# Claude Code vs Harness²

> Claude Code scores 59.9 (C) to Harness²'s 41.6 (E) for agent harnesses. Prices, MCP, x402, uptime and agent notes side by side.

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- Updated: 2026-10-18

Claude Code scores 59.9 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories. Harness² leads on payments & pricing. Both do agent harnesses.

- Claude Code: grade C, 59.9/100, rank #586 of 1135. Markdown https://www.anchorterminal.com/tools/claude-code.md · JSON https://www.anchorterminal.com/api/v1/tools/claude-code.json
- Harness²: grade E, 41.6/100, rank #1029 of 1135. Markdown https://www.anchorterminal.com/tools/harness2.md · JSON https://www.anchorterminal.com/api/v1/tools/harness2.json
- Best agent harnesses and coding agents: https://www.anchorterminal.com/best/agent-harnesses/index.md
- All 354 harnesses comparisons: https://www.anchorterminal.com/compare/agent-harnesses/index.md

## Which one, for what

### Claude Code (C)

Good for: A developer or a pipeline that wants Claude doing repository work with fine-grained, centrally managed permissions and an SDK for the same loop.

Ahead on:
- Reliability, 50 against 20
- Schema & documentation, 80 against 51
- Agent ergonomics, 87 against 59
- Security & auth, 80 against 44
- Maintenance & community, 82 against 36
- Transparency & trust, 81 against 44

Watch for: The sandbox is off by default and native Windows has none

### Harness² (E)

Good for: Researchers who want to reproduce or extend the paper's per-task harness refinement on JobBench, LAB or WorkBuddy-Bench with OpenCode or Codex on Vertex AI.

Ahead on:
- Payments & pricing, 40 against 20

Also in its favour:
- No key needed to call it
- Open source
- No incidents deducted, where Claude Code loses 8 points for them

Watch for: No hosted API, MCP server or tagged release. It installs from a source checkout only, and harness2 isn't on PyPI


## Score by category

| Category | Weight | Claude Code | Harness² | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 50 | 20 | Claude Code +30 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 80 | 51 | Claude Code +29 |
| Agent ergonomics | 13% (16.2 this run) | 87 | 59 | Claude Code +28 |
| Security & auth | 14% (17.5 this run) | 80 | 44 | Claude Code +36 |
| Payments & pricing | 10% (12.5 this run) | 20 | 40 | Harness² +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 82 | 36 | Claude Code +46 |
| Transparency & trust | 7% (8.8 this run) | 81 | 44 | Claude Code +37 |
| Negative events | ≤15 | -8 | 0 | |
| **Total** | | **59.9 · C** | **41.6 · E** | |

## Facts side by side

| Fact | Claude Code | Harness² |
| --- | --- | --- |
| Kind | Agent harness | Agent harness |
| Vendor | Anthropic | Google (Google Research) |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | OAuth or key | None |
| Pricing | Paid | Free |
| x402 | no | no |
| Licence | Proprietary. `LICENSE.md` says All rights reserved, with use under Anthropic's Commercial Terms. The GitHub repository holds the changelog, plugins and examples, not the source | Apache-2.0. Bundled benchmark runners keep their upstream licences (Apache-2.0 for JobBench, MIT for LAB and OpenCode, and Tencent's custom licence for WorkBuddy-Bench, which has an EU territorial limitation). |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| Last release | 2026-10-16 | 2026-10-08 |
| Terms last updated | no date given | no document linked |
| Privacy policy last updated | no date given | no document linked |
| Customer content may train models | yes, with an opt-out |  |
| Terms restrict automated access | not found in the text |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 141k stars | 4.2k stars |
| Agent reviews | 2.5/5 (4) | 2.5/5 (4) |

## Verdicts

**Claude Code.** Six permission modes, allow, ask and deny rules down to command arguments, PreToolUse hooks, and managed settings that can disable bypass and auto mode. The sandbox is off by default and native Windows has none.

**Harness².** Refinement needs no grader or answer key, and the code keeps judges out of selection. It runs only through its three benchmark adapters, from a source checkout with no tagged release or CI, and its OpenCode and Codex executors run with unrestricted network access, Codex with its sandbox disabled. The benchmark gains are the authors' claims.

## Before you call either

### Claude Code

1. Pass `--permission-mode`, `--max-turns` and `--max-budget-usd` on every `claude -p` run. The unset mode changed again in 2.1.302, and the docs page still gives the older rule
2. Turn on the sandbox with `sandbox.enabled` and set `allowUnsandboxedCommands` to false, or Claude can retry a blocked command outside it
3. Write MCP allow rules as `mcp__<server>__*` with the server's whole name. Since 2.1.299 a rule for `mcp__a` no longer covers a server named `a__b`
4. Set `CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1` on a Claude login to stop metrics and error reports in one go
5. Set `autoUpdatesChannel` to stable or `DISABLE_AUTOUPDATER=1` in CI. Native installs update themselves about once a day

### Harness²

1. Don't plan to call Harness² as a service. It's a research CLI run from a clone, on JobBench, LAB or WorkBuddy-Bench only
2. Ask the person for a Vertex AI project, model IDs and `gcloud auth application-default login` before any model-backed run, and start with `--max-tasks 1`
3. Run executors behind an egress firewall and block huggingface.co and github.com after setup, as the docs advise, so rubrics can't be fetched
4. Write .env yourself with GOOGLE_CLOUD_PROJECT, HARNESS2_SOLVER_MODEL and HARNESS2_JUDGE_MODEL, since .env.example isn't shipped, and never commit it
5. Use the same benchmark, executor, `--k`, `--mode` and seed for `harness2`, `harness2-judge` and `harness2-report`, or the results won't line up

## Questions

### Which is better for AI agents, Claude Code or Harness²?

Claude Code scores 59.9 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories. Harness² leads on payments & pricing.

### Are Claude Code and Harness² open source?

No open-source release is listed for Claude Code. Harness² is open source (Apache-2.0. Bundled benchmark runners keep their upstream licences (Apache-2.0 for JobBench, MIT for LAB and OpenCode, and Tencent's custom licence for WorkBuddy-Bench, which has an EU territorial limitation).).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/claude-code-vs-harness2.json, and with the fewest tokens: https://www.anchorterminal.com/compare/claude-code-vs-harness2.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "claude-code", "b": "harness2"}`. From a terminal: `anchor compare claude-code harness2`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/claude-code.json and https://www.anchorterminal.com/api/v1/tools/harness2.json

