A public tiff is unfolding on X (formerly Twitter) platform between David Sacks of Craft Ventures and the All-In podcast and Paul Graham who’s largely known for his involvement with Y Combinator.

While the animus is only now being made public, the manner in which Graham replied to Sacks makes it appear as though it’s been simmering for years.

Here’s a summary of the accusations being thrown around and why this decade-long beef hasn’t been squashed.

Zenefits and Conrad Parker

Sacks and Graham’s online feud is largely down to Conrad Parker, a well-known Silicon Valley tech VC who founded and led a software as a service (SaaS) company called Zenefits. Sacks was brought on board as the company’s COO, while a16z was its largest investor.

At some point, it became clear that Zenefits was suffering from serious insurance compliance issues, which caught the attention of the Securities and Exchange Commission (SEC) and several state attorney generals. This resulted in numerous settlements, including one with the SEC in which neither Zenefits nor Parker admitted guilt but paid out hundreds of thousands of dollars in penalties.

However, before these settlements occurred (at least according to Parker) a16z approached him and asked him to resign as CEO in favor of Sacks. At this point, things get murky. Parker claims that a resignation announcement was drafted that was complimentary to both him and Sacks, but was scrapped without his knowledge, with the announcement instead reading quite negatively toward Parker.

A Forbes article from the time shows that Sacks said, “The fact is that many of our internal processes, controls, and actions around compliance have been inadequate, and some decisions have just been plain wrong. As a result, Parker has resigned.”

As Parker tells it, once the so-called coup occurred, “David [Sacks] was not really interested in making Zenefits successful, and almost every decision he made at the company was wrong.” Knowing this, Parker went on to found Rippling, which offers a near-identical product to the one he was building at Zenefits.

Rippling has raised billions of dollars from investors like Y Combinator, Peter Thiel’s Founders Fund, and Sequoia Capital. Meanwhile, Zenefits crashed and burned, eventually getting acquired by TriNet for significantly less than its one-time value of over $4 billion.

Read more: David Sacks-backed Michelle Tandler shutters another business

Sacks and Graham trade insults online

Sacks quickly went on a media blitz after becoming CEO of Zenefits, claiming that, despite being COO, he had no knowledge of the problems at the company because “sales were never reported to [him] and legal and compliance were never reported to .”

It could be argued that his inability to discover these failures despite being the COO is a form of negligence and a dereliction of duty, but, regardless, Sacks was never charged with anything by any regulator or attorney general.

While Parker has been making the rounds for years — from podcasts to appearances at conferences and interviews with the media — to discuss the way that Sacks got him removed from Zenefits and eventually destroyed the company, he’s also been keen to suggest that Sacks and investors in Zenefits had him sign an NDA before his resignation so that he would be unable to defend himself from accusations.

Eventually, this all culminated in Parker’s recent tweet that read, “Let me tell you, coups are this man’s specialty” — referring to a Sacks tweet in which he claimed that Kamala Harris becoming the new Democratic Party presidential nominee is a ‘coup.’

Sacks responded by stating that “[Parker was] sanctioned by the SEC. Nobody else, only . But [he’s] spent the last decade trying to shift the blame onto others for [his] own poor ethics.” He added a second tweet where he called Parker “a whiny little bitch.”

This series of tweets brought Graham into the conversation. Graham co-founded Y Combinator, which is one of the larger investors in Parker’s new company, Rippling. Graham responded to Sacks by saying, “Do you really want the full story of what you did to Parker to be told publicly? Because it’s the worst case of an investor maltreating a founder that I’ve ever heard, and I’ve heard practically all of them.”

Graham also added in a now-deleted tweet that he was “talking to another investor about whether [Sacks is] the most evil person in Silicon Valley. [The investor] thought about it for a few seconds, and agreed that he couldn’t think of anyone worse.”

The back and forth continued with Sacks accusing Graham of being an anti-semitic bully and anti-semitic. Sacks’ All-In bestie Chamath Palihapitiya also weighed in, stating, “There is so much to say about this” and suggesting the podcast will be releasing an episode about the entire affair.