diff --git a/functions/pipes/anthropic/main.py b/functions/pipes/anthropic/main.py
index 44b8e8e..e9bd6b2 100644
--- a/functions/pipes/anthropic/main.py
+++ b/functions/pipes/anthropic/main.py
@@ -20,22 +20,52 @@
 class Pipe:
     class Valves(BaseModel):
         ANTHROPIC_API_KEY: str = Field(default="")
+        ENABLE_1M_CONTEXT: bool = Field(
+            default=False,
+            description="Enable 1M token context window for compatible Sonnet 4/4.5 models (requires Tier 4 access)",
+        )
 
     def __init__(self):
         self.type = "manifold"
         self.id = "anthropic"
         self.name = "anthropic/"
         self.valves = self.Valves(
-            **{"ANTHROPIC_API_KEY": os.getenv("ANTHROPIC_API_KEY", "")}
+            **{
+                "ANTHROPIC_API_KEY": os.getenv("ANTHROPIC_API_KEY", ""),
+                "ENABLE_1M_CONTEXT": os.getenv("ANTHROPIC_ENABLE_1M_CONTEXT", "false").lower() == "true"
+            }
         )
         self.MAX_IMAGE_SIZE = 5 * 1024 * 1024  # 5MB per image
-        
+
         # Model cache
         self._model_cache: Optional[List[Dict[str, str]]] = None
         self._model_cache_time: float = 0
         self._cache_ttl = int(os.getenv("ANTHROPIC_MODEL_CACHE_TTL", "600"))
 
-    def get_anthropic_models_from_api(self, force_refresh: bool = False) -> List[Dict[str, str]]:
+    def _is_1m_compatible_model(self, model_id: str) -> bool:
+        """
+        Check if a model is compatible with the 1M token context window.
+        Currently supports Claude Sonnet 4 and Sonnet 4.5.
+
+        Args:
+            model_id: The model identifier
+
+        Returns:
+            True if the model supports 1M context window
+        """
+        compatible_models = [
+            "claude-sonnet-4-5",
+            "claude-4-sonnet",
+            "claude-sonnet-4",
+        ]
+
+        # Check if model_id starts with or contains any compatible model identifier
+        model_lower = model_id.lower()
+        return any(compatible in model_lower for compatible in compatible_models)
+
+    def get_anthropic_models_from_api(
+        self, force_refresh: bool = False
+    ) -> List[Dict[str, str]]:
         """
         Retrieve available Anthropic models from the API.
         Uses caching to reduce API calls.
@@ -69,35 +99,38 @@ def get_anthropic_models_from_api(self, force_refresh: bool = False) -> List[Dic
                 "anthropic-version": "2023-06-01",
                 "content-type": "application/json",
             }
-            
+
             response = requests.get(
-                "https://api.anthropic.com/v1/models",
-                headers=headers,
-                timeout=10
+                "https://api.anthropic.com/v1/models", headers=headers, timeout=10
             )
-            
+
             if response.status_code != 200:
                 raise Exception(f"HTTP Error {response.status_code}: {response.text}")
-            
+
             data = response.json()
             models = []
-            
+
             for model in data.get("data", []):
-                models.append({
-                    "id": model["id"],
-                    "name": model.get("display_name", model["id"]),
-                })
-            
+                models.append(
+                    {
+                        "id": model["id"],
+                        "name": model.get("display_name", model["id"]),
+                    }
+                )
+
             # Update cache
             self._model_cache = models
             self._model_cache_time = current_time
-            
+
             return models
-            
+
         except Exception as e:
             print(f"Error fetching Anthropic models: {e}")
             return [
-                {"id": "error", "name": f"Could not fetch models from Anthropic: {str(e)}"}
+                {
+                    "id": "error",
+                    "name": f"Could not fetch models from Anthropic: {str(e)}",
+                }
             ]
 
     def get_anthropic_models(self) -> List[Dict[str, str]]:
@@ -199,6 +232,12 @@ def pipe(self, body: dict) -> Union[str, Generator, Iterator]:
             "content-type": "application/json",
         }
 
+        # Add beta header for 1M context window if enabled and using compatible model
+        model_id = body["model"][body["model"].find(".") + 1 :]
+        if self.valves.ENABLE_1M_CONTEXT and self._is_1m_compatible_model(model_id):
+            headers["anthropic-beta"] = "context-1m-2025-08-07"
+            print(f"Using 1M context window for model: {model_id}")
+
         url = "https://api.anthropic.com/v1/messages"
 
         try: