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Hi, I'm Sean.

Co-founder & CTO at B3, building a crypto agent & decentralized inference — previously Coinbase. I sweat the small details in software, and leave the good parts (components, free tools & writeups) out in the open here.

Sean Geng

Components

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Writing

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Building agents that live in your messages preview

Building agents that live in your messages

Agents feel best inside the apps you already text in — iMessage, Telegram, WhatsApp, Slack. But iMessage gives you no buttons, and a Slack bot has to juggle many users and orgs at once. Two very different engineering problems, one goal: make the agent feel like a person. How to architect both, with the gotchas.

agents
ai
messaging
The honest guide to LLM model routing preview

The honest guide to LLM model routing

Auto-routing picks a cheap model for easy prompts and a frontier model for hard ones — automatically. The papers claim 85–98% savings. An independent benchmark found a commercial router doing worse than no routing at all. The real number is ~20–25%, and here's exactly why.

ai
llm
routing
Turning WebGL into ASCII, every frame preview

Turning WebGL into ASCII, every frame

A three.js plane rendered to a hidden canvas, then read pixel-by-pixel and rewritten as ASCII characters in a <pre>. The trick is sampling the render at one pixel per glyph. From B3's ai-arena.

three
webgl
shaders
A loading bar that lurches like a real one preview

A loading bar that lurches like a real one

Real loads stutter — a burst, a pause, a crawl at the end. This pure-CSS laser beam fakes that with a hand-tuned width track and two offset flickering glows. No JS. Pulled from basement.fun.

css
animation
loader
A game cartridge card, in flat CSS preview

A game cartridge card, in flat CSS

A 2D cartridge card with molded-plastic edges, built from one clip-path polygon stacked four times. No 3D, no canvas — just layered shapes, a noise texture, and a luminance-aware accent. Pulled from basement.fun.

css
clip-path
card
Read the recon list as a defense checklist preview

Read the recon list as a defense checklist

A list of email and social OSINT tools made the rounds framed for phishing. Flip it: the same tools are what an attacker runs before a targeted email, so run them on yourself first. What your address leaks, and how to shut it down.

security
osint
phishing