fix(anthropic): use native output capability (#33235)

* fix(anthropic): route native structured output

Use model capability metadata so new native structured-output models do not require transformation allowlist changes.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(anthropic): pass provider to capability

Co-authored-by: Cursor <cursoragent@cursor.com>

* test(anthropic): cover dotted model IDs

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(anthropic): handle remote capability lag

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

litellm/llms/anthropic/chat/transformation.py

@@ -1441,24 +1441,10 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
                     output_key=param,
                 )
             elif param == "response_format" and isinstance(value, dict):
-                if any(
-                    substring in model
-                    for substring in {
-                        "sonnet-4.5",
-                        "sonnet-4-5",
-                        "opus-4.1",
-                        "opus-4-1",
-                        "opus-4.5",
-                        "opus-4-5",
-                        "opus-4.6",
-                        "opus-4-6",
-                        "opus-4.7",
-                        "opus-4-7",
-                        "sonnet-4.6",
-                        "sonnet-4-6",
-                        "sonnet_4.6",
-                        "sonnet_4_6",
-                    }
+                if AnthropicConfig._supports_model_capability(
+                    model,
+                    "supports_native_structured_output",
+                    self._resolved_provider,
                 ):
                     _output_format = self.map_response_format_to_anthropic_output_format(value)
                     if _output_format is not None:

litellm/llms/anthropic/common_utils.py

@@ -340,11 +340,15 @@ class AnthropicModelInfo(BaseLLMModelInfo):
     def _get_model_capability(model: str, key: str) -> Optional[bool]:
         """Read boolean capability ``key`` from the model map, or None when
         no entry declares it."""
+        from litellm.utils import _get_bundled_model_cost_map
+
         try:
-            for cand in AnthropicModelInfo._model_map_lookup_candidates(model):
-                value = litellm.model_cost.get(cand, {}).get(key)
-                if isinstance(value, bool):
-                    return value
+            candidates = AnthropicModelInfo._model_map_lookup_candidates(model)
+            for model_cost in (litellm.model_cost, _get_bundled_model_cost_map()):
+                for cand in candidates:
+                    value = model_cost.get(cand, {}).get(key)
+                    if isinstance(value, bool):
+                        return value
         except Exception:
             pass
         return None

litellm/model_prices_and_context_window_backup.json

@@ -11331,6 +11331,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11362,6 +11363,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_web_search": true
@@ -11424,6 +11426,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_max_reasoning_effort": true,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11479,6 +11482,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11506,6 +11510,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11559,6 +11564,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_output_config": true
@@ -11586,6 +11592,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_output_config": true
@@ -11614,6 +11621,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "provider_specific_entry": {
@@ -11648,6 +11656,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "provider_specific_entry": {
@@ -11682,6 +11691,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11718,6 +11728,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11788,6 +11799,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,

model_prices_and_context_window.json

@@ -11331,6 +11331,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11362,6 +11363,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_web_search": true
@@ -11424,6 +11426,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_max_reasoning_effort": true,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11479,6 +11482,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11506,6 +11510,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true
     },
@@ -11559,6 +11564,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_output_config": true
@@ -11586,6 +11592,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "supports_output_config": true
@@ -11614,6 +11621,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "provider_specific_entry": {
@@ -11648,6 +11656,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_tool_choice": true,
         "supports_vision": true,
         "provider_specific_entry": {
@@ -11682,6 +11691,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11718,6 +11728,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,
@@ -11788,6 +11799,7 @@
         "supports_prompt_caching": true,
         "supports_reasoning": true,
         "supports_response_schema": true,
+        "supports_native_structured_output": true,
         "supports_sampling_params": false,
         "supports_tool_choice": true,
         "supports_vision": true,

tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py

@@ -957,15 +957,15 @@ def test_anthropic_structured_output_beta_header():
 @pytest.mark.parametrize(
     "model_name",
     [
-        "claude-opus-4-6-20250918",
-        "claude-opus-4.6-20250918",
+        "claude-opus-4-8",
+        "claude-opus-4-6-20260205",
         "claude-opus-4-5-20251101",
         "claude-opus-4.5-20251101",
     ],
 )
 def test_opus_uses_native_structured_output(model_name):
     """
-    Test that Opus 4.5 and 4.6 models use native Anthropic structured outputs
+    Test that supported Opus models use native Anthropic structured outputs
     (output_format) rather than the tool-based workaround.
     """
     config = AnthropicConfig()
@@ -1005,6 +1005,43 @@ def test_opus_uses_native_structured_output(model_name):
     assert optional_params.get("json_mode") is True
 
 
+def test_native_structured_output_uses_bundled_capability_when_remote_map_lags(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    model = "claude-opus-4-8"
+    monkeypatch.setattr(
+        litellm,
+        "model_cost",
+        {model: {"supports_response_schema": True}},
+    )
+    litellm.get_model_info.cache_clear()
+
+    try:
+        optional_params = AnthropicConfig().map_openai_params(
+            non_default_params={
+                "response_format": {
+                    "type": "json_schema",
+                    "json_schema": {
+                        "name": "answer",
+                        "schema": {
+                            "type": "object",
+                            "properties": {"answer": {"type": "string"}},
+                            "required": ["answer"],
+                        },
+                    },
+                }
+            },
+            optional_params={},
+            model=model,
+            drop_params=False,
+        )
+    finally:
+        litellm.get_model_info.cache_clear()
+
+    assert "output_format" in optional_params
+    assert "tools" not in optional_params
+
+
 def test_non_structured_output_model_uses_tool_workaround():
     """
     Test that models NOT in the native structured output list still use the

tests/test_litellm/test_claude_opus_4_8_config.py

@@ -95,6 +95,8 @@ def test_opus_4_8_model_pricing_and_capabilities():
         assert info["supports_tool_choice"] is True
         assert info["supports_vision"] is True
 
+    assert model_data["claude-opus-4-8"]["supports_native_structured_output"] is True
+
 
 def test_opus_4_8_bedrock_regional_model_pricing():
     model_data = _load_root_cost_map()
@@ -165,6 +167,7 @@ def test_opus_4_8_present_in_bundled_backup():
         "azure_ai/claude-opus-4-8",
     ):
         assert model_name in backup, f"Missing from backup cost map: {model_name}"
+    assert backup["claude-opus-4-8"]["supports_native_structured_output"] is True
 
 
 def test_opus_4_8_registered_for_bedrock_converse():