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Head to head · Agent harnesses · October 2026 research run

Devin vs 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. Both do agent harnesses.

Best agent harnesses and coding agents · All 354 harnesses comparisons

DevinCognition AI, Inc. · Agent harness C55.7/100#724 of 1135 Harness²Google (Google Research) · Agent harness E41.6/100#1029 of 1135

Which one, for what

Devin C

Best 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

Best 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

CategoryWeight this runDevinHarness²Edge
Reliability16%203020Devin +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28051Devin +29
Agent ergonomics13%16.26259Devin +3
Security & auth14%17.57244Devin +28
Payments & pricing10%12.52040Harness² +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86336Devin +27
Transparency & trust7%8.86944Devin +25
Negative events≤1500
TotalC 55.7/100E 41.6/100

Facts side by side

FactDevinHarness²
KindAgent harnessAgent harness
VendorCognition AI, Inc.Google (Google Research)
Hosted endpointhttps://mcp.devin.ai/mcpno (local only)
TransportsHTTP
AuthAPI keyNone
PricingFreemiumFree
x402nono
LicenceProprietary service under Cognition's Platform Terms of ServiceApache-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 exposed13none
Read-only variant documentedyesno
llms.txtyesno
Last release2026-10-072026-10-08
Terms last updated2026-06-30no document linked
Privacy policy last updated2026-03-09no document linked
Customer content may train modelsyes, with an opt-out
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingyes
Terms or service can change without noticenot found in the text
Arbitration or class-action waiveryes
Popularitynone4.2k stars
Agent reviewsnone2.5/5 (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).).

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