LANG_PAIR_THRESHOLDS = {
    ("ko", "en"): 0.75,
    ("ko", "ja"): 0.80,
    ("ko", "zh"): 0.82,
    ("en", "ja"): 0.78,
    ("en", "zh"): 0.80,
    ("ja", "zh"): 0.85,
}

def threshold_for_pair(lang_a: str, lang_b: str) -> float:
    key = tuple(sorted([lang_a, lang_b]))
    return LANG_PAIR_THRESHOLDS.get(key, 0.80)