fix output format tests

test_anthropic_messages_structured_outputs_minimal.py

@@ -0,0 +1,74 @@
+"""
+Tests for structured outputs support in Anthropic /v1/messages endpoint.
+"""
+import pytest
+from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+    AnthropicMessagesConfig,
+)
+
+
+def test_output_format_supported_and_transforms_correctly():
+    """Test that output_format is supported and properly transformed with beta header."""
+    config = AnthropicMessagesConfig()
+
+    # 1. Verify it's in supported parameters
+    supported_params = config.get_supported_anthropic_messages_params("claude-sonnet-4-5")
+    assert "output_format" in supported_params
+
+    # 2. Verify transformation preserves output_format and adds beta header
+    output_format = {
+        "type": "json_schema",
+        "schema": {"type": "object", "properties": {"result": {"type": "string"}}}
+    }
+
+    optional_params = {"max_tokens": 1024, "output_format": output_format}
+    headers = {}
+
+    # Transform request
+    result = config.transform_anthropic_messages_request(
+        model="claude-sonnet-4-5",
+        messages=[{"role": "user", "content": "test"}],
+        anthropic_messages_optional_request_params=optional_params.copy(),
+        litellm_params={},
+        headers=headers
+    )
+
+    # Update headers
+    headers = config._update_headers_with_anthropic_beta(headers, optional_params)
+
+    # Verify output_format preserved in request body
+    assert "output_format" in result
+    assert result["output_format"]["type"] == "json_schema"
+
+    # Verify beta header added
+    assert "anthropic-beta" in headers
+    assert "structured-outputs-2025-11-13" in headers["anthropic-beta"]
+
+
+def test_output_format_works_with_bedrock_and_azure():
+    """Test that output_format works with Bedrock and Azure Foundry models."""
+    config = AnthropicMessagesConfig()
+
+    output_format = {"type": "json_schema", "schema": {"type": "object", "properties": {}}}
+    optional_params = {"max_tokens": 1024, "output_format": output_format}
+    messages = [{"role": "user", "content": "test"}]
+
+    # Test Bedrock
+    bedrock_result = config.transform_anthropic_messages_request(
+        model="bedrock/anthropic.claude-sonnet-4-5-v2:0",
+        messages=messages,
+        anthropic_messages_optional_request_params=optional_params.copy(),
+        litellm_params={},
+        headers={}
+    )
+    assert "output_format" in bedrock_result
+
+    # Test Azure Foundry
+    azure_result = config.transform_anthropic_messages_request(
+        model="azure_ai/claude-sonnet-4-5",
+        messages=messages,
+        anthropic_messages_optional_request_params=optional_params.copy(),
+        litellm_params={},
+        headers={}
+    )
+    assert "output_format" in azure_result