On September 9th, 2026, a 27-year-old researcher named Jacob Coxon posted that he had resigned from Anthropic that day. He’d spent three years doing pretraining research, first at OpenAI, then at Anthropic. Neither company, he wrote, is acting responsibly.
People leave AI labs over safety concerns fairly often, and the posts rarely travel far. This one hit 46 million views inside a day, mostly because of what happened next.
Who they are
Coxon is a British researcher with a mathematics background who spent three years inside the two labs at the front of the field. His name is on the GPT-4o system card and on OpenAI research into making the inner workings of transformers legible. He joined Anthropic earlier in 2026, and he’s been clear about why: its reputation for taking safety seriously.
That matters for reading what he said. He didn’t accuse Anthropic of faking its safety work. His argument was that the company understands the stakes and is racing anyway, because it believes nobody else will act responsibly, and that competition makes even genuine caution insufficient. He’s now leaving the industry entirely.
Why they matter
His timeline is short and specific. He told the Wall Street Journal that on the most aggressive scenarios, things could be out of control by the end of next year. He also reported that people inside the labs have started using the words crunchtime and endgame, which is a strange vocabulary for an industry insisting everything is under control.
Then Evan Hubinger, who leads alignment science at Anthropic, backed him publicly. Hubinger wrote that he puts the odds above 10 percent that AI kills all humans within the decade, and that the company doesn’t yet have a plan for aligning superintelligence. A sitting executive confirming a departing researcher’s warning is the part with no real precedent.
Anthropic’s response to press was to point at Hubinger’s own follow-up post, which noted the company’s risk assessment holds that today’s systems are unlikely to gain that kind of power. Which is true, and also not quite what anyone was arguing about.
What they’ve said or done
The line from the thread that traveled: they are “racing straight to self-improving superintelligence and gambling with our lives.”
Coxon isn’t the first to go. Mrinank Sharma, who ran Anthropic’s Safeguards Research team, resigned in February 2026 over related concerns. What’s different this time is that nobody at the company said he was wrong.