재시도·회로 차단기·예비 경로는 서로 다른 실패를 막아

import time

class Breaker:
    def __init__(self, threshold=5, cool_down=30):
        self.fails = 0
        self.opened_at = 0
        self.threshold = threshold
        self.cool_down = cool_down

    def allow(self) -> bool:
        if self.fails < self.threshold:
            return True
        return (time.time() - self.opened_at) > self.cool_down

    def record(self, ok: bool):
        if ok:
            self.fails = 0
        else:
            self.fails += 1
            if self.fails == self.threshold:
                self.opened_at = time.time()

breaker = Breaker()

def call_with_breaker(*args):
    if not breaker.allow():
        return fallback(*args)
    try:
        out = client.messages.create(*args)
        breaker.record(True)
        return out
    except Exception:
        breaker.record(False)
        raise

def call_with_fallback(messages):
    try:
        return claude_sonnet(messages)
    except (RateLimitError, InternalServerError):
        try:
            return claude_haiku(messages)  # 더 싼 Anthropic 모델
        except Exception:
            return openai_gpt(messages)  # cross-provider 마지막 수단