---
title: "Discussion on \"A 4B Open Model Matches GPT-5.6 Sol on Retrieval at 100× Lower Cost\" | Hashnode"
description: "Discussion on \"A 4B Open Model Matches GPT-5.6 Sol on Retrieval at 100× Lower Cost\". How Castform and Neon use RL post-training, hybrid search, and existing company data to turn small open models into specialized retrieval agents."
url: "https://hashnode.com/posts/a-4b-open-model-matches-gpt-56-sol-on-retrieval-at-100-lower-cost-mtatj4bo/6a8f8cb04a38a507cab9ebad"
---

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# [A 4B Open Model Matches GPT-5.6 Sol on Retrieval at 100× Lower Cost](https://blog.zyvop.com/a-4b-open-model-matches-gpt-56-sol-on-retrieval-at-100-lower-cost-mtatj4bo?utm_source=hashnode&utm_medium=feed)

How Castform and Neon use RL post-training, hybrid search, and existing company data to turn small open models into specialized retrieval agents.

Aug 27 · 9 min read · blog.zyvop.com  
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