Elon Musk sent an email to Twitter Inc. employees requiring them to pledge to stay with the company, working long hours at “high intensity” during its transformation, or to accept a buyout. 

Staff will have to complete the online form by 5 p.m. New York time on Thursday or accept three months severance. For Twitter to succeed, “we will need to be extremely hardcore,” Musk said in the email, which was seen by Bloomberg. 

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“Only exceptional performance will constitute a passing grade,” the email said.

Twitter employees have been reaching out to lawyers for advice on how to respond, according to people familiar with the matter.

A representative for Twitter didn't immediately respond to a request for comment. The Washington Post reported the memo earlier. 

Musk said in the note that Twitter will be more dominated by engineers going forward, making up the majority of remaining employees and having the greatest influence at the company, which he called a “software and servers company” at its heart. Design and product management functions will “still be very important and report to me,” he said. 

The billionaire announced plans to fire about 3,700 people in his first week in control of the company. The cuts, which included most of Twitter's senior management, have upset many of the remaining employees. Musk's changes have also led to a lack of communication internally and concerns about product breakdowns and technical outages, according to current and former staffers. 

Since then, Musk has continued to purge employees who have criticized him, sometimes via Twitter.

Musk has warned since his US$44 billion acquisition last month that Twitter could face bankruptcy if it doesn't start generating more cash. He has told employees they can expect to work 80-hour weeks and fewer office perks like free food, and ended the company's work-from-home policy with a few exceptions.