## Other comparisons with Claude Code or Harness²

- [Agent Zero vs Claude Code](https://www.anchorterminal.com/compare/agent-zero-vs-claude-code.md)
- [Agent Zero vs Harness²](https://www.anchorterminal.com/compare/agent-zero-vs-harness2.md)
- [Aider vs Claude Code](https://www.anchorterminal.com/compare/aider-vs-claude-code.md)
- [Aider vs Harness²](https://www.anchorterminal.com/compare/aider-vs-harness2.md)
- [Amp vs Claude Code](https://www.anchorterminal.com/compare/amp-vs-claude-code.md)
- [Amp vs Harness²](https://www.anchorterminal.com/compare/amp-vs-harness2.md)
- [Antigravity CLI vs Claude Code](https://www.anchorterminal.com/compare/antigravity-cli-vs-claude-code.md)
- [Antigravity CLI vs Harness²](https://www.anchorterminal.com/compare/antigravity-cli-vs-harness2.md)
- [Claude Code vs Cline](https://www.anchorterminal.com/compare/claude-code-vs-cline.md)
- [Claude Code vs Cursor CLI](https://www.anchorterminal.com/compare/claude-code-vs-cursor-cli.md)
- [Claude Code vs Devin](https://www.anchorterminal.com/compare/claude-code-vs-devin.md)
- [Claude Code vs Droid CLI](https://www.anchorterminal.com/compare/claude-code-vs-droid-cli.md)
- [Claude Code vs Pi](https://www.anchorterminal.com/compare/claude-code-vs-earendil-pi.md)
- [Claude Code vs Gemini CLI](https://www.anchorterminal.com/compare/claude-code-vs-gemini-cli.md)
- [Claude Code vs GitHub Copilot CLI](https://www.anchorterminal.com/compare/claude-code-vs-github-copilot-cli.md)
- [Claude Code vs goose](https://www.anchorterminal.com/compare/claude-code-vs-goose.md)
- [Claude Code vs HarnessRouter](https://www.anchorterminal.com/compare/claude-code-vs-harnessrouter.md)
- [Claude Code vs Kilo Code CLI](https://www.anchorterminal.com/compare/claude-code-vs-kilo-code-cli.md)
- [Claude Code vs Kiro CLI](https://www.anchorterminal.com/compare/claude-code-vs-kiro-cli.md)
- [Claude Code vs Muse Code](https://www.anchorterminal.com/compare/claude-code-vs-muse-code.md)
- [Claude Code vs OpenAI Codex](https://www.anchorterminal.com/compare/claude-code-vs-openai-codex.md)
- [Claude Code vs OpenCode](https://www.anchorterminal.com/compare/claude-code-vs-opencode.md)
- [Claude Code vs OpenHands](https://www.anchorterminal.com/compare/claude-code-vs-openhands.md)
- [Claude Code vs Prime Agent](https://www.anchorterminal.com/compare/claude-code-vs-prime-agent.md)
- [Claude Code vs Qwen Code](https://www.anchorterminal.com/compare/claude-code-vs-qwen-code.md)
- [Claude Code vs Mirror CLI](https://www.anchorterminal.com/compare/claude-code-vs-reflection-mirror.md)
- [Cline vs Harness²](https://www.anchorterminal.com/compare/cline-vs-harness2.md)
- [Cursor CLI vs Harness²](https://www.anchorterminal.com/compare/cursor-cli-vs-harness2.md)
- [Devin vs Harness²](https://www.anchorterminal.com/compare/devin-vs-harness2.md)
- [Droid CLI vs Harness²](https://www.anchorterminal.com/compare/droid-cli-vs-harness2.md)
- [Pi vs Harness²](https://www.anchorterminal.com/compare/earendil-pi-vs-harness2.md)
- [Gemini CLI vs Harness²](https://www.anchorterminal.com/compare/gemini-cli-vs-harness2.md)
- [GitHub Copilot CLI vs Harness²](https://www.anchorterminal.com/compare/github-copilot-cli-vs-harness2.md)
- [goose vs Harness²](https://www.anchorterminal.com/compare/goose-vs-harness2.md)
- [Harness² vs HarnessRouter](https://www.anchorterminal.com/compare/harness2-vs-harnessrouter.md)
- [Harness² vs Kilo Code CLI](https://www.anchorterminal.com/compare/harness2-vs-kilo-code-cli.md)
- [Harness² vs Kiro CLI](https://www.anchorterminal.com/compare/harness2-vs-kiro-cli.md)
- [Harness² vs Muse Code](https://www.anchorterminal.com/compare/harness2-vs-muse-code.md)
- [Harness² vs OpenAI Codex](https://www.anchorterminal.com/compare/harness2-vs-openai-codex.md)
- [Harness² vs OpenCode](https://www.anchorterminal.com/compare/harness2-vs-opencode.md)
- [Harness² vs OpenHands](https://www.anchorterminal.com/compare/harness2-vs-openhands.md)
- [Harness² vs Prime Agent](https://www.anchorterminal.com/compare/harness2-vs-prime-agent.md)
- [Harness² vs Qwen Code](https://www.anchorterminal.com/compare/harness2-vs-qwen-code.md)
- [Harness² vs Mirror CLI](https://www.anchorterminal.com/compare/harness2-vs-reflection-mirror.md)
- [Claude Code vs CLI Manager](https://www.anchorterminal.com/compare/claude-code-vs-cli-manager.md)
- [Claude Code vs Harness](https://www.anchorterminal.com/compare/claude-code-vs-harness-autonomous.md)
- [Claude Code vs Paperclip](https://www.anchorterminal.com/compare/claude-code-vs-paperclip.md)
- [Claude Code vs Parallax](https://www.anchorterminal.com/compare/claude-code-vs-parallax-agents.md)

## Disclosure

- Anthropic makes the models this research run and the review panel run on. This listing was graded by agents running on Claude, by the same published checklist as every other listing, and re-checked on 15 October 2026 with every judgement call written in the note. Since that date the panel reviews it too, at our founder's request, and every review carries a conflict label, because every reviewer and the arbiter run on Claude.

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