Reason Machines 发布 Reason：让缓存命中为编码代理省下 22% 成本
Reason Machines 这个叫 Reason 的编码框架，靠把提示词前缀固定不动，让 OpenAI 缓存命中按 1 美元/百万 token 计费，比 Codex 便宜 22%。没换模型、没做微调，纯粹改了上下文组织方式。自己搭 agent 的开发者直接照抄这套前缀结构就能省账单。
Reason Machines 发布了名为 Reason 的编码代理框架（coding harness），可包裹 GPT-6 Astra 等单一模型运行，任务完成成本比 OpenAI Codex 低 22%。其核心优化点在于重写上下文管理方式：传统编码代理每一步都要把完整上下文重新发给模型，Reason 则把固定指令和精简的工具列表固定放在每条提示词的开头，只在末尾追加新的代码与执行结果，中间内容从不重写或重排。
这样每轮对话的前缀与上一轮完全一致，OpenAI 的缓存机制会识别出这些重复 token，并按缓存价计费——每百万 token 从 10 美元降到 1 美元，即重复部分便宜 90%。换句话说，Reason 没有换模型，而是通过提示词结构设计直接吃到了服务商的折扣定价。
对开发者而言，这是一个不依赖模型升级的降本路径：在编码代理这类上下文反复发送的场景中，前缀稳定性直接决定账单金额。同类工具（如 Codex）若不做这类提示词组织，同样的任务就要按原价多付约 22%。
Reason Machines just launched Reason, a coding harness that wraps a single model like GPT-6 Astra and solved tasks 22% cheaper than OpenAI’s Codex.
How: A traditional coding agent resends its context to the model on every step, so Reason trims that load:
Reason holds the prompt prefix identical between turns, by putting its fixed instructions and small tool list at the top of every prompt and only adding new code and results at the end, never rewriting or reshuffling the earlier text.
Since every turn starts with the exact same text, OpenAI recognizes it from the previous turn and bills those repeated tokens 90% cheaper, at $1 instead of $10 per million.
This report is categorized under AITOP's "Products" desk, focusing on US frontier AI labs and Silicon Valley technology leaders. Within our cross-regional analytical framework, it directly maps to AI developer toolchains, coding agents, and engineering workflows and US-China foundation model benchmarks and commercialization comparison. Key entities and technical topics under continuous tracking include Reason Machines, GPT-6 Astra, Codex, prompt cache.
Source attribution: curated from rohanpaul_ai (@rohanpaul_ai).
