fix(proxy): do not fall back to another provider credential when the resolved provider is not in the entry

_extract_credential_from_entry used the provider hint only as a preference. When the resolved provider had no key in the model_config entry it fell through to the first credential in the entry, so a team whose defaultconfig only named anthropic had that key injected into requests the router resolved to openai, and OpenAI rejected them with a 401

With this change a resolved provider that the entry does not configure returns None, so the deployment keeps its own credentials. The first-entry fallback is kept for the case where no provider could be resolved at all, which is the historical single-provider behaviour #27517 preserved on purpose

The changed assertion in test_extract_credential_provider_hint_prefers_exact_match and the new test_apply_overrides_single_provider_default_does_not_leak_to_other_providers both fail on the parent commit and pass here

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

litellm/proxy/litellm_pre_call_utils.py

@@ -2605,21 +2605,23 @@ def _extract_credential_from_entry(entry: dict, provider: str | None = None) ->
 
     Entry structure: {"azure": {"litellm_credentials": "name"}, ...}
 
-    When provider is given (e.g. "azure"), tries an exact provider match first.
-    Falls back to the first credential found across all provider keys.
+    When provider is given (e.g. "azure") and the entry has a key for it, that
+    provider's credential is used. When provider is given but the entry has no
+    key for it, the entry does not apply to this request and None is returned,
+    so the deployment keeps its own credentials. Only when no provider could be
+    resolved at all does this fall back to the first credential in the entry.
     """
     if not isinstance(entry, dict):
         return None
 
-    # Prefer exact provider match when provider hint is available
-    if provider and provider in entry:
-        provider_config = entry[provider]
+    if provider:
+        provider_config = entry.get(provider)
         if isinstance(provider_config, dict):
             credential_name = provider_config.get("litellm_credentials")
             if credential_name:
                 return credential_name
+        return None
 
-    # Fall back to first available provider
     for provider_config in entry.values():
         if isinstance(provider_config, dict):
             credential_name = provider_config.get("litellm_credentials")

tests/test_litellm/proxy/test_litellm_pre_call_utils.py

@@ -4967,9 +4967,9 @@ def test_extract_credential_provider_hint_prefers_exact_match():
     result = _extract_credential_from_entry(entry)
     assert result in ("openai-cred", "azure-cred")
 
-    # Unknown provider falls back to first available
-    result = _extract_credential_from_entry(entry, provider="bedrock")
-    assert result in ("openai-cred", "azure-cred")
+    # A resolved provider that the entry does not configure gets no credential,
+    # otherwise a bedrock request would be sent with an openai or azure key
+    assert _extract_credential_from_entry(entry, provider="bedrock") is None
 
 
 def test_resolve_provider_hint_from_model_name():
@@ -5965,6 +5965,55 @@ def test_apply_overrides_provider_prefix_in_model_skips_router_lookup(
     router.get_deployment_by_model_group_name.assert_not_called()
 
 
+def test_apply_overrides_single_provider_default_does_not_leak_to_other_providers(
+    setup_test_credentials,
+):
+    """
+    A team whose defaultconfig only names anthropic must not have that key
+    injected into requests the router resolves to a different provider. Before
+    this fix an unprefixed gpt-4o-mini request on such a team was sent to OpenAI
+    with the team's sk-ant key and got a 401 back.
+    """
+    litellm.credential_list.append(
+        CredentialItem(
+            credential_name="anthropic-team-1",
+            credential_info={},
+            credential_values={"api_key": "sk-ant-key-for-team-1"},
+        )
+    )
+    team_metadata = {
+        "model_config": {"defaultconfig": {"anthropic": {"litellm_credentials": "anthropic-team-1"}}}
+    }
+
+    router = MagicMock()
+    openai_deployment = MagicMock()
+    openai_deployment.litellm_params.model = "openai/gpt-4o-mini"
+    openai_deployment.litellm_params.custom_llm_provider = "openai"
+    anthropic_deployment = MagicMock()
+    anthropic_deployment.litellm_params.model = "anthropic/claude-sonnet-4-6"
+    anthropic_deployment.litellm_params.custom_llm_provider = "anthropic"
+    router.get_deployment_by_model_group_name.side_effect = lambda model_group_name: {
+        "gpt-4o-mini": openai_deployment,
+        "claude-sonnet-4.6": anthropic_deployment,
+    }.get(model_group_name)
+
+    openai_data = {"model": "gpt-4o-mini"}
+    _apply_credential_overrides_from_model_config(
+        data=openai_data,
+        user_api_key_dict=UserAPIKeyAuth(api_key="test-key", team_metadata=team_metadata),
+        llm_router=router,
+    )
+    assert "api_key" not in openai_data
+
+    anthropic_data = {"model": "claude-sonnet-4.6"}
+    _apply_credential_overrides_from_model_config(
+        data=anthropic_data,
+        user_api_key_dict=UserAPIKeyAuth(api_key="test-key", team_metadata=team_metadata),
+        llm_router=router,
+    )
+    assert anthropic_data["api_key"] == "sk-ant-key-for-team-1"
+
+
 def _make_request_mock(path: str, headers: dict) -> MagicMock:
     request_mock = MagicMock(spec=Request)
     request_mock.url = MagicMock()