OpenAI said last night that Sam Altman would return to the company as CEO, capping days of high drama and marathon discussions about the future of the startup at the center of the global artificial intelligence boom.

Following his surprise dismissal on Friday, Altman had briefly joined Microsoft as the head of artificial intelligence research along with the ChatGPT maker's former President Greg Brockman and other staff.

The developments come less than a year after OpenAI kicked off a generative AI frenzy with the launch of viral chatbot ChatGPT and bagged Microsoft as an investor, among other big names.

November 17 - OpenAI board fires CEO, co-founder Sam Altman and President Greg Brockman quits after being removed from the board. Company names Mira Murati as interim CEO.

Greg Brockman, president and co-founder of OpenAI

November 18 - Altman's firing was over a "breakdown in communication between Sam and the board," and not "malfeasance", COO Brad Lightcap says in an internal memo.

November 18 - Early investor Khosla Ventures says it wants Altman back at OpenAI, "but will back him in whatever he does next".

November 18 - Some employees contemplated quitting if Altman was not restored as CEO by the end of the weekend, while others expressed support for joining his new venture, people familiar with the matter said.

November 19 - Altman discusses a possible return to the company, considers launching new AI startup, source tells Reuters.

November 20 - Microsoft CEO Satya Nadella says the Windows maker has hired Altman, Brockman and their colleagues to lead a new advanced AI research team.

November 20 - OpenAI appoints former Twitch boss Emmett Shear as interim CEO. Shear pledges probe into Altman's exit. OpenAI board approaches rival Anthropic's CEO on merger, for taking top job, sources say.

Emmet Shear

November 20 - Nearly all OpenAI staff threaten to quit and join Altman at Microsoft if board does not resign, according to a letter seen by Reuters.

November 20 - Some investors in OpenAI explore legal recourse against the company's board, sources familiar with the matter told Reuters.

November 21 - OpenAI said Altman will return as CEO with a new initial board of Bret Taylor, Larry Summers, and Adam D'Angelo. Brockman will also returning to the startup.