António Hernández

@fidelke

Senior Implementation Engineer at Atlan

Košice, SlovakiaJoined June 2026

About

I'm an engineer who builds systems and writes about what actually happens when I do. I'm currently working through the craft of AI agent engineering from the ground up - documenting the experiments, the failures, and the moments that change my mental model. No polished takes. Just the build log.

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António Hernández's blogs

Agent Build Logagentbuildlog.hashnode.dev2 posts

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I Wrote 40 Test Cases Before Writing Any Agent Code. Here's What Happened.

1d ago · 8 min read · The idea felt a bit backwards at first. You write tests after you have something to test, right? That's how it usually works. But I kept thinking about a pattern I'd noticed: every time I'd improved a

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I've Built AI Agents. Now I'm Learning to Build Them Properly - From the Ground Up.

2d ago · 3 min read · I've been working with AI agents for a while now. I can get something working. I can ship a demo. But there's a gap between "it works" and "I understand why it works" - and an even bigger gap between

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António Hernández

About

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António Hernández's blogs

Recently published

I Wrote 40 Test Cases Before Writing Any Agent Code. Here's What Happened.

I've Built AI Agents. Now I'm Learning to Build Them Properly - From the Ground Up.

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António Hernández

About

Available for

António Hernández's blogs

Recently published

I Wrote 40 Test Cases Before Writing Any Agent Code. Here's What Happened.

I've Built AI Agents. Now I'm Learning to Build Them Properly - From the Ground Up.