A decade ago, Elon Musk and Sam Altman bonded over a shared concern about the dangers of artificial intelligence. That led them in 2015 to create OpenAI, a nonprofit A.I. lab that had the aim of benefiting humanity.

In 2018, Mr. Musk departed OpenAI after a power struggle with Mr. Altman. Mr. Musk later expressed dismay that the lab had turned into a for-profit company. Over the years, the two men have increasingly made barbed comments about each other, including when Mr. Altman was briefly ousted from OpenAI in November before being reinstated.

On Thursday, Mr. Musk sued Mr. Altman and OpenAI, accusing them of breaching the founding contract between Mr. Musk and Mr. Altman by putting profits and commercial interests ahead of the public good in developing A.I.

Here’s what Mr. Musk and Mr. Altman have said about each other over the years, and what they have jointly said.

What Mr. Musk has said about Mr. Altman

Post on X, in November:

“What matters is having directors who deeply understand AI and will stand up to Sam. Human civilization is at stake here.”

At The New York Times’s DealBook Summit, in November:

“I have mixed feelings about Sam. The ring of power can corrupt, and he has the ring of power. So I don’t know.”

“I’m quite concerned that there’s some dangerous element of A.I. that they’ve created.”

In this week’s lawsuit:

“Mr. Altman caused OpenAI to radically depart from its original mission and historical practice of making its technology and knowledge available to the public.”

What Mr. Altman has said about Mr. Musk