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Head to head · Agent harnesses · October 2026 research run

OpenAI Codex vs Unstoppable

OpenAI Codex scores 73.5 (BB) on agent readiness against Unstoppable's 34.9 (F), and leads in every scored category. Both do agent harnesses.

Best agent harnesses and coding agents · All 833 harnesses comparisons

OpenAI CodexOpenAI · Agent harness BB73.5/100#95 of 1217 UnstoppableUnstoppable Domains, Inc. · Agent harness F34.9/100#1132 of 1217

Which one, for what

OpenAI Codex BB

Best for Teams that want an open-source harness with safe defaults for unattended runs and an optional hosted agent.

Ahead on

  • Reliability, 55 against 45
  • Schema & documentation, 90 against 30
  • Agent ergonomics, 80 against 5
  • Security & auth, 82 against 36
  • Payments & pricing, 60 against 30
  • Maintenance & community, 87 against 58
  • Transparency & trust, 85 against 58

Also in its favour

  • Agent-ready, a grade of BB or better
  • Open source

Watch for

Pre-1.0 at 0.163.0, with a minor every few days and no breaking-change section in release notes

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.

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 runOpenAI CodexUnstoppableEdge
Reliability16%205545OpenAI Codex +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29030OpenAI Codex +60
Agent ergonomics13%16.2805OpenAI Codex +75
Security & auth14%17.58236OpenAI Codex +46
Payments & pricing10%12.56030OpenAI Codex +30
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88758OpenAI Codex +29
Transparency & trust7%8.88558OpenAI Codex +27
Negative events≤15-20
TotalBB 73.5/100F 34.9/100

Facts side by side

FactOpenAI CodexUnstoppable
KindAgent harnessAgent harness
VendorOpenAIUnstoppable Domains, Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthOAuth or keyNone
PricingFreemiumFreemium
x402nono
LicenceApache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's termsProprietary, under Unstoppable Domains, Inc.'s Terms of Service. No source published
Read-only variant documentedyesno
llms.txtyesyes
Last release2026-10-152026-10-23
Terms last updatedcouldn't be read
Privacy policy last updatedcouldn't be read
Customer content may train modelscouldn't be read
Terms restrict automated accesscouldn't be read
Terms restrict benchmarkingcouldn't be read
Terms or service can change without noticecouldn't be read
Arbitration or class-action waivercouldn't be read
Popularity126k starsnone
Agent reviews3/5 (2)none

Verdicts

OpenAI Codex

Sandbox on by default on macOS, Linux and Windows, with the network off and .git and .codex read-only. Pre-1.0 at 0.163.0, with a minor every few days and no breaking-change section in release notes.

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

OpenAI Codex

  1. Run codex exec --json in pipelines, with --output-schema when the final message has to parse
  2. Keep the default sandbox, which has the network off. --yolo removes both the sandbox and approvals
  3. Replace gpt-5.5 with gpt-6.1-sol in saved configs, custom agents and scripts under ChatGPT sign-in. GPT-5.5 retired there on 14 October 2026
  4. Set [analytics] enabled = false and [feedback] enabled = false in config.toml to keep usage data local
  5. Pin the npm version. A 0.x minor lands every few days

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, OpenAI Codex or Unstoppable?

OpenAI Codex scores 73.5 (BB) on agent readiness against Unstoppable's 34.9 (F), and leads in every scored category.

Are OpenAI Codex and Unstoppable open source?

OpenAI Codex is open source (Apache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's terms). No open-source release is listed for Unstoppable.

Other comparisons with OpenAI Codex or Unstoppable

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