diff --git a/litellm/litellm_core_utils/reasoning_content_utils.py b/litellm/litellm_core_utils/reasoning_content_utils.py
index ace40b18bc8..b307a85804e 100644
--- a/litellm/litellm_core_utils/reasoning_content_utils.py
+++ b/litellm/litellm_core_utils/reasoning_content_utils.py
@@ -10,23 +10,24 @@ from litellm.types.llms.openai import AllMessageValues
 
 
 def normalize_reasoning_content(
-    messages: Sequence[AllMessageValues], *, forward: bool = True
+    messages: Sequence[AllMessageValues], *, forward: bool = True, normalize: bool = True
 ) -> list[AllMessageValues]:  # mutable-ok: provider request contract
     def normalize_message(message: AllMessageValues) -> AllMessageValues:
         if message["role"] != "assistant":
             return message
+        if not normalize and forward:
+            return message
         history: Final[Mapping[str, object]] = message
+        removed_fields: Final = ("reasoning", "reasoning_content") if normalize else ("reasoning_content",)
         reasoning: Final = (
             history.get("reasoning") if history.get("reasoning") is not None else history.get("reasoning_content")
         )
         normalized: Final[Mapping[str, object]] = MappingProxyType(
             {
-                **MappingProxyType(
-                    {key: value for key, value in history.items() if key not in ("reasoning", "reasoning_content")}
-                ),
+                **MappingProxyType({key: value for key, value in history.items() if key not in removed_fields}),
                 **(
                     MappingProxyType({"reasoning": reasoning})
-                    if forward and reasoning is not None
+                    if normalize and forward and reasoning is not None
                     else MappingProxyType({})
                 ),
             }
diff --git a/litellm/llms/hosted_vllm/chat/transformation.py b/litellm/llms/hosted_vllm/chat/transformation.py
index fe28e11a2ee..be3c4206f5c 100644
--- a/litellm/llms/hosted_vllm/chat/transformation.py
+++ b/litellm/llms/hosted_vllm/chat/transformation.py
@@ -155,15 +155,11 @@ class HostedVLLMChatConfig(OpenAIGPTConfig):
         litellm_params: dict,  # mutable-ok: provider request contract
         headers: dict,  # mutable-ok: provider request contract
     ) -> dict:  # mutable-ok: provider request contract
-        request_messages: Final = (
-            normalize_reasoning_content(messages, forward=litellm_params.get("forward_reasoning_content") is True)
-            if litellm_params.get("reasoning_content_field") == "reasoning"
-            else deepcopy(messages)
+        request_messages: Final = normalize_reasoning_content(
+            messages,
+            forward=litellm_params.get("forward_reasoning_content") is True,
+            normalize=litellm_params.get("reasoning_content_field") == "reasoning",
         )
-        if litellm_params.get("forward_reasoning_content") is not True:
-            for message in request_messages:
-                if message["role"] == "assistant":
-                    message.pop("reasoning_content", None)
         return super().transform_request(model, request_messages, optional_params, litellm_params, headers)
 
     async def async_transform_request(
diff --git a/litellm/types/router.py b/litellm/types/router.py
index c8a53f3467b..a7695622051 100644
--- a/litellm/types/router.py
+++ b/litellm/types/router.py
@@ -358,7 +358,10 @@ class GenericLiteLLMParams(CredentialLiteLLMParams, CustomPricingLiteLLMParams):
     model_config = ConfigDict(extra="allow", arbitrary_types_allowed=True)
     merge_reasoning_content_in_choices: bool | None = False
     forward_reasoning_content: bool | None = None
-    reasoning_content_field: Literal["reasoning_content", "reasoning"] | None = None
+    reasoning_content_field: str | None = Field(
+        default=None,
+        description="Historical assistant reasoning field: reasoning_content (default) or reasoning.",
+    )
     model_info: dict | None = None
     mock_response: str | ModelResponse | Exception | Any | None = None
 
