Why it mattersA hosted preview or sandbox platform that spins up thousands of dev servers a day has been paying Node runtime and toolchain memory per user, and Lovable's write-up is the first production report of a Rust binary that reads Vite config unchanged and replaces the engine underneath.
Lovable, the browser-based AI app builder, is rolling its preview servers over to OJ, a Rust binary that runs a React app the way Vite does. The company published an announcement and open-sourced the project under MIT on September 18. The repository at github.com/lovablelabs/oj has 429 stars, verified against the GitHub API on the same day.
What OJ is and is not
OJ, internally nicknamed Orange Juice, reads a project's existing Vite config and serves the app from a single Rust binary. Lovable says the design is motivated by the preview use case rather than by general developer use: Lovable runs around a million sandboxes a day, one preview each, and each Vite instance brings a JavaScript runtime, installs a toolchain into the project, and holds a lot of memory. Across thousands of previews that is what determined cold start time and how many sandboxes could stay warm.
Lovable frames OJ as an experimental engine underneath the preview, not a general Vite fork: the plugins and config a project already depends on keep working, and a builder does not configure anything. The company says the rollout is gradual and only widens as apps keep running unchanged on OJ.
The numbers Lovable published
The company ran OJ next to Vite on the same projects, one synthetic app with 10,000 components and several real open-source Vite apps run unchanged. The headline in the post is roughly a 4x faster cold start on the synthetic benchmark, and memory measured in hundreds of megabytes instead of gigabytes on the real apps. On those real apps Lovable reports memory a third to an eighth of Vite's. The company flags a caveat that the cold-start comparison is not fully like-for-like, because Vite starts with certain phases the raw OJ number does not include. Memory is the number Lovable says decides how many previews can run at once.
The engineer
The author, Raphael Amorim, is named on Lovable's post as an engineer at the company and the creator of OJ. His public track record includes the Rio terminal and the Jam language, both in Rust, and prior work at Spotify and Viaplay. That is worth stating because a plausible-sounding claim of a Rust drop-in for Vite is a common piece of open-source bait, and this one is coming from a named engineer with a public history of shipping Rust developer tools.
What a team can do with it today
Nothing on the Lovable side, if you already use Lovable, since the rollout is a percentage-based flag on their platform. Outside Lovable, the code and license are now public: a team running a hosted preview product, a sandbox service, an internal review environment or a CI harness that spins up per-branch previews can try OJ against its own React apps and see if the memory number holds. The fair test is memory rather than cold start, because the cold-start number carries a caveat Lovable stated in the post.
Source
Source: Lovable
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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