From ee87603cd9df3427bf5ec356d6583cc6bb4b4e18 Mon Sep 17 00:00:00 2001
From: Andrew Serong <14988353+andrewserong@users.noreply.github.com>
Date: Fri, 20 Feb 2026 12:55:49 +1100
Subject: [PATCH 1/3] Client-side media processing: Disable in Gutenberg just
 for now

---
 lib/compat/plugin/media.php             | 16 ++++++++++++++
 lib/load.php                            |  3 +++
 phpunit/bootstrap.php                   |  5 +++++
 phpunit/media/media-processing-test.php | 29 +++++++++++++++----------
 4 files changed, 42 insertions(+), 11 deletions(-)
 create mode 100644 lib/compat/plugin/media.php

diff --git a/lib/compat/plugin/media.php b/lib/compat/plugin/media.php
new file mode 100644
index 00000000000000..9f7711c788589b
--- /dev/null
+++ b/lib/compat/plugin/media.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * Disables client-side media processing by default in the Gutenberg plugin.
+ *
+ * Client-side media processing is being polished during the 7.0 cycle.
+ * It is disabled by default in the plugin until known issues are resolved,
+ * but can still be enabled via the filter.
+ *
+ * @see https://github.com/WordPress/gutenberg/issues/75302
+ * @see https://github.com/WordPress/gutenberg/issues/75605
+ *
+ * @package gutenberg
+ */
+
+// @core-merge: Do not merge this into WordPress core.
+add_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
diff --git a/lib/load.php b/lib/load.php
index 5b0674274a2063..2ae504cf5bd3d6 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -110,6 +110,9 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/compat/wordpress-7.0/kses.php';
 require __DIR__ . '/compat/wordpress-7.0/media.php';
 
+// Gutenberg plugin compat: disable client-side media processing by default.
+require __DIR__ . '/compat/plugin/media.php';
+
 // Experimental features.
 require __DIR__ . '/experimental/block-editor-settings-mobile.php';
 require __DIR__ . '/experimental/blocks.php';
diff --git a/phpunit/bootstrap.php b/phpunit/bootstrap.php
index 19667b25979b8e..a9c91e0d7522e5 100644
--- a/phpunit/bootstrap.php
+++ b/phpunit/bootstrap.php
@@ -96,6 +96,11 @@ function fail_if_died( $message ) {
 // Enable the widget block editor.
 tests_add_filter( 'gutenberg_use_widgets_block_editor', '__return_true' );
 
+// Enable client-side media processing for tests.
+// The Gutenberg plugin disables this by default (lib/compat/plugin/media.php),
+// but tests need the media functions to be loaded.
+tests_add_filter( 'wp_client_side_media_processing_enabled', '__return_true', 20 );
+
 // Start up the WP testing environment.
 require $_tests_dir . '/includes/bootstrap.php';
 
diff --git a/phpunit/media/media-processing-test.php b/phpunit/media/media-processing-test.php
index 0208361005f4df..43d7d88278811e 100644
--- a/phpunit/media/media-processing-test.php
+++ b/phpunit/media/media-processing-test.php
@@ -202,25 +202,31 @@ public function test_gutenberg_override_media_templates(): void {
 	}
 
 	/**
-	 * Tests that client-side media processing is enabled by default.
+	 * Tests that client-side media processing is disabled by default in the Gutenberg plugin.
+	 *
+	 * The core compat layer defaults to true, but the Gutenberg plugin
+	 * adds a filter to disable it by default (lib/compat/plugin/media.php)
+	 * until known issues are resolved.
 	 *
 	 * @covers ::gutenberg_is_client_side_media_processing_enabled
 	 */
-	public function test_client_side_media_processing_enabled_by_default() {
-		$this->assertTrue( gutenberg_is_client_side_media_processing_enabled() );
+	public function test_client_side_media_processing_disabled_by_default_in_plugin() {
+		// Remove the test bootstrap override to check the plugin's actual default.
+		remove_filter( 'wp_client_side_media_processing_enabled', '__return_true', 20 );
+		$enabled = gutenberg_is_client_side_media_processing_enabled();
+		// Restore the test bootstrap override.
+		add_filter( 'wp_client_side_media_processing_enabled', '__return_true', 20 );
+
+		$this->assertFalse( $enabled );
 	}
 
