Not your run of the mill Chromium based browser (openai.com)

OpenAI launched ChatGPT Atlas, a desktop browser that embeds ChatGPT as a full-time web co-pilot by rethinking how Chromium is integrated. Instead of embedding Chromium in the main app process, Atlas runs Chromium in an isolated service layer called OWL (OpenAI’s Web Layer). The front-end is rebuilt natively with SwiftUI, AppKit and Metal, while the OWL Host (Chromium) and OWL Client (Atlas UI) communicate via Mojo IPC with custom Swift and TypeScript bindings. This decoupling yields near-instant startup, resilience to Chromium jank or crashes, smaller upstream diffs, and drastically faster iteration because OWL ships as a prebuilt binary so most engineers don’t need to build Chromium locally. Technically, OWL exposes a concise Swift API (Session, Profile, WebView, WebContentRenderer, LayerHost/Client) and uses delegated compositing: Chromium’s gfx::AcceleratedWidget is backed by a CALayer embedded in the native UI (via private CALayerHost), keeping GPU compositing and view geometry synchronized. Input events are translated into Blink’s WebInputEvent model in the client and forwarded to the renderer; agent-generated events go directly to the renderer to preserve sandboxing. Agent browsing also composites popup widgets into a single frame for model context and runs ephemeral “logged-out” sessions using Chromium StoragePartition in-memory stores. The architecture enables richer UI, safer agentic automation, and a faster developer loop for building web–AI experiences.