diff --git a/inc/rest.php b/inc/rest.php
index 6e70298c..59d8be1c 100644
--- a/inc/rest.php
+++ b/inc/rest.php
@@ -709,7 +709,7 @@ public function poll_optimized_images( WP_REST_Request $request ) {
 		$api_key = $request->get_param( 'api_key' );
 		$request = new Optml_Api();
 		$images  = $request->get_optimized_images( $api_key );
-		if ( ! isset( $images['list'] ) || empty( $images['list'] ) ) {
+		if ( is_wp_error( $images ) || ! is_array( $images ) || empty( $images['list'] ) ) {
 			return $this->response( [] );
 		}
 
diff --git a/tests/test-poll-optimized-images.php b/tests/test-poll-optimized-images.php
new file mode 100644
index 00000000..929d7e56
--- /dev/null
+++ b/tests/test-poll-optimized-images.php
@@ -0,0 +1,219 @@
+<?php
+/**
+ * Tests for optimized-images REST polling.
+ *
+ * @package Optimole-WP
+ */
+
+/**
+ * Class Test_Poll_Optimized_Images.
+ */
+class Test_Poll_Optimized_Images extends WP_UnitTestCase {
+	/**
+	 * HTTP mock callback for the current test.
+	 *
+	 * @var callable|null
+	 */
+	private $http_mock;
+
+	/**
+	 * Set up the test environment before each test.
+	 */
+	public function setUp(): void {
+		parent::setUp();
+		$settings = new Optml_Settings();
+		$settings->update(
+			'service_data',
+			[
+				'cdn_key'    => 'test123',
+				'cdn_secret' => '12345',
+				'whitelist'  => [ 'example.com' ],
+			]
+		);
+		add_filter( 'pre_http_request', [ $this, 'filter_pre_http_request' ], 10, 3 );
+	}
+
+	/**
+	 * Clean up after each test.
+	 */
+	public function tearDown(): void {
+		parent::tearDown();
+		remove_filter( 'pre_http_request', [ $this, 'filter_pre_http_request' ], 10 );
+		$this->http_mock = null;
+	}
+
+	/**
+	 * Route HTTP mocks for dashboard stats/images requests.
+	 *
+	 * @param false|array|WP_Error $preempt Whether to preempt.
+	 * @param array                $args    Request args.
+	 * @param string               $url     Request URL.
+	 * @return false|array|WP_Error
+	 */
+	public function filter_pre_http_request( $preempt, $args, $url ) {
+		if ( strpos( $url, 'stats/images' ) === false ) {
+			return $preempt;
+		}
+		if ( is_callable( $this->http_mock ) ) {
+			return call_user_func( $this->http_mock, $preempt, $args, $url );
+		}
+		return $preempt;
+	}
+
+	/**
+	 * Call poll_optimized_images and return decoded REST payload.
+	 *
+	 * @return array{data: mixed, code: string|int}
+	 */
+	private function poll() {
+		$rest     = new Optml_Rest();
+		$request  = new WP_REST_Request( 'GET' );
+		$request->set_param( 'api_key', 'test-key' );
+		$response = $rest->poll_optimized_images( $request );
+		$this->assertInstanceOf( WP_REST_Response::class, $response );
+		return $response->get_data();
+	}
+
+	/**
+	 * Transport WP_Error must not fatal; polling returns an empty list.
+	 */
+	public function test_poll_returns_empty_list_on_transport_wp_error() {
+		$this->http_mock = function () {
+			return new WP_Error( 'http_request_failed', 'Could not connect' );
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertSame( [], $payload['data'] );
+	}
+
+	/**
+	 * Non-200 API payload with an error field becomes WP_Error in Optml_Api::request().
+	 */
+	public function test_poll_returns_empty_list_on_api_error_payload() {
+		$this->http_mock = function () {
+			return [
+				'headers'  => [],
+				'body'     => wp_json_encode(
+					[
+						'code'  => 500,
+						'error' => 'upstream failed',
+					]
+				),
+				'response' => [
+					'code'    => 200,
+					'message' => 'OK',
+				],
+			];
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertSame( [], $payload['data'] );
+	}
+
+	/**
+	 * Empty API body is documented as false and must not fatal.
+	 */
+	public function test_poll_returns_empty_list_on_false_api_result() {
+		$this->http_mock = function () {
+			return [
+				'headers'  => [],
+				'body'     => '',
+				'response' => [
+					'code'    => 200,
+					'message' => 'OK',
+				],
+			];
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertSame( [], $payload['data'] );
+	}
+
+	/**
+	 * Successful payload without a list is treated as empty.
+	 */
+	public function test_poll_returns_empty_list_when_list_missing() {
+		$this->http_mock = function () {
+			return [
+				'headers'  => [],
+				'body'     => wp_json_encode(
+					[
+						'code' => 200,
+						'data' => [ 'count' => 0 ],
+					]
+				),
+				'response' => [
+					'code'    => 200,
+					'message' => 'OK',
+				],
+			];
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertSame( [], $payload['data'] );
+	}
+
+	/**
+	 * Successful payload with an empty list is treated as empty.
+	 */
+	public function test_poll_returns_empty_list_when_list_empty() {
+		$this->http_mock = function () {
+			return [
+				'headers'  => [],
+				'body'     => wp_json_encode(
+					[
+						'code' => 200,
+						'data' => [ 'list' => [] ],
+					]
+				),
+				'response' => [
+					'code'    => 200,
+					'message' => 'OK',
+				],
+			];
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertSame( [], $payload['data'] );
+	}
+
+	/**
+	 * A valid list is returned (URLs rewritten through Optimole).
+	 */
+	public function test_poll_returns_images_from_list() {
+		$this->http_mock = function () {
+			return [
+				'headers'  => [],
+				'body'     => wp_json_encode(
+					[
+						'code' => 200,
+						'data' => [
+							'list' => [
+								[
+									'url' => 'https://example.com/photo.jpg',
+									'key' => 'AbC',
+								],
+							],
+						],
+					]
+				),
+				'response' => [
+					'code'    => 200,
+					'message' => 'OK',
+				],
+			];
+		};
+
+		$payload = $this->poll();
+		$this->assertSame( 'success', $payload['code'] );
+		$this->assertCount( 1, $payload['data'] );
+		$this->assertArrayHasKey( 'url', $payload['data'][0] );
+		$this->assertArrayNotHasKey( 'key', $payload['data'][0] );
+		$this->assertStringContainsString( 'example.com/photo.jpg', $payload['data'][0]['url'] );
+	}
+}