Set the oven to 250ºF (120ºC). Lightly spray a baking sheet or roasting pan with cooking spray.
In a large bowl, combine 8 cups of Crispix cereal with 2 cups of pecan halves. Stir to evenly distribute.
In a saucepan over medium-high heat, combine ½ cup dark brown sugar, ½ cup light corn syrup, and ½ cup salted butter. Stir occasionally until it comes to a boil and the sugar fully dissolves.
Remove the pan from heat. Stir in 1 teaspoon vanilla extract and ½ teaspoon baking soda until the mixture turns light and foamy.
Immediately pour the caramel over the cereal and pecans. Gently toss with a spatula until everything is evenly coated.
Spread the coated mixture onto the prepared pan in an even layer. Bake for 1 hour, stirring every 15 minutes to prevent sticking and ensure even baking.
Pour the mix onto wax or parchment paper to cool completely. Once cooled, break into bite-sized pieces and enjoy.