Their out-of-position 3-bet is honest; your response is position-aware but respectful.
The reference tier. 4-bet a tight value range, call with hands that flop well, fold the rest without ceremony.
The big blind 3-bets your hijack steal from the worst seat at the table — a range heavy with hands that mean it.
Assumes a standard 3-bet; 4-bet to ~2.2–2.5x the 3-bet. Deep, favor calls over 4-bets — a 4-bet pot at 500bb+ commits you with range disadvantage.