Article URL: https://lockwood.dev/ai/2026/07/27/how-is-the-bun-rewrite-in-rust-going.html Comments URL: https://news.ycombinator.com/item?id=49067854 Points: 162 # Comments: 106

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. 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. 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”. 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: 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: 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: 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.