Karpathy's Perception Stack: Soft/Hard Routing and the Fall of Vibe Coding
Roger_M_Taylor · x · 2026-08-08
The post analyzes the core mechanisms within modern agent loops, drawing on Andrej Karpathy's early theories on the agentic perception stack, and recommends a related deep dive article.
- Soft Routing vs. Hard Routing: Karpathy once described agents using a reinforcement loop with a language interface, where "soft attention" allows gradients to flow through, making it easy to train and adopted by 90% of models. Modern agent loops face a similar choice: soft routing (always on but continuously costly) versus hard routing (commit, act, verify).
- The Fatal Flaw of Vibe Coding: The cited article points out that by 2026, Vibe Coding fails not because models lack intelligence, but due to "Spec Engineering." Agents repeatedly ship the wrong things on the exact same codebase primarily because of a lack of rigorous specification constraints.
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