Kieran’s Substack - The AI Marketing Generalist

Kieran’s Substack - The AI Marketing Generalist

The Rise of the 'AI Brains'. And Why Everyone Is Building One.

From Karpathy's LLM Wiki to Brian Halligan's digital twin, how the smartest people in tech are building AI systems that think, remember, and act on their behalf.

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Kieran Flanagan
Jul 03, 2026
∙ Paid

When Andrej Karpathy posted about building an “LLM Wiki” in April and garnered 19.6 million views, he started a trend: an army of geeks building their own “AI brains.”

I’m one of them. So is Brian Halligan, the former CEO of HubSpot and now partner at Sequoia, who revealed he’d built an AI agent trained on his entire life that now attends his Zoom meeti…

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