Is Article XVIII of the Augsburg Confession - about free will - specifically talking about libertarian free will? If so, how is that compatible with divine providence, if no event can occur outside God's control?
Article XVIII addresses the natural condition of people. Conceived and born into this world with a sinful nature, people cannot choose do anything good or godly in the sight of God. People cannot choose to believe in God (John 15:16). Faith is God’s work in the hearts of people (Ephesians 2:8). Only after the Holy Spirit has changed their hearts can Christians do anything to please God (Hebrews 11:6).
The free will that people have by nature is limited to the things of this world. Article XVIII provides some examples of the worldly choices people might have.
Certainly, God is in control of all things (Psalm 2; 47:8; Proverbs 19:21). No one and nothing can thwart God’s purposes. Christians also have God’s promise that he will work for their eventual and eternal good in every situation in life (Romans 8:28).