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durable-harness
Vercel's adapters that run existing coding-agent harnesses (Pi, OpenCode, fx, Claude Code, Codex) as durable agents on a Workflow SDK World, so a crash or function timeout resumes the turn instead of losing it.
Added November 1, 2026Published October 20, 2026
Each agent session is a workflow run. The conversation, the turn in flight and every model and tool call go into the run's event log: an intent is recorded before a call and the outcome after it. If a function dies, a new one reads the log and resumes the turn on another machine. Completed calls aren't repeated, and a tool marked replay: 'never' is never run twice.
Pi (through durable-harness/pi-durable, the recommended path), OpenCode and fx run inside functions. Model-chosen commands and files go to a virtual workspace whose files live in the session log, or to the session's own Vercel Sandbox. Claude Code and Codex always run in their own sandbox, never in a shared function. withDurableHarness in next.config.ts discovers the agents in a Next.js app.
Local development uses the Workflow SDK's local World with no setup. On Vercel the sessions show up in Agent Runs, and self-hosting works with the Postgres World or another World. It's on 0.0.x and marked experimental, Apache-2.0. Write-up: Making every harness durable · docs: Agent harnesses.
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