( '' ) ?? array() as $name ) {
+					// Spread attributes which are boolean; don’t replace those with values.
+					if ( str_starts_with( $name, '...' ) && true === $processor->get_attribute( $name ) ) {
+						$processor->remove_attribute( $name );
+						$spread_name = substr( $name, 3 );
+						if ( isset( $spread_name, $args[ $spread_name ] ) && is_array( $args[ $spread_name ] ) ) {
+							$spread_args = $args[ $spread_name ];
+							foreach ( $spread_args as $arg_name => $arg_value ) {
+								if ( is_string( $arg_name ) && ( true === $arg_value || is_string( $arg_value ) ) ) {
+									$processor->set_attribute( $arg_name, $arg_value );
+								} else if ( is_string( $arg_name ) && in_array( $arg_value, array( false, null ), true ) ) {
+									$processor->remove_attribute( $arg_name );
+								}
+							}
+						}
+
+						continue;
+					}
+
+					$raw_attr = $processor->get_raw_attribute( $name )->text;
+					$last_c   = $raw_attr[ strlen( $raw_attr ) - 1 ];
+
+					// Bit syntax cannot appear in unquoted attributes.
+					if ( '"' !== $last_c && "'" !== $last_c ) {
+						continue;
+					}
+
+					$value   = substr( $raw_attr, strcspn( $raw_attr, $last_c ) + 1, -1 );
+					$matches = null;
+					$bits    = preg_match_all( "~</{$bit_pattern}>~", $value, $matches, PREG_SET_ORDER | PREG_OFFSET_CAPTURE );
+					if ( 0 === $bits || false === $bits ) {
+						continue;
+					}
+
+					$updated = array();
+					$was_at  = 0;
+					foreach ( $matches as $match ) {
+						$updated[] = substr( $value, $was_at, $match[0][1] - $was_at );
+						$was_at    = $match[0][1] + strlen( $match[0][0] );
+						$arg_name  = $match['VAR'][0];
+
+						if ( isset( $arg_name, $args[ $arg_name ] ) && is_string( $args[ $arg_name ] ) ) {
+							$updated[] = self::escape( $name, $args[ $arg_name ] );
+						}
+					}
+
+					$updated[] = substr( $value, $was_at );
+					$decoded   = WP_HTML_Decoder::decode_attribute( implode( '', $updated ) );
+					if ( ! $processor->set_attribute( $name, $decoded ) ) {
+						$processor->remove_attribute( $name );
+					}
+				}
+			}
+
+			if ( '#funky-comment' === $token_type ) {
+				$text = $processor->get_modifiable_text();
+				if ( 1 !== preg_match( "~^{$bit_pattern}$~", $text, $match ) ) {
+					continue;
+				}
+
+				if ( isset( $match['VAR'], $args[ $match['VAR'] ] ) && is_string( $args[ $match['VAR'] ] ) ) {
+					$processor->raw_replace_token( self::escape( null, $args[ $match['VAR'] ] ) );
+				}
+			}
+		}
+
+		return self::$sentinel_class::wrap( $template, $processor->deferred_updates );
+	}
+
+	public static function render( $compiled ): string {
+		return $compiled->unwrap();
+	}
+
+	private static function escape( $attr_name, string $plaintext ): string {
+		if ( isset( $attr_name ) && in_array( strtolower( $attr_name ), wp_kses_uri_attributes(), true ) ) {
+			return esc_url( $plaintext );
+		}
+
+		return strtr(
+			$plaintext,
+			array(
+				'<' => '&lt;',
+				'>' => '&gt;',
+				'&' => '&amp;',
+				'"' => '&quot;',
+				"'" => '&apos;',
+			)
+		);
+	}
+
+	/**
+	 * Ensures that the sentinel class is dynamically generated at boot.
+	 * This class is to never be serialized or instantiated outside of
+	 * this parent class.
+	 *
+	 * @since 7.0
+	 */
+	private static function ensure_sentinel(): void {
+		if ( isset( self::$sentinel_class ) ) {
+			return;
+		}
+
+		self::$sentinel_class = new class () {
+			private $html = '';
+
+			private $updates = array();
+
+			public static function wrap( string $html, array $updates ): self {
+				$wrapper = new self();
+				$wrapper->html = $html;
+				$wrapper->updates = $updates;
+				return $wrapper;
+			}
+
+			public function unwrap(): string {
+				$processor = new class( $this->html ) extends WP_HTML_Tag_Processor {
+					public function flood( $updates ) {
+						$this->lexical_updates = $updates;
+					}
+				};
+
+				$processor->flood( $this->updates );
+				return $processor->get_updated_html();
+			}
+		};
+	}
+}