fix(#111): invalidate Elementor 4.2 element cache on data writes

MCP-created pages rendered empty on Elementor 4.2.x: create-page writes empty
[] data, an intermediate render caches an empty _elementor_element_cache, and
the plugin's raw update_post_meta() write path never invalidated it (Elementor
only clears it in Document::save(), which the CLI/proxy fallback bypasses). On a
persistent object cache (WP Engine) the stale empty entry survives every content
write, so the page serves the cached empty render forever.

Add EMCP_Tools_Data::init() — an added/updated_post_meta hook that clears
_elementor_element_cache whenever _elementor_data changes, from ANY write path —
plus an explicit clear in the save fallback. Also fixes delayed visibility of
edits to existing pages. Root-caused + fix live-verified on Elementor 4.2.2.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

includes/class-bootstrap.php

@@ -326,6 +326,9 @@ class EMCP_Tools_Bootstrap {
 			99
 		);
 
+		// Invalidate Elementor's rendered-element cache on any _elementor_data
+		// write, so MCP-created/edited pages never serve a stale empty render (#111).
+		EMCP_Tools_Data::init();
 		// Content search index: install-on-init + incremental re-index on save/delete.
 		EMCP_Tools_Search_Index::init();
 		EMCP_Tools_Change_Blobs::init();

includes/class-elementor-data.php

@@ -20,6 +20,42 @@ if ( ! defined( 'ABSPATH' ) ) {
  */
 class EMCP_Tools_Data {
 
+	/** Elementor 4.2's rendered-element cache meta (Document::CACHE_META_KEY). */
+	const ELEMENT_CACHE_META = '_elementor_element_cache';
+
+	/**
+	 * Register global hooks. Invalidates Elementor's rendered-element cache
+	 * (`_elementor_element_cache`) whenever a post's `_elementor_data` changes,
+	 * from ANY write path — our MCP tools' raw `update_post_meta()` writes, the
+	 * editor, or an import.
+	 *
+	 * Elementor 4.2's Element Cache stores rendered HTML in post meta. Elementor
+	 * clears it in `Document::save()`, but our CLI/proxy fallback writes data with
+	 * raw `update_post_meta()` and bypasses that. On a persistent object cache
+	 * (e.g. WP Engine) a stale/empty entry then survives every content write, so a
+	 * page created via MCP — written while its data was still the empty `[]`,
+	 * rendered (caching empty), then filled — keeps serving the cached empty
+	 * render forever. This restores Elementor's invalidation universally, and also
+	 * fixes the delayed visibility of edits to existing pages. See issue #111.
+	 */
+	public static function init(): void {
+		add_action( 'added_post_meta', array( __CLASS__, 'flush_element_cache_on_data_write' ), 10, 3 );
+		add_action( 'updated_post_meta', array( __CLASS__, 'flush_element_cache_on_data_write' ), 10, 3 );
+	}
+
+	/**
+	 * Clear the rendered-element cache when `_elementor_data` is written.
+	 *
+	 * @param int    $meta_id  Meta row id (unused).
+	 * @param int    $post_id  Post id.
+	 * @param string $meta_key Meta key.
+	 */
+	public static function flush_element_cache_on_data_write( $meta_id, $post_id, $meta_key ): void {
+		if ( '_elementor_data' === $meta_key ) {
+			delete_post_meta( (int) $post_id, self::ELEMENT_CACHE_META );
+		}
+	}
+
 	/**
 	 * Whether Elementor's document manager is available.
 	 *
@@ -316,6 +352,12 @@ class EMCP_Tools_Data {
 			// Invalidate Elementor CSS cache so it regenerates on next page view.
 			delete_post_meta( $post_id, '_elementor_css' );
 
+			// Invalidate Elementor 4.2's rendered-element cache — the update above
+			// fires the meta hook that clears it, but do it explicitly too so a
+			// re-save of identical data (which skips the hook) still refreshes a
+			// stale/empty cached render. See init() + issue #111.
+			delete_post_meta( $post_id, self::ELEMENT_CACHE_META );
+
 			$upload_dir = wp_get_upload_dir();
 			$css_path   = $upload_dir['basedir'] . '/elementor/css/post-' . $post_id . '.css';
 			if ( file_exists( $css_path ) ) {

tests/ElementCacheFlushTest.php

@@ -0,0 +1,31 @@
+<?php
+/**
+ * Public unit test for EMCP_Tools_Data::flush_element_cache_on_data_write() —
+ * the issue #111 fix that invalidates Elementor 4.2's rendered-element cache
+ * whenever `_elementor_data` is written (so MCP-created pages never serve a
+ * stale/empty cached render). Behaviour is fully live-verified on a real
+ * Elementor 4.2.2 site; this pins the key-matching logic.
+ *
+ * @package EMCP_Tools
+ */
+
+require_once dirname( __DIR__ ) . '/includes/class-elementor-data.php';
+
+class ElementCacheFlushTest extends \PHPUnit\Framework\TestCase {
+
+	protected function setUp(): void {
+		emcp_test_reset();
+		$GLOBALS['emcp_test']['deleted_meta'] = array();
+	}
+
+	public function test_clears_element_cache_when_elementor_data_written() {
+		EMCP_Tools_Data::flush_element_cache_on_data_write( 5, 42, '_elementor_data' );
+		$this->assertContains( array( 42, '_elementor_element_cache' ), $GLOBALS['emcp_test']['deleted_meta'] );
+	}
+
+	public function test_ignores_other_meta_keys() {
+		EMCP_Tools_Data::flush_element_cache_on_data_write( 5, 42, '_edit_lock' );
+		EMCP_Tools_Data::flush_element_cache_on_data_write( 5, 42, '_elementor_css' );
+		$this->assertSame( array(), $GLOBALS['emcp_test']['deleted_meta'] );
+	}
+}

tests/bootstrap.php

@@ -153,6 +153,14 @@ function get_post( $post_id ) {
 	return $GLOBALS['emcp_test']['posts'][ (int) $post_id ] ?? null;
 }
 
+if ( ! function_exists( 'delete_post_meta' ) ) {
+	// Records deletions in $GLOBALS['emcp_test']['deleted_meta'] as [post_id, key].
+	function delete_post_meta( $post_id, $key, $value = '' ) {
+		$GLOBALS['emcp_test']['deleted_meta'][] = array( (int) $post_id, (string) $key );
+		return true;
+	}
+}
+
 function get_permalink( $post = null ): string {
 	return 'http://example.test/?p=' . ( is_object( $post ) ? (int) $post->ID : (int) $post );
 }