Thomas Ptacek · 2026-09-25 · notable
What Even Is an OS Now — Thomas Ptacek leaves Fly.io to build an AI phone
Thomas Ptacek argues that AI lets users build their own apps, which removes the reason operating systems wall apps off from each other. He is leaving Fly.io to work on a phone that builds apps on request.
If everyone can build their own software, the OS stops needing to protect you from strangers' apps.
What is it?
In "What Even Is an OS Now?", Thomas Ptacek argues that "the impact of AI on computing hasn't yet sunk in." The first-order change is that users can now build applications themselves in plain language. The essay also announces that Ptacek is "parting company with Fly.io to work with Kurt on a new project": a smartphone that builds apps for you on the device, whenever you ask.
How does it work?
The second-order argument is about security design. Modern operating systems exist to partition applications and control how they talk, because we install software written by strangers. Ptacek claims that when most programs are made by and for one or two people — a forecast for one Chicago neighbourhood, a custom commute route — that isolation model loses its main job.
Why does it matter?
The claim that app isolation is losing its main job cuts against decades of OS security design, and the essay drew more than 200 points on Hacker News. It is also a product signal: Ptacek is betting a new company on phones without prefab apps.
Who is it for?
developers and security engineers thinking about AI-era platforms