diff --git a/src/wp-includes/HTML_To_Markdown_Converter.php b/src/wp-includes/HTML_To_Markdown_Converter.php
new file mode 100644
index 0000000000000..48221eaf6b227
--- /dev/null
+++ b/src/wp-includes/HTML_To_Markdown_Converter.php
@@ -0,0 +1,464 @@
+<?php
+/**
+ * HTML-to-Markdown converter used by the Markdown feeds experiment.
+ *
+ * This is intentionally small and conservative: it focuses on producing a
+ * readable Markdown representation of typical WordPress post content without
+ * introducing external parsing dependencies.
+ *
+ * @package WordPress\AI
+ */
+
+declare( strict_types=1 );
+
+//namespace WordPress\AI\Experiments\Markdown_Feeds;
+//
+//use WP_HTML_Processor;
+//use WP_HTML_Tag_Processor;
+
+/**
+ * Converts HTML fragments into Markdown.
+ *
+ * @since x.x.x
+ */
+final class HTML_To_Markdown_Converter {
+	/**
+	 * Converts HTML to Markdown.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $html HTML to convert.
+	 * @return string Markdown output.
+	 */
+	public function convert( string $html ): string {
+		$processor = $this->create_processor( $html );
+		if ( ! $processor ) {
+			return trim( wp_strip_all_tags( $html ) );
+		}
+
+		$markdown = $this->convert_with_processor( $processor );
+
+		if (
+			$processor instanceof WP_HTML_Processor
+			&& WP_HTML_Processor::ERROR_UNSUPPORTED === $processor->get_last_error()
+			&& class_exists( WP_HTML_Tag_Processor::class )
+		) {
+			$markdown = $this->convert_with_processor( new WP_HTML_Tag_Processor( $html ) );
+		}
+
+		return trim( $this->cleanup( $markdown ) );
+	}
+
+	/**
+	 * Creates the best available HTML processor for conversion.
+	 *
+	 * Uses the HTML Processor in fragment mode when available, and falls back to
+	 * the Tag Processor for broader tag tolerance.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $html HTML string.
+	 * @return \WP_HTML_Tag_Processor|\WP_HTML_Processor|null Processor instance.
+	 */
+	private function create_processor( string $html ) {
+		$processor = null;
+
+		if ( class_exists( WP_HTML_Processor::class ) ) {
+			$processor = WP_HTML_Processor::create_fragment( $html );
+
+			if ( ! $processor ) {
+				$processor = new WP_HTML_Processor( $html );
+			}
+		} elseif ( class_exists( WP_HTML_Tag_Processor::class ) ) {
+			$processor = new WP_HTML_Tag_Processor( $html );
+		}
+
+		return $processor;
+	}
+
+	/**
+	 * Converts HTML into Markdown using a provided HTML API processor.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param \WP_HTML_Tag_Processor|\WP_HTML_Processor $processor Processor instance.
+	 * @return string Markdown output.
+	 */
+	private function convert_with_processor( $processor ): string {
+		$markdown = '';
+
+		$at_line_start    = true;
+		$blockquote_depth = 0;
+		$in_pre           = false;
+
+		$link_stack = array();
+		$list_stack = array();
+
+		// Table state.
+		$in_table        = false;
+		$current_row     = array();
+		$is_header_row   = false;
+		$header_row_done = false;
+
+		while ( $processor->next_token() ) {
+			$token_name = $processor->get_token_name();
+
+			if ( '#text' === $token_name ) {
+				$text = (string) $processor->get_modifiable_text();
+
+				// If we're in a table cell, collect text for the cell.
+				if ( $in_table && ! empty( $current_row ) ) {
+					$cell_index                  = count( $current_row ) - 1;
+					$current_row[ $cell_index ] .= trim( (string) preg_replace( '/\s+/', ' ', $text ) );
+					continue;
+				}
+
+				$this->append_text( $markdown, $text, $at_line_start, $blockquote_depth, $in_pre );
+				continue;
+			}
+
+			// Skip script/style entirely.
