refactor: update HTTP handlers to respect disable_default_user_agent

Modify http_handler.py and httpx_handler.py to check the
disable_default_user_agent flag and return empty headers when disabled.
This allows users to override the User-Agent header completely.

litellm/llms/custom_httpx/http_handler.py

@@ -50,9 +50,27 @@ try:
 except Exception:
     version = "0.0.0"
 
-headers = {
-    "User-Agent": f"litellm/{version}",
-}
+def get_default_headers() -> dict:
+    """
+    Get default headers for HTTP requests.
+    
+    Respects litellm.disable_default_user_agent flag to allow users to disable
+    the automatic User-Agent header injection or override it completely.
+    
+    Returns:
+        dict: Default headers (may be empty if user disabled defaults)
+    """
+    import litellm
+    
+    if getattr(litellm, "disable_default_user_agent", False):
+        return {}
+    
+    return {
+        "User-Agent": f"litellm/{version}",
+    }
+
+# Initialize headers - will be empty if disable_default_user_agent is True
+headers = get_default_headers()
 
 # https://www.python-httpx.org/advanced/timeouts
 _DEFAULT_TIMEOUT = httpx.Timeout(timeout=5.0, connect=5.0)
@@ -371,13 +389,16 @@ class AsyncHTTPHandler:
             shared_session=shared_session,
         )
 
+        # Get default headers - will be empty if disable_default_user_agent is True
+        default_headers = get_default_headers()
+
         return httpx.AsyncClient(
             transport=transport,
             event_hooks=event_hooks,
             timeout=timeout,
             verify=ssl_config,
             cert=cert,
-            headers=headers,
+            headers=default_headers,
             follow_redirects=True,
         )
 
@@ -899,6 +920,9 @@ class HTTPHandler:
         # /path/to/client.pem
         cert = os.getenv("SSL_CERTIFICATE", litellm.ssl_certificate)
 
+        # Get default headers - will be empty if disable_default_user_agent is True
+        default_headers = get_default_headers() if not disable_default_headers else None
+
         if client is None:
             transport = self._create_sync_transport()
 
@@ -908,7 +932,7 @@ class HTTPHandler:
                 timeout=timeout,
                 verify=ssl_config,
                 cert=cert,
-                headers=headers if not disable_default_headers else None,
+                headers=default_headers,
                 follow_redirects=True,
             )
         else:

litellm/llms/custom_httpx/httpx_handler.py

@@ -7,9 +7,27 @@ try:
 except Exception:
     version = "0.0.0"
 
-headers = {
-    "User-Agent": f"litellm/{version}",
-}
+def get_default_headers() -> dict:
+    """
+    Get default headers for HTTP requests.
+    
+    Respects litellm.disable_default_user_agent flag to allow users to disable
+    the automatic User-Agent header injection or override it completely.
+    
+    Returns:
+        dict: Default headers (may be empty if user disabled defaults)
+    """
+    import litellm
+    
+    if getattr(litellm, "disable_default_user_agent", False):
+        return {}
+    
+    return {
+        "User-Agent": f"litellm/{version}",
+    }
+
+# Initialize headers - will be empty if disable_default_user_agent is True
+headers = get_default_headers()
 
 
 class HTTPHandler: