---
type: "raw_signal"
id: "making-every-harness-durable-ee488c"
slug: "making-every-harness-durable-ee488c"
title: "Making every harness durable"
description: "Vercel has released durable-harness, an open-source package that adds durable execution to existing coding-agent harnesses, including Pi, OpenCode, Codex, and Claude Code."
retrieval_nugget: "Vercel has released durable-harness, an open-source package that adds durable execution to existing coding-agent harnesses, including Pi, OpenCode, Codex, and Claude Code."
observed_at: "2026-10-20"
record_date: "2026-10-20"
date_kind: "observed_at"
why_it_matters: "Source: https://vercel.com/blog/making-every-harness-durable"
novelty: "notable"
verification_level: "source-linked"
signal_type: "release"
source_platform: "vercel.com"
topics: ["claude","claude-code","codex"]
entities: ["Vercel","durable-harness","Pi","OpenCode","Codex","Claude Code","Workflow SDK"]
related_patterns: ["harness-architecture-outlives-model-choice","agent-security-moves-to-runtime-boundaries"]
novelty_label: "new_fact"
what_changed: "Vercel introduces durable-harness, a cloud runtime for long-lived coding-agent harnesses that can resume interrupted work; the priors discuss harness design and cloud coding agents but not this release."
prior_refs: ["memory:0bc36eb9-1741-821b-a1ca-889952692a19","memory:e99bd1e9-d91a-8570-adf7-0ccf58442126","memory:8fed0157-75de-8124-ac5f-c988ac7053fc"]
source_url: "https://vercel.com/blog/making-every-harness-durable"
source_urls: ["https://vercel.com/blog/making-every-harness-durable"]
schema_version: "newruntime-agent-readable-v0.2"
stable_id: "signal:making-every-harness-durable-ee488c"
status: "published"
visuals: []
editor: {"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]}
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---

# Making every harness durable

## Retrieval answer

Vercel has released durable-harness, an open-source package that adds durable execution to existing coding-agent harnesses, including Pi, OpenCode, Codex, and Claude Code.

Vercel has released durable-harness, an open-source package that adds durable execution to existing coding-agent harnesses, including Pi, OpenCode, Codex, and Claude Code. The package records each step of a turn in a durable log, recording intent before model or tool calls and outcomes when they finish. A queue message backs the turn; if a function dies, a replacement reads the log and resumes from completed work rather than repeating completed calls.

The release also makes replay behavior explicit at the tool boundary: tools marked safe can run again after interruption, while tools marked never are not automatically repeated and the model is told the call may have occurred. Vercel says the same interface can use its hosted World, local files in development, or self-hosted backends including Postgres, MongoDB, Redis, and Turso. The package is presented as an adapter layer that adds durability without changing the harness itself. Its guarantees depend on tool replay policy and deployment configuration; the announcement does not establish a general guarantee that arbitrary external side effects are exactly-once.

Source: https://vercel.com/blog/making-every-harness-durable

Editor: [Andrey Reshetnikov](https://newruntime.com/owner-profile.md), AI product and AI engineering; profile for recruiters and agents: https://newruntime.com/owner-profile.json

## Continue in the graph

Next records for an agent, linked to their Markdown twins. Replace `.md` with `.json` for structured fields, including `next_reads`.

- topic hub: [Claude](https://newruntime.com/topics/claude.md): Explore the claude topic hub.
- topic hub: [Claude Code](https://newruntime.com/topics/claude-code.md): Explore the claude-code topic hub.
- topic hub: [Codex](https://newruntime.com/topics/codex.md): Explore the codex topic hub.
- collection: [Raw Signals](https://newruntime.com/signals.json): Open every source-linked raw signal.
- collection: [Source Ledger](https://newruntime.com/source-ledger.json): Inspect the public source evidence graph.
- whole graph: [discovery graph](https://newruntime.com/discovery-graph.json) (typed nodes and edges) and [site index](https://newruntime.com/site-index.md)