diff --git a/langfuse/_client/resource_manager.py b/langfuse/_client/resource_manager.py
index a61101fe3..8c9d5c41b 100644
--- a/langfuse/_client/resource_manager.py
+++ b/langfuse/_client/resource_manager.py
@@ -677,6 +677,11 @@ def _init_tracer_provider(
         otel_trace_api.set_tracer_provider(provider)
 
     else:
+        if sample_rate is not None and sample_rate < 1:
+            langfuse_logger.warning(
+                "Configuration: sample_rate was ignored because an OpenTelemetry TracerProvider is already registered. "
+                "Configure the sampler on your own TracerProvider instead."
+            )
         if id_generator is not None:
             langfuse_logger.warning(
                 "Configuration: id_generator was ignored because an OpenTelemetry TracerProvider is already registered. "
diff --git a/langfuse/_task_manager/score_ingestion_consumer.py b/langfuse/_task_manager/score_ingestion_consumer.py
index 1dce00f80..b1854c2ba 100644
--- a/langfuse/_task_manager/score_ingestion_consumer.py
+++ b/langfuse/_task_manager/score_ingestion_consumer.py
@@ -187,7 +187,10 @@ def execute_task_with_backoff(batch: List[Any]) -> None:
                     and 400 <= int(e.status) < 500
                     and int(e.status) != 429  # retry if rate-limited
                 ):
-                    return
+                    # Non-retryable 4xx: the batch is permanently lost.
+                    # Raise so handle_exception logs the loss instead of
+                    # silently pretending the batch was delivered.
+                    raise e
 
                 raise e