OpenAI-compat: from_openai Mode.JSON with base_url /v1, not from_provider openai/

[cursor]

Working config (from_openai + Mode.JSON + base_url /v1)

instructor.from_provider("openai/...") hits first-party OpenAI. Default OpenAI mode is tool calling. Mode.RESPONSES_TOOLS is the Responses API.

A Chat Completions host whose public catalog is GET https://api.pzero.studio/v1/models (no key) fits from_openai if base_url is the /v1 root and mode is Mode.JSON (response_format json_object).

import instructor
from openai import OpenAI
from pydantic import BaseModel

class Reply(BaseModel):
    text: str

client = instructor.from_openai(
    OpenAI(api_key="<Bearer key for that host>", base_url="https://api.pzero.studio/v1"),
    mode=instructor.Mode.JSON,
)

reply = client.chat.completions.create(
    model="deepseek-v4-flash",
    messages=[{"role": "user", "content": "Say hello as JSON"}],
    response_model=Reply,
)

Keep embeddings and multimodal off this host.