diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/blocks/button.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/blocks/button.php	Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,80 @@
+<?php
+/**
+ * Server-side rendering of the `core/button` block.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Renders the `core/button` block on the server,
+ *
+ * @since 6.6.0
+ *
+ * @param array    $attributes The block attributes.
+ * @param string   $content    The block content.
+ * @param WP_Block $block      The block object.
+ *
+ * @return string The block content.
+ */
+function render_block_core_button( $attributes, $content ) {
+	$p = new WP_HTML_Tag_Processor( $content );
+
+	/*
+	 * The button block can render an `<a>` or `<button>` and also has a
+	 * `<div>` wrapper. Find the a or button tag.
+	 */
+	$tag = null;
+	while ( $p->next_tag() ) {
+		$tag = $p->get_tag();
+		if ( 'A' === $tag || 'BUTTON' === $tag ) {
+			break;
+		}
+	}
+
+	/*
+	 * If this happens, the likelihood is there's no block content,
+	 * or the block has been modified by a plugin.
+	 */
+	if ( null === $tag ) {
+		return $content;
+	}
+
+	// If the next token is the closing tag, the button is empty.
+	$is_empty = true;
+	while ( $p->next_token() && $tag !== $p->get_token_name() && $is_empty ) {
+		if ( '#comment' !== $p->get_token_type() ) {
+			/**
+			 * Anything else implies this is not empty.
+			 * This might include any text content (including a space),
+			 * inline images or other HTML.
+			 */
+			$is_empty = false;
+		}
+	}
+
+	/*
+	 * When there's no text, render nothing for the block.
+	 * See https://github.com/WordPress/gutenberg/issues/17221 for the
+	 * reasoning behind this.
+	 */
+	if ( $is_empty ) {
+		return '';
+	}
+
+	return $content;
+}
+
+/**
+ * Registers the `core/button` block on server.
+ *
+ * @since 6.6.0
+ */
+function register_block_core_button() {
+	register_block_type_from_metadata(
+		__DIR__ . '/button',
+		array(
+			'render_callback' => 'render_block_core_button',
+		)
+	);
+}
+add_action( 'init', 'register_block_core_button' );