fix: address review — add provider metadata, keep routing out of core utils, add tests

- add mizumi entries to provider_endpoints_support.json and
  litellm/provider_endpoints_support_backup.json so the provider
  documentation validation passes
- drop the provider-specific elif from get_llm_provider_logic.py:
  endpoint autodetection is handled generically via
  JSONProviderRegistry.get_by_base_url + openai_compatible_endpoints,
  so no provider-specific code is needed outside llms/
- keep the mizumi entry in openai_compatible_providers free of
  trailing source comments
- add tests/test_litellm/llms/openai_like/test_mizumi_provider.py
  covering provider registration, JSON config, prefixed-model
  resolution, api_base autodetection, MIZUMI_API_KEY env handling,
  and chat/completions URL assembly (all offline)

litellm/constants.py

@@ -893,6 +893,7 @@ openai_compatible_endpoints: Final[list] = [
     "https://pinstripes.io/v1",
     "https://api.meta.ai/v1",
     "https://api.cognition.ai/v1",
+    "https://api.mizumi.co/v1",
     "https://api.scx.ai/v1",
     "https://gigachat.devices.sberbank.ru/api/v1",
 ]
@@ -965,6 +966,7 @@ openai_compatible_providers: Final[list] = [
     "darkbloom",
     "meta",  # Meta Model API (Muse Spark) - JSON-configured provider
     "cognition",
+    "mizumi",
     "scx-ai",
 ]
 openai_text_completion_compatible_providers: Final[list] = [  # providers that support `/v1/completions`

litellm/llms/openai_like/providers.json

@@ -180,6 +180,11 @@
     "api_key_env": "COGNITION_API_KEY",
     "api_base_env": "COGNITION_API_BASE"
   },
+  "mizumi": {
+    "base_url": "https://api.mizumi.co/v1",
+    "api_key_env": "MIZUMI_API_KEY",
+    "api_base_env": "MIZUMI_API_BASE"
+  },
   "pinstripes": {
     "base_url": "https://pinstripes.io/v1",
     "api_key_env": "PINSTRIPES_API_KEY",

litellm/provider_endpoints_support_backup.json

@@ -545,6 +545,23 @@
         "a2a": false
       }
     },
+    "mizumi": {
+      "display_name": "Mizumi (`mizumi`)",
+      "url": "https://docs.litellm.ai/docs/providers/mizumi",
+      "endpoints": {
+        "chat_completions": true,
+        "messages": false,
+        "responses": false,
+        "embeddings": false,
+        "image_generations": false,
+        "audio_transcriptions": false,
+        "audio_speech": false,
+        "moderations": false,
+        "batches": false,
+        "rerank": false,
+        "a2a": false
+      }
+    },
     "cohere": {
       "display_name": "Cohere (`cohere`)",
       "url": "https://docs.litellm.ai/docs/providers/cohere",

litellm/types/utils.py

@@ -4010,6 +4010,7 @@ class LlmProviders(str, Enum):
     LIBERTAI = "libertai"
     PINSTRIPES = "pinstripes"
     COGNITION = "cognition"
+    MIZUMI = "mizumi"
     SCX_AI = "scx-ai"
     DARKBLOOM = "darkbloom"
     META = "meta"

provider_endpoints_support.json

@@ -580,6 +580,23 @@
         "a2a": false
       }
     },
+    "mizumi": {
+      "display_name": "Mizumi (`mizumi`)",
+      "url": "https://docs.litellm.ai/docs/providers/mizumi",
+      "endpoints": {
+        "chat_completions": true,
+        "messages": false,
+        "responses": false,
+        "embeddings": false,
+        "image_generations": false,
+        "audio_transcriptions": false,
+        "audio_speech": false,
+        "moderations": false,
+        "batches": false,
+        "rerank": false,
+        "a2a": false
+      }
+    },
     "cohere": {
       "display_name": "Cohere (`cohere`)",
       "url": "https://docs.litellm.ai/docs/providers/cohere",

