diff --git a/litellm/litellm_core_utils/prompt_templates/common_utils.py b/litellm/litellm_core_utils/prompt_templates/common_utils.py
index 2d26b5dd1e2..07d5e6314dd 100644
--- a/litellm/litellm_core_utils/prompt_templates/common_utils.py
+++ b/litellm/litellm_core_utils/prompt_templates/common_utils.py
@@ -1004,7 +1004,7 @@ def _has_legacy_defs(schema: object) -> bool:
     return "definitions" in schema or (isinstance(components, dict) and isinstance(components.get("schemas"), dict))
 
 
-# Schema-bomb budget for ``unpack_legacy_defs``: cap the cumulative JSON-byte
+# Schema-bomb budget for ``$ref`` inlining: cap the cumulative JSON-byte
 # size of every inlined target. A byte cap is the universal measure of
 # expansion -- it simultaneously bounds ref-count fan-out, node-count
 # amplification, and scalar-byte amplification (large ``description`` /
@@ -1012,14 +1012,14 @@ def _has_legacy_defs(schema: object) -> bool:
 # inline well under 1MB; 10MB sits two orders of magnitude above that, well
 # below memory-pressure territory, and rejects request-supplied bombs before
 # the proxy materialises them.
-_LEGACY_DEFS_MAX_INLINED_BYTES: Final = 10_000_000
+DEFS_MAX_INLINED_BYTES: Final = 10_000_000
 
 
 def unpack_legacy_defs(
     schema: dict,
     *,
     copy: bool = False,
-    max_inlined_bytes: int = _LEGACY_DEFS_MAX_INLINED_BYTES,
+    max_inlined_bytes: int = DEFS_MAX_INLINED_BYTES,
 ) -> dict:
     """Inline ``$ref``s backed by draft-04 ``definitions`` / OpenAPI
     ``components.schemas``. ``$defs`` is left untouched.
diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index 31713f8f085..ef4ad7011c5 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -1267,13 +1267,14 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
         import copy
 
         from litellm.litellm_core_utils.prompt_templates.common_utils import (
+            DEFS_MAX_INLINED_BYTES,
             unpack_defs,
         )
 
         json_schema = copy.deepcopy(json_schema)
         defs: Final = json_schema.pop("$defs", json_schema.pop("definitions", {}))
         if defs:
-            unpack_defs(json_schema, defs)
+            unpack_defs(json_schema, defs, max_inlined_bytes=DEFS_MAX_INLINED_BYTES)
 
         # Filter out unsupported fields for Anthropic's output_format API
         filtered_schema: Final = self.filter_anthropic_output_schema(json_schema)
diff --git a/litellm/model_prices_and_context_window_backup.json b/litellm/model_prices_and_context_window_backup.json
index db147c17c4f..e6c6cab0631 100644
--- a/litellm/model_prices_and_context_window_backup.json
+++ b/litellm/model_prices_and_context_window_backup.json
@@ -12011,6 +12011,7 @@
         "output_cost_per_token": 5e-06,
         "supports_assistant_prefill": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_computer_use": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
@@ -12033,6 +12034,7 @@
         "output_cost_per_token": 5e-06,
         "supports_assistant_prefill": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_computer_use": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
@@ -12254,6 +12256,7 @@
         "supports_assistant_prefill": false,
         "supports_computer_use": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
         "supports_reasoning": true,
diff --git a/model_prices_and_context_window.json b/model_prices_and_context_window.json
index db147c17c4f..e6c6cab0631 100644
--- a/model_prices_and_context_window.json
+++ b/model_prices_and_context_window.json
@@ -12011,6 +12011,7 @@
         "output_cost_per_token": 5e-06,
         "supports_assistant_prefill": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_computer_use": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
@@ -12033,6 +12034,7 @@
         "output_cost_per_token": 5e-06,
         "supports_assistant_prefill": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_computer_use": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
@@ -12254,6 +12256,7 @@
         "supports_assistant_prefill": false,
         "supports_computer_use": true,
         "supports_function_calling": true,
+        "supports_native_structured_output": true,
         "supports_pdf_input": true,
         "supports_prompt_caching": true,
         "supports_reasoning": true,
diff --git a/tests/test_litellm/llms/anthropic/test_anthropic_structured_output.py b/tests/test_litellm/llms/anthropic/test_anthropic_structured_output.py
index 2701991c01c..2f66a7259d3 100644
--- a/tests/test_litellm/llms/anthropic/test_anthropic_structured_output.py
+++ b/tests/test_litellm/llms/anthropic/test_anthropic_structured_output.py
@@ -46,9 +46,7 @@ class TestAnthropicStructuredOutput:
             "json_schema": json_schema["json_schema"],
         }
 
