From c676e0c134173c17f4038f93ce75c463bba0063c Mon Sep 17 00:00:00 2001
From: Sameer Kankute <sameer@berri.ai>
Date: Wed, 11 Feb 2026 14:18:57 +0530
Subject: [PATCH] Fix: remove x-anthropic-billing block

---
 litellm/llms/anthropic/chat/transformation.py |  7 +++
 .../messages/transformation.py                | 45 +++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index 82aa7390188..0c7dfc13dbc 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -931,6 +931,7 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
         Translate system message to anthropic format.
 
         Removes system message from the original list and returns a new list of anthropic system message content.
+        Filters out system messages containing x-anthropic-billing-header metadata.
         """
         system_prompt_indices = []
         anthropic_system_message_list: List[AnthropicSystemMessageContent] = []
@@ -942,6 +943,9 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
                     # Skip empty text blocks - Anthropic API raises errors for empty text
                     if not system_message_block["content"]:
                         continue
+                    # Skip system messages containing x-anthropic-billing-header metadata
+                    if system_message_block["content"].startswith("x-anthropic-billing-header:"):
+                        continue
                     anthropic_system_message_content = AnthropicSystemMessageContent(
                         type="text",
                         text=system_message_block["content"],
@@ -960,6 +964,9 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
                         text_value = _content.get("text")
                         if _content.get("type") == "text" and not text_value:
                             continue
+                        # Skip system messages containing x-anthropic-billing-header metadata
+                        if _content.get("type") == "text" and text_value and text_value.startswith("x-anthropic-billing-header:"):
+                            continue
                         anthropic_system_message_content = (
                             AnthropicSystemMessageContent(
                                 type=_content.get("type"),
diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 043a70f3c67..4b0fb14a824 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -52,6 +52,40 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
             # TODO: Add Anthropic `metadata` support
             # "metadata",
         ]
+    
+    @staticmethod
+    def _filter_billing_headers_from_system(system_param):
+        """
+        Filter out x-anthropic-billing-header metadata from system parameter.
+        
+        Args:
+            system_param: Can be a string or a list of system message content blocks
+            
+        Returns:
+            Filtered system parameter (string or list), or None if all content was filtered
+        """
+        if isinstance(system_param, str):
+            # If it's a string and starts with billing header, filter it out
+            if system_param.startswith("x-anthropic-billing-header:"):
+                return None
+            return system_param
+        elif isinstance(system_param, list):
+            # Filter list of system content blocks
+            filtered_list = []
+            for content_block in system_param:
+                if isinstance(content_block, dict):
+                    text = content_block.get("text", "")
+                    content_type = content_block.get("type", "")
+                    # Skip text blocks that start with billing header
+                    if content_type == "text" and text.startswith("x-anthropic-billing-header:"):
+                        continue
+                    filtered_list.append(content_block)
+                else:
+                    # Keep non-dict items as-is
+                    filtered_list.append(content_block)
+            return filtered_list if len(filtered_list) > 0 else None
+        else:
+            return system_param
 
     def get_complete_url(
         self,
@@ -123,6 +157,17 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                 message="max_tokens is required for Anthropic /v1/messages API",
                 status_code=400,
             )
+        
+        # Filter out x-anthropic-billing-header from system messages
+        system_param = anthropic_messages_optional_request_params.get("system")
+        if system_param is not None:
+            filtered_system = self._filter_billing_headers_from_system(system_param)
+            if filtered_system is not None and len(filtered_system) > 0:
+                anthropic_messages_optional_request_params["system"] = filtered_system
+            else:
+                # Remove system parameter if all content was filtered out
+                anthropic_messages_optional_request_params.pop("system", None)
+        
         ####### get required params for all anthropic messages requests ######
         verbose_logger.debug(f"TRANSFORMATION DEBUG - Messages: {messages}")
         anthropic_messages_request: AnthropicMessagesRequest = AnthropicMessagesRequest(