A choice to accept or reject an offer before acceptance is not the same as khiyar al-shart. The first situation arises before the contract is concluded.
In the stipulated option, a contract has been made, but an agreed right to affirm or unwind it remains for a specified period.
1. “I offer you this book” awaits acceptance.
2. “I accept, provided I have two days to decide” can establish the stipulated option if both parties agree.