+			if ( 'SCRIPT' === $token_name || 'STYLE' === $token_name ) {
+				continue;
+			}
+
+			$is_closer = $processor->is_tag_closer();
+
+			if ( 'BR' === $token_name ) {
+				$this->append_newline( $markdown, $at_line_start );
+				continue;
+			}
+
+			if ( 'HR' === $token_name && ! $is_closer ) {
+				$this->ensure_blank_line( $markdown, $at_line_start );
+				$this->append_line( $markdown, '---', $at_line_start, $blockquote_depth );
+				$this->ensure_blank_line( $markdown, $at_line_start );
+				continue;
+			}
+
+			if ( ( 'P' === $token_name || 'DIV' === $token_name ) && $is_closer ) {
+				if ( ! $in_pre ) {
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				}
+				continue;
+			}
+
+			if ( 'BLOCKQUOTE' === $token_name ) {
+				if ( $is_closer ) {
+					$blockquote_depth = max( 0, $blockquote_depth - 1 );
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				} else {
+					++$blockquote_depth;
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				}
+				continue;
+			}
+
+			if ( 'PRE' === $token_name ) {
+				if ( $is_closer ) {
+					if ( ! $at_line_start ) {
+						$this->append_newline( $markdown, $at_line_start );
+					}
+					$this->append_line( $markdown, '```', $at_line_start, $blockquote_depth );
+					$this->ensure_blank_line( $markdown, $at_line_start );
+					$in_pre = false;
+				} else {
+					$this->ensure_blank_line( $markdown, $at_line_start );
+					$this->append_line( $markdown, '```', $at_line_start, $blockquote_depth );
+					$in_pre = true;
+				}
+				continue;
+			}
+
+			if ( 'CODE' === $token_name && ! $in_pre ) {
+				$markdown     .= '`';
+				$at_line_start = false;
+				continue;
+			}
+
+			if ( 'STRONG' === $token_name || 'B' === $token_name ) {
+				$markdown     .= '**';
+				$at_line_start = false;
+				continue;
+			}
+
+			if ( 'EM' === $token_name || 'I' === $token_name ) {
+				$markdown     .= '*';
+				$at_line_start = false;
+				continue;
+			}
+
+			if ( 'A' === $token_name ) {
+				if ( $is_closer ) {
+					$href = array_pop( $link_stack );
+					if ( $href ) {
+						$markdown .= '](' . $href . ')';
+					} else {
+						$markdown .= ']';
+					}
+				} else {
+					$link_stack[] = (string) $processor->get_attribute( 'href' );
+					$markdown    .= '[';
+				}
+				$at_line_start = false;
+				continue;
+			}
+
+			if ( 'IMG' === $token_name && ! $is_closer ) {
+				$src = (string) $processor->get_attribute( 'src' );
+				if ( '' === $src ) {
+					continue;
+				}
+
+				$alt = (string) $processor->get_attribute( 'alt' );
+				$this->append_text( $markdown, '![' . $alt . '](' . $src . ')', $at_line_start, $blockquote_depth, true );
+				continue;
+			}
+
+			// Figure element (contains image + optional caption).
+			if ( 'FIGURE' === $token_name ) {
+				$this->ensure_blank_line( $markdown, $at_line_start );
+				continue;
+			}
+
+			// Figure caption - render as italic text on new line.
+			if ( 'FIGCAPTION' === $token_name ) {
+				if ( ! $is_closer ) {
+					$this->ensure_newline( $markdown, $at_line_start );
+					$markdown     .= '*';
+					$at_line_start = false;
+				} else {
+					$markdown .= '*';
+				}
+				continue;
+			}
+
+			// Citation in blockquotes - prefix with em dash.
