diff --git a/litellm/integrations/langfuse/langfuse_otel.py b/litellm/integrations/langfuse/langfuse_otel.py
index e7e4b16e866..8a36b45707e 100644
--- a/litellm/integrations/langfuse/langfuse_otel.py
+++ b/litellm/integrations/langfuse/langfuse_otel.py
@@ -146,7 +146,7 @@ class LangfuseOtelLogger(OpenTelemetry):
         )
         if not isinstance(request_metadata, dict):
             return
-        observation_metadata: Final = {
+        observation_metadata: Final = {  # mutable-ok: stays a real dict for safe_dumps and .get reads below
             key: value
             for key, value in log_requester_metadata(redact_user_api_key_info(metadata=request_metadata)).items()
             if value is not None
diff --git a/litellm/integrations/otel/mappers/langfuse.py b/litellm/integrations/otel/mappers/langfuse.py
index 40adf2363d9..a5857a7b856 100644
--- a/litellm/integrations/otel/mappers/langfuse.py
+++ b/litellm/integrations/otel/mappers/langfuse.py
@@ -12,6 +12,7 @@ the JSON-serialized payloads. ``trace_attributes`` maps the caller's trace contr
 
 import json
 from collections.abc import Callable
+from types import MappingProxyType
 from typing import Final
 
 from litellm.integrations.otel.mappers.base import AttributeMap, AttrValue, SpanData
@@ -60,7 +61,9 @@ class LangfuseMapper:
         "langfuse.observation.id": lambda d: d.identity.call_id or None,
         "langfuse.trace.metadata.team_id": lambda d: d.identity.team_id or None,
         "langfuse.trace.metadata.team_alias": lambda d: d.identity.team_alias or None,
-        **{f"{LANGFUSE_TRACE_METADATA_PREFIX}{name}": _identity_field(name) for name in TRACE_IDENTITY_FIELDS},
+        **MappingProxyType(
+            {f"{LANGFUSE_TRACE_METADATA_PREFIX}{name}": _identity_field(name) for name in TRACE_IDENTITY_FIELDS}
+        ),
     }
 
     # Sub-tables folded into their respective JSON blobs.
@@ -80,7 +83,13 @@ class LangfuseMapper:
 
     # JSON-payload attributes: each builder returns the serialized blob or None.
     _BLOB_ATTRS: dict[str, Callable[[LLMCallSpanData], AttrValue | None]] = {
-        LANGFUSE_OBSERVATION_METADATA: lambda d: safe_dumps(dict(d.request_metadata)) if d.request_metadata else None,
+        LANGFUSE_OBSERVATION_METADATA: lambda d: (
+            safe_dumps(  # mutable-ok: safe_dumps only serializes real dicts
+                dict(d.request_metadata)
+            )
+            if d.request_metadata
+            else None
+        ),
         "langfuse.observation.model.parameters": lambda d: json_if(
             collect(LangfuseMapper._MODEL_PARAMS, d.request_params)
         ),
diff --git a/litellm/integrations/otel/model/metadata.py b/litellm/integrations/otel/model/metadata.py
index 8dc7b2f858a..b8558c743d8 100644
--- a/litellm/integrations/otel/model/metadata.py
+++ b/litellm/integrations/otel/model/metadata.py
@@ -423,11 +423,16 @@ def exported_request_metadata(payload: StandardLoggingPayload) -> Mapping[str, o
     """The request metadata as the logging callbacks export it: ``user_api_key_*``
     dropped when ``litellm.redact_user_api_key_info`` is on, header keys nested
     under ``requester_metadata``, ``None`` values dropped."""
-    raw_meta: Final = cast(Mapping[str, object], payload.get("metadata") or {})
-    redacted: Final[Mapping[str, object]] = cast(
-        Mapping[str, object], redact_user_api_key_info(metadata=dict(raw_meta))
+    raw_meta: Final = cast(  # cast-ok: StandardLoggingPayload.get returns Any | None
+        Mapping[str, object], payload.get("metadata") or MappingProxyType({})
+    )
+    redacted: Final = cast(  # cast-ok: redact_user_api_key_info is untyped
+        Mapping[str, object],
+        redact_user_api_key_info(metadata=dict(raw_meta)),  # mutable-ok: the redactor requires a real dict
+    )
+    exported: Final = cast(  # cast-ok: log_requester_metadata is untyped
+        Mapping[str, object], log_requester_metadata(redacted)
     )
-    exported: Final[Mapping[str, object]] = cast(Mapping[str, object], log_requester_metadata(redacted))
     return MappingProxyType({key: value for key, value in exported.items() if value is not None})
 
 
diff --git a/litellm/integrations/otel/model/payloads.py b/litellm/integrations/otel/model/payloads.py
index c1d421b5d52..3fda279f732 100644
--- a/litellm/integrations/otel/model/payloads.py
+++ b/litellm/integrations/otel/model/payloads.py
@@ -388,7 +388,7 @@ class LLMCallSpanData:
     response_cost: float | None
     server: ServerInfo | None
     identity: RequestIdentity
-    request_metadata: Mapping[str, object] = field(default_factory=lambda: cast(Mapping[str, object], {}))
+    request_metadata: Mapping[str, object] = field(default_factory=dict)
     is_streaming: bool | None = None
     cost: LLMCost = field(default_factory=LLMCost)
     tools: tuple[ToolDefinition, ...] = ()