 	/**
-	 * Tests that client-side media processing can be disabled via filter.
+	 * Tests that client-side media processing can be enabled via filter.
 	 *
 	 * @covers ::gutenberg_is_client_side_media_processing_enabled
 	 */
-	public function test_client_side_media_processing_can_be_disabled() {
-		add_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
-		$enabled = gutenberg_is_client_side_media_processing_enabled();
-		remove_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
-
-		$this->assertFalse( $enabled );
+	public function test_client_side_media_processing_can_be_enabled() {
+		$this->assertTrue( gutenberg_is_client_side_media_processing_enabled() );
 	}
 
 	/**
@@ -242,11 +248,12 @@ public function test_compat_rest_controller_used_when_filter_disabled() {
 	}
 
 	/**
-	 * Tests that the 6.9 compat REST controller is not used when filter is enabled (default).
+	 * Tests that the 6.9 compat REST controller is not used when filter is enabled.
 	 *
 	 * @covers ::gutenberg_override_attachments_rest_controller
 	 */
 	public function test_compat_rest_controller_not_used_when_filter_enabled() {
+		// Feature is enabled via test bootstrap filter at priority 20.
 		$result = gutenberg_override_attachments_rest_controller( array(), 'attachment' );
 
 		$this->assertSame( array(), $result );

From 48b8392b637a2b576b28adc14a3bf10be11f1bc9 Mon Sep 17 00:00:00 2001
From: Andrew Serong <14988353+andrewserong@users.noreply.github.com>
Date: Fri, 20 Feb 2026 13:14:50 +1100
Subject: [PATCH 2/3] Try to fix failing test

---
 phpunit/media/media-processing-test.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/phpunit/media/media-processing-test.php b/phpunit/media/media-processing-test.php
index 43d7d88278811e..e8b2afbcdf16c0 100644
--- a/phpunit/media/media-processing-test.php
+++ b/phpunit/media/media-processing-test.php
@@ -235,11 +235,14 @@ public function test_client_side_media_processing_can_be_enabled() {
 	 * @covers ::gutenberg_override_attachments_rest_controller
 	 */
 	public function test_compat_rest_controller_used_when_filter_disabled() {
+		// Remove the test bootstrap override so the disable filter takes effect.
+		remove_filter( 'wp_client_side_media_processing_enabled', '__return_true', 20 );
 		add_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
 
 		$result = gutenberg_override_attachments_rest_controller( array(), 'attachment' );
 
 		remove_filter( 'wp_client_side_media_processing_enabled', '__return_false' );
+		add_filter( 'wp_client_side_media_processing_enabled', '__return_true', 20 );
 
 		$this->assertSame(
 			array( 'rest_controller_class' => 'Gutenberg_REST_Attachments_Controller_6_9' ),

From dea0272a4bf5fd4e9e2ec3fd9217fe9cdcaad812 Mon Sep 17 00:00:00 2001
From: Andrew Serong <14988353+andrewserong@users.noreply.github.com>
Date: Fri, 20 Feb 2026 13:35:44 +1100
Subject: [PATCH 3/3] Update docblock

---
 lib/compat/plugin/media.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/compat/plugin/media.php b/lib/compat/plugin/media.php
index 9f7711c788589b..eafd8b054aea32 100644
--- a/lib/compat/plugin/media.php
+++ b/lib/compat/plugin/media.php
@@ -6,6 +6,9 @@
  * It is disabled by default in the plugin until known issues are resolved,
  * but can still be enabled via the filter.
  *
+ * Remove this file when the linked issues are resolved and the plugin
+ * is ready to match Core's default.
+ *
  * @see https://github.com/WordPress/gutenberg/issues/75302
  * @see https://github.com/WordPress/gutenberg/issues/75605
  *