+			if ( 'CITE' === $token_name ) {
+				if ( ! $is_closer ) {
+					$markdown     .= '— ';
+					$at_line_start = false;
+				}
+				continue;
+			}
+
+			if ( 'UL' === $token_name || 'OL' === $token_name ) {
+				if ( $is_closer ) {
+					array_pop( $list_stack );
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				} else {
+					$list_stack[] = array(
+						'type'  => $token_name,
+						'index' => 0,
+					);
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				}
+				continue;
+			}
+
+			if ( 'LI' === $token_name && ! $is_closer ) {
+				$this->ensure_newline( $markdown, $at_line_start );
+
+				$depth  = count( $list_stack );
+				$indent = str_repeat( '  ', max( 0, $depth - 1 ) );
+
+				$marker = '-';
+				if ( $depth > 0 && 'OL' === $list_stack[ $depth - 1 ]['type'] ) {
+					++$list_stack[ $depth - 1 ]['index'];
+					$marker = (string) $list_stack[ $depth - 1 ]['index'] . '.';
+				}
+
+				$this->append_text(
+					$markdown,
+					$indent . $marker . ' ',
+					$at_line_start,
+					$blockquote_depth,
+					true
+				);
+
+				continue;
+			}
+
+			// Table handling.
+			if ( 'TABLE' === $token_name ) {
+				if ( $is_closer ) {
+					$in_table        = false;
+					$header_row_done = false;
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				} else {
+					$in_table = true;
+					$this->ensure_blank_line( $markdown, $at_line_start );
+				}
+				continue;
+			}
+
+			if ( 'THEAD' === $token_name || 'TBODY' === $token_name || 'TFOOT' === $token_name ) {
+				// Skip these structural elements; we detect headers via TH tags.
+				continue;
+			}
+
+			if ( 'TR' === $token_name ) {
+				if ( $is_closer ) {
+					// Output the row.
+					if ( ! empty( $current_row ) ) {
+						$row_line = '| ' . implode( ' | ', $current_row ) . ' |';
+						$this->append_line( $markdown, $row_line, $at_line_start, $blockquote_depth );
+
+						// Add separator after header row.
+						if ( $is_header_row && ! $header_row_done ) {
+							$separator = '|' . str_repeat( ' --- |', count( $current_row ) );
+							$this->append_line( $markdown, $separator, $at_line_start, $blockquote_depth );
+							$header_row_done = true;
+						}
+					}
+					$current_row   = array();
+					$is_header_row = false;
+				}
+				continue;
+			}
+
+			if ( 'TH' === $token_name ) {
+				if ( ! $is_closer ) {
+					$current_row[] = '';
+					$is_header_row = true;
+				}
+				continue;
+			}
+
+			if ( 'TD' === $token_name ) {
+				if ( ! $is_closer ) {
+					$current_row[] = '';
+				}
+				continue;
+			}
+
+			if ( ! $token_name || ! preg_match( '/^H([1-6])$/', $token_name, $matches ) ) {
+				continue;
+			}
+
+			if ( $is_closer ) {
+				$this->ensure_blank_line( $markdown, $at_line_start );
+			} else {
+				$level = (int) $matches[1];
+				$this->ensure_blank_line( $markdown, $at_line_start );
+				$this->append_text(
+					$markdown,
+					str_repeat( '#', $level ) . ' ',
+					$at_line_start,
+					$blockquote_depth,
+					true
+				);
+			}
+			continue;
+		}
+
+		return $markdown;
+	}
+
+	/**
+	 * Appends plain text to the Markdown output.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown          Markdown buffer.
+	 * @param string $text              Text to append.
+	 * @param bool   $at_line_start     Whether output is at the start of a line.
+	 * @param int    $blockquote_depth  Current blockquote depth.
+	 * @param bool   $preserve_whitespace Whether to preserve whitespace.
