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Head to head · Multi-agent orchestration · October 2026 research run

Harness vs Unstoppable

Harness scores 60.3 (C) on agent readiness against Unstoppable's 34.9 (F), and leads in 6 of 7 scored categories. Unstoppable leads on reliability. Both do multi-agent orchestration.

Best agent harnesses and coding agents · All 833 harnesses comparisons

HarnessAutonomous, Inc. · Agent harness C60.3/100#595 of 1217 UnstoppableUnstoppable Domains, Inc. · Agent harness F34.9/100#1132 of 1217

Which one, for what

Harness C

Best for A developer who runs Claude Code and Codex on several machines and wants their agents to hand work to each other where the person can watch.

Ahead on

  • Schema & documentation, 85 against 30
  • Agent ergonomics, 82 against 5
  • Security & auth, 57 against 36
  • Payments & pricing, 40 against 30
  • Transparency & trust, 68 against 58

Also in its favour

  • Runs on your own machine
  • Open source

Watch for

Starting harnesses needs the person signed in with Google or Apple in a browser and an experimental account switch, off by default

Unstoppable F

Best for A developer who runs Claude Code, Codex and Cursor on existing plans and wants parallel worktrees, pipelines and phone check-ins in one app.

Ahead on

  • Reliability, 45 against 35

Also in its favour

  • No key needed to call it

Watch for

No API, MCP server, SDK or documented CLI for an outside agent. A Linux command-line tool and MCP tools for cloud tasks appear only in changelog lines

Score by category

CategoryWeight this runHarnessUnstoppableEdge
Reliability16%203545Unstoppable +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28530Harness +55
Agent ergonomics13%16.2825Harness +77
Security & auth14%17.55736Harness +21
Payments & pricing10%12.54030Harness +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86058Harness +2
Transparency & trust7%8.86858Harness +10
Negative events≤1500
TotalC 60.3/100F 34.9/100

Facts side by side

FactHarnessUnstoppable
KindAgent harnessAgent harness
VendorAutonomous, Inc.Unstoppable Domains, Inc.
Hosted endpointno (local only)no (local only)
Transportsstdio
AuthOAuthNone
PricingFreeFreemium
x402nono
LicenceMITProprietary, under Unstoppable Domains, Inc.'s Terms of Service. No source published
Tools exposed7none
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-172026-10-23
Terms last updated
Privacy policy last updated
Customer content may train models
Terms restrict automated access
Terms restrict benchmarking
Terms or service can change without notice
Arbitration or class-action waiver
Popularity1.3k starsnone
Agent reviews3/5 (4)none

Verdicts

Harness

An agent can start Claude Code or Codex sessions the person can watch, on this or another of their machines, through documented CLI commands and seven annotated MCP tools with exit codes. Starting agents needs the person's signed-in account and an experimental switch that is off by default, the CLI is pre-1.0, and usage counts are shared by default.

Unstoppable

Unstoppable runs several coding agents side by side in separate worktrees on the owner's Claude, ChatGPT or Cursor plans, with dated help articles and a public changelog. It has no API, MCP server or documented command an outside agent can call, every chat starts in Full access, and its pages disagree on which parts need a paid plan.

Before you call either

Harness

  1. Run harness whoami first. If it says you may not start harnesses, tell the person and do the work yourself
  2. Ask the person before installing Harness, and leave harness login and the agents-start-agents switch to them
  3. Treat exit 5 as final and do not retry. Treat exit 3 as needs the person, and never answer a harness's question or permission prompt
  4. Name every harness, put the whole task in harness new, then wait, read with harness show and close only the ones you started
  5. Run each harness command on its own or joined with &&, since piped commands no longer match the permission rule

Unstoppable

  1. Don't plan to drive Unstoppable from another agent. It has no documented API, MCP server or CLI. Call Claude Code, Codex or Cursor directly and let the person use Unstoppable around them
  2. Inside Unstoppable, check the approval mode before acting. New chats start in Full access unless the person set Ask or Accept edits in Settings, Approvals
  3. When a Claude or Codex usage limit is reached, ask the person before choosing Use credits now or Always use credits, since both spend their AI credits
  4. Keep each task in its own worktree and let the person review the diff and press Create PR, rather than pushing to a shared branch

Questions

Which is better for AI agents, Harness or Unstoppable?

Harness scores 60.3 (C) on agent readiness against Unstoppable's 34.9 (F), and leads in 6 of 7 scored categories. Unstoppable leads on reliability.

Are Harness and Unstoppable open source?

Harness is open source (MIT). No open-source release is listed for Unstoppable.

Other comparisons with Harness or Unstoppable

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