Vercel's durable-harness lets cloud coding agents pick up after a crash

Vercel has released durable-harness, an open-source package that keeps an agent's session in a log so it can survive crashes, function timeouts and redeploys. It works with harnesses people already use, including Pi, OpenCode, Codex and Claude Code. Before each model or tool call it records what it is about to do, then records the result; if the process dies, a new one reads the log and carries on. Finished model calls are not run or billed again, and each tool is marked either safe to repeat, like a lookup, or never to repeat, like a refund, in which case the model is told the call may already have happened. It runs on Vercel, on your own machine with local files, or on your own servers with Postgres, MongoDB, Redis or Turso. Vercel published the post on 19 October.