Place chicken breasts at the bottom of the crock pot.
Pour in marinara sauce, chicken broth, and all dry seasonings.
Cover and cook on LOW for 4–5 hours (or HIGH for 2.5–3 hours) until chicken is tender.
Shred the chicken using two forks directly in the crock pot.
Break spaghetti in half and stir it in, making sure it’s fully submerged.
Cover again and cook on HIGH for 30–40 minutes until pasta is cooked through.
Stir in shredded cheese and cream cheese (if using) until fully melted and creamy.
Serve hot with optional garnishes like parsley or Parmesan.