Sunil Pai builds infrastructure for AI agents at Cloudflare. He founded PartyKit, the real-time application platform acquired by Cloudflare in 2024, and previously worked on React and developer tooling for Cloudflare Workers.[1][2]
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X Career
Pai is a principal systems engineer at Cloudflare, working on agents and long-running AI systems. His earlier work spans the React core team, social virtual reality at Oculus, and developer tooling for Cloudflare Workers. That background connects interactive interfaces with the infrastructure needed to keep applications running and synchronized.[1][4]
Contributions
PartyKit and real-time applications
PartyKit makes it easier to build applications in which several people share changing state, such as collaborative editors and multiplayer games. It wraps Cloudflare Durable Objects, which retain state across requests, in a developer platform with familiar JavaScript and React integrations. Cloudflare announced its acquisition of PartyKit on April 5, 2024. The acquisition announcement, co-written by Pai, traces the project to experiments with Durable Objects in 2022.[2]
Keeping agents running
Pai co-authored the February 2025 introduction of Cloudflare’s Agents SDK. The framework combines model calls with persistent state, scheduled work and live connections to a user interface. This addresses a practical problem: an agent may need to remember a task, wait for input and resume later, rather than complete everything in one request. The SDK runs agents on Durable Objects and includes interfaces for synchronizing their state with React applications.[5]
Ideas
In his October 2026 essay Do you actually like hard problems?, Pai distinguishes familiar technical puzzles from problems that combine engineering with product decisions and organizational constraints. He describes his own work shifting from writing difficult code toward deciding how a problem should be approached. The essay is a personal account of changing engineering work, rather than evidence that AI has eliminated the need for programming expertise.[6]
Tools, writing & talks
Writing, research & talks
Start here
Making Cloudflare the best platform for building AI Agentsblog.cloudflare.comAn introduction to agents, persistent state and the first Agents SDK, with JavaScript examples that connect a model to a running application.
Start with this introduction to see why an agent needs persistent state, tools and a running application. The JavaScript examples connect those ideas to Cloudflare’s Agents SDK.
Co-authored technical introduction · February 2025[5]Sunil Pai of Cloudflare discusses Code Mode, dynamic isolates and why he thinks Workers and Durable Objects can host long-running agents better than Anthropic's managed offering. The talk frames the emerging architecture for agent platforms.
Catalog workOriginal sourceCloudflare's VP of AI and agents lead walk through the new agents offering, how it builds on Durable Objects and AI Gateway, and what it means for developers deploying agents on Cloudflare.
Catalog workOriginal source- Do you actually like hard problems?sunilpai.dev
A short essay about the shift from solving familiar programming problems to exercising engineering and product judgment.
Authored essay · October 2026[6]
Tools
- Cloudflare Agents
github.comA framework for persistent agents with scheduled tasks and synchronized interfaces. Start with the introduction for the architecture, then use the examples if you know JavaScript.