diff --git a/tests/test_litellm/llms/hosted_vllm/chat/test_hosted_vllm_chat_transformation.py b/tests/test_litellm/llms/hosted_vllm/chat/test_hosted_vllm_chat_transformation.py
index 0b70e763f34..e17e490b47f 100644
--- a/tests/test_litellm/llms/hosted_vllm/chat/test_hosted_vllm_chat_transformation.py
+++ b/tests/test_litellm/llms/hosted_vllm/chat/test_hosted_vllm_chat_transformation.py
@@ -586,6 +586,7 @@ async def test_reasoning_field_sdk_router_final_wire(
                 ("legacy", {}),
                 ("normalized", {"reasoning_content_field": "reasoning"}),
                 ("explicit-default", {"reasoning_content_field": "reasoning_content"}),
+                ("unknown", {"reasoning_content_field": "unknown"}),
             )
         ],
         num_retries=0,
@@ -602,7 +603,9 @@ async def test_reasoning_field_sdk_router_final_wire(
                 "usage": {"prompt_tokens": 10, "completion_tokens": 1, "total_tokens": 11},
             },
         )
-        for alias, field in (("normalized", "reasoning"), ("legacy", None), ("explicit-default", "reasoning_content")):
+        for alias, field in (
+            ("normalized", "reasoning"), ("legacy", None), ("explicit-default", "reasoning_content"), ("unknown", "unknown")
+        ):
             kwargs: Final = (
                 {"model": alias, "messages": messages}
                 if via_router
@@ -637,7 +640,7 @@ async def test_reasoning_field_sdk_router_final_wire(
             assert "reasoning_content_field" not in payload
             assert "forward_reasoning_content" not in payload
             assert messages == original
-        assert route.call_count == 3
+        assert route.call_count == 4
 
 
 @pytest.mark.asyncio
diff --git a/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py b/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
index ba7bfdcdc21..fc1490a03de 100644
--- a/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
+++ b/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
@@ -1170,7 +1170,7 @@ class TestUpdateModel:
     @pytest.mark.asyncio
     @pytest.mark.parametrize("reasoning_field", [None, "reasoning_content", "reasoning"])
     @pytest.mark.parametrize("forward", [None, False, True])
-    async def test_update_model_clears_cache_after_db_write(self, reasoning_field, forward):
+    async def test_update_model_clears_cache_after_db_write(self, reasoning_field, forward, monkeypatch):
         """
         Regression test for the stale-router bug: POST /model/update must refresh
         the in-memory router after persisting to LiteLLM_ProxyModelTable, otherwise
@@ -1186,13 +1186,16 @@ class TestUpdateModel:
             updateLiteLLMParams,
         )
 
+        from litellm.proxy.common_utils.encrypt_decrypt_utils import decrypt_value_helper
+
+        monkeypatch.setenv("LITELLM_SALT_KEY", "sk-test-reasoning-field")
         model_id = "db-model-under-test"
 
         existing_row = MagicMock()
         existing_row.litellm_params = {
             "model": "openai/gpt-4o-mini",
             "api_key": "sk-existing",
-            "reasoning_content_field": "reasoning",
+            "reasoning_content_field": encrypt_value_helper("reasoning"),
             "forward_reasoning_content": True,
         }
         existing_row.model_dump.return_value = {
@@ -1228,10 +1231,6 @@ class TestUpdateModel:
                 "litellm.proxy.management_endpoints.model_management_endpoints.ModelManagementAuthChecks.can_user_make_model_call",
                 new=AsyncMock(return_value=None),
             ),
-            patch(
-                "litellm.proxy.management_endpoints.model_management_endpoints.encrypt_value_helper",
-                side_effect=lambda value: value,
-            ),
             patch(
                 "litellm.proxy.management_endpoints.model_management_endpoints.clear_cache",
                 new=AsyncMock(
@@ -1254,7 +1253,9 @@ class TestUpdateModel:
             mock_prisma.db.litellm_proxymodeltable.update.assert_awaited_once()
             mock_clear_cache.assert_awaited_once_with()
             stored = json.loads(mock_prisma.db.litellm_proxymodeltable.update.call_args.kwargs["data"]["litellm_params"])
-            assert stored["reasoning_content_field"] == (reasoning_field or "reasoning")
+            assert decrypt_value_helper(stored["reasoning_content_field"], key="reasoning_content_field") == (reasoning_field or "reasoning")
+            if reasoning_field is None:
+                assert stored["reasoning_content_field"] == existing_row.litellm_params["reasoning_content_field"]
             assert stored["forward_reasoning_content"] is (True if forward is None else forward)
 
