Most AI agents on serverless platforms share the same fatal flaw: they can't survive a restart. If the underlying worker crashes or cold-starts mid-task, the agent's progress disappears. The typical workaround is to keep tasks short and stateless — which means you cannot run a 10-minute research loop, a multi-file refactor, or an autonomous investigation that makes 50 external calls. Cloudflare's Project Think, announced during Agents Week 2026 (April 2026), is a direct answer to that constraint. It ships a set of primitives — fiber checkpointing, sub-agents, a persistent Session API, and a 5-tier execution ladder — all wired into an opinionated base class ( @cloudflare/think ) that runs on Durable Objects. Effloow Lab inspected the SDK packages, confirmed installability, and traced the API surface from official docs and the open-source cloudflare/agents repository. The following is a source-based guide to how Project Think works and when to use it.…