Make the buns: In the bowl of a large stand mixer, fitted with a dough hook, dissolve yeast in warm milk. Let stand 5 minutes until foamy. Mix in agave, oil, eggs, salt, and 4 cups flour on medium speed until dough pulls away from sides of bowl into a ball. (if dough seems too sticky, add additional flour by the tablespoon until it comes together)
Turn dough onto a floured surface and knead until smooth and elastic. Place in a greased bowl, turning once to grease top. Cover with plastic wrap and let rise in a warm place until doubled, about 1 hour.
Make the topping: In a medium saucepan over medium heat, melt butter. Whisk in sugar, and agave. Bring caramel to a simmer, stirring occasionally until caramel begins to thicken and turns golden brown, about 5 minutes. Remove from heat and stir in baking soda and toasted pecans. Immediately spread into the bottom of a 9x13 baking pan. Set aside.
Assemble the buns: Punch risen dough down. On a floured surface, roll into a 12x18 rectangle. Spread butter to within 1/2-in of edges and sprinkle sugar and cinnamon over butter, patting flat. Roll up tightly along the long side and pinch edges to seal. Cut into 1/2 to 1-in rolls and place swirl-side up over pecan-caramel sauce in pan. Cover pan with plastic wrap and refrigerate overnight. NOTE: if baking immediately, let buns rise 30 minutes at room temperature then bake as directed.
The next morning, remove sticky buns from refrigerator and remove plastic wrap. Bake at 375F 20-25 minutes or until golden-brown and caramel is bubbly. Remove from oven and let stand 5 minutes, then invert onto a serving tray. (if any pecans and caramel stick to pan, scrape off with a spatula and drizzle over buns) Enjoy sticky buns warm!