Michael Seibel announced late Wednesday on X that after more than 12 years at the famed accelerator Y Combinator, he is transitioning to a “partner emeritus” role.

Y Combinator CEO Garry Tan shared the news separately in a company blog post, highlighting Seibel’s long history with the outfit. Seibel first joined YC as a founder, going through the program twice — once with the streaming startup Justin.TV and later with the streaming app Socialcam. Seibel later served as a group partner, managing director, and CEO of the YC accelerator.

Notably, Seibel had already stepped back into a less operational group partner role recently. In a YC blog post last year, he wrote that he was ready to “hand over my leadership responsibilities,” with the transition becoming “effective” after the accelerator’s winter batch of startups completed the program.

A dozen years is a long tenure for anyone, but Seibel’s departure may have been set in motion as early as 2022, when Tan was appointed President and CEO. The move reportedly surprised some YC employees — partly because Tan was running a separate venture fund at the time outside of YC, but also because they believed Seibel to be next in line for the role.

We’ve reached out to Seibel for comment. In the meantime, he shared in his X post that after taking this coming summer to relax, he’s eager to “help government better serve its citizens.” He added, “Government was the passion of my youth, and I’m excited to reengage.” Seibel signed off by thanking Y Combinator founders Paul Graham and Jessica Livingston for “changing my life.”

The news comes roughly two weeks before YC’s spring batch of founders kick off their own tour of duty; the program will run from April through June.

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