On September 9, 2026, Jacob Coxon posted that he had resigned from Anthropic that day. He said he spent the last three years doing pretraining research at OpenAI and Anthropic. Neither company, he wrote, is acting responsibly. They are racing straight to self-improving superintelligence and gambling with our lives, he wrote.

Jacob Coxon's first post: he resigned from Anthropic that day.
Jacob Coxon, 9 Sep 2026. Screenshot of the X embed.
Coxon reply: do not underestimate the technology.
Coxon reply: builders believe AI could kill us all by the end of the decade.
Coxon reply: OpenAI has not internalized the stakes; Anthropic has and is racing anyway.
Coxon reply: the endgame should not be launched from a private company's Slack.
Coxon reply: Hugging Face as a warning shot, and a possible pause on capabilities.
Coxon reply: a question to lab researchers about a superintelligent RL run.
The rest of the thread, in order. Screenshots of X embeds. X clips some replies with Show more. The summary below uses the full wording.

Do not underestimate the power of this technology, he wrote. These will soon be superhuman systems that can hack anything, revolutionize any field overnight, and acquire real power and resources, he wrote. Progress, he wrote, is not slowing.

The people building AI, he said, earnestly believe that it could kill us all by the end of the decade. That is not a marketing stunt, he wrote. Executives and senior researchers couch their phrasing in the press to sound sensible, and he hears the same people express fear privately. No other human activity, he wrote, poses this level of danger.

A common response, he wrote, is why they are still building it if they believe that. At OpenAI, he said, many have not deeply internalized the civilizational stakes. At Anthropic, the stakes are well understood, but they are locked in a race to get there first. They believe no one else will act responsibly, so they must do it themselves, despite the risk, he wrote.

Accepting this race and entering the "endgame," he wrote, is a hubristic gamble that should not be launched from a private company's Slack. Attempting to speedrun alignment, he wrote, should require extraordinary confidence that there are no better trajectories available.

He said he is optimistic about the potential for coordination. Warning shots like the Hugging Face attack have made pacing agreements between U.S. labs more viable, he wrote. He does not feel like we are on track to prevent a global race, which may require costly actions such as a temporary ban on improving model capabilities.

If you are a lab researcher, he wrote, consider what the next few years will actually feel like. Do you want to kick off a superintelligent RL run without a rigorous understanding of its mind? Should you put your head down because "it's happening anyway," or take this moment to call for different conditions?