feels like everyone is converging on durable agents lately: pi durable, cloudflare agents on durable objects, vercel's durable harness

Yep, I think that all harnesses will require native durability, and pi-durable is a step in the right direction. I'm skeptical of bolted-on durability, like vercel's durable-harness, because they have to neuter the harness for things they can't reliably make durable (e.g. https://github.com/vercel-labs/durable-harness/blob/fb056a3c...)