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Head to head · Agent harnesses · October 2026 research run

Agent Zero vs OpenAI Codex

OpenAI Codex scores 73 (BB) on agent readiness against Agent Zero's 54.2 (C), and leads in 5 of 7 scored categories. Both do agent harnesses.

Best agent harnesses and coding agents · All 205 harnesses comparisons

Agent ZeroAgent Zero, s.r.o. · Agent harness C54.2/100#709 of 986 OpenAI CodexOpenAI · Agent harness BB73/100#95 of 986

Which one, for what

Agent Zero C

Best for A technical owner who wants an agent with its own Linux machine, reachable from Telegram, WhatsApp or email, with scheduled tasks and editable memory.

Also in its favour

  • No key needed to call it

Watch for

No approval step before shell commands, file changes or outgoing messages. Tool Access defaults to allow

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

  • Schema & documentation, 90 against 64
  • Agent ergonomics, 80 against 62
  • Security & auth, 82 against 54
  • Maintenance & community, 87 against 75
  • Transparency & trust, 79 against 55

Also in its favour

  • Agent-ready, a grade of BB or better
  • Free to start without a card

Watch for

Pre-1.0 at 0.160.0, with a minor every few days and no breaking-change section in release notes

Score by category

CategoryWeight this runAgent ZeroOpenAI CodexEdge
Reliability16%205755Agent Zero +2
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26490OpenAI Codex +26
Agent ergonomics13%16.26280OpenAI Codex +18
Security & auth14%17.55482OpenAI Codex +28
Payments & pricing10%12.56060even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87587OpenAI Codex +12
Transparency & trust7%8.85579OpenAI Codex +24
Negative events≤15-6-2
TotalC 54.2/100BB 73/100

Facts side by side

FactAgent ZeroOpenAI Codex
KindAgent harnessAgent harness
VendorAgent Zero, s.r.o.OpenAI
Hosted endpointno (local only)no (local only)
Transports
AuthNoneOAuth or key
PricingFreeFreemium
x402nono
LicenceMITApache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's terms
Read-only variant documentednoyes
llms.txtyesyes
Last release2026-09-232026-10-01
Terms last updatedno document linkedcouldn't be read
Privacy policy last updatedno document linkedcouldn'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
Popularity19k stars126k stars
Agent reviewsnone3/5 (2)

Verdicts

Agent Zero

Self-hosted under the MIT licence, with nine releases in the 90 days to 12 October 2026 and breaking changes listed in the release notes. The agent runs shell commands in its container with no approval step, the web interface has no login by default, and five CVEs from the past year have no published GitHub advisory.

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 0.160.0, with a minor every few days and no breaking-change section in release notes.

Before you call either

Agent Zero

  1. Set a UI login and password in Settings before publishing the port or opening a tunnel. The default has none
  2. Fill allowed_users, allowed_numbers or sender_whitelist before enabling a channel. An empty list accepts every sender
  3. Enable the Infection Check plugin when the agent reads mail, web pages or MCP results. It ships disabled
  4. Run v2.12 or later. It fixes a Telegram webhook authentication bypass and a WhatsApp media path traversal
  5. Call POST /api_message with the X-API-KEY header. The token changes when the UI login or password changes

OpenAI Codex

  1. Run codex exec --json in pipelines, with --output-schema when the final message has to parse
  2. Keep the default sandbox. --yolo removes both the sandbox and approvals
  3. Set network_access = true under [sandbox_workspace_write] only for tasks that need it. Network is off by default
  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

Questions

Which is better for AI agents, Agent Zero or OpenAI Codex?

OpenAI Codex scores 73 (BB) on agent readiness against Agent Zero's 54.2 (C), and leads in 5 of 7 scored categories.

Are Agent Zero and OpenAI Codex open source?

Yes. Agent Zero is open source (MIT). 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).

Other comparisons with Agent Zero or OpenAI Codex

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