fix(image-pipeline): surface per-image failures in the event log

Two gaps made posts 650/657 appear to silently "lose" their featured
images on 2026-04-20:

1. The batch provider tagged each failed key with ['error' => ...] but
   the ERROR log line it emitted didn't identify which key failed, so
   operators couldn't tell image_a from image_b in the event log when
   one of two parallel requests died.

2. Image_Pipeline::process_image_a/_b folded the per-key error into
   $result['errors'] and returned silently, with no WARNING row. Ops
   only learned about the miss when the outer catch in the caller fired
   — and on the 2026-04-20 incident that outer catch didn't fire, so
   nothing was logged at all except an unrelated pricing warning.

Fix:

- class-open-router-image-batch.php: collect_result() takes the request
  key as its first argument and every Logger::error message reads
  'OpenRouter batch image gen <class> for key "<key>": <detail>'.
  Matches the shape of OpenRouter_Image_Support::log_retry.

- class-image-pipeline.php: process_image_a and process_image_b now
  emit a Logger::warning('image_pipeline') row whenever $image_data is
  missing or carries an error key, in addition to pushing to
  $result['errors']. The warning fires whether or not the outer catch
  runs.

Test: ImagePipelineTest::test_partial_batch_failure_emits_warning_log_row
mocks $wpdb, runs the pipeline with image_a erroring, and asserts at
least one warning/image_pipeline row was inserted.

No behavior change beyond logging; cost impact zero.

Part of the v0.8.0 image bundle (issues from thread image-mime-bug).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

includes/core/class-image-pipeline.php

@@ -165,7 +165,14 @@ class PRAutoBlogger_Image_Pipeline {
 	private function process_image_a( int $post_id, array $batch_results, array $captions, array &$result ): void {
 		$image_data = $batch_results['image_a'] ?? null;
 		if ( ! $image_data || isset( $image_data['error'] ) ) {
-			$result['errors'][] = $image_data['error'] ?? 'Image A missing from batch results.';
+			$err_msg            = $image_data['error'] ?? 'Image A missing from batch results.';
+			$result['errors'][] = $err_msg;
+			// Log at WARNING so the path is visible even if the outer catch in the
+			// caller doesn't fire. See thread image-mime-bug Issue 2.
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Image A generation failed for post %d: %s', $post_id, $err_msg ),
+				'image_pipeline'
+			);
 			return;
 		}
 
@@ -196,7 +203,14 @@ class PRAutoBlogger_Image_Pipeline {
 	private function process_image_b( int $post_id, array $batch_results, array $captions, array &$result ): void {
 		$image_data = $batch_results['image_b'] ?? null;
 		if ( ! $image_data || isset( $image_data['error'] ) ) {
-			$result['errors'][] = $image_data['error'] ?? 'Image B missing from batch results.';
+			$err_msg            = $image_data['error'] ?? 'Image B missing from batch results.';
+			$result['errors'][] = $err_msg;
+			// Log at WARNING so the path is visible even if the outer catch in the
+			// caller doesn't fire. See thread image-mime-bug Issue 2.
+			PRAutoBlogger_Logger::instance()->warning(
+				sprintf( 'Image B generation failed for post %d: %s', $post_id, $err_msg ),
+				'image_pipeline'
+			);
 			return;
 		}
 

includes/providers/class-open-router-image-batch.php

@@ -130,6 +130,7 @@ class PRAutoBlogger_OpenRouter_Image_Batch {
 		$results = [];
 		foreach ( $handles as $key => $entry ) {
 			$results[ $key ] = $this->collect_result(
+				(string) $key,
 				$entry['handle'],
 				$entry['model'],
 				$entry['req'],
@@ -169,21 +170,35 @@ class PRAutoBlogger_OpenRouter_Image_Batch {
 	/**
 	 * Parse the result of one cURL handle into image data or error.
 	 *
+	 * All failure paths emit `Logger::error` at the point they fold the
+	 * request into an `['error' => ...]` array — tagged with the request
+	 * `$key` so the pipeline can attribute which of the parallel images
+	 * failed (image_a vs image_b) without cross-referencing timestamps.
+	 *
+	 * @param string      $key    Request key from the batch map (e.g. "image_a").
 	 * @param \CurlHandle $ch     Individual cURL handle (completed).
 	 * @param string      $model  Resolved model id.
 	 * @param array       $req    Original request array.
 	 * @param float       $start  Microtime when this handle was created.
 	 *
 	 * @return array Image data array or `{error: string}`.
+	 *
+	 * Side effects: writes `Logger::error` on any failure path.
 	 */
-	private function collect_result( $ch, string $model, array $req, float $start ): array {
+	private function collect_result( string $key, $ch, string $model, array $req, float $start ): array {
 		$latency_ms = (int) ( ( microtime( true ) - $start ) * 1000 );
 
 		// phpcs:ignore WordPress.WP.AlternativeFunctions.curl_curl_errno
 		$curl_errno = curl_errno( $ch );
 		if ( 0 !== $curl_errno ) {
 			// phpcs:ignore WordPress.WP.AlternativeFunctions.curl_curl_error
-			$msg = sprintf( 'cURL error %d: %s', $curl_errno, curl_error( $ch ) );
+			$detail = curl_error( $ch );
+			$msg    = sprintf(
+				'OpenRouter batch image gen cURL error %d for key "%s": %s',
+				$curl_errno,
+				$key,
+				$detail
+			);
 			PRAutoBlogger_Logger::instance()->error( $msg, 'openrouter-image-batch' );
 			return [ 'error' => $msg ];
 		}
@@ -194,7 +209,12 @@ class PRAutoBlogger_OpenRouter_Image_Batch {
 		$raw = (string) curl_multi_getcontent( $ch );
 
 		if ( $http_code >= 400 ) {
-			$msg = sprintf( 'HTTP %d: %s', $http_code, substr( $raw, 0, 300 ) );
+			$msg = sprintf(
+				'OpenRouter batch image gen HTTP %d for key "%s": %s',
+				$http_code,
+				$key,
+				substr( $raw, 0, 300 )
+			);
 			PRAutoBlogger_Logger::instance()->error( $msg, 'openrouter-image-batch' );
 			return [ 'error' => $msg ];
 		}
@@ -202,11 +222,13 @@ class PRAutoBlogger_OpenRouter_Image_Batch {
 		try {
 			$image_bytes = $this->support->extract_image_bytes( $raw );
 		} catch ( \Throwable $e ) {
-			PRAutoBlogger_Logger::instance()->error(
-				'Batch parse error: ' . $e->getMessage(),
-				'openrouter-image-batch'
+			$msg = sprintf(
+				'OpenRouter batch image gen parse error for key "%s": %s',
+				$key,
+				$e->getMessage()
 			);
-			return [ 'error' => $e->getMessage() ];
+			PRAutoBlogger_Logger::instance()->error( $msg, 'openrouter-image-batch' );
+			return [ 'error' => $msg ];
 		}
 
 		return [