fix(logging): emit startup warnings as WARNING records in JSON mode

litellm/_logging.py

@@ -943,17 +943,18 @@ def print_startup_message(message: str) -> None:
     if litellm.suppress_startup_output is True:
         return
     frame: Final = inspect.currentframe()
-    _write_startup_message(message, frame.f_back if frame is not None else None)
+    _write_startup_message(message, frame.f_back if frame is not None else None, logging.INFO)
 
 
 def print_startup_warning(message: str) -> None:
-    """Write a boot-time warning exactly as print_startup_message writes a message, even with
-    suppress_startup_output on, since it names something the operator has to fix."""
+    """Write a boot-time warning as print_startup_message writes a message, even with suppress_startup_output
+    on, since it names something the operator has to fix. With JSON logs on it is a WARNING record, on
+    stdout where the print put it, so a collector that filters on the level field keeps it."""
     frame: Final = inspect.currentframe()
-    _write_startup_message(message, frame.f_back if frame is not None else None)
+    _write_startup_message(message, frame.f_back if frame is not None else None, logging.WARNING)
 
 
-def _write_startup_message(message: str, caller: FrameType | None) -> None:
+def _write_startup_message(message: str, caller: FrameType | None, level: int) -> None:
     if not litellm.json_logs:
         print(terminal_text(message), flush=True)  # noqa: T201  # plain mode: this is the operator-terminal print it replaces
         return
@@ -962,7 +963,7 @@ def _write_startup_message(message: str, caller: FrameType | None) -> None:
         return
     record: Final = verbose_proxy_logger.makeRecord(
         verbose_proxy_logger.name,
-        logging.INFO,
+        level,
         caller.f_code.co_filename if caller is not None else __file__,
         caller.f_lineno if caller is not None else 0,
         text,
@@ -992,8 +993,8 @@ def _write_startup_message(message: str, caller: FrameType | None) -> None:
 
 
 def _startup_json_handler() -> logging.Handler:
-    """The proxy's JSON handler on stdout, filters included, for one startup message."""
-    handler: Final = LevelRoutingStreamHandler()
+    """The proxy's JSON handler on stdout, filters included, for one startup message or warning."""
+    handler: Final = logging.StreamHandler(sys.stdout)
     handler.setFormatter(JsonFormatter())
     handler.addFilter(_secret_filter)
     handler.addFilter(_correlation_filter)

tests/unit/proxy/policy_engine/test_init_policies.py

@@ -111,8 +111,8 @@ def test_policy_table_is_one_json_record_in_json_mode(monkeypatch, capfd):
 
 
 def test_missing_attachments_warning_is_a_second_json_record(monkeypatch, capfd):
-    """Without attachments the table and the yellow warning are two INFO records on stdout, where the two
-    prints put them."""
+    """Without attachments the table and the yellow warning are an INFO and a WARNING record on stdout,
+    where the two prints put them."""
     monkeypatch.setattr(litellm, "json_logs", True)
     monkeypatch.setattr(sys, "excepthook", sys.excepthook)
     turn_on_json()
@@ -126,4 +126,4 @@ def test_missing_attachments_warning_is_a_second_json_record(monkeypatch, capfd)
         "\n".join(("LiteLLM Policy Engine: Loaded 1 policies", "", *POLICY_ROWS)),
         NO_ATTACHMENTS_WARNING,
     ]
-    assert {record["level"] for record in records} == {"INFO"}
+    assert [record["level"] for record in records] == ["INFO", "WARNING"]

tests/unit/proxy/test_proxy_cli.py

@@ -4252,8 +4252,8 @@ class TestEnforcePrismaMigrationCheckNoticeAroundTheConfigRead:
 
 def test_granian_flag_notices_are_json_records_in_json_mode(monkeypatch, capfd):
     """The yellow notices for the flags Granian ignores (`--max_requests_before_restart`, `--ciphers`) are
-    printed while the launcher starts; with json_logs on they are INFO records on stdout like every other
-    line, not plaintext between the records."""
+    printed while the launcher starts; with json_logs on they are WARNING records on stdout after the INFO
+    start line, not plaintext between the records."""
     pytest.importorskip("granian")
     monkeypatch.setattr(litellm, "json_logs", True)
     monkeypatch.setattr(sys, "excepthook", sys.excepthook)  # turn_on_json swaps it; put it back at teardown
@@ -4284,4 +4284,4 @@ def test_granian_flag_notices_are_json_records_in_json_mode(monkeypatch, capfd):
         "(Granian uses workers_lifetime in seconds, not a per-request limit).",
         "LiteLLM: --ciphers is not applied when using --run_granian.",
     ]
-    assert {record["level"] for record in records} == {"INFO"}
+    assert [record["level"] for record in records] == ["INFO", "WARNING", "WARNING"]

tests/unit/test_logging.py

@@ -1914,7 +1914,8 @@ def test_print_startup_warning_still_prints_when_suppressed(
     monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str], json_logs: bool
 ):
     """A warning names something the operator has to fix, like an ignored flag or a failed migration diff,
-    so suppress_startup_output leaves it in place, at the caller's location in JSON mode."""
+    so suppress_startup_output leaves it in place. In JSON mode it is a WARNING record at the caller's
+    location, on stdout where the print put it, so a collector's WARNING filter keeps it."""
     monkeypatch.setattr(litellm, "json_logs", json_logs)
     monkeypatch.setattr(litellm, "suppress_startup_output", True)
     monkeypatch.setattr(sys, "excepthook", sys.excepthook)
@@ -1930,6 +1931,7 @@ def test_print_startup_warning_still_prints_when_suppressed(
     if json_logs:
         record: Final = json.loads(lines[0])
         assert record["message"] == "LiteLLM: --ciphers is not applied when using --run_granian."
+        assert record["level"] == "WARNING"
         assert str(record["logger"]).startswith("test_logging.py:"), record["logger"]
     else:
         assert lines[0] == "LiteLLM: --ciphers is not applied when using --run_granian."