From e9df4458c7928490d5ec1dc917908107a98bba70 Mon Sep 17 00:00:00 2001
From: Yucheng He <yucheng@berri.ai>
Date: Thu, 3 Sep 2026 17:17:38 -0700
Subject: [PATCH] fix(otel v2): keep the destination merge immutable

The per-backend var merge seeded a plain dict and the gated exporter list a plain
list, both of which the LIT budget counts. Wrap the merge in MappingProxyType and
hand the exporters back as a tuple.
---
 litellm/integrations/otel/presets/utils.py |  8 ++++---
 litellm/proxy/litellm_pre_call_utils.py    | 28 +++++++++++++---------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/litellm/integrations/otel/presets/utils.py b/litellm/integrations/otel/presets/utils.py
index e132b8854ab..2d7598b63c3 100644
--- a/litellm/integrations/otel/presets/utils.py
+++ b/litellm/integrations/otel/presets/utils.py
@@ -19,7 +19,9 @@ def ensure_mappers(mapper_names: Iterable[str], *names: str) -> list[str]:
     return result
 
 
-def credential_gated_exporters(exporters: "Iterable[ExporterSpec]", owner: "ExporterOwner") -> "list[ExporterSpec]":
+def credential_gated_exporters(
+    exporters: "Iterable[ExporterSpec]", owner: "ExporterOwner"
+) -> "tuple[ExporterSpec, ...]":
     """``exporters`` with the operator's destination replaced by a header-gated one.
 
     Used when a credential-mandatory backend is asked to build without the operator's
@@ -29,10 +31,10 @@ def credential_gated_exporters(exporters: "Iterable[ExporterSpec]", owner: "Expo
     span would be printed to stdout, and the gated spec keeps the owner so the
     override filter still recognises which backend this provider speaks for.
     """
-    return [
+    return (
         *(spec for spec in exporters if not _is_unconfigured_placeholder(spec)),
         ExporterSpec(owner=owner, requires_headers=True),
-    ]
+    )
 
 
 def _is_unconfigured_placeholder(spec: "ExporterSpec") -> bool:
diff --git a/litellm/proxy/litellm_pre_call_utils.py b/litellm/proxy/litellm_pre_call_utils.py
index 924203e9d8a..aed9933424b 100644
--- a/litellm/proxy/litellm_pre_call_utils.py
+++ b/litellm/proxy/litellm_pre_call_utils.py
@@ -1028,19 +1028,25 @@ def resolve_tenant_otel_destinations(
         if (callback := _get_validated_callback_metadata(item=item, source="otel-destination")) is not None
         if callback.callback_type != "failure"
     )
-    merged: Final = {
-        name: {
-            var: value
-            for callback in callbacks
-            if callback.callback_name == name
-            for var, value in callback.callback_vars.items()
-        }
-        for name in dict.fromkeys(callback.callback_name for callback in callbacks)
-    }
     return tuple(
         destination
-        for name, callback_vars in merged.items()
-        if (destination := destination_for(name, _tenant_otel_params(callback_vars))) is not None
+        for name in dict.fromkeys(callback.callback_name for callback in callbacks)
+        if (
+            destination := destination_for(
+                name,
+                _tenant_otel_params(
+                    MappingProxyType(
+                        {
+                            var: value
+                            for callback in callbacks
+                            if callback.callback_name == name
+                            for var, value in callback.callback_vars.items()
+                        }
+                    )
+                ),
+            )
+        )
+        is not None
     )