diff --git a/litellm/llms/openai_like/dynamic_config.py b/litellm/llms/openai_like/dynamic_config.py
index a5728f08483..d4952ffe7f2 100644
--- a/litellm/llms/openai_like/dynamic_config.py
+++ b/litellm/llms/openai_like/dynamic_config.py
@@ -2,8 +2,9 @@
 Dynamic configuration class generator for JSON-based providers.
 """
 
-from collections.abc import Coroutine
-from typing import Any, Final, Literal, overload
+from collections.abc import Coroutine, Mapping
+from types import MappingProxyType
+from typing import Any, Final, Literal, cast, overload
 
 from litellm._logging import verbose_logger
 from litellm.litellm_core_utils.prompt_templates.common_utils import (
@@ -13,9 +14,37 @@ from litellm.llms.openai.chat.gpt_transformation import OpenAIGPTConfig
 from litellm.llms.openai_like.chat.transformation import OpenAILikeChatConfig
 from litellm.secret_managers.main import get_secret_str
 from litellm.types.llms.openai import AllMessageValues
+from litellm.types.utils import ServiceTier
 
 from .json_loader import SimpleProviderConfig
 
+_SERVICE_TIER_TO_COMPLETION_WINDOW: Final[Mapping[str, str]] = MappingProxyType(
+    {
+        ServiceTier.FLEX.value: "flex",
+        ServiceTier.BALANCED.value: "balanced",
+        ServiceTier.PRIORITY.value: "asap",
+        "default": "asap",
+    }
+)
+
+
+def _apply_service_tier_as_completion_window(body: Mapping[str, object]) -> dict[str, object]:
+    service_tier: Final = body.get("service_tier")
+    window: Final[str | None] = (
+        _SERVICE_TIER_TO_COMPLETION_WINDOW.get(service_tier.lower()) if isinstance(service_tier, str) else None
+    )
+    metadata: Final[dict[str, object]] = (
+        cast(dict[str, object], body["metadata"]) if isinstance(body.get("metadata"), dict) else {}
+    )
+    new_body: Final[dict[str, object]] = {key: value for key, value in body.items() if key != "service_tier"}
+    if window is None or "completion_window" in metadata:
+        return new_body
+    return {**new_body, "metadata": {**metadata, "completion_window": window}}
+
+
+def _service_tier_as_completion_window_enabled(provider: SimpleProviderConfig) -> bool:
+    return provider.special_handling.get("service_tier_as_completion_window") is True
+
 
 def create_config_class(provider: SimpleProviderConfig):
     """Generate config class dynamically from JSON configuration"""
@@ -89,6 +118,28 @@ def create_config_class(provider: SimpleProviderConfig):
 
             return api_base
 
+        def transform_request(
+            self,
+            model: str,
+            messages: list[AllMessageValues],
+            optional_params: dict[str, object],
+            litellm_params: dict[str, object],
+            headers: dict[str, object],
+        ) -> dict[str, object]:
+            body: Final[dict[str, object]] = cast(
+                dict[str, object],
+                super().transform_request(
+                    model=model,
+                    messages=messages,
+                    optional_params=optional_params,
+                    litellm_params=litellm_params,
+                    headers=headers,
+                ),
+            )
+            if _service_tier_as_completion_window_enabled(provider):
+                return _apply_service_tier_as_completion_window(body)
+            return body
+
         def get_supported_openai_params(self, model: str) -> list:
             """Get supported OpenAI params, excluding tool-related params for models
             that don't support function calling."""
@@ -225,19 +276,25 @@ def create_responses_config_class(provider: SimpleProviderConfig):
             self,
             model: str,
             input: str | ResponseInputParam,
-            response_api_optional_request_params: dict,
+            response_api_optional_request_params: dict[str, object],
             litellm_params: GenericLiteLLMParams,
-            headers: dict,
-        ) -> dict:
+            headers: dict[str, object],
+        ) -> dict[str, object]:
             if provider.special_handling.get("force_store_false"):
                 response_api_optional_request_params["store"] = False
-            return super().transform_responses_api_request(
-                model=model,
-                input=input,
-                response_api_optional_request_params=response_api_optional_request_params,
-                litellm_params=litellm_params,
-                headers=headers,
+            body: Final[dict[str, object]] = cast(
+                dict[str, object],
+                super().transform_responses_api_request(
+                    model=model,
+                    input=input,
+                    response_api_optional_request_params=response_api_optional_request_params,
+                    litellm_params=litellm_params,
+                    headers=headers,
+                ),
             )
+            if _service_tier_as_completion_window_enabled(provider):
+                return _apply_service_tier_as_completion_window(body)
+            return body
 
     _responses_config_cache[provider.slug] = JSONProviderResponsesConfig
     return JSONProviderResponsesConfig
diff --git a/litellm/llms/openai_like/json_loader.py b/litellm/llms/openai_like/json_loader.py
index 4bee08b03c5..140f7cba1eb 100644
--- a/litellm/llms/openai_like/json_loader.py
+++ b/litellm/llms/openai_like/json_loader.py
@@ -3,6 +3,7 @@ JSON-based provider configuration loader for OpenAI-compatible providers.
 """
 
 import json
+from collections.abc import Mapping
 from pathlib import Path
 from typing import Final
 
@@ -20,7 +21,7 @@ class SimpleProviderConfig:
         self.base_class = data.get("base_class", "openai_gpt")
         self.param_mappings = data.get("param_mappings", {})
         self.constraints = data.get("constraints", {})
-        self.special_handling = data.get("special_handling", {})
+        self.special_handling: Mapping[str, object] = data.get("special_handling", {})
         self.supported_endpoints = data.get("supported_endpoints", [])
         self.unsupported_params: Final = tuple(data.get("unsupported_params", ()))
 
diff --git a/litellm/llms/openai_like/providers.json b/litellm/llms/openai_like/providers.json
index bd9f3b415df..6e15a33c341 100644
--- a/litellm/llms/openai_like/providers.json
+++ b/litellm/llms/openai_like/providers.json
@@ -206,6 +206,9 @@
     "api_key_env": "SAIL_API_KEY",
     "api_base_env": "SAIL_API_BASE",
     "supported_endpoints": ["/v1/chat/completions", "/v1/responses", "/v1/messages"],
+    "special_handling": {
+      "service_tier_as_completion_window": true
+    },
     "param_mappings": {
       "max_tokens": "max_completion_tokens"
     },