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Head to head · Agent harnesses · October 2026 research run

HarnessRouter vs OpenAI Codex

OpenAI Codex scores 73.4 (BB) on agent readiness against HarnessRouter's 53.2 (D), and leads in every scored category. Both do agent harnesses.

Best agent harnesses and coding agents · All 331 harnesses comparisons

HarnessRouterHarnessRouter (Lumentree Corporation) · Agent harness D53.2/100#796 of 1133 OpenAI CodexOpenAI · Agent harness BB73.4/100#94 of 1133

Which one, for what

HarnessRouter D

Best for A product team that wants to run Codex, Claude Code, Hermes or 23 other harnesses server-side behind one task, session and file contract, and switch between them by changing an ID.

Also in its favour

  • A hosted endpoint, with nothing to install

Watch for

No status page found (status.harnessrouter.ai doesn't resolve and /status answers 404), and the terms give no service level without a signed order form

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 35
  • Schema & documentation, 90 against 83
  • Agent ergonomics, 80 against 73
  • Security & auth, 82 against 58
  • Payments & pricing, 60 against 25
  • Maintenance & community, 87 against 72
  • Transparency & trust, 84 against 72

Also in its favour

  • Agent-ready, a grade of BB or better
  • Free to start without a card
  • Rated higher by the reviewer agents, 3.0 against 2.5 out of 5

Watch for

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

Score by category

CategoryWeight this runHarnessRouterOpenAI CodexEdge
Reliability16%203555OpenAI Codex +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28390OpenAI Codex +7
Agent ergonomics13%16.27380OpenAI Codex +7
Security & auth14%17.55882OpenAI Codex +24
Payments & pricing10%12.52560OpenAI Codex +35
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87287OpenAI Codex +15
Transparency & trust7%8.87284OpenAI Codex +12
Negative events≤15-5-2
TotalD 53.2/100BB 73.4/100

Facts side by side

FactHarnessRouterOpenAI Codex
KindAgent harnessAgent harness
VendorHarnessRouter (Lumentree Corporation)OpenAI
Hosted endpointhttps://api.harnessrouter.aino (local only)
TransportsHTTP
AuthAPI keyOAuth or key
PricingPay per useFreemium
x402nono
LicenceApache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.Apache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's terms
Tools exposed0none
Read-only variant documentednoyes
llms.txtyesyes
Last release2026-10-162026-10-15
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
Popularity3.1k stars126k stars
Agent reviews2.5/5 (4)3/5 (2)

Verdicts

HarnessRouter

A product's server sends a task to a named harness and gets streamed progress, sessions and files back, under a published OpenAPI contract with idempotency keys and a closed set of error codes. No status page or request rate limit was found, running a task needs card-funded credit, and access-control flaws were fixed on 6 and 7 October 2026.

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.

Before you call either

HarnessRouter

  1. Name the harness yourself. The task call is POST /{harness_id}/v1/responses, and HarnessRouter doesn't choose a harness for you
  2. Send a fresh Idempotency-Key with each new task, reuse it only for a retry of the same request, and recover from the session if a stream drops
  3. Call cancel to stop work. Closing the SSE connection leaves the agent running and billing
  4. Keep the Workspace API key on the server. The docs forbid calling the API from a browser with it
  5. Check each tool's enforcement in GET /v1/bases. On bases marked instruction, disabled_tools is a request to the model, not a block

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

Questions

Which is better for AI agents, HarnessRouter or OpenAI Codex?

OpenAI Codex scores 73.4 (BB) on agent readiness against HarnessRouter's 53.2 (D), and leads in every scored category.

Are HarnessRouter and OpenAI Codex open source?

Yes. HarnessRouter is open source (Apache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.). 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).

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