diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 7135102db01..308bf367d06 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -42,6 +42,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
             "tool_choice",
             "thinking",
             "context_management",
+            "output_format",
             # TODO: Add Anthropic `metadata` support
             # "metadata",
         ]
@@ -169,27 +170,32 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
     ) -> dict:
         """
         Auto-inject anthropic-beta headers based on features used.
-        
+
         Handles:
         - context_management: adds 'context-management-2025-06-27'
         - tool_search: adds provider-specific tool search header
-        
+        - output_format: adds 'structured-outputs-2025-11-13'
+
         Args:
             headers: Request headers dict
-            optional_params: Optional parameters including tools, context_management
+            optional_params: Optional parameters including tools, context_management, output_format
             custom_llm_provider: Provider name for looking up correct tool search header
         """
         beta_values: set = set()
-        
+
         # Get existing beta headers if any
         existing_beta = headers.get("anthropic-beta")
         if existing_beta:
             beta_values.update(b.strip() for b in existing_beta.split(","))
-        
+
         # Check for context management
         if optional_params.get("context_management") is not None:
             beta_values.add(ANTHROPIC_BETA_HEADER_VALUES.CONTEXT_MANAGEMENT_2025_06_27.value)
-        
+
+        # Check for structured outputs
+        if optional_params.get("output_format") is not None:
+            beta_values.add(ANTHROPIC_BETA_HEADER_VALUES.STRUCTURED_OUTPUT_2025_09_25.value)
+
         # Check for tool search tools
         tools = optional_params.get("tools")
         if tools:
@@ -198,8 +204,8 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                 # Use provider-specific tool search header
                 tool_search_header = get_tool_search_beta_header(custom_llm_provider)
                 beta_values.add(tool_search_header)
-        
+
         if beta_values:
             headers["anthropic-beta"] = ",".join(sorted(beta_values))
-        
+
         return headers