diff --git a/litellm/constants.py b/litellm/constants.py
index a292b654778..cdd3c3d5540 100644
--- a/litellm/constants.py
+++ b/litellm/constants.py
@@ -950,6 +950,7 @@ openai_compatible_endpoints: Final[list] = [
     "https://api.cognition.ai/v1",
     "https://api.scx.ai/v1",
     "https://gigachat.devices.sberbank.ru/api/v1",
+    "https://api.y-api.bestvirtualgoods.com/v1",
 ]
 
 
@@ -1023,6 +1024,7 @@ openai_compatible_providers: Final[list] = [
     "cognition",
     "scx-ai",
     "sail",
+    "y-api",  # Y-API - JSON-configured provider
 ]
 
 OPENAI_AUDIO_TRANSCRIPTION_PROVIDERS: Final = frozenset({"openai"} | frozenset(openai_compatible_providers))
@@ -1051,6 +1053,7 @@ openai_text_completion_compatible_providers: Final[list] = [  # providers that s
     "lambda_ai",
     "hyperbolic",
     "wandb",
+    "y-api",
 ]
 _openai_like_providers: Final[list] = [
     "predibase",
diff --git a/litellm/llms/openai_like/providers.json b/litellm/llms/openai_like/providers.json
index ae09b48bd1e..cb9676d88be 100644
--- a/litellm/llms/openai_like/providers.json
+++ b/litellm/llms/openai_like/providers.json
@@ -206,5 +206,18 @@
     "api_key_env": "SAIL_API_KEY",
     "api_base_env": "SAIL_API_BASE",
     "supported_endpoints": ["/v1/chat/completions", "/v1/responses", "/v1/messages"]
+  },
+  "y-api": {
+    "base_url": "https://api.y-api.bestvirtualgoods.com/v1",
+    "api_key_env": "YAPI_API_KEY",
+    "api_base_env": "YAPI_API_BASE",
+    "param_mappings": {
+      "max_tokens": "max_completion_tokens"
+    },
+    "supported_endpoints": [
+      "/v1/chat/completions",
+      "/v1/responses",
+      "/v1/messages"
+    ]
   }
 }
diff --git a/litellm/provider_endpoints_support_backup.json b/litellm/provider_endpoints_support_backup.json
index 1fcb7600a5e..b604cec811c 100644
--- a/litellm/provider_endpoints_support_backup.json
+++ b/litellm/provider_endpoints_support_backup.json
@@ -2624,6 +2624,15 @@
         "messages": true,
         "responses": true
       }
+    },
+    "y-api": {
+      "display_name": "Y-API (`y-api`)",
+      "url": "https://docs.litellm.ai/docs/providers/y-api",
+      "endpoints": {
+        "chat_completions": true,
+        "messages": true,
+        "responses": true
+      }
     }
   },
   "endpoints": {
diff --git a/litellm/proxy/public_endpoints/provider_create_fields.json b/litellm/proxy/public_endpoints/provider_create_fields.json
index 8bd7ed81583..ae41fa91c90 100644
--- a/litellm/proxy/public_endpoints/provider_create_fields.json
+++ b/litellm/proxy/public_endpoints/provider_create_fields.json
@@ -3601,6 +3601,34 @@
     ],
     "default_model_placeholder": "gpt-3.5-turbo"
   },
+  {
+    "provider": "Y_API",
+    "provider_display_name": "Y-API",
+    "litellm_provider": "y-api",
+    "credential_fields": [
+      {
+        "key": "api_base",
+        "label": "API Base",
+        "placeholder": "https://api.y-api.bestvirtualgoods.com/v1",
+        "tooltip": "Y-API base URL (defaults to https://api.y-api.bestvirtualgoods.com/v1)",
+        "required": false,
+        "field_type": "text",
+        "options": null,
+        "default_value": null
+      },
+      {
+        "key": "api_key",
+        "label": "API Key",
+        "placeholder": null,
+        "tooltip": null,
+        "required": true,
+        "field_type": "password",
+        "options": null,
+        "default_value": null
+      }
+    ],
+    "default_model_placeholder": "y-api/deepseek/deepseek-v4-flash"
+  },
   {
     "provider": "CURSOR",
     "provider_display_name": "Cursor",
diff --git a/litellm/types/utils.py b/litellm/types/utils.py
index 8862df9dc22..36c87dfb6f3 100644
--- a/litellm/types/utils.py
+++ b/litellm/types/utils.py
@@ -4142,6 +4142,7 @@ class LlmProviders(str, Enum):
     DARKBLOOM = "darkbloom"
     META = "meta"
     SAIL = "sail"
+    Y_API = "y-api"
     LITELLM_AGENT = "litellm_agent"
     CURSOR = "cursor"
     BEDROCK_MANTLE = "bedrock_mantle"
diff --git a/provider_endpoints_support.json b/provider_endpoints_support.json
index 790a050a878..642f1c9ee59 100644
--- a/provider_endpoints_support.json
+++ b/provider_endpoints_support.json
@@ -3087,6 +3087,23 @@
         "rerank": false,
         "a2a": false
       }
+    },
+    "y-api": {
+      "display_name": "Y-API (`y-api`)",
+      "url": "https://docs.litellm.ai/docs/providers/y-api",
+      "endpoints": {
+        "chat_completions": true,
+        "messages": true,
+        "responses": true,
+        "embeddings": false,
+        "image_generations": false,
+        "audio_transcriptions": false,
+        "audio_speech": false,
+        "moderations": false,
+        "batches": false,
+        "rerank": false,
+        "a2a": false
+      }
     }
   },
   "endpoints": {
diff --git a/tests/unit/llms/openai_like/test_y_api_provider.py b/tests/unit/llms/openai_like/test_y_api_provider.py
new file mode 100644
index 00000000000..2de96d4b014
--- /dev/null
+++ b/tests/unit/llms/openai_like/test_y_api_provider.py
@@ -0,0 +1,247 @@
+"""
+Tests for Y-API provider configuration and integration.
