From ee8600b05b92518836af0ed75674548de3969c41 Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Sat, 3 Oct 2026 13:33:08 -0700
Subject: [PATCH] fix(prometheus): pick the series tracker with isinstance so
 every path of _admits returns

---
 litellm/integrations/prometheus.py | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/litellm/integrations/prometheus.py b/litellm/integrations/prometheus.py
index 7dda308c731..9533b275bd1 100644
--- a/litellm/integrations/prometheus.py
+++ b/litellm/integrations/prometheus.py
@@ -239,17 +239,13 @@ class _LabeledMetric:
                 assert_never(self._tracker)
 
     def _admits(self, kept_values: tuple[str, ...]) -> bool:
-        match self._tracker:
-            case SharedPrometheusSeriesAdmissions():
-                return self._limits.max_series is None or self._tracker.admit_series(
-                    metric_name=self._metric_name, label_values=kept_values, max_series=self._limits.max_series
-                )
-            case BoundedPrometheusSeriesTracker():
-                return self._tracker.admit_series(
-                    metric=self._metric, metric_name=self._metric_name, label_values=kept_values, limits=self._limits
-                )
-            case _:
-                return assert_never(self._tracker)
+        if isinstance(self._tracker, SharedPrometheusSeriesAdmissions):
+            return self._limits.max_series is None or self._tracker.admit_series(
+                metric_name=self._metric_name, label_values=kept_values, max_series=self._limits.max_series
+            )
+        return self._tracker.admit_series(
+            metric=self._metric, metric_name=self._metric_name, label_values=kept_values, limits=self._limits
+        )
 
     def _kept_values(self, values: tuple[object, ...]) -> tuple[str, ...]:
         return tuple(