Brandon Silverman’s last day at Facebook was Oct. 8, and like many others who have sold their companies to a Silicon Valley giant, had their shares vest and departed, he planned to take a year off to spend time with his children and figure out what to do next.

He had been at the social media giant since it acquired his startup, CrowdTangle, in 2016. And he had watched that project, which tracks the content that draws attention on Facebook, emerge as perhaps the single most important window into what was actually happening on the megaplatform. But his project had increasingly become an irritant to his bosses, as it revealed the extent to which Facebook users engaged with hyperpartisan right-wing politics and misleading health information.

While Silverman no longer works at Facebook, he hasn’t quite left the company behind. Instead, he has spent the weeks since his exit working with a bipartisan group of U.S. senators on legislation that would, among other things, force the giant social media platforms to provide the sort of transparency that got him marginalized at Facebook.