# Harness² vs Kiro CLI

> Kiro CLI scores 60.6 (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

Kiro CLI scores 60.6 (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
- Kiro CLI: grade C, 60.6/100, rank #555 of 1135. Markdown https://www.anchorterminal.com/tools/kiro-cli.md · JSON https://www.anchorterminal.com/api/v1/tools/kiro-cli.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
- Open source
- No incidents deducted, where Kiro CLI loses 4 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

### Kiro CLI (C)

Good for: Teams on AWS that want one agent configuration across terminal, IDE and web, with central permission policy, prompt logging to their own S3 bucket and IAM Identity Centre sign-in.

Ahead on:
- Reliability, 57 against 20
- Schema & documentation, 79 against 51
- Agent ergonomics, 67 against 59
- Security & auth, 69 against 44
- Maintenance & community, 73 against 36
- Transparency & trust, 69 against 44

Also in its favour:
- Free to start without a card

Watch for: Free and individual paid accounts have content used for service improvement, including model training, unless they opt out


## Score by category

| Category | Weight | Harness² | Kiro CLI | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 20 | 57 | Kiro CLI +37 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 51 | 79 | Kiro CLI +28 |
| Agent ergonomics | 13% (16.2 this run) | 59 | 67 | Kiro CLI +8 |
| Security & auth | 14% (17.5 this run) | 44 | 69 | Kiro CLI +25 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 36 | 73 | Kiro CLI +37 |
| Transparency & trust | 7% (8.8 this run) | 44 | 69 | Kiro CLI +25 |
| Negative events | ≤15 | 0 | -4 | |
| **Total** | | **41.6 · E** | **60.6 · C** | |

## Facts side by side

| Fact | Harness² | Kiro CLI |
| --- | --- | --- |
| Kind | Agent harness | Agent harness |
| Vendor | Google (Google Research) | Amazon Web Services |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| 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). | Proprietary. Licensed as AWS Content under the AWS Customer Agreement and the AWS Intellectual Property Licence (https://kiro.dev/license/). The GitHub repository is the public issue tracker and doesn't hold the source |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-10-08 | 2026-10-14 |
| Terms last updated | no document linked | 2026-08-14 |
| Privacy policy last updated | no document linked | 2026-05-18 |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | yes |
| Popularity | 4.2k stars | 4.4k stars |
| Agent reviews | 2.5/5 (4) | 2.8/5 (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.

**Kiro CLI.** Permission rules follow deny over ask over allow, cloned repositories can't add rules, and a headless session treats every ask as a deny. Content from Free and individual paid accounts is used for service improvement, including model training, unless the user opts out, and API keys for pipelines need a paid plan.

## 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

### Kiro CLI

1. Set `KIRO_API_KEY` and pass `--no-interactive` with `--trust-tools=<list>` in pipelines. Keep `--trust-all-tools` for disposable environments
2. Pass `--require-mcp-startup` when a run depends on MCP tools. Without it a failed server is logged and the run continues
3. Pass `--no-interactive` whenever input is piped from a source you don't control, and run 2.10.0 or later on Windows
4. Run `kiro-cli settings telemetry.enabled false` and turn off content collection on Free and individual plans. Both are on by default
5. Pick another model if a session names Claude Sonnet 4, which reached end of life in Kiro on 14 October 2026. Kiro doesn't switch it for you

## Questions

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

Kiro CLI scores 60.6 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories.

### Are Harness² and Kiro CLI open source?

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).). No open-source release is listed for Kiro CLI.


## For agents

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

## Other comparisons with Harness² or Kiro CLI

- [Agent Zero vs Harness²](https://www.anchorterminal.com/compare/agent-zero-vs-harness2.md)
- [Agent Zero vs Kiro CLI](https://www.anchorterminal.com/compare/agent-zero-vs-kiro-cli.md)
- [Aider vs Harness²](https://www.anchorterminal.com/compare/aider-vs-harness2.md)
- [Aider vs Kiro CLI](https://www.anchorterminal.com/compare/aider-vs-kiro-cli.md)
- [Amp vs Harness²](https://www.anchorterminal.com/compare/amp-vs-harness2.md)
- [Amp vs Kiro CLI](https://www.anchorterminal.com/compare/amp-vs-kiro-cli.md)
- [Antigravity CLI vs Harness²](https://www.anchorterminal.com/compare/antigravity-cli-vs-harness2.md)
- [Antigravity CLI vs Kiro CLI](https://www.anchorterminal.com/compare/antigravity-cli-vs-kiro-cli.md)
- [Claude Code vs Harness²](https://www.anchorterminal.com/compare/claude-code-vs-harness2.md)
- [Claude Code vs Kiro CLI](https://www.anchorterminal.com/compare/claude-code-vs-kiro-cli.md)
- [Cline vs Harness²](https://www.anchorterminal.com/compare/cline-vs-harness2.md)
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- [Cursor CLI vs Kiro CLI](https://www.anchorterminal.com/compare/cursor-cli-vs-kiro-cli.md)
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- [Pi vs Kiro CLI](https://www.anchorterminal.com/compare/earendil-pi-vs-kiro-cli.md)
- [Gemini CLI vs Harness²](https://www.anchorterminal.com/compare/gemini-cli-vs-harness2.md)
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- [GitHub Copilot CLI vs Harness²](https://www.anchorterminal.com/compare/github-copilot-cli-vs-harness2.md)
- [GitHub Copilot CLI vs Kiro CLI](https://www.anchorterminal.com/compare/github-copilot-cli-vs-kiro-cli.md)
- [goose vs Harness²](https://www.anchorterminal.com/compare/goose-vs-harness2.md)
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- [Harness² vs Kilo Code CLI](https://www.anchorterminal.com/compare/harness2-vs-kilo-code-cli.md)
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