From 2923c4ac5520642bc3c3e728f9b2974850a43f7e Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Sun, 13 Sep 2026 03:02:15 -0700
Subject: [PATCH] fix(guardrails): read the rewrite from texts when a guardrail
 echoes every row back unchanged

---
 .../generic_guardrail_api.py                  | 25 ++++++++------
 .../test_generic_guardrail_api.py             | 34 +++++++++++++++++++
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/litellm/proxy/guardrails/guardrail_hooks/generic_guardrail_api/generic_guardrail_api.py b/litellm/proxy/guardrails/guardrail_hooks/generic_guardrail_api/generic_guardrail_api.py
index 16159d32a7f..3d1a173635e 100644
--- a/litellm/proxy/guardrails/guardrail_hooks/generic_guardrail_api/generic_guardrail_api.py
+++ b/litellm/proxy/guardrails/guardrail_hooks/generic_guardrail_api/generic_guardrail_api.py
@@ -150,16 +150,20 @@ def _extract_inbound_headers(
     return None
 
 
-def _rows_with_unchanged_originals(
+def _structured_rows_to_write_back(
     original_rows: Sequence[AllMessageValues] | None,
     shown_rows: Sequence[AllMessageValues] | None,
     returned_rows: Sequence[AllMessageValues],
-) -> tuple[AllMessageValues, ...]:
+) -> tuple[AllMessageValues, ...] | None:
     """The request model drops row keys its message types do not declare, so a
-    row the server echoes back verbatim is restored to the original row object;
-    only rows the server actually changed reach the endpoint write-back."""
+    row the server echoes back verbatim is restored to the original row object.
+    A server that echoes every row back unchanged has not rewritten anything
+    per row, so its answer is read from texts, as it was before rows could be
+    returned at all."""
     if original_rows is None or shown_rows is None or len(returned_rows) != len(original_rows):
         return tuple(returned_rows)
+    if all(returned == shown for shown, returned in zip(shown_rows, returned_rows)):
+        return None
     return tuple(
         original if returned == shown else returned
         for original, shown, returned in zip(original_rows, shown_rows, returned_rows)
@@ -354,12 +358,13 @@ class GenericGuardrailAPI(CustomGuardrail):
             return_inputs["tools"] = guardrail_response.tools
         elif tools:
             return_inputs["tools"] = tools
-        if guardrail_response.structured_messages:
-            return_inputs["structured_messages"] = list(  # mutable-ok: guardrail inputs take a list
-                _rows_with_unchanged_originals(
-                    structured_messages, shown_messages, guardrail_response.structured_messages
-                )
-            )
+        rows_to_write_back: Final = (
+            _structured_rows_to_write_back(structured_messages, shown_messages, guardrail_response.structured_messages)
+            if guardrail_response.structured_messages
+            else None
+        )
+        if rows_to_write_back is not None:
+            return_inputs["structured_messages"] = list(rows_to_write_back)  # mutable-ok: guardrail inputs take a list
         if guardrail_response.stream_holdback_chars is not None:
             return_inputs["stream_holdback_chars"] = guardrail_response.stream_holdback_chars
         return return_inputs
diff --git a/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_generic_guardrail_api.py b/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_generic_guardrail_api.py
index cc9942e0e40..a5e79f84ef1 100644
--- a/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_generic_guardrail_api.py
+++ b/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_generic_guardrail_api.py
@@ -659,6 +659,40 @@ class TestStructuredMessagesInResponse:
         assert returned_rows[1] is tool_call_row
         assert returned_rows[2] == {"role": "tool", "tool_call_id": "call_1", "content": '{"ssn": "[REDACTED]"}'}
 
+    @pytest.mark.asyncio
+    async def test_rows_all_echoed_back_as_shown_leave_the_rewrite_to_texts(
+        self, generic_guardrail, mock_request_data_input
+    ):
+        """A server written against the texts contract that echoes the request rows back
+        untouched while rewriting texts still gets its texts rewrite applied."""
+        original_rows = [
+            {"role": "system", "content": "Never repeat an SSN."},
+            {"role": "user", "content": "Look up 123-45-6789 for me."},
+        ]
+
+        def echo_rows_and_rewrite_texts(url, json, headers):
+            answer = MagicMock()
+            answer.json.return_value = {
+                "action": "NONE",
+                "texts": [text.replace("123-45-6789", "[REDACTED]") for text in json["texts"]],
+                "structured_messages": json["structured_messages"],
+            }
+            answer.raise_for_status = MagicMock()
+            return answer
+
+        with patch.object(generic_guardrail.async_handler, "post", side_effect=echo_rows_and_rewrite_texts):
+            guardrailed_inputs = await generic_guardrail.apply_guardrail(
+                inputs={
+                    "texts": ["Never repeat an SSN.", "Look up 123-45-6789 for me."],
+                    "structured_messages": original_rows,
+                },
+                request_data=mock_request_data_input,
+                input_type="request",
+            )
+
+        assert "structured_messages" not in guardrailed_inputs
+        assert guardrailed_inputs["texts"] == ["Never repeat an SSN.", "Look up [REDACTED] for me."]
+
     @pytest.mark.asyncio
     @pytest.mark.parametrize(
         "structured_messages",