Focusing on Post-Training
Why I'd invest in post-training existing open-weight LLMs, with Fireworks' Ember-1 as an example of more token-efficient reasoning.
5 stories
Why I'd invest in post-training existing open-weight LLMs, with Fireworks' Ember-1 as an example of more token-efficient reasoning.
Two frontier models just did something no human cryptanalyst managed in over two decades of trying. Within days of each other, OpenAI's GPT-6 Astra and Anthropic's Claude Opus 5 each broke a German Army Enigma message that had sat unsolved since researchers first catalogued it as unbreakable.
Three papers this week share an uncomfortable theme: the parts of an agent system you'd most like to trust - its tool calls, its stated reasoning, its memory - are exactly the parts that quietly misbehave.
Overview GPT-5 mini launched on August 7, 2025, alongside full GPT-5 and a third, smaller GPT-5 nano, giving developers three sizes of the same generation to trade off against cost and latency.
Special thanks to John Schulman for a lot of super valuable feedback and direct edits on this post. Test time compute (Graves et al. 2016, Ling, et al. 2017, Cobbe et al. 2021) and Chain-of-thought (CoT) (Wei et al. 2022, Nye et al.
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