How is the Bun Rewrite in Rust going?
How is the Bun Rewrite in Rust going?
Bun 用 Rust 重写进展如何？
I think it’s important to be very Canny when someone makes a claim that supports a company’s large valuation. The Bun rewrite seems well positioned as proof-positive that AI and specifically Anthropic’s AI can do the work of open-source maintainers, for some money, but faster. 我认为，当有人提出支持公司高估值的声明时，保持精明（Canny）非常重要。Bun 的重写似乎被定位为确凿的证据，证明 AI——特别是 Anthropic 的 AI——能够以更快的速度完成开源维护者的工作，尽管需要一定的成本。
On the 8th of July 2026 Jarred Summner of Bun fame posted about “Rewriting Bun in Rust”. At the time, I felt pretty Canny, having already read about Anthropic’s C compiler and Cursor’s FastRender web browser. It seems like there is a lot of valuation money riding on the coding capabilities of AI, and a lot of marketing about those capabilities. It’s not a huge stretch to link the acquisition of Bun by Anthropic with the choice to rewrite Bun with an Anthropic tool. 2026 年 7 月 8 日，Bun 的知名开发者 Jarred Summner 发布了关于“用 Rust 重写 Bun”的文章。当时，我已经读过关于 Anthropic 的 C 编译器和 Cursor 的 FastRender 网络浏览器的相关信息，因此我对此保持相当警惕。看起来，大量的估值资金正押注在 AI 的编程能力上，且围绕这些能力存在大量的营销宣传。将 Anthropic 收购 Bun 与选择使用 Anthropic 工具重写 Bun 联系起来，这并不牵强。
In his article Jarred claims that over 11 days (between 3rd and 14th May 2026) and at a cost of $165,000 for Anthropic API calls the rewrite was done and then merged to main. This represents a cost of $15,000 dollars a day, a cost well outside the means of many open source maintainers. This number doesn’t seem to include the leviathan whirring of the CI/CD in the org’s Buildkite cluster, which appears to have been constantly whirring ever since the “rewrite” was “completed”. Jarred 在文章中声称，在 11 天内（2026 年 5 月 3 日至 14 日），花费 16.5 万美元的 Anthropic API 调用费用，重写工作便已完成并合并到主分支。这意味着每天的成本高达 1.5 万美元，这对于许多开源维护者来说是难以承受的。这个数字似乎还不包括该组织 Buildkite 集群中庞大的 CI/CD 运行成本，自“重写”被“完成”以来，该集群似乎一直在持续运转。
Why do I put those two words in scare quotes? Well, on the 9th of July a peer of mine in a group chat said something unsurprising given our current environment - breathlessly proclaiming that the era of AI had emerged, and its herald was the “Rewriting Bun in Rust” blog post. So, I decided to look into this. Since the 9th I’ve been having a closer look at the claims and the code, and today I cloned the Bun repo: Receiving objects: 100% (1200304/1200304), 1.23 GiB | 11.97 MiB/s, done. 我为什么要给这两个词加上引号？嗯，7 月 9 日，我的一位同行在群聊中说了一些在当前环境下并不令人惊讶的话——他激动地宣称 AI 时代已经到来，而“用 Rust 重写 Bun”的博客文章就是其先驱。因此，我决定一探究竟。自 9 日以来，我一直在仔细研究这些声明和代码，今天我克隆了 Bun 的仓库：接收对象：100% (1200304/1200304), 1.23 GiB | 11.97 MiB/s，完成。
As of today, the 27th of July 2026, a six week period after the rewrite was merged to main, there’s still no release tag. It’s now been 11 weeks since the last Bun release tag: 2026-05-12 15:12:49 -0700 (tag: bun-v1.3.14) The last time there wasn’t a Bun release in a month was between the 26th of October 2022 and the 7th of December 2022 when there was a gap of six weeks and November was skipped, between v0.2.2 and v0.3.0: 2022-12-07 00:37:40 -0800 (tag: bun-v0.3.0) 2022-10-26 21:06:02 -0700 (tag: bun-v0.2.2) 截至今天（2026 年 7 月 27 日），即重写合并到主分支后的六周，仍然没有发布标签。距离上一个 Bun 发布标签已经过去了 11 周：2026-05-12 15:12:49 -0700 (tag: bun-v1.3.14)。上一次 Bun 一个月内没有发布是在 2022 年 10 月 26 日至 2022 年 12 月 7 日之间，当时有六周的空档期，跳过了 11 月，即 v0.2.2 和 v0.3.0 之间：2022-12-07 00:37:40 -0800 (tag: bun-v0.3.0) 2022-10-26 21:06:02 -0700 (tag: bun-v0.2.2)。
On the 9th of July, the number of open pull requests from robobun (a proxy for PRs made by claude code) was 1277. As of this moment, on the 27th of July that number is 2475 open PRs. I don’t claim to know for sure but as far as I can see the process of merging to main with Buildkite checks completed seems to take 40-ish minutes (sometimes it looks like it takes up to an hour and a half). At this rate if we want to merge all the open Claude PRs it’ll only take running the pipeline for 86 days, continuously. Generously, some of these PRs don’t deal with Rust code. 7 月 9 日，来自 robobun（由 Claude 代码生成的 PR 的代理）的待处理拉取请求（PR）数量为 1277 个。截至目前（7 月 27 日），这个数字已达到 2475 个。我不敢断言，但据我观察，完成 Buildkite 检查并合并到主分支的过程似乎需要 40 分钟左右（有时看起来长达一个半小时）。照此速度，如果我们要合并所有待处理的 Claude PR，仅运行流水线就需要连续 86 天。宽容地讲，其中一些 PR 并不涉及 Rust 代码。
