diff --git a/litellm/litellm_core_utils/realtime_streaming.py b/litellm/litellm_core_utils/realtime_streaming.py
index a09b6701e8d..4ae17785804 100644
--- a/litellm/litellm_core_utils/realtime_streaming.py
+++ b/litellm/litellm_core_utils/realtime_streaming.py
@@ -79,6 +79,7 @@ class _ClientWebSocket(_ScopedWebSocket, Protocol):
 
 _SESSION_FIELDS: Final = TypeAdapter(dict[str, object])
 _NO_SESSION_FIELDS: Final[Mapping[str, object]] = MappingProxyType({})
+_SESSION_MERGE_MAX_DEPTH: Final = 8
 
 
 class _SessionUpdateFrame(TypedDict):
@@ -86,15 +87,17 @@ class _SessionUpdateFrame(TypedDict):
     session: ReadOnly[Mapping[str, object]]
 
 
-def _merge_session_fields(base: Mapping[str, object], update: Mapping[str, object]) -> Mapping[str, object]:
+def _merge_session_fields(
+    base: Mapping[str, object], update: Mapping[str, object], depth: int = 0
+) -> Mapping[str, object]:
     def merged_value(key: str) -> object:
         if key not in update:
             return base[key]
         value: Final = update[key]
         base_value: Final = base.get(key)
-        if isinstance(value, Mapping) and isinstance(base_value, Mapping):
+        if depth < _SESSION_MERGE_MAX_DEPTH and isinstance(value, Mapping) and isinstance(base_value, Mapping):
             return _merge_session_fields(
-                _SESSION_FIELDS.validate_python(base_value), _SESSION_FIELDS.validate_python(value)
+                _SESSION_FIELDS.validate_python(base_value), _SESSION_FIELDS.validate_python(value), depth + 1
             )
         return value
 
diff --git a/tests/code_coverage_tests/recursive_detector.py b/tests/code_coverage_tests/recursive_detector.py
index e9f87ba6cae..4ac150d788b 100644
--- a/tests/code_coverage_tests/recursive_detector.py
+++ b/tests/code_coverage_tests/recursive_detector.py
@@ -67,6 +67,7 @@ IGNORE_FUNCTIONS = [
     "_redact_agent_params_tree",  # max depth set (default 10), same shape as _redact_sensitive_litellm_params.
     "_restore_redacted_nested_value",  # max depth set (default 10), mirrors _redact_agent_params_tree on the write side.
     "_unqualified",  # bounded by the qualifier depth of a static TypedDict annotation (Annotated, Required/NotRequired, ReadOnly around one type, no cycles possible).
+    "_merge_session_fields",  # max depth set (_SESSION_MERGE_MAX_DEPTH); deeper mappings are replaced wholesale by the later session.update.
 ]
 
 
diff --git a/tests/test_litellm/litellm_core_utils/test_realtime_streaming.py b/tests/test_litellm/litellm_core_utils/test_realtime_streaming.py
index 859afa01e96..a4ed017d7df 100644
--- a/tests/test_litellm/litellm_core_utils/test_realtime_streaming.py
+++ b/tests/test_litellm/litellm_core_utils/test_realtime_streaming.py
@@ -10,6 +10,7 @@ import litellm
 from litellm.integrations.custom_guardrail import CustomGuardrail
 from litellm.litellm_core_utils.realtime_streaming import (
     RealTimeStreaming,
+    _merge_session_fields,
     client_sent_openai_beta_realtime_header,
 )
 from litellm.llms.xai.realtime.transformation import XAIRealtimeNormalizer
@@ -2462,6 +2463,20 @@ async def test_default_mode_merges_nested_audio_settings_across_session_updates(
     assert setup["generationConfig"]["speechConfig"]["voiceConfig"]["prebuiltVoiceConfig"]["voiceName"] == "Kore"
 
 
+def test_merge_session_fields_replaces_nested_mappings_wholesale_past_the_depth_cap():
+    def nested(levels: int, key: str) -> dict:
+        return {key: levels, **({"child": nested(levels - 1, key)} if levels else {})}
+
+    def level(node, depth: int):
+        return node if depth == 0 else level(node["child"], depth - 1)
+
+    merged = _merge_session_fields(nested(10, "keep"), nested(10, "new"))
+
+    assert all({"keep", "new"} <= set(level(merged, depth)) for depth in range(9))
+    assert "keep" not in level(merged, 9)
+    assert level(merged, 9)["new"] == 1
+
+
 @pytest.mark.asyncio
 async def test_default_mode_acknowledges_each_held_session_update_before_any_backend_frame(monkeypatch):
     """A client that waits for session.updated before sending content must not