+	 */
+	private function append_text( string &$markdown, string $text, bool &$at_line_start, int $blockquote_depth, bool $preserve_whitespace = false ): void {
+		if ( '' === $text ) {
+			return;
+		}
+
+		$text = str_replace( array( "\r\n", "\r" ), "\n", $text );
+
+		if ( ! $preserve_whitespace ) {
+			$text = preg_replace( '/\\s+/u', ' ', $text );
+		}
+
+		if ( $at_line_start && 0 < $blockquote_depth ) {
+			$markdown .= str_repeat( '> ', $blockquote_depth );
+		}
+
+		$markdown     .= $text;
+		$at_line_start = false;
+	}
+
+	/**
+	 * Appends a newline.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown      Markdown buffer.
+	 * @param bool   $at_line_start Whether output is at the start of a line.
+	 */
+	private function append_newline( string &$markdown, bool &$at_line_start ): void {
+		$markdown     .= "\n";
+		$at_line_start = true;
+	}
+
+	/**
+	 * Appends a full line and ensures the buffer ends at a new line.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown         Markdown buffer.
+	 * @param string $line             Line content.
+	 * @param bool   $at_line_start    Whether output is at the start of a line.
+	 * @param int    $blockquote_depth Current blockquote depth.
+	 */
+	private function append_line( string &$markdown, string $line, bool &$at_line_start, int $blockquote_depth ): void {
+		$this->ensure_newline( $markdown, $at_line_start );
+		$this->append_text( $markdown, $line, $at_line_start, $blockquote_depth, true );
+		$this->append_newline( $markdown, $at_line_start );
+	}
+
+	/**
+	 * Ensures output starts on a new line.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown      Markdown buffer.
+	 * @param bool   $at_line_start Whether output is at the start of a line.
+	 */
+	private function ensure_newline( string &$markdown, bool &$at_line_start ): void {
+		if ( $at_line_start ) {
+			return;
+		}
+
+		$this->append_newline( $markdown, $at_line_start );
+	}
+
+	/**
+	 * Ensures output ends with a blank line.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown      Markdown buffer.
+	 * @param bool   $at_line_start Whether output is at the start of a line.
+	 */
+	private function ensure_blank_line( string &$markdown, bool &$at_line_start ): void {
+		$markdown      = rtrim( $markdown, "\n" );
+		$markdown     .= "\n\n";
+		$at_line_start = true;
+	}
+
+	/**
+	 * Cleans up excessive whitespace and newlines.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $markdown Markdown buffer.
+	 * @return string Cleaned buffer.
+	 */
+	private function cleanup( string $markdown ): string {
+		// Remove trailing whitespace from lines.
+		$markdown = preg_replace( "/[ \\t]+\\n/", "\n", $markdown );
+		// Remove leading whitespace from lines (except in code blocks).
+		$markdown = preg_replace( "/\\n[ \\t]+(?!\\s*```)/", "\n", (string) $markdown );
+		// Collapse multiple blank lines.
+		$markdown = preg_replace( "/\\n{3,}/", "\n\n", (string) $markdown );
+		return (string) $markdown;
+	}
+}
diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 0bcd2d6b15acb..b87bb18e9aa06 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -416,6 +416,8 @@
 add_action( 'do_feed_rss', 'do_feed_rss', 10, 0 );
 add_action( 'do_feed_rss2', 'do_feed_rss2', 10, 1 );
 add_action( 'do_feed_atom', 'do_feed_atom', 10, 1 );
+add_action( 'do_feed_markdown', 'do_feed_markdown', 10, 1 );
+add_action( 'init', 'wp_register_markdown_feed' );
 add_action( 'do_pings', 'do_all_pings', 10, 0 );
 add_action( 'do_all_pings', 'do_all_pingbacks', 10, 0 );
 add_action( 'do_all_pings', 'do_all_enclosures', 10, 0 );
diff --git a/src/wp-includes/feed-markdown.php b/src/wp-includes/feed-markdown.php
new file mode 100644
index 0000000000000..8871e1ad34393
--- /dev/null
+++ b/src/wp-includes/feed-markdown.php
@@ -0,0 +1,57 @@
+<?php
+/**
+ * Markdown Feed Template for displaying posts as Markdown text.
