diff --git a/includes/Classifai/Features/TextToSpeech.php b/includes/Classifai/Features/TextToSpeech.php
index 6e5ca065b..ad525b3b1 100644
--- a/includes/Classifai/Features/TextToSpeech.php
+++ b/includes/Classifai/Features/TextToSpeech.php
@@ -398,7 +398,8 @@ public function rest_endpoint_callback( WP_REST_Request $request ) {
 			$results = $this->run( $request->get_param( 'id' ), 'synthesize' );
 
 			if ( $results && ! is_wp_error( $results ) ) {
-				$attachment_id = $this->save( $results, $request->get_param( 'id' ) );
+				// An integer result means the provider returned a cached attachment ID
+				$attachment_id = is_int( $results ) ? $results : $this->save( $results, $request->get_param( 'id' ) );
 
 				if ( ! is_wp_error( $attachment_id ) ) {
 					return rest_ensure_response(
@@ -676,7 +677,10 @@ public function generate_text_to_speech_audio( int $post_id, ?int $calling_user_
 		$results = $this->run( $post_id, 'synthesize' );
 
 		if ( $results && ! is_wp_error( $results ) ) {
-			$this->save( $results, $post_id );
+			// An integer result means the provider returned a cached attachment ID
+			if ( ! is_int( $results ) ) {
+				$this->save( $results, $post_id );
+			}
 			delete_post_meta( $post_id, '_classifai_text_to_speech_error' );
 		} elseif ( is_wp_error( $results ) ) {
 			update_post_meta(
diff --git a/tests/Integration/Features/TextToSpeechTest.php b/tests/Integration/Features/TextToSpeechTest.php
index 8f54ecdec..a3ec19b79 100644
--- a/tests/Integration/Features/TextToSpeechTest.php
+++ b/tests/Integration/Features/TextToSpeechTest.php
@@ -125,4 +125,32 @@ public function test_save_replaces_existing_audio() {
 		$this->assertSame( $second, (int) get_post_meta( $post_id, TextToSpeech::AUDIO_ID_KEY, true ) );
 		$this->assertNull( get_post( $first ), 'The old audio attachment is deleted.' );
 	}
+
+	/**
+	 * When the provider returns a cached attachment ID (content unchanged), the
+	 * existing audio must be left intact rather than overwritten with the
+	 * numeric ID coerced to a string.
+	 *
+	 * @covers ::generate_text_to_speech_audio
+	 */
+	public function test_cached_audio_is_not_overwritten() {
+		$feature = new TextToSpeech();
+		$post_id = self::factory()->post->create( [ 'post_content' => 'Some content to read.' ] );
+		$this->as_user_with_role( 'administrator' );
+		$this->enable_feature();
+
+		// Seed a previously generated audio attachment.
+		$attachment_id = $feature->save( 'real-audio-bytes', $post_id );
+		$audio_file    = get_attached_file( $attachment_id );
+
+		// Mark the saved content hash so the provider's cached branch is taken.
+		update_post_meta( $post_id, TextToSpeech::AUDIO_HASH_KEY, md5( $feature->normalize_post_content( $post_id ) ) );
+
+		$feature->generate_text_to_speech_audio( $post_id );
+
+		// The attachment must be untouched: same ID, same file, same bytes.
+		$this->assertSame( $attachment_id, (int) get_post_meta( $post_id, TextToSpeech::AUDIO_ID_KEY, true ) );
+		$this->assertNotNull( get_post( $attachment_id ), 'The cached audio attachment is preserved.' );
+		$this->assertSame( 'real-audio-bytes', file_get_contents( $audio_file ) );
+	}
 }