Star AI researcher Andrew Tulloch is reportedly leaving Meta, less than a year after he was offered an eye-watering pay package.

Tulloch was reportedly offered a package that could have been worth as much as $1.5 billion with top bonuses and extraordinary stock performance. However, he turned it down before later agreeing to join Meta for an undisclosed sum, reportedly recruited personally by CEO Mark Zuckerberg.

Tulloch did not say where he was heading next when he announced his departure to colleagues on Wednesday, and it is unclear why he has decided to leave, The Wall Street Journal and Semafor reported.

Tulloch's hiring was considered a coup for Meta as the company spent heavily to recruit top researchers in an attempt to catch up with frontier model firms in the artificial intelligence race. It was not his first stint at the company, however, having previously spent 11 years at Meta before joining OpenAI in 2023 and later co-founding Thinking Machines Lab, led by former OpenAI CTO Mira Murati.

His decision follows other recent high-profile departures from AI firms, including Google chief scientist Jeff Dean's exit to launch a new AI startup, and Anthropic researcher Jacob Coxon's resignation after a short stint amid his claims that "AI could end humanity by 2030."

Meta Muse

Tulloch's exit comes just one day after Meta launched Muse, a personal AI agent that can keep working after users close the app.

Muse can handle tasks including sending emails, booking travel, opening a browser, filling out forms, and negotiating on a user's behalf, as well as more advanced, longer-term goals, Meta said in a blog post. Muse is powered by Meta's latest model, Muse Spark, and works through its own app or directly in WhatsApp.

Early analyst reactions pointed to a "more promising than expected" product cycle.

"We have been playing around with the new Muse app and came away positively surprised with the polish of the app, the breadth of functionality, the integration of a news feed, the ability to take action, and introduction with a free tier," Mizuho analysts wrote in a note to clients on Wednesday.