fix(rate-limiting): resolve the authoritative metadata bucket at success accounting too

async_log_success_event's kwargs is Logging.model_call_details, not the
router's flat request kwargs admission sees: metadata/litellm_metadata
are never top-level there, only nested under kwargs["litellm_params"].
Resolving the field name against kwargs itself always defaulted to
"metadata", so on LITELLM_METADATA_ROUTES (/v1/messages, /responses,
batches, bedrock, files) this read the caller's native, tag-less
metadata instead of the real, server-computed litellm_metadata.tags
admission already used -- silently skipping token/dollar accounting
for every successful call on those routes. Resolve against
kwargs["litellm_params"] instead, mirroring what admission already
does one level up.

litellm/proxy/hooks/tag_rate_limiter.py

@@ -886,7 +886,16 @@ class _PROXY_TagRateLimiter(  # pyright: ignore[reportUnusedClass]  # only refer
         if not configured:
             return
 
-        metadata_variable_name: Final = get_metadata_variable_name_from_kwargs(kwargs)
+        # kwargs here is Logging.model_call_details, not the router's flat
+        # request kwargs admission sees: metadata/litellm_metadata are never
+        # top-level here, only nested under kwargs["litellm_params"] (see
+        # Logging.update_environment_variables). Resolving the field name
+        # against kwargs itself always picks the "metadata" default, so on
+        # LITELLM_METADATA_ROUTES (/v1/messages, /responses, ...) this read
+        # the caller's native, tag-less metadata instead of the real,
+        # server-computed litellm_metadata.tags admission already used.
+        litellm_params_for_metadata: Final = kwargs.get("litellm_params") or kwargs
+        metadata_variable_name: Final = get_metadata_variable_name_from_kwargs(litellm_params_for_metadata)
         tags: Final = _get_tags_from_request_kwargs(kwargs, metadata_variable_name=metadata_variable_name)
         if not tags:
             return

tests/test_litellm/proxy/hooks/test_tag_rate_limiter.py

@@ -475,6 +475,53 @@ async def test_log_success_event_increments_configured_units(time_controller):
     assert await limiter.internal_usage_cache.async_get_cache(key=request_key, litellm_parent_otel_span=None) is None
 
 
+@pytest.mark.asyncio
+async def test_log_success_event_reads_nested_litellm_metadata_when_that_is_authoritative(time_controller):
+    """
+    kwargs here is Logging.model_call_details: on LITELLM_METADATA_ROUTES
+    (/v1/messages, /responses, ...) metadata/litellm_metadata are never
+    top-level keys, only nested under kwargs["litellm_params"] -- and the
+    caller's own native "metadata" can be present there with no tags at all,
+    while the real, server-computed tags live in "litellm_metadata".
+    """
+    limiter = _make_limiter(time_controller)
+    router = litellm.Router(
+        model_list=[
+            _deployment(
+                "grp",
+                "dep-1",
+                {
+                    "token_limits": {
+                        "limits": [{"name": "daily", "tag_id": "end_user_id", "limit": 500000, "period_seconds": 86400}]
+                    }
+                },
+            )
+        ]
+    )
+    limiter.update_variables(llm_router=router)
+
+    kwargs = {
+        "litellm_params": {
+            "metadata": {"tags": []},
+            "litellm_metadata": {"tags": ["end_user_id:u1"]},
+        },
+        "standard_logging_object": {
+            "model_group": "grp",
+            "model_id": "dep-1",
+            "total_tokens": 42,
+            "response_cost": 0.01,
+        },
+    }
+    await limiter.async_log_success_event(kwargs=kwargs, response_obj=None, start_time=0, end_time=0)
+    await asyncio.sleep(0)
+
+    now = time_controller.now().timestamp()
+    token_key = f"{{tag_rl:grp:tokens:daily:end_user_id:chain:u1}}:{int(now) // 86400}"
+    assert (
+        float(await limiter.internal_usage_cache.async_get_cache(key=token_key, litellm_parent_otel_span=None)) == 42.0
+    )
+
+
 # ---------------------------------------------------------------------------
 # concurrency limits -- reserve at admission, release on success/failure
 # ---------------------------------------------------------------------------