+ *
+ * Accessible via /?feed=markup or /feed/markup/ depending on permalink settings.
+ *
+ * @package WordPress
+ * @since 6.7.0
+ */
+
+// Output Markdown so clients can render appropriately.
+header( 'Content-Type: text/html; charset=' . get_option( 'blog_charset' ), true );
+
+// Ensure full content is used.
+// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- Used intentionally to ensure full content in feed.
+$more = 1;
+
+include_once 'HTML_To_Markdown_Converter.php';
+
+$__wp_md_converter = new HTML_To_Markdown_Converter();
+
+// Feed header as Markdown.
+echo '# ' . wp_strip_all_tags( get_bloginfo( 'name' ) ) . ' — ' . __( 'Markdown Feed', 'default' ) . "\n\n";
+$desc = get_bloginfo( 'description' );
+if ( $desc ) {
+	echo wp_strip_all_tags( $desc ) . "\n\n";
+}
+
+echo __( 'Feed URL:', 'default' ) . ' <' . esc_url_raw( get_self_link() ) . ">\n\n";
+
+if ( have_posts() ) :
+	while ( have_posts() ) :
+		the_post();
+
+		$title     = wp_strip_all_tags( get_the_title() );
+		$permalink = get_permalink();
+		$date_r    = get_post_time( 'r', true );
+		$content   = get_post_field( 'post_content', get_the_ID() );
+
+		// Post block in Markdown.
+		echo "## [" . $title . "]("
+			. $permalink . ")\n";
+		echo '*' . __( 'Published:', 'default' ) . '* ' . $date_r . "\n\n";
+
+		$html = apply_filters( 'the_content', $content );
+		$md   = $__wp_md_converter->convert( (string) $html );
+		$md   = trim( $md );
+		if ( $md !== '' ) {
+			echo $md . "\n\n";
+		}
+
+		// Separator.
+		echo "---\n\n";
+	endwhile;
+else :
+	echo __( 'No posts found.', 'default' );
+endif;
diff --git a/src/wp-includes/fonts/class-wp-font-collection.php b/src/wp-includes/fonts/class-wp-font-collection.php
index b915e3ea58d0d..fb514b4e9eed2 100644
--- a/src/wp-includes/fonts/class-wp-font-collection.php
+++ b/src/wp-includes/fonts/class-wp-font-collection.php
@@ -156,6 +156,7 @@ private function load_from_json( $file_or_url ) {
 	 *                        else an instance of WP_Error on failure.
 	 */
 	private function load_from_file( $file ) {
+
 		$data = wp_json_file_decode( $file, array( 'associative' => true ) );
 		if ( empty( $data ) ) {
 			return new WP_Error( 'font_collection_decode_error', __( 'Error decoding the font collection JSON file contents.' ) );
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 4b6330a697780..8593c56cff8c5 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -1697,6 +1697,31 @@ function do_feed_atom( $for_comments ) {
 	}
 }
 
+/**
+ * Loads the MarkDown Feed Template.
+ *
+ * A simple HTML feed that outputs post content with MarkDown preserved.
+ *
+ * @since 6.7.0
+ *
+ * @see load_template()
+ *
+ * @param bool $for_comments Unused. Present for parity with other feed handlers.
+ */
+function do_feed_markdown( $for_comments ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+
+	load_template( ABSPATH . WPINC . '/feed-markdown.php' );
+}
+
+/**
+ * Registers the Markup feed rewrite and hook.
+ *
+ * @since 6.7.0
+ */
+function wp_register_markdown_feed() {
+	add_feed( 'markdown', 'do_feed_markdown' );
+}
+
 /**
  * Displays the default robots.txt file content.
  *