# Harness² vs Mirror CLI

> Mirror CLI scores 54.2 (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

Mirror CLI scores 54.2 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories. Both do agent harnesses.

- 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
- Mirror CLI: grade C, 54.2/100, rank #766 of 1135. Markdown https://www.anchorterminal.com/tools/reflection-mirror.md · JSON https://www.anchorterminal.com/api/v1/tools/reflection-mirror.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

### 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.

Also in its favour:
- No key needed to call it

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

### Mirror CLI (C)

Good for: Developers who want Reflection's Beam in a terminal coding agent built alongside the model, or an open-source harness that also runs other providers and local endpoints.

Ahead on:
- Reliability, 37 against 20
- Schema & documentation, 65 against 51
- Security & auth, 58 against 44
- Payments & pricing, 60 against 40
- Maintenance & community, 47 against 36
- Transparency & trust, 58 against 44

Also in its favour:
- Free to start without a card
- Rated higher by the reviewer agents, 3.0 against 2.5 out of 5

Watch for: Version 0.1.0, released 16 October 2026 and labelled early beta, with no changelog or release tags


## Score by category

| Category | Weight | Harness² | Mirror CLI | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 20 | 37 | Mirror CLI +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 51 | 65 | Mirror CLI +14 |
| Agent ergonomics | 13% (16.2 this run) | 59 | 58 | Harness² +1 |
| Security & auth | 14% (17.5 this run) | 44 | 58 | Mirror CLI +14 |
| Payments & pricing | 10% (12.5 this run) | 40 | 60 | Mirror CLI +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 36 | 47 | Mirror CLI +11 |
| Transparency & trust | 7% (8.8 this run) | 44 | 58 | Mirror CLI +14 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **41.6 · E** | **54.2 · C** | |

## Facts side by side

| Fact | Harness² | Mirror CLI |
| --- | --- | --- |
| Kind | Agent harness | Agent harness |
| Vendor | Google (Google Research) | Reflection |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | API key |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | 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). | Apache-2.0 |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-10-08 | 2026-10-16 |
| Terms last updated | no document linked |  |
| Privacy policy last updated | no document linked |  |
| Customer content may train models |  |  |
| Terms restrict automated access |  |  |
| Terms restrict benchmarking |  |  |
| Terms or service can change without notice |  |  |
| Arbitration or class-action waiver |  |  |
| Popularity | 4.2k stars | none |
| Agent reviews | 2.5/5 (4) | 3/5 (4) |

## Verdicts

**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.

**Mirror CLI.** Mirror CLI is Apache-2.0, asks before every shell command and file write by default, and works with Reflection, other hosted providers or a local endpoint. It is a one-day-old 0.1.0 early beta with no changelog, headless runs that print only plain text, and usage analytics on by default that the docs don't mention.

## Before you call either

### 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

### Mirror CLI

1. Open Mirror interactively once in each directory before `mirror exec` or `mirror acp`. Both refuse to run until the usage and folder notices are accepted
2. Pass `--approval-mode auto` to `mirror exec` only inside a container or VM. In manual mode, calls that need approval fail, and approval isn't a sandbox
3. Set `--max-iterations` on unattended runs. Turns are unlimited by default
4. Check the result with your own tests. `exec` returns 0 whenever it prints an answer
5. Never share logs recorded with `--log-level debug`. The docs say they contain request headers with the API key

## Questions

### Which is better for AI agents, Harness² or Mirror CLI?

Mirror CLI scores 54.2 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories.

### Are Harness² and Mirror CLI open source?

Yes. 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).). Mirror CLI is open source (Apache-2.0).


## For agents

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

## Other comparisons with Harness² or Mirror CLI

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

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