Dexter Horthy: Why We Stopped Trusting AI to Write the Plan

HumanLayer CEO Dexter Horthy on why his team's bet on spec driven development nearly wrecked their own codebase, and what changed his mind about reviewing AI-written code. Dexter walks through the "YOLO pull request" experiment that ran for months before the codebase became unusable, the "dumb zone" that limits how much context you can hand a model, and why he now believes there will always be alpha in reviewing something.

What we cover:
– How HumanLayer's "read the plan, skip the code" experiment quietly broke their own codebase
– Why context windows have a "dumb zone," and what that means for context engineering
– Sean Grove's idea that specs, not code, are becoming the durable artifact
– Building overnight agents that review and fix code before a human ever sees it
– Why treating software development like a factory changes how bugs compound
– What Dexter thinks his advice on reviewing AI-written code will look like in 12 months

Chapters:
00:00:00 - Introduction
00:02:15 - Meet Dexter Horthy, CEO of HumanLayer
00:06:03 - The "dumb zone": why more context makes models dumber
00:06:40 - Sean Grove's "the spec is the new code"
00:09:22 - The YOLO pull-request experiment that broke their codebase
00:11:09 - Letting the model own the architecture
00:17:03 - Planning as expected-pain management
00:28:15 - Slop Code Bench and the maintainability oracle problem
00:37:59 - Why software factories aren't like car factories
00:42:49 - "There will always be alpha in reviewing something"

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Where do you land on the determinism-to-adaptability slider — plan tightly, or let the agent run? Tell us in the comments.