Frontend Engineer (React)

We're ProjectX, backed by Y Combinator, and we're building Infinity (infinity.projectx.cloud) -- an entirely new cloud-native OS that runs in your browser. Launch native, desktop-class apps inside a virtualised workspace, with a native window manager, terminal, and file manager, all inside a single browser tab.

Every app runs on its own dedicated compute. No shared machines, no shared VMs -- one heavy workload never starves another, and resources of every app stays fully isolated.

who we're looking for

Someone to work alongside us and own the parts that make Infinity feel native. If this is you, you've got these down:

• 3+ years building complex, interaction-heavy web UIs.
• Strong React + TypeScript -- including knowing when not to use React: refs over state for hot paths, effect discipline, understanding what re-renders and why.
• Browser event model -- pointer events and pointer capture, capture vs bubble phase, keyboard event routing, how iframes affect both.
• Rendering performance -- layout vs paint vs composite, CSS transforms, requestAnimationFrame, diagnosing jank with the DevTools Performance panel.
• Async state machines -- designing reconnect/backoff logic, reasoning about race conditions and cancellation (AbortController), avoiding stale-closure bugs.
• Complex client state -- comfortable reasoning about state spread across stores, contexts, and component state, and about derived state and its trade-offs.
• Testing state-heavy code -- extracting pure logic, faking I/O boundaries (sockets, timers), writing tests that simulate failure modes.
• Comfortable reading and working within a large, dense existing codebase.

*Preffered Experience: *

• Experience with xterm.js, noVNC/VNC, WebRTC, or remote-desktop/streaming products
• Virtualized list/grid experience (TanStack Virtual or hand-rolled)
• Cross-origin iframe work: postMessage protocols, sandboxing, focus management
• Having built a canvas/design tool, editor, IDE, game UI, whiteboard, or window manager
• Binary protocols over WebSocket; SSE
• Familiarity with our stack (Zustand, Vite, Radix, Tailwind v4, Framer Motion) -- nice, but easily learned

*Skills: *

React, TypeScript, WebSockets, Server-Sent Events (SSE), Browser APIs, Pointer Events, Rendering Performance, State Management, Zustand, Async Programming, Frontend Testing, Vite, Tailwind CSS