tests/test_litellm/llms/openai_like/test_mizumi_provider.py

@@ -0,0 +1,143 @@
+"""
+Tests for the Mizumi provider identity.
+
+Mizumi (https://mizumi.co) serves an OpenAI-compatible /v1/chat/completions surface, but it
+must resolve to its own `mizumi` provider so OpenAI-specific pricing and provider-level
+reporting never apply to its traffic.
+
+All tests are offline: no network access is required.
+"""
+
+import json
+from pathlib import Path
+
+import pytest
+
+import litellm
+
+
+class TestMizumiProviderIdentity:
+    def test_mizumi_is_a_registered_provider(self):
+        from litellm import LlmProviders
+
+        assert LlmProviders.MIZUMI.value == "mizumi"
+        assert "mizumi" in litellm.provider_list
+
+    def test_mizumi_json_config(self):
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        mizumi = JSONProviderRegistry.get("mizumi")
+        assert mizumi is not None
+        assert mizumi.base_url == "https://api.mizumi.co/v1"
+        assert mizumi.api_key_env == "MIZUMI_API_KEY"
+        assert mizumi.api_base_env == "MIZUMI_API_BASE"
+
+    def test_mizumi_in_openai_compatible_providers(self):
+        from litellm.constants import openai_compatible_providers
+
+        assert "mizumi" in openai_compatible_providers
+
+    def test_prefixed_model_resolves_to_mizumi_not_openai(self):
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        model, provider, _, api_base = get_llm_provider(
+            model="mizumi/gpt-5.5",
+            custom_llm_provider=None,
+            api_base=None,
+            api_key=None,
+        )
+
+        assert model == "gpt-5.5"
+        assert provider == "mizumi"
+        assert api_base == "https://api.mizumi.co/v1"
+
+    def test_explicit_api_base_and_key_win(self):
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        _, provider, api_key, api_base = get_llm_provider(
+            model="mizumi/gpt-5.5",
+            custom_llm_provider=None,
+            api_base="https://mizumi.internal.example/v1",
+            api_key="sk-test",
+        )
+
+        assert provider == "mizumi"
+        assert api_base == "https://mizumi.internal.example/v1"
+        assert api_key == "sk-test"
+
+    def test_api_base_autodetects_mizumi(self, monkeypatch: pytest.MonkeyPatch):
+        """Endpoint autodetection works off the JSON config alone.
+
+        Regression guard: no provider-specific branch exists in
+        get_llm_provider_logic.py — the generic JSONProviderRegistry fallback
+        must pick Mizumi up from its registered base URL.
+        """
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        monkeypatch.setenv("MIZUMI_API_KEY", "sk-mizumi-env")
+
+        _, provider, api_key, api_base = get_llm_provider(
+            model="gpt-5.5",
+            custom_llm_provider=None,
+            api_base="https://api.mizumi.co/v1",
+            api_key=None,
+        )
+
+        assert provider == "mizumi"
+        assert api_base == "https://api.mizumi.co/v1"
+        assert api_key == "sk-mizumi-env"
+
+    def test_autodetected_api_base_keeps_the_caller_api_key(self, monkeypatch: pytest.MonkeyPatch):
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        monkeypatch.setenv("MIZUMI_API_KEY", "sk-mizumi-env")
+
+        _, provider, api_key, _ = get_llm_provider(
+            model="gpt-5.5",
+            custom_llm_provider=None,
+            api_base="https://api.mizumi.co/v1",
+            api_key="sk-mizumi-caller",
+        )
+
+        assert provider == "mizumi"
+        assert api_key == "sk-mizumi-caller"
+
+    def test_env_api_key_is_read_from_mizumi_variable(self, monkeypatch: pytest.MonkeyPatch):
+        from litellm.llms.openai_like.dynamic_config import create_config_class
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+        monkeypatch.setenv("MIZUMI_API_KEY", "sk-mizumi-env")
+
+        provider = JSONProviderRegistry.get("mizumi")
+        assert provider is not None
+
+        api_base, api_key = create_config_class(provider)()._get_openai_compatible_provider_info(None, None)
+        assert api_base == "https://api.mizumi.co/v1"
+        assert api_key == "sk-mizumi-env"
+
+    def test_complete_url_appends_chat_completions(self):
+        from litellm.llms.openai_like.dynamic_config import create_config_class
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        provider = JSONProviderRegistry.get("mizumi")
+        assert provider is not None
+        config = create_config_class(provider)()
+
+        url = config.get_complete_url(
+            api_base="https://api.mizumi.co/v1",
+            api_key="sk-test",
+            model="mizumi/gpt-5.5",
+            optional_params={},
+            litellm_params={},
+            stream=False,
+        )
+
+        assert url == "https://api.mizumi.co/v1/chat/completions"
+
+    def test_supported_endpoints_matrix(self):
+        matrix = json.loads((Path(litellm.__file__).parent / "provider_endpoints_support_backup.json").read_text())
+
+        endpoints = matrix["providers"]["mizumi"]["endpoints"]
+        assert endpoints["chat_completions"] is True
+        assert endpoints["embeddings"] is False