Preheat oven to 250°F and line a large baking tray with parchment paper. Set aside.

In a large mixing bowl, combine rice chex cereal, corn chex cereal, pretzels, and peanuts. Mix gently to avoid breaking the cereal pieces.

In a saucepan over medium heat, add butter, brown sugar, and corn syrup. Stir continuously until the butter is melted and the mixture is smooth.

Allow the mixture to come to a gentle boil. Let it boil without stirring for 2 to 3 minutes so the caramel thickens properly.

Remove the saucepan from heat. Carefully stir in baking soda and vanilla extract. The mixture will foam and become lighter.

Slowly pour the caramel sauce over the cereal mixture in batches. Use a spatula to gently fold and coat all the ingredients evenly.

Transfer the coated mixture onto the prepared baking tray. Spread into an even layer without pressing too firmly.

Bake in the oven for 45 minutes. Stir the mixture every 15 minutes to ensure even coating and prevent burning.

Remove from oven and allow the mixture to cool completely on the tray. This helps the caramel harden and become crisp.

Once cooled, break into clusters and store in an airtight container at room temperature.