July 20, 2026
Spreadsheet drama, but make it finance
Jane Street: Incremental
A fancy math tool drops, and the comments instantly turn into Wall Street vs. nerds
TLDR: Jane Street released Incremental, a tool that keeps large calculations up to date without redoing all the work every time data changes. Commenters immediately split between impressed fans and veterans saying, basically, “cute—Wall Street was doing this ages ago,” with one lone "Kobe!" adding pure internet chaos.
Jane Street has unveiled Incremental, a tool for building big chains of calculations that update quickly when one input changes instead of recalculating everything from scratch. In plain English: think of a giant spreadsheet, trading dashboard, or app screen that can refresh the smart way instead of the slow, brute-force way. Sounds useful, sure—but the real fireworks were in the comments, where the crowd treated the launch like a reunion episode for finance veterans, programming purists, and drive-by meme lords.
The strongest reaction was basically: "nice idea, but haven’t people been doing this forever?" One commenter casually flexed that they built something similar for a fund seven years ago, while another said Goldman Sachs had a version of this thinking 30 years ago and even had dramatic internal debates about something called "Node Purpling"—which sounds less like software and more like a band opening for Radiohead. Then came the skeptical crowd asking the classic internet question: is this actually new, or just old stuff in nicer packaging? One user openly admitted they’d never fully understood how this differs from the familiar "observable" style of passing updates around.
Still, Jane Street got real love too. A fan praised the company for taking research-y, hard-to-use ideas and turning them into tools normal developers can actually pick up, even if only for the design docs. And because no comment thread can stay serious for long, the very first reaction was simply "Kobe!"—a perfect chaotic buzzer-beater for a discussion about elegant efficiency.
Key Points
- •Incremental is a library for building complex computations that update efficiently when their inputs change.
- •The library is inspired by Umut Acar and collaborators’ work on self-adjusting computations.
- •The article highlights spreadsheet-like calculations as one application area for Incremental.
- •Another cited use case is constructing GUI views that efficiently incorporate new data.
- •The article points readers to detailed documentation, a blog post, and a video for learning the library.