Dex Horthy has spent the past year studying what happens to a codebase when you let AI write all of it and stop reading the output. His answer has a name: slop. And it's not just about sloppy prompting.
In this episode, the HumanLayer founder Dex Horthy joins Shane and Abhi to draw the software factory on a whiteboard — the whole pipeline that builds the thing that builds the thing — and show exactly where teams tear out the parts that were holding quality up. He moves from the naive factory to the fully agentic one to the "lights-off" version where humans stop reading code entirely, then explains why that dream quietly rots a codebase after three to six months.
Dex, Shane, and Abhi also talk about how coding models are trained. Every benchmark rewards one thing: did the test pass? Nowhere in the loop does a model get punished for leaving behind code that a smaller model, or a human six months later, can't work in. That gap is why architecture planning, sprint planning, and code review still can't be skipped.
You'll also hear why you're not drowning in PRs so much as drowning in bad ones, what a longer-horizon benchmark that actually catches slop would look like, and how many times Dex has watched the HumanLayer launch film.
🔗 DEX HORTHY / HUMANLAYER
Dex on X: https://x.com/dexhorthy
HumanLayer: https://humanlayer.dev
AI Agents Hour is a weekly livestream by Mastra CPO Shane Thomas and CTO Abhi Aiyer. Mondays 12PM Pacific.
📚 MASTRA RESOURCES
Mastra: https://mastra.ai
Mastra on X: https://x.com/mastra_ai
Mastra Discord: https://mastra.ai/community/discord
Mastra GitHub: https://github.com/mastra-ai
Learn Mastra: https://mastra.ai/learn
Principles of Building AI Agents: https://mastra.ai/books/principles-of-building-ai-agents
Patterns for Building AI Agents: https://mastra.ai/books/patterns-of-building-ai-agents
WHAT IS MASTRA
Mastra is an open-source TypeScript framework designed for building and shipping AI-powered applications and agents with minimal friction. It supports the full lifecycle of agent development — from prototype to production.
CHAPTERS
0:00 Cold open
0:14 Bringing on Dex Horthy
1:16 The HumanLayer launch film
3:31 Cutting through the AI hype
4:07 Defending the terms that matter
5:26 "I want to build a software factory"
5:58 What a software factory actually is
9:08 Agentic code review, testing, and feedback loops
13:35 The lights-off software factory
14:32 Why code quality decays over time
15:36 What RL actually rewards
17:29 Don't sacrifice planning or review
18:05 Getting the PR to 95% before review
19:21 Drowning in bad PRs, not PRs
20:22 Building longer-horizon benchmarks
21:46 Trying HumanLayer
