Preheat oven to 250°F. Line a counter or table with parchment paper for cooling.

Combine Crispix cereal and pecan halves in a large bowl.

In a saucepan, heat brown sugar, corn syrup, and butter until boiling. Remove from heat and stir in vanilla and baking soda.

Pour caramel over cereal and pecans. Toss gently to coat.

Spread mixture into a 9×13-inch baking dish. Bake 1 hour, stirring every 20 minutes.

Pour mixture onto parchment and cool completely. Break into clusters.