We do not attain Salvation by works, nor do we maintain it by works. Salvation is complete and eternal once gained. Tetelestai! (Ephesians 2:8-9)
Everything after is Sanctification and Purification.
Once we have been reborn, we can not be unborn.
Because it is predicated on a promise He made, a covenant He can not break, and not an action or inaction on our part, and no work can earn, or maintain.
No one (including ourselves) can pluck us from His hands. (John 10:28-29)
Paul tells us that nothing can separate us from the love of God. (Romans 8:35, 38-39)
And in (Philippians 1:5-6) Paul tells us that He will finish the work He started in us.
OSAS is true, but only for the true believer in Christ. None of us know that disposition of another truly but Christ and that person themselves.
Some will find out they are lacking that relationship, and have deceived themselves. Offering up a list of works to qualify their dispute.
Those who have been truly saved will have evidence of His presence in their lives, and change in their heart also.
He not only saves us from sin and the world, but from ourselves as well.