Prep the pan: Heat oven to 350°F. Line an 8×8 pan with parchment paper, letting it hang over two sides so you can lift the bars out.
Mix the dry: In a large bowl, stir together oats, whole wheat flour, arrowroot, baking soda, salt, and cinnamon.
Mix the wet: In a second bowl, whisk melted plant butter, monkfruit, applesauce, agave, and vanilla until smooth.
Combine: Pour wet into dry and stir until everything is evenly coated. The dough should look thick and sticky, like oatmeal cookie dough. If it looks dry or crumbly, add plant milk 1 tablespoon at a time, just until it presses together easily. Stop as soon as it holds.
Fold in chocolate chips.
Rest, then press: Let the dough sit on the counter for 10 minutes. This helps the oats and whole wheat soften so the bars bake up chewy, not dry.
Press the dough firmly into the pan. Pressing matters for that dense, store-bought bar texture.
Bake 16 to 20 minutes. Start checking at 16. Pull when the edges look set and lightly golden, and the center looks set on top but still soft underneath.
Cool in the pan at least 45 minutes. For the cleanest slices and best chew, chill 30 minutes after cooling, then lift out and slice.