fix: add wp_supports_ai() and related constant + filter

src/wp-includes/ai-client.php

@@ -9,6 +9,27 @@
 
 use WordPress\AiClient\AiClient;
 
+/**
+ * Returns whether AI features are supported in the current environment.
+ *
+ * @since 7.0.0
+ */
+function wp_supports_ai(): bool {
+	// Constant check gives a hard short-circuit for environments that cannot be overridden with a filter, such as wp-config.php settings or hosting provider configurations.
+	if ( defined( 'WP_DISABLE_AI' ) && WP_DISABLE_AI ) {
+		return false;
+	}
+
+	/**
+	 * Filters whether the current request should use AI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param bool $is_enabled Whether the current request should use AI. Default true.
+	 */
+	return (bool) apply_filters( 'wp_supports_ai', true );
+}
+
 /**
  * Creates a new AI prompt builder using the default provider registry.
  *

src/wp-includes/ai-client/class-wp-ai-client-prompt-builder.php

@@ -166,6 +166,11 @@ class WP_AI_Client_Prompt_Builder {
 	 */
 	public function __construct( ProviderRegistry $registry, $prompt = null ) {
 		try {
+			if ( ! wp_supports_ai() ) {
+				// The catch block will convert this to a WP_Error.
+				throw new \RuntimeException( __( 'AI features are not supported in the current environment.' ) );
+			}
+
 			$this->builder = new PromptBuilder( $registry, $prompt );
 		} catch ( Exception $e ) {
 			$this->builder = new PromptBuilder( $registry );

src/wp-includes/connectors.php

@@ -17,7 +17,7 @@
  * @access private
  */
 function _wp_connectors_add_settings_menu_item(): void {
-	if ( ! class_exists( '\WordPress\AiClient\AiClient' ) || ! function_exists( 'wp_connectors_wp_admin_render_page' ) ) {
+	if ( ! wp_supports_ai() || ! class_exists( '\WordPress\AiClient\AiClient' ) || ! function_exists( 'wp_connectors_wp_admin_render_page' ) ) {
 		return;
 	}
 
@@ -117,6 +117,10 @@ function _wp_connectors_get_real_api_key( string $option_name, callable $mask_ca
  * @return array<string, array{provider: string, label: string, description: string, mask: callable, sanitize: callable}> Provider settings keyed by setting name.
  */
 function _wp_connectors_get_provider_settings(): array {
+	if ( ! wp_supports_ai() ) {
+		return array();
+	}
+
 	$providers = array(
 		'google'    => array(
 			'name' => 'Google',

tests/phpunit/tests/ai-client/wpAiClientPrompt.php

@@ -30,4 +30,23 @@ public function test_returns_independent_instances() {
 
 		$this->assertNotSame( $builder1, $builder2 );
 	}
+
+	/**
+	 * Tests that returns a WP_AI_Client_Prompt_Builder instance even when AI is not supported, but that the builder contains an error.
+	 */
+	public function test_returns_error_builder_when_ai_not_supported() {
+		// Temporarily disable AI support for this test.
+		add_filter( 'wp_supports_ai', '__return_false' );
+		$builder = wp_ai_client_prompt();
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $builder );
+
+		// Check the $error prop is a real WP_Error with the expected message.
+		$reflection = new ReflectionClass( $builder );
+		$error_prop = $reflection->getProperty( 'error' );
+		$error_prop->setAccessible( true );
+		$error = $error_prop->getValue( $builder );
+
+		$this->assertInstanceOf( WP_Error::class, $error );
+		$this->assertSame( 'AI features are not supported in the current environment.', $error->get_error_message() );
+	}
 }

tests/phpunit/tests/ai-client/wpSupportsAI.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * Tests for wp_supports_ai().
+ *
+ * @group ai-client
+ * @covers ::wp_supports_ai
+ */
+
+class Tests_WP_Supports_AI extends WP_UnitTestCase {
+	/**
+	* {@inheritDoc}
+	*/
+	public function tear_down() {
+		// Remove the WP_DISABLE_AI constant if it was defined during tests.
+		remove_all_filters( 'wp_supports_ai' );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Test that wp_supports_ai() defaults to true.
+	 *
+	 * @ticket 64591
+	 */
+	public function test_defaults_to_true() {
+		$this->assertTrue( wp_supports_ai() );
+	}
+
+	/**
+	 * Tests that the wp_supports_ai filter can disable/enable AI features.
+	 */
+	public function test_filter_can_disable_ai_features() {
+		add_filter( 'wp_supports_ai', '__return_false' );
+		$this->assertFalse( wp_supports_ai() );
+
+		// Try a later filter to re-enable AI and confirm that it works.
+		add_filter( 'wp_supports_ai', '__return_true' );
+		$this->assertTrue( wp_supports_ai() );
+	}
+}

tests/phpunit/tests/connectors/wpConnectorsGetProviderSettings.php

@@ -43,4 +43,16 @@ public function test_provider_values_match_expected() {
 		$this->assertSame( 'openai', $settings['connectors_ai_openai_api_key']['provider'] );
 		$this->assertSame( 'anthropic', $settings['connectors_ai_anthropic_api_key']['provider'] );
 	}
+
+	/**
+	 * Tests providers return an empty array when AI is not supported
+	 */
+	public function test_returns_empty_array_when_ai_not_supported() {
+		// Temporarily disable AI support for this test.
+		add_filter( 'wp_supports_ai', '__return_false' );
+
+		$settings = _wp_connectors_get_provider_settings();
+		$this->assertIsArray( $settings );
+		$this->assertEmpty( $settings );
+	}
 }