Further investigation was warranted. I initially clicked through some of the PRs and found some extremely reviewed ones. At this point I began to suspect that much of the cost of the rewrite was off the books. While $15k a day in tokens widened my eyes a little (and maybe I’m naive, maybe that’s low), I hadn’t seen the numbers for the CI/CD costs of Buildkite, and as you might have noticed from above, some PRs were written by Anthropic employees. 进一步调查是有必要的。我最初点击查看了一些 PR，发现其中一些经过了极其细致的审查。此时我开始怀疑，重写的大部分成本并未计入账面。虽然每天 1.5 万美元的 Token 费用让我有些吃惊（也许我太天真了，也许这算低的），但我还没看到 Buildkite 的 CI/CD 成本数据，而且正如你可能从上面注意到的，一些 PR 是由 Anthropic 员工编写的。
When I did analysis of the data it became clear to me that the project was ticking along with more Claude credits and more Anthropic employee involvement: One of the assumptions I’ve made here is that Jarred Summner’s commits during the rewrite were using Claude. It’s pretty clear that there was a big spike in Claude usage when the rewrite began. It seems like, now, Anthropic employee and Robobun involvement in Rust is ramping up: It’s nice to see that the Anthropic employees involved seemed to have a good work-life balance, taking breaks on the weekend. But, it looks like that period is over. It seems like we’re ramping up to something, and there’s still no release tag. 当我分析数据时，很明显该项目正在消耗更多的 Claude 额度，并有更多的 Anthropic 员工参与：我在这里做出的假设之一是，Jarred Summner 在重写期间的提交使用了 Claude。很明显，重写开始时 Claude 的使用量激增。现在看来，Anthropic 员工和 Robobun 在 Rust 方面的参与度正在增加：很高兴看到参与的 Anthropic 员工似乎有良好的工作与生活平衡，在周末休息。但是，这段时间似乎已经结束了。看起来我们正在为某事蓄力，但仍然没有发布标签。
What’s pretty obvious to me is that we can’t take it at face value that the rewrite is “done” or that it was “done” for $165k USD. The Bun team never made that claim, but I’ve seen and heard those breathless claims that the rewrite is proof of something, and I do still think we need to be Canny about claims that support a large valuation. Anthropic is dogfooding this, the machine is still ticking along, and Anthropic employees are directly involved. If we imagine that the rewrite is still costing $10k a day, we’re approaching $800k in money spent on this rewrite. 对我来说显而易见的是，我们不能仅凭表面价值就认为重写已经“完成”，或者它是以 16.5 万美元“完成”的。Bun 团队从未做出过这种声明，但我已经看到并听到了那些激动人心的说法，称这次重写证明了什么。我仍然认为，对于那些支持高估值的声明，我们需要保持精明。Anthropic 正在“吃自己的狗粮”（内部使用），机器仍在运转，且 Anthropic 员工直接参与其中。如果我们假设重写每天仍在消耗 1 万美元，那么这次重写花费的资金已接近 80 万美元。
— I’m not a primitivist when it comes to AI. Work I’ve done on ML and AI has been some of the work I’ve been most proud of. This current hype cycle is, however, the worst I’ve ever seen the hype get. Back in 2015 I had to plead with management, trying to get them to understand that a black-box bunch of linear algebra that was better than humans at a quantitative task was, just, better. Now it seems like the world has completely reversed, and management is so forthright in their belief that AI is good, that they want it rubbed on everything. And those valuations are sometimes contingent on AI eating everything: ——在 AI 方面，我不是原始主义者。我在机器学习和 AI 方面所做的工作是我最引以为豪的成就之一。然而，当前的炒作周期是我见过最糟糕的。回到 2015 年，我不得不恳求管理层，试图让他们明白，一套在定量任务上优于人类的黑盒线性代数模型，就是“更好”。现在情况似乎完全反转了，管理层对“AI 是好的”这一信念如此坚定，以至于他们想把 AI 应用到一切事物上。而这些估值有时取决于 AI 是否能吞噬一切：
In my tiniest mouse voice ever I want to ask probably the most relevant question one can ask about a Business Thing: Was it worth the money and are the companies worth the valuation? Are we done yet? 我用最微弱的声音想问一个关于商业事务最相关的问题：这笔钱花得值吗？这些公司配得上这样的估值吗？我们还没完吗？
P.S. Anthropic’s C compiler and Cursor’s FastRender web browser haven’t had any commits for months. 附注：Anthropic 的 C 编译器和 Cursor 的 FastRender 网络浏览器已经好几个月没有任何提交了。
P.P.S. I’m looking for a job. 再附注：我正在找工作。