fix(logging): take the scrubbed exception message off the traceback when the payload has none

When the failure payload could not be built, scrubbed_exception_text found the
marker only in the logged traceback and handed Langfuse, Traceloop, OTel v1 and
MLflow an empty message. Use the exception lines that end the scrubbed traceback.

litellm/litellm_core_utils/redact_messages.py

@@ -583,6 +583,7 @@ def scrubbed_exception_text(model_call_details: Mapping[str, object]) -> tuple[s
     """
     The error message and traceback a failure logged when redaction scrubbed the request's text out of
     either, for callbacks that would otherwise record the raw exception. ``None`` when nothing was scrubbed.
+    Without a logged error message, the message is the exception text that ends the traceback.
     """
     payload: Final = _as_mapping(model_call_details.get("standard_logging_object")) or {}
     error_information: Final = _as_mapping(payload.get("error_information")) or {}
@@ -593,10 +594,14 @@ def scrubbed_exception_text(model_call_details: Mapping[str, object]) -> tuple[s
     )
     if not any(isinstance(text, str) and REDACTED_BY_LITELLM in text for text in (message, traceback_text)):
         return None
-    return (
-        message if isinstance(message, str) else "",
-        traceback_text if isinstance(traceback_text, str) else "",
-    )
+    logged_traceback_text: Final = traceback_text if isinstance(traceback_text, str) else ""
+    return (message if isinstance(message, str) else _exception_text(logged_traceback_text), logged_traceback_text)
+
+
+def _exception_text(traceback_text: str) -> str:
+    """The lines after the last indented frame line of ``traceback_text``."""
+    lines: Final = reversed(traceback_text.rstrip().splitlines())
+    return "\n".join(reversed(tuple(itertools.takewhile(lambda line: not line.startswith(" "), lines))))
 
 
 def redacted_standard_logging_payload(payload: Mapping[str, object]) -> Mapping[str, object]:

tests/unit/litellm_core_utils/test_redact_messages.py

@@ -2202,6 +2202,21 @@ def test_scrubbed_exception_text_reports_a_scrub_of_the_logged_traceback() -> No
     assert scrubbed_exception_text(model_call_details) == ("outer", "ValueError: bad: redacted-by-litellm")
 
 
+def test_scrubbed_exception_text_reads_the_message_off_the_traceback_without_a_logged_message() -> None:
+    traceback_text: Final = (
+        "Traceback (most recent call last):\n"
+        '  File "main.py", line 1, in completion\n'
+        "    raise BadRequestError(message)\n"
+        "BadRequestError: Invalid content: 'redacted-by-litellm'\n"
+        "Received Messages=['redacted-by-litellm']\n"
+    )
+
+    assert scrubbed_exception_text({"traceback_exception": traceback_text}) == (
+        "BadRequestError: Invalid content: 'redacted-by-litellm'\nReceived Messages=['redacted-by-litellm']",
+        traceback_text,
+    )
+
+
 def test_scrubbed_error_information_for_request_scrubs_only_when_the_request_redacts() -> None:
     error_information: Final = StandardLoggingPayloadErrorInformation(
         error_code="400", error_class="BadRequestError", error_message=f"bad: {PROMPT}", traceback=f"tb {PROMPT}"