In this Nov 6, 2023 file photo, Sam Altman (left) appears onstage with Microsoft CEO Satya Nadella at OpenAI's first developer conference in San Francisco, the United States. (PHOTO / AP)

SAN FRANCISCO – OpenAI on Wednesday said it reached an agreement for Sam Altman to return as CEO days after his ouster, capping frenzied discussions about the future of the startup at the center of the artificial intelligence boom.

In addition to Altman's return, the company agreed in principle to partly reconstitute the board of directors that had dismissed him. Former Salesforce co-CEO Bret Taylor and former U.S. Treasury Secretary Larry Summers will join Quora CEO and current director Adam D'Angelo, OpenAI said.

READ MORE: OpenAI investors mull suing the board after CEO's firing

Sam Altman said in a post on X "i'm looking forward to returning to openai."

I love OpenAI, and everything I’ve done over the past few days has been in service of keeping this team and its mission together.

Sam Altman

His return caps a tumultuous weekend that saw Altman agree to move to OpenAI's financial backer Microsoft to head a new research team there. That followed a rejection by OpenAI's board of his first attempt to return to the startup, on Sunday, by naming ex-Twitch boss Emmett Shear as interim CEO.

“i love openai, and everything i’ve done over the past few days has been in service of keeping this team and its mission together,” Altman wrote on X.

In a post on X, Shear celebrated the late-night outcome Tuesday, which he said followed "~72 very intense hours of work."

Altman's dismissal had brought uncertainty for both OpenAI and Microsoft, which had moved quickly to control damage over the weekend by vowing to hire him and Greg Brockman, president of the startup.

Brockman, who had quit after Altman was ousted, said in a post on X that he was "getting back to coding tonight."

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Nearly all of OpenAI's more than 700-strong staff on Monday had threatened to leave unless the board stepped down and reinstated Altman and Brockman, according to a letter reviewed by Reuters.

In a statement on X, Microsoft CEO Satya Nadella welcomed the changes to OpenAI's board.

"We believe this is a first essential step on a path to more stable, well-informed, and effective governance," he said.