OpenAI recently released its first open-weights model since GPT-2, entering a field led by DeepSeek and Alibaba's Qwen.YC's Ankit Gupta breaks down everything you need to know about these top OSS models, including what sets them apart under the hood. He’ll compare their approaches to mixture-of-experts, long-context training, and post-training techniques that shape reasoning and alignment—and explore how different design choices lead to surprisingly similar performance.