fix: tolerate spotify version suffixes and surface rerank failures

backend/app/pipeline/orchestrator.py

@@ -177,27 +177,44 @@ class RecommendationPipeline:
         history: tuple[ConversationTurn, ...],
         selection: _TrackSelection,
     ) -> AsyncGenerator[PipelineTrackEvent | PipelineWarningEvent]:
-        """Stream one rerank, retry once on invalid output, then fall back."""
-        correction: str | None = None
-        for _ in range(2):
-            if selection.is_full:
-                return
-            try:
-                async for event in self._rerank_once(
-                    intent, taste_summary, history, selection, correction
-                ):
-                    yield event
-                return
-            except RecommenderOutputError as error:
-                correction = (
-                    f"Validation failed: {error}."
-                    f" Already emitted track ids: {selection.describe_selected_ids()}."
-                )
+        """Stream the rerank with one corrected retry, then fall back."""
+        try:
+            async for event in self._rerank_with_one_retry(
+                intent, taste_summary, history, selection
+            ):
+                yield event
+            return
+        except RecommenderOutputError as error:
+            _log_rerank_failure(attempt=2, error=error)
 
         yield PipelineWarningEvent(code=RERANK_FALLBACK_CODE, message=RERANK_FALLBACK_MESSAGE)
         for event in selection.fill_from_pool(RERANK_FALLBACK_JUSTIFICATION):
             yield event
 
+    async def _rerank_with_one_retry(
+        self,
+        intent: Intent,
+        taste_summary: str,
+        history: tuple[ConversationTurn, ...],
+        selection: _TrackSelection,
+    ) -> AsyncGenerator[PipelineTrackEvent]:
+        """Rerank once; on invalid output, retry once with a correction."""
+        try:
+            async for event in self._rerank_once(intent, taste_summary, history, selection, None):
+                yield event
+            return
+        except RecommenderOutputError as error:
+            _log_rerank_failure(attempt=1, error=error)
+            if selection.is_full:
+                return
+            correction = (
+                f"Validation failed: {error}."
+                f" Already emitted track ids: {selection.describe_selected_ids()}."
+            )
+
+        async for event in self._rerank_once(intent, taste_summary, history, selection, correction):
+            yield event
+
     async def _rerank_once(
         self,
         intent: Intent,
@@ -219,6 +236,11 @@ class RecommendationPipeline:
                 yield selection.select(item.track_id, item.justification)
 
 
+def _log_rerank_failure(attempt: int, error: RecommenderOutputError) -> None:
+    """Log one invalid rerank attempt with its validation reason."""
+    structlog.get_logger().warning("rerank_attempt_failed", attempt=attempt, error=str(error))
+
+
 def _log_completion(selection: _TrackSelection, taste: CompressedTasteProfile) -> None:
     """Log how many recommendations were served and how many are new."""
     new_track_count = sum(track.id not in taste.known_track_ids for track in selection.selected)