From 627b667688e2c368433ef83066ca54235a201fba Mon Sep 17 00:00:00 2001
From: "devin-ai-integration[bot]"
 <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Date: Wed, 21 Oct 2026 00:05:33 +0000
Subject: [PATCH] fix(decisions): log non-UTF-8 bytes as base64 so the request
 reaches validation and gets a 400 (#47564)

Co-authored-by: devin-ai-integration[bot] <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Backport of #47564 to stable/1.105.x.
Cherry-picked from ce63f48ed2ee3a18b7860b72f292e90ebeb1a986 (main).
---
 litellm/decisions/call.py         |  2 +-
 tests/unit/decisions/test_call.py | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/litellm/decisions/call.py b/litellm/decisions/call.py
index 1d75d6942f0..4299736bcff 100644
--- a/litellm/decisions/call.py
+++ b/litellm/decisions/call.py
@@ -160,7 +160,7 @@ def _jsonable_fallback(value: object) -> object:
 
 def _logged_request_message(caller_request: object) -> ChatCompletionUserMessage:
     caller_fields: Final = _LOGGED_FIELDS_ADAPTER.validate_python(
-        to_jsonable_python(caller_request, fallback=_jsonable_fallback)
+        to_jsonable_python(caller_request, fallback=_jsonable_fallback, bytes_mode="base64")
     )
     sent_fields: Final = json.dumps(
         dict((name, value) for name, value in caller_fields.items() if value not in (None, [], {}))
diff --git a/tests/unit/decisions/test_call.py b/tests/unit/decisions/test_call.py
index 0aec79ceb09..138d9dba906 100644
--- a/tests/unit/decisions/test_call.py
+++ b/tests/unit/decisions/test_call.py
@@ -1,3 +1,4 @@
+import base64
 import json
 from collections.abc import Mapping
 from datetime import datetime, timezone
@@ -100,3 +101,20 @@ def test_decisions_request_is_logged_even_when_its_questions_fail_validation():
 
     logged: Final = _logged_request(logging_obj)
     assert logged["questions"][0]["instructions"] == QUESTION_TEXT
+
+
+def test_non_utf8_bytes_in_the_request_are_logged_and_rejected_with_a_400():
+    logging_obj: Final = _logging_obj("adecisions")
+    raw_input: Final = b"\xff\xfe not utf-8"
+
+    with pytest.raises(litellm.BadRequestError):
+        _prepare_decisions_call(
+            **CONNECTION,
+            decision_input=raw_input,
+            questions=[{"type": "predicate", "instructions": QUESTION_TEXT}],
+            kwargs={"litellm_logging_obj": logging_obj},
+        )
+
+    logged: Final = _logged_request(logging_obj)
+    assert base64.urlsafe_b64decode(logged["input"]) == raw_input
+    assert logged["questions"][0]["instructions"] == QUESTION_TEXT