-        output_format = config.map_response_format_to_anthropic_output_format(
-            response_format
-        )
+        output_format = config.map_response_format_to_anthropic_output_format(response_format)
 
         # Verify that maxItems is filtered out for Anthropic
         assert output_format is not None
@@ -82,9 +80,7 @@ class TestAnthropicStructuredOutput:
             "json_schema": json_schema["json_schema"],
         }
 
-        output_format = config.map_response_format_to_anthropic_output_format(
-            response_format
-        )
+        output_format = config.map_response_format_to_anthropic_output_format(response_format)
 
         assert output_format is not None
         transformed_schema = output_format["schema"]
@@ -112,9 +108,7 @@ class TestAnthropicStructuredOutput:
             "json_schema": json_schema["json_schema"],
         }
 
-        output_format = config.map_response_format_to_anthropic_output_format(
-            response_format
-        )
+        output_format = config.map_response_format_to_anthropic_output_format(response_format)
 
         assert output_format is not None
         transformed_schema = output_format["schema"]
@@ -125,10 +119,7 @@ class TestAnthropicStructuredOutput:
         # Nested maxItems should also be removed
         if "$defs" in transformed_schema:
             nested_item_schema = transformed_schema["$defs"].get("NestedItem", {})
-            if (
-                "properties" in nested_item_schema
-                and "tags" in nested_item_schema["properties"]
-            ):
+            if "properties" in nested_item_schema and "tags" in nested_item_schema["properties"]:
                 assert "maxItems" not in nested_item_schema["properties"]["tags"]
 
     def test_other_constraints_preserved(self):
@@ -153,9 +144,7 @@ class TestAnthropicStructuredOutput:
             "json_schema": json_schema["json_schema"],
         }
 
-        output_format = config.map_response_format_to_anthropic_output_format(
-            response_format
-        )
+        output_format = config.map_response_format_to_anthropic_output_format(response_format)
 
         assert output_format is not None
         transformed_schema = output_format["schema"]
@@ -177,3 +166,41 @@ class TestAnthropicStructuredOutput:
         assert "description" in age_schema
         assert "minimum value: 0" in age_schema["description"]
         assert "maximum value: 150" in age_schema["description"]
+
+
+class TestAnthropicOutputFormatSchemaBudget:
+    """The $defs inlining in map_response_format_to_anthropic_output_format is byte-bounded."""
+
+    @staticmethod
+    def _response_format(schema: dict) -> dict:
+        return {"type": "json_schema", "json_schema": {"name": "out", "schema": schema}}
+
+    def test_schema_bomb_rejected(self):
+        """A compact request whose $defs expand past the byte budget raises instead of materialising."""
+        from litellm.llms.anthropic.chat.transformation import AnthropicConfig
+
+        big = {"type": "string", "description": "x" * 200_000}
+        schema = {
+            "type": "object",
+            "$defs": {"Big": big},
+            "properties": {f"p{i}": {"$ref": "#/$defs/Big"} for i in range(60)},
+        }
+
+        with pytest.raises(ValueError, match="budget"):
+            AnthropicConfig().map_response_format_to_anthropic_output_format(self._response_format(schema))
+
+    def test_normal_defs_still_resolve(self):
+        from litellm.llms.anthropic.chat.transformation import AnthropicConfig
+
+        schema = {
+            "type": "object",
+            "$defs": {"Item": {"type": "string", "description": "an item"}},
+            "properties": {"a": {"$ref": "#/$defs/Item"}, "b": {"$ref": "#/$defs/Item"}},
+        }
+
+        output_format = AnthropicConfig().map_response_format_to_anthropic_output_format(self._response_format(schema))
+        assert output_format is not None
+        resolved = output_format["schema"]["properties"]
+        assert resolved["a"]["type"] == "string"
+        assert resolved["b"]["type"] == "string"
+        assert "$ref" not in str(resolved)