$ cat ~/map/durable-harness.md

durable-harness

Runs pi and other coding agents as resumable workflow runs — a crash mid-turn picks up from the event log.

tools✓ Oct 19

npm install durable-harness @earendil-works/pi-durable @earendil-works/chord @earendil-works/pi-ai just-bash

## TL;DR

Vercel Labs' experimental library that runs coding-agent harnesses — pi via its own durable Harness — as workflow runs on a Workflow SDK World, where the conversation, the turn in flight, and every model and tool call land in an event log a crashed run resumes from.

## Key points

• $Each session is one workflow run: its conversation, the turn in flight, and every model and tool call are recorded in the run's event log.
• $A crash anywhere resumes the turn from the log on another machine, and a tool call that is not safe to repeat is never run twice.
• $Pi's recommended integration is the durable-harness/pi-durable adapter, which opens pi's own durable Harness on a World-backed storage; a plain durable-harness/pi adapter also exists.
• $OpenCode and fx get their own adapters, while Claude Code and Codex run only in the session's own Vercel Sandbox, never in a shared function.
• $Model-chosen commands and files execute on a virtual workspace or in the session's sandbox, never on the machine that drives the session.
• $Local development uses the Workflow SDK's local World with no configuration; production runs on Vercel or a self-hosted World such as the Postgres World.
• $Experimental 0.0.x software — the API may change between releases.

## FAQ

## References

• README (quick start, harnesses, run anywhere) ↗
• Vercel agent harnesses docs (pi) ↗

Last updated: Nov 4, 2026