fix: prevent N×M reply explosion in HuggingFaceLocalGenerator with multiple stop_words

haystack/components/generators/hugging_face_local.py

@@ -260,6 +260,7 @@ def run(
 
         if self.stop_words:
             # the output of the pipeline includes the stop word
-            replies = [reply.replace(stop_word, "").rstrip() for reply in replies for stop_word in self.stop_words]
+            for stop_word in self.stop_words:
+                replies = [reply.replace(stop_word, "").rstrip() for reply in replies]
 
         return {"replies": replies}

releasenotes/notes/fix-hf-local-stop-words-cross-product-31d12d96c57c442b.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes ``HuggingFaceLocalGenerator`` so that when multiple ``stop_words`` are configured the generator returns exactly N replies instead of N×M replies. Previously the list comprehension created a cross-product, duplicating replies and leaving some stop words unstripped.

test/components/generators/test_hugging_face_local_generator.py

@@ -420,6 +420,22 @@ def test_run_stop_words_removal(self):
         results = generator.run(prompt="irrelevant")
         assert results == {"replies": ["Hello"]}
 
+    def test_run_multiple_stop_words_removal(self):
+        """Test that multiple stop words are all removed without producing N*M replies."""
+        generator = HuggingFaceLocalGenerator(
+            model="Qwen/Qwen3-0.6B", task="text-generation", stop_words=["STOP", "END"]
+        )
+        generator.pipeline = Mock(
+            return_value=[
+                {"generated_text": "Paris is the capital. STOP"},
+                {"generated_text": "France is in Europe. STOP"},
+            ]
+        )
+        generator.stopping_criteria_list = Mock()
+        results = generator.run(prompt="irrelevant")
+        # Should return exactly 2 replies, both stop words stripped
+        assert results == {"replies": ["Paris is the capital.", "France is in Europe."]}
+
     @pytest.mark.integration
     def test_stop_words_criteria_using_hf_tokenizer(self):
         """