Karpathy joins Anthropic, and Altman jokes his way to 13K likes

The afternoon of May 19 brought one tweet that genuinely stopped people mid-scroll, a Sam Altman one-liner that hit harder than most product launches, and Boris Cherny's postcard from London — four high-signal posts from three authors across the window.

Andrej Karpathy — former Tesla AI director, OpenAI founding team, author of Andrej Karpathy's Neural Networks: Zero to Hero — announced he joined Anthropic. 1 The post went to 115,500 likes and nearly 15 million views within hours. Boris Cherny, who leads Claude Code, retweeted it immediately.

No role announced, no press release — just a short note about getting back to R&D and plans to resume education work "in time." The education part is a nod to his long-running lecture series and the karpathy.io tutorials that many practitioners treat as foundational reading. What Anthropic gets is someone with a rare dual fluency: deep researcher and unusually effective teacher of technical ideas.

Sam Altman posted a one-liner about Codex rate limits that earned 13,278 likes: 2

"Tibo" is Thibault S., who manages usage limits on the Codex team. The joke landed because it names something every heavy Codex user already feels — the weekly cap is a constant friction point. That it got 13K likes on a Tuesday evening says something about the scale of the user base now actively running into those limits. The day before, Altman had posted that "chatgpt has gotten soooo much better with the latest update" (15,350 likes) — this pair of posts shows him running the product-advocacy and community-friction channels at the same time.

Earlier in the window, Boris Cherny posted from the Code with Claude London developer event — the first in-person Claude Code gathering. 3

The post pulled 3,785 likes. Alongside the London event, Anthropic launched self-hosted sandboxes in public beta and MCP tunnels in research preview — the two announcements that appeared in bcherny's retweets later that day. The London event is notable as a signal that Anthropic is starting to run field-level developer events, not just shipping release notes.

@SophiaFioren's history-and-art account produced the window's only non-AI post worth flagging: a photograph of the Order of Saint Alexander Nevsky star, a Russian ceremonial medal from the second half of the 19th century. 4 It reached 142 likes — modest by her recent standards but consistent with her daily posting cadence of historical objects that reliably hold the mid-tier engagement.