 
@@ -6243,3 +6244,39 @@ def test_model_patch_preserves_reasoning_field_unless_explicit(field, forward, m
     ) == (field or "reasoning")
     assert deployment.litellm_params.reasoning_content_field == "reasoning"
     assert deployment.litellm_params.forward_reasoning_content is True
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("field", ["reasoning_content", "reasoning"])
+async def test_reasoning_field_encrypted_db_round_trip(field, monkeypatch):
+    from litellm.proxy.common_utils.encrypt_decrypt_utils import decrypt_value_helper
+    from litellm.proxy.management_endpoints.model_management_endpoints import get_db_model, update_db_model
+
+    monkeypatch.setenv("LITELLM_SALT_KEY", "sk-test-reasoning-field")
+    initial = Deployment(
+        model_name="reasoning-test",
+        litellm_params=LiteLLM_Params(model="openai/reasoning-test", forward_reasoning_content=True),
+        model_info=ModelInfo(id="reasoning-row"),
+    )
+    first = update_db_model(
+        db_model=initial,
+        updated_patch=updateDeployment(litellm_params=updateLiteLLMParams(reasoning_content_field=field)),
+    )
+    encrypted = json.loads(first["litellm_params"])
+    assert encrypted["reasoning_content_field"] != field
+    raw = {"model_name": first["model_name"], "litellm_params": encrypted, "model_info": {"id": "reasoning-row"}}
+    deployment = Deployment(**raw)
+    assert deployment.litellm_params.reasoning_content_field == encrypted["reasoning_content_field"]
+    row = MagicMock()
+    row.model_dump.return_value = raw
+    prisma = MagicMock()
+    prisma.db.litellm_proxymodeltable.find_unique = AsyncMock(return_value=row)
+    loaded = await get_db_model("reasoning-row", prisma)
+    assert loaded.litellm_params.reasoning_content_field == encrypted["reasoning_content_field"]
+    second = update_db_model(
+        db_model=loaded, updated_patch=updateDeployment(litellm_params=updateLiteLLMParams(tpm=123))
+    )
+    stored = json.loads(second["litellm_params"])
+    assert stored["reasoning_content_field"] == encrypted["reasoning_content_field"]
+    assert stored["forward_reasoning_content"] is True
+    assert decrypt_value_helper(stored["reasoning_content_field"], key="reasoning_content_field") == field
diff --git a/ui/litellm-dashboard/src/lib/http/schema.d.ts b/ui/litellm-dashboard/src/lib/http/schema.d.ts
index a90fce927ca..ce427314159 100644
--- a/ui/litellm-dashboard/src/lib/http/schema.d.ts
+++ b/ui/litellm-dashboard/src/lib/http/schema.d.ts
@@ -29882,8 +29882,11 @@ export interface components {
             } | null;
             /** Quality Router Default Model */
             quality_router_default_model?: string | null;
-            /** Reasoning Content Field */
-            reasoning_content_field?: ("reasoning_content" | "reasoning") | null;
+            /**
+             * Reasoning Content Field
+             * @description Historical assistant reasoning field: reasoning_content (default) or reasoning.
+             */
+            reasoning_content_field?: string | null;
             /** Region Name */
             region_name?: string | null;
             /** Regional Endpoint Uplift Multiplier */
@@ -40100,8 +40103,11 @@ export interface components {
             } | null;
             /** Quality Router Default Model */
             quality_router_default_model?: string | null;
-            /** Reasoning Content Field */
-            reasoning_content_field?: ("reasoning_content" | "reasoning") | null;
+            /**
+             * Reasoning Content Field
+             * @description Historical assistant reasoning field: reasoning_content (default) or reasoning.
+             */
+            reasoning_content_field?: string | null;
             /** Region Name */
             region_name?: string | null;
             /** Regional Endpoint Uplift Multiplier */