+
+Y-API is a JSON-configured OpenAI-compatible relay. Its model ids keep the
+upstream organization prefix, so they contain a slash of their own
+(`y-api/deepseek/deepseek-v4-flash`) -- provider resolution must split on the
+first slash only.
+"""
+
+import litellm
+
+BASE_URL = "https://api.y-api.bestvirtualgoods.com/v1"
+
+
+class TestYApiProviderConfig:
+    """Test Y-API provider configuration"""
+
+    def test_y_api_in_provider_list(self):
+        """Test that y-api is in the provider list"""
+        from litellm import LlmProviders
+
+        assert hasattr(LlmProviders, "Y_API")
+        assert LlmProviders.Y_API.value == "y-api"
+        assert "y-api" in litellm.provider_list
+
+    def test_y_api_json_config_exists(self):
+        """Test that y-api is configured in providers.json"""
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        assert JSONProviderRegistry.exists("y-api")
+
+        y_api = JSONProviderRegistry.get("y-api")
+        assert y_api is not None
+        assert y_api.base_url == BASE_URL
+        assert y_api.api_key_env == "YAPI_API_KEY"
+        assert y_api.api_base_env == "YAPI_API_BASE"
+        assert y_api.param_mappings == {"max_tokens": "max_completion_tokens"}
+
+    def test_y_api_supported_endpoints(self):
+        """Test the endpoints declared for y-api"""
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        y_api = JSONProviderRegistry.get("y-api")
+        assert y_api is not None
+        assert "/v1/chat/completions" in y_api.supported_endpoints
+        assert "/v1/responses" in y_api.supported_endpoints
+        assert "/v1/messages" in y_api.supported_endpoints
+        assert JSONProviderRegistry.supports_responses_api("y-api") is True
+
+    def test_y_api_provider_resolution_with_nested_model_id(self):
+        """Test that provider resolution finds y-api and keeps the nested model id"""
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        model, provider, api_key, api_base = get_llm_provider(
+            model="y-api/deepseek/deepseek-v4-flash",
+            custom_llm_provider=None,
+            api_base=None,
+            api_key=None,
+        )
+
+        assert model == "deepseek/deepseek-v4-flash"
+        assert provider == "y-api"
+        assert api_base == BASE_URL
+
+    def test_y_api_api_base_override(self):
+        """Test that an explicit api_base / api_key overrides the default"""
+        from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
+
+        model, provider, api_key, api_base = get_llm_provider(
+            model="y-api/deepseek/deepseek-v4-flash",
+            custom_llm_provider=None,
+            api_base="https://custom.example.com/v1",
+            api_key="sk-test",
+        )
+
+        assert provider == "y-api"
+        assert api_base == "https://custom.example.com/v1"
+        assert api_key == "sk-test"
+
+    def test_y_api_router_config(self):
+        """Test that y-api can be used in Router configuration"""
+        from litellm import Router
+
+        router = Router(
+            model_list=[
+                {
+                    "model_name": "y-api-chat",
+                    "litellm_params": {
+                        "model": "y-api/deepseek/deepseek-v4-flash",
+                        "api_key": "test-key",
+                    },
+                }
+            ]
+        )
+
+        assert len(router.model_list) == 1
+        assert router.model_list[0]["model_name"] == "y-api-chat"
+
+    def test_y_api_supported_endpoints_matrix(self):
+        """The documented matrix lists y-api with the endpoints it actually serves."""
+        import json
+        from pathlib import Path
+
+        import litellm as _litellm
+
+        matrix_path = (
+            Path(_litellm.__file__).parent.parent / "provider_endpoints_support.json"
+        )
+        matrix = json.loads(matrix_path.read_text())
+
+        assert "y-api" in matrix["providers"]
+        endpoints = matrix["providers"]["y-api"]["endpoints"]
+        assert endpoints["chat_completions"] is True
+        assert endpoints["messages"] is True
+        assert endpoints["responses"] is True
+        # embeddings is advertised false: GET /v1/models returns no embedding
+        # model, and POST /v1/embeddings answers
+        # "No available channel for model ... under group y-api (distributor)".
