Mr. Messinger was awarded 1.25 million restricted stock units for his additional duties. After his departure, Twitter’s heads of product, design and engineering will report directly to Mr. Dorsey. Edward Ho, a vice president of engineering, will take over Mr. Messinger’s engineering duties as general manager reporting to Mr. Dorsey.

“I’ll be working even closer with our engineering and design teams to ensure we continue to be the fastest and best service to show what’s happening in the world,” Mr. Dorsey said in a statement.

Mr. Messinger’s supporters at Twitter lauded what they described as his cerebral approach, but he also had detractors who said he was indecisive and sometimes did not take enough concrete steps to make changes happen, according to three former Twitter employees who spoke on the condition of anonymity because the interactions were private.

Mr. Messinger did not say what he would do after leaving Twitter. A person with knowledge of Mr. Messinger’s plans, who asked to remain anonymous because the person was not authorized to speak publicly, said Mr. Messinger did not plan to head to a competing social network like Facebook or Snapchat.