Structured output doesn't work for Anthropic in Agent API

Bug Reports
,
1

Minimal reproduction

import asyncio
import os

from perplexity import AsyncPerplexity
from pydantic import BaseModel

PERPLEXITY_API_KEY = os.environ["PERPLEXITY_API_KEY"]
MODEL = "anthropic/claude-opus-5"


class BrandEquality(BaseModel):
    aliases: bool
    explanation: str


async def main() -> None:
    client = AsyncPerplexity(api_key=PERPLEXITY_API_KEY)
    try:
        response = await client.responses.create(
            model=MODEL,
            input=[
                {
                    "type": "message",
                    "role": "user",
                    "content": (
                        "In the context of tax advisory services in Denmark, are "
                        "'Grant Thornton' and 'Grant Thornton Danmark' aliases for "
                        "the same brand?"
                    ),
                }
            ],
            instructions=(
                "Determine whether the two names uniquely identify the same brand "
                "in the supplied context."
            ),
            tools=[{"type": "web_search", "search_context_size": "low"}],
            reasoning={"effort": "high"},
            max_output_tokens=128_000,
            response_format={
                "type": "json_schema",
                "json_schema": {
                    "name": "BrandEquality",
                    "schema": BrandEquality.model_json_schema(),
                },
            },
        )
    finally:
        await client.close()

    print(response.output)
    print(response.output_text)


if __name__ == "__main__":
    asyncio.run(main())

Response or error

perplexity.BadRequestError: Error code: 400 - {'error': {'message': 'invalid request', 'type': 'invalid_request', 'code': 400}}

Additional context

  • Models from other vendors work fine: OpenAI, xAI, Gemini.
  • If you run it many-many times, you may see 1-2 of successful requests.