Gaseous chlorine
Also, the term “bleach” is a bit misleading. In your question you specify sodium hypochlorite which is chlorine bleach and this is the bleach that will cause problems when mixed with an acid. There are other bleachs like percarbonate, hydrogen perodixde (of which percarbs are made) which are known as “oxygen bleach”. Percarbs and hydrogen peroxide are weak acids but still should never be mixed with any other chemicals for safety. These type of bleach are far safer to handle and are color safe.
Sorry to get outside of the original question, but one of my goals on earth is get people to understand the differences between bleaches. It’s a lofty goal and I appreciate you asking the question so I could pretend to know something.