diff --git a/proxy/routes/proxy.py b/proxy/routes/proxy.py
index b460a06..6196a1e 100644
--- a/proxy/routes/proxy.py
+++ b/proxy/routes/proxy.py
@@ -2,7 +2,7 @@
 
 from enum import Enum
 
-from fastapi import APIRouter, HTTPException
+from fastapi import APIRouter, Depends, Header, HTTPException, Request
 
 proxy = APIRouter()
 
@@ -19,8 +19,25 @@ class LLMProvider(str, Enum):
         return provider in {provider.value for provider in cls}
 
 
-@proxy.post("/{username}/{dataset_name}/{llm_provider}")
-async def chat_completion(username: str, dataset_name: str, llm_provider: str):
+def validate_headers(invariant_authorization: str = Header(None)):
+    """Require the Invariant-Authorization header to be present"""
+    if invariant_authorization is None:
+        raise HTTPException(
+            status_code=400, detail="Missing Invariant-Authorization header"
+        )
+    return invariant_authorization
+
+
+@proxy.post(
+    "/{username}/{dataset_name}/{llm_provider}",
+    dependencies=[Depends(validate_headers)],
+)
+async def chat_completion(
+    request: Request,
+    username: str,
+    dataset_name: str,
+    llm_provider: str,
+):
     """Proxy call to a language model provider"""
 
     if not LLMProvider.is_valid(llm_provider):