From cc692e8514b453cb1ae65b09d0c6fa5e52655c01 Mon Sep 17 00:00:00 2001
From: moe-berri <moe@berri.ai>
Date: Wed, 28 Oct 2026 13:56:09 -0700
Subject: [PATCH] fix(proxy): clarify atomic model provider updates

---
 .../model_management_endpoints.py             |  6 +++-
 .../test_model_management_endpoints.py        | 28 +++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/litellm/proxy/management_endpoints/model_management_endpoints.py b/litellm/proxy/management_endpoints/model_management_endpoints.py
index 3caec435b7b..7f6e5ef38f6 100644
--- a/litellm/proxy/management_endpoints/model_management_endpoints.py
+++ b/litellm/proxy/management_endpoints/model_management_endpoints.py
@@ -434,7 +434,11 @@ def _raise_on_unloadable_patch(db_model: Deployment, patch_data: updateDeploymen
         Router.resolve_deployment_provider(reloaded.litellm_params)
     except Exception as e:  # noqa: BLE001  # the router drops the deployment on any exception from this check
         raise ProxyException(
-            message=f"The router cannot load this deployment, so the update was not saved: {e}",
+            message=(
+                "The router cannot load this deployment, so the update was not saved. "
+                "Use a provider-prefixed model or include model and custom_llm_provider together in the same update. "
+                f"Provider error: {e}"
+            ),
             type=ProxyErrorTypes.validation_error.value,
             code=status.HTTP_400_BAD_REQUEST,
             param="litellm_params.model",
diff --git a/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py b/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
index 54d4d684431..09a480b86f2 100644
--- a/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
+++ b/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
@@ -10229,6 +10229,34 @@ class TestPatchModelRejectsParamsTheRouterDrops:
         assert exc_info.value.param == "litellm_params.model"
         assert "@cf/cloudflare/clef-flash" in exc_info.value.message
 
+    def test_model_and_provider_can_be_updated_together_after_model_only_rejection(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        from litellm.proxy.management_endpoints.model_management_endpoints import (
+            _raise_on_unloadable_patch,
+            update_db_model,
+        )
+        from litellm.proxy.proxy_server import proxy_config
+
+        monkeypatch.setenv("LITELLM_SALT_KEY", "fake-atomic-model-patch-test-salt")
+        stored: Final = self._stored(model="cloudflare/clef-flash")
+        with pytest.raises(ProxyException) as exc_info:
+            _raise_on_unloadable_patch(
+                stored, updateDeployment(litellm_params=updateLiteLLMParams(model="atomic-test-model"))
+            )
+        assert exc_info.value.code == "400"
+        assert "include model and custom_llm_provider together in the same update" in exc_info.value.message
+
+        combined: Final = updateDeployment(
+            litellm_params=updateLiteLLMParams(model="atomic-test-model", custom_llm_provider="openai")
+        )
+        _raise_on_unloadable_patch(stored, combined)
+        saved: Final = json.loads(update_db_model(db_model=stored, updated_patch=combined)["litellm_params"])
+        reloaded: Final = {key: proxy_config.resolve_db_litellm_param(key, value) for key, value in saved.items()}
+        assert reloaded["model"] == "atomic-test-model"
+        assert reloaded["custom_llm_provider"] == "openai"
+        assert self._router_loads(reloaded)
+
     def test_patch_not_touching_routing_params_is_never_judged(self, monkeypatch: pytest.MonkeyPatch) -> None:
         from litellm.proxy.management_endpoints.model_management_endpoints import _raise_on_unloadable_patch