Lilian Weng, co-founder of Thinking Machines Lab, has returned to OpenAI.

Weng had left OpenAI along with a handful of other employees to co-found the competing AI startup, which was helmed by Mira Murati, OpenAI’s former CTO. Weng recently shared a note that after being “absent for a month” to focus on her health leading up to Thinking Machines Lab’s first model release, Inkling, she was making the decision to leave behind “consistent stress and workload” to pursue “a scoped role in a more predictable place.” She is reportedly already back at OpenAI.