The idea that salvation is synergistic is indeed Arminianism. Salvation is completely of God. Salvation is all of God. Even our subsequent "cooperation" is a monergistic working of God in the elect:

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Therefore, my beloved, as you have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling; 13 for it is God who works in you both to will and to do for His good pleasure. (Philippians 2:12-13 NKJ)

God knows everything we will do before we do it and He knows all the number of our days. In other words, our entire life is already laid out and God knows it all from before the creation of the world and on to eternity in heaven:

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<For the Chief Musician. A Psalm of David.> O LORD, You have searched me and known me. 2 You know my sitting down and my rising up; You understand my thought afar off. 3 You comprehend my path and my lying down, And are acquainted with all my ways. 4 For there is not a word on my tongue, But behold, O LORD, You know it altogether. 5 You have hedged me behind and before, And laid Your hand upon me. 6 Such knowledge is too wonderful for me; It is high, I cannot attain it. 7 Where can I go from Your Spirit? Or where can I flee from Your presence? 8 If I ascend into heaven, You are there; If I make my bed in hell, behold, You are there. 9 If I take the wings of the morning, And dwell in the uttermost parts of the sea, 10 Even there Your hand shall lead me, And Your right hand shall hold me. 11 If I say, "Surely the darkness shall fall on me," Even the night shall be light about me; 12 Indeed, the darkness shall not hide from You, But the night shines as the day; The darkness and the light are both alike to You. 13 For You formed my inward parts; You covered me in my mother's womb. 14 I will praise You, for I am fearfully and wonderfully made; Marvelous are Your works, And that my soul knows very well. 15 My frame was not hidden from You, When I was made in secret, And skillfully wrought in the lowest parts of the earth. 16 Your eyes saw my substance, being yet unformed. And in Your book they all were written, The days fashioned for me, When as yet there were none of them. (Psalm 139:1-16 NKJ)

For "who has known the mind of the LORD that he may instruct Him?" But we have the mind of Christ. (1 Corinthians 2:16 NKJ)