fix(proxy): populate Exception.args so str(ProxyException) returns message (LIT-3094) (#29015)

* fix(proxy): populate Exception.args so str(ProxyException) returns message

Adds super().__init__(self.message) to ProxyException.__init__ so that
str(exc) returns the stored message instead of empty string. Fixes LIT-3094.

* test(proxy): regression tests for ProxyException.args (LIT-3094)

* fix(proxy): populate Exception.args so str(ProxyException) returns message (LIT-3094)

* fix(proxy): clean up unintended drift; keep only ProxyException.args fix (LIT-3094)

(cherry picked from commit 1fe911d89d)

litellm/proxy/_types.py

@@ -3695,6 +3695,11 @@ class ProxyException(Exception):
         provider_specific_fields: Optional[dict] = None,
     ):
         self.message = str(message)
+        # Populate Exception.args so str(self) returns the message.
+        # Without this, logging paths that call str(original_exception)
+        # (e.g. StandardLoggingPayloadSetup.get_error_information) record an
+        # empty error_message for ProxyException-based failures. See LIT-3094.
+        super().__init__(self.message)
         self.type = type
         self.param = param
         self.openai_code = openai_code or code

tests/test_litellm/proxy/test_proxy_types.py

@@ -87,3 +87,76 @@ def test_user_api_key_auth_hashes_authorization_header_form_of_key():
         assert from_header.api_key == baseline.api_key
         assert from_header.token == baseline.token
         assert not from_header.api_key.lower().startswith("bearer")
+
+
+# === Regression tests for LIT-3094: ProxyException must populate Exception.args
+# so logging integrations using str(exc) record a non-empty error_message. ===
+
+
+def test_proxy_exception_str_returns_message():
+    """str(ProxyException) must return the stored message, not '' (LIT-3094)."""
+    from litellm.proxy._types import ProxyException
+
+    msg = "key not allowed to access model"
+    exc = ProxyException(message=msg, type="auth_error", param=None, code=401)
+    assert str(exc) == msg
+    assert exc.args == (msg,)
+    assert exc.message == msg
+
+
+def test_proxy_exception_populates_standard_logging_error_message():
+    """The full logging path used by proxy callbacks must capture the message
+    instead of recording an empty error_message (LIT-3094 report)."""
+    from litellm.litellm_core_utils.litellm_logging import (
+        StandardLoggingPayloadSetup,
+    )
+    from litellm.proxy._types import ProxyException
+
+    msg = "Authentication Error, Invalid proxy server token passed."
+    exc = ProxyException(message=msg, type="auth_error", param=None, code=401)
+    info = StandardLoggingPayloadSetup.get_error_information(original_exception=exc)
+    assert info["error_message"] == msg
+    assert info["error_class"] == "ProxyException"
+    assert info["error_code"] == "401"
+
+
+def test_proxy_exception_to_dict_unchanged():
+    """to_dict() shape must remain backwards-compatible after the fix."""
+    from litellm.proxy._types import ProxyException
+
+    exc = ProxyException(
+        message="boom", type="invalid_request_error", param="model", code=400
+    )
+    d = exc.to_dict()
+    assert d == {
+        "message": "boom",
+        "type": "invalid_request_error",
+        "param": "model",
+        "code": "400",
+    }
+
+
+def test_proxy_exception_routing_code_override_still_works():
+    """The 'No healthy deployment available' -> 429 remapping must survive
+    the super().__init__() addition."""
+    from litellm.proxy._types import ProxyException
+
+    exc = ProxyException(
+        message="No healthy deployment available for model=foo",
+        type="router_error",
+        param=None,
+        code=500,
+    )
+    assert exc.code == "429"
+    assert str(exc) == "No healthy deployment available for model=foo"
+
+
+def test_proxy_exception_non_string_message_coerced():
+    """Non-string `message` must still be coerced to str via self.message =
+    str(message), and Exception.args must reflect the coerced value."""
+    from litellm.proxy._types import ProxyException
+
+    exc = ProxyException(message=42, type="x", param=None, code=400)
+    assert exc.message == "42"
+    assert str(exc) == "42"
+    assert exc.args == ("42",)