Fix crash when scorer LLM response is blocked by content filter

pyrit/score/scorer.py

@@ -17,6 +17,7 @@
 )
 
 from pyrit.exceptions import (
+    BadRequestException,
     InvalidJsonException,
     PyritException,
     pyrit_json_retry,
@@ -729,6 +730,7 @@ async def _score_value_with_llm_async(
                 score_value still needs to be normalized and validated.
 
         Raises:
+            BadRequestException: If the scorer's LLM response is blocked by content filtering.
             ValueError: If required keys are missing from the response or if the response format is invalid.
             InvalidJsonException: If the response is not valid JSON.
             Exception: For other unexpected errors during scoring.
@@ -781,6 +783,17 @@ async def _score_value_with_llm_async(
 
         response_json: str = ""
         try:
+            # A content-filter block yields a single error piece with no parseable text piece,
+            # so raise a clear error here instead of failing on the missing text piece below.
+            if all(piece.is_blocked() for piece in response[0].message_pieces):
+                raise BadRequestException(
+                    message=(
+                        f"The scorer's LLM response was blocked by content filtering while scoring "
+                        f"prompt ID: {scored_prompt_id}. Consider using a scorer endpoint with "
+                        f"content filtering disabled for red-teaming workflows."
+                    )
+                )
+
             # Get the text piece which contains the JSON response containing the score_value and rationale from the LLM
             text_piece = next(
                 piece for piece in response[0].message_pieces if piece.converted_value_data_type == "text"

tests/unit/score/test_scorer.py

@@ -1548,6 +1548,39 @@ async def test_score_value_with_llm_skips_reasoning_piece(good_json):
     assert result.score_rationale == "Valid response"
 
 
+async def test_score_value_with_llm_raises_when_scorer_response_blocked():
+    """When the scorer's own LLM response is blocked by content filtering, raise BadRequestException."""
+    from pyrit.exceptions import BadRequestException
+
+    chat_target = MagicMock(PromptTarget)
+    chat_target.get_identifier.return_value = get_mock_target_identifier("MockChatTarget")
+
+    blocked_piece = MessagePiece(
+        role="assistant",
+        original_value="",
+        original_value_data_type="error",
+        converted_value="",
+        converted_value_data_type="error",
+        conversation_id="test-convo",
+        response_error="blocked",
+    )
+    blocked_response = Message(message_pieces=[blocked_piece])
+    chat_target.send_prompt_async = AsyncMock(return_value=[blocked_response])
+
+    scorer = MockScorer()
+
+    with pytest.raises(BadRequestException, match="blocked by content filtering"):
+        await scorer._score_value_with_llm_async(
+            prompt_target=chat_target,
+            system_prompt="system_prompt",
+            message_value="message_value",
+            message_data_type="text",
+            scored_prompt_id="test-prompt-id",
+            category="category",
+            objective="task",
+        )
+
+
 # ── Helpers for score_blocked_content tests ──────────────────────────────────