Understanding and Implementing Qwen3 From Scratch

Previously, I compared the most notable open-weight architectures of 2025 in The Big LLM Architecture Comparison. Then, I zoomed in and discussed the various architecture components in From GPT-2 to gpt-oss: Analyzing the Architectural Advances on a conceptual level. Since all good things come in threes, before covering some of the noteworthy research highlights of this summer, I wanted to now dive into these architectures hands-on, in code. By following along, you will understand how it actually works under the hood and gain building blocks you can adapt for your own experiments or projects.