Already have a harness: PiHarness. Chat where you assemble each model call: AIChatAgent; let the framework run it: Think. Not chat but need state, scheduling or MCP: Agent.
Pi 1.0 and the experimental Pi Durable package shipped together in early October 2026. Pi Durable turns every model request, tool call and compaction into a task that writes a checkpoint, so a killed process resumes from its last checkpoint; Cloudflare followed with PiHarness on Durable Objects. The key design decision is classifying tools as safe or unsafe to replay.