+        assert endpoints["embeddings"] is False
+
+    def test_y_api_runtime_supported_endpoints_matrix(self):
+        """The runtime-served backup matrix (GET /public/supported_endpoints) lists y-api."""
+        import json
+        from pathlib import Path
+
+        import litellm as _litellm
+
+        backup_path = (
+            Path(_litellm.__file__).parent / "provider_endpoints_support_backup.json"
+        )
+        matrix = json.loads(backup_path.read_text())
+
+        assert "y-api" in matrix["providers"]
+        endpoints = matrix["providers"]["y-api"]["endpoints"]
+        assert endpoints["chat_completions"] is True
+        assert endpoints["messages"] is True
+        assert endpoints["responses"] is True
+
+
+class TestYApiDashboardRegistration:
+    """The Add Model form must offer Y-API.
+
+    `test_every_backend_provider_is_listed_in_add_model_or_frozen_as_unlisted`
+    fails if a provider exists in `LlmProviders` without an entry here, so this
+    is the difference between "selectable in the UI" and "silently dropped into
+    the frozen unlisted set".
+    """
+
+    @staticmethod
+    def _provider_create_fields():
+        import json
+        from pathlib import Path
+
+        import litellm
+
+        path = (
+            Path(litellm.__file__).parent
+            / "proxy"
+            / "public_endpoints"
+            / "provider_create_fields.json"
+        )
+        with open(path) as f:
+            return json.load(f)
+
+    def test_y_api_is_selectable_in_the_add_model_form(self):
+        entries = [
+            e
+            for e in self._provider_create_fields()
+            if e["litellm_provider"] == "y-api"
+        ]
+        assert (
+            len(entries) == 1
+        ), "y-api must appear exactly once in provider_create_fields.json"
+
+        entry = entries[0]
+        assert entry["provider"] == "Y_API"
+        assert entry["provider_display_name"] == "Y-API"
+        assert entry["default_model_placeholder"].startswith("y-api/")
+
+        fields = {f["key"]: f for f in entry["credential_fields"]}
+        assert fields["api_key"]["required"] is True
+        assert fields["api_key"]["field_type"] == "password"
+        assert fields["api_base"]["required"] is False
+        # The base URL is surfaced as the placeholder so admins can see the
+        # default without it being written into config.
+        assert fields["api_base"]["placeholder"] == BASE_URL
+
+    def test_y_api_is_returned_by_the_public_providers_fields_endpoint(self):
+        """The endpoint the Add Model dropdown actually reads from."""
+        from fastapi import FastAPI
+        from fastapi.testclient import TestClient
+
+        from litellm.proxy.public_endpoints.public_endpoints import router
+
+        app_instance = FastAPI()
+        app_instance.include_router(router)
+        test_client = TestClient(app_instance)
+
+        response = test_client.get("/public/providers/fields")
+        assert response.status_code == 200
+        providers = {p["litellm_provider"] for p in response.json()}
+        assert "y-api" in providers
+
+
+class TestYApiTokenParamMapping:
+    """`max_tokens` has to reach this relay as `max_completion_tokens`.
+
+    The `openai/*` models y-api fronts reject the legacy name outright:
+
+        Unsupported parameter: 'max_tokens' is not supported with this model.
+        Use 'max_completion_tokens' instead.
+
+    LiteLLM's `openai_gpt` base class does not translate it for this provider --
+    the model ids are not in the OpenAI cost map, so the caller's `max_tokens`
+    is forwarded verbatim. These tests drive the transformation the provider
+    actually applies to caller params, rather than reading the config, because
+    the config alone cannot show which parameter name leaves the process.
+    """
+
+    @staticmethod
+    def _map(**params):
+        from litellm.llms.openai_like.dynamic_config import create_config_class
+        from litellm.llms.openai_like.json_loader import JSONProviderRegistry
+
+        provider = JSONProviderRegistry.get("y-api")
+        config = create_config_class(provider)()
+        return config.map_openai_params(
+            non_default_params=dict(params),
+            optional_params={},
+            model="gpt-5.6-luna",
+            drop_params=False,
+        )
+
+    def test_max_tokens_is_rewritten(self):
+        mapped = self._map(max_tokens=16)
+        assert mapped["max_completion_tokens"] == 16
+        assert "max_tokens" not in mapped
+
+    def test_max_completion_tokens_passes_through(self):
+        mapped = self._map(max_completion_tokens=16)
+        assert mapped["max_completion_tokens"] == 16
+        assert "max_tokens" not in mapped
+
+    def test_absent_cap_sends_neither(self):
+        mapped = self._map()
+        assert "max_tokens" not in mapped
+        assert "max_completion_tokens" not in mapped