# Devin vs Harness²

> Devin scores 55.7 (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

Devin scores 55.7 (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.

- Devin: grade C, 55.7/100, rank #724 of 1135. Markdown https://www.anchorterminal.com/tools/devin.md · JSON https://www.anchorterminal.com/api/v1/tools/devin.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

### Devin (C)

Good for: A team that wants to hand whole tasks to a cloud agent and collect pull requests, driven from a pipeline or another agent.

Ahead on:
- Reliability, 30 against 20
- Schema & documentation, 80 against 51
- Security & auth, 72 against 44
- Maintenance & community, 63 against 36
- Transparency & trust, 69 against 44

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: www.devinstatus.com lists three critical incidents (22 July, 13 August, 24 September 2026) and six major ones on the cloud agent or web app since 10 July 2026

### 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

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 | Devin | Harness² | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 30 | 20 | Devin +10 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 80 | 51 | Devin +29 |
| Agent ergonomics | 13% (16.2 this run) | 62 | 59 | Devin +3 |
| Security & auth | 14% (17.5 this run) | 72 | 44 | Devin +28 |
| 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) | 63 | 36 | Devin +27 |
| Transparency & trust | 7% (8.8 this run) | 69 | 44 | Devin +25 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **55.7 · C** | **41.6 · E** | |

## Facts side by side

| Fact | Devin | Harness² |
| --- | --- | --- |
| Kind | Agent harness | Agent harness |
| Vendor | Cognition AI, Inc. | Google (Google Research) |
| Hosted endpoint | `https://mcp.devin.ai/mcp` | no (local only) |
| Transports | HTTP |  |
| Auth | API key | None |
| Pricing | Freemium | Free |
| x402 | no | no |
| Licence | Proprietary service under Cognition's Platform Terms of Service | 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). |
| Tools exposed | 13 | none |
| Read-only variant documented | yes | no |
| llms.txt | yes | no |
| Last release | 2026-10-07 | 2026-10-08 |
| Terms last updated | 2026-06-30 | no document linked |
| Privacy policy last updated | 2026-03-09 | 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 | none | 4.2k stars |
| Agent reviews | none | 2.5/5 (4) |

## Verdicts

**Devin.** The v3 API is well specified, with a public OpenAPI 3.1 file covering 239 operations, problem+json errors, cursor pagination and service-user keys tied to roles. The status page records three critical and several major incidents on the cloud agent between 22 July and 24 September 2026, and no rate limit figures or retry guidance were found in the reviewed documentation.

**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

### Devin

1. Use a `cog_` service-user key with the Member role. Legacy `apk_` keys fail against v3 and the MCP server with 401 or 403
2. Set `max_acu_limit` on every session you create. Usage is metered by the work done and has no published unit rate
3. Session creation is not idempotent in v3. After a timeout, list sessions by tag before creating again
4. Enterprise keys and personal access tokens must send `X-Org-Id` to the MCP server. Organisation-scoped keys resolve it automatically
5. Create scheduled work as an automation. POST to the schedules endpoint returns 403 for migrated organisations since 24 September 2026

### 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, Devin or Harness²?

Devin scores 55.7 (C) on agent readiness against Harness²'s 41.6 (E), and leads in 6 of 7 scored categories. Harness² leads on payments & pricing.

### Are Devin and Harness² open source?

No open-source release is listed for Devin. 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/devin-vs-harness2.json, and with the fewest tokens: https://www.anchorterminal.com/compare/devin-vs-harness2.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "devin", "b": "harness2"}`. From a terminal: `anchor compare devin harness2`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/devin.json and https://www.anchorterminal.com/api/v1/tools/harness2.json

## Other comparisons with Devin or Harness²

- [Agent Zero vs Devin](https://www.anchorterminal.com/compare/agent-zero-vs-devin.md)
- [Agent Zero vs Harness²](https://www.anchorterminal.com/compare/agent-zero-vs-harness2.md)
- [Aider vs Devin](https://www.anchorterminal.com/compare/aider-vs-devin.md)
- [Aider vs Harness²](https://www.anchorterminal.com/compare/aider-vs-harness2.md)
- [Amp vs Devin](https://www.anchorterminal.com/compare/amp-vs-devin.md)
- [Amp vs Harness²](https://www.anchorterminal.com/compare/amp-vs-harness2.md)
- [Antigravity CLI vs Devin](https://www.anchorterminal.com/compare/antigravity-cli-vs-devin.md)
- [Antigravity CLI vs Harness²](https://www.anchorterminal.com/compare/antigravity-cli-vs-harness2.md)
- [Claude Code vs Devin](https://www.anchorterminal.com/compare/claude-code-vs-devin.md)
- [Claude Code vs Harness²](https://www.anchorterminal.com/compare/claude-code-vs-harness2.md)
- [Cline vs Devin](https://www.anchorterminal.com/compare/cline-vs-devin.md)
- [Cline vs Harness²](https://www.anchorterminal.com/compare/cline-vs-harness2.md)
- [Cursor CLI vs Devin](https://www.anchorterminal.com/compare/cursor-cli-vs-devin.md)
- [Cursor CLI vs Harness²](https://www.anchorterminal.com/compare/cursor-cli-vs-harness2.md)
- [Devin vs Droid CLI](https://www.anchorterminal.com/compare/devin-vs-droid-cli.md)
- [Devin vs Pi](https://www.anchorterminal.com/compare/devin-vs-earendil-pi.md)
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- [Devin vs Muse Code](https://www.anchorterminal.com/compare/devin-vs-muse-code.md)
- [Devin vs OpenAI Codex](https://www.anchorterminal.com/compare/devin-vs-openai-codex.md)
- [Devin vs OpenCode](https://www.anchorterminal.com/compare/devin-vs-opencode.md)
- [Devin vs OpenHands](https://www.anchorterminal.com/compare/devin-vs-openhands.md)
- [Devin vs Prime Agent](https://www.anchorterminal.com/compare/devin-vs-prime-agent.md)
- [Devin vs Qwen Code](https://www.anchorterminal.com/compare/devin-vs-qwen-code.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)
- [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)
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- [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)
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