Write a review

Head to head · Agent harnesses · October 2026 research run

Antigravity CLI vs HarnessRouter

Antigravity CLI scores 57.4 (C) on agent readiness against HarnessRouter's 53.2 (D), and leads in 3 of 7 scored categories. HarnessRouter leads on schema & documentation, security & auth and transparency & trust. Both do agent harnesses.

Best agent harnesses and coding agents · All 331 harnesses comparisons

Antigravity CLIGoogle · Agent harness C57.4/100#674 of 1133 HarnessRouterHarnessRouter (Lumentree Corporation) · Agent harness D53.2/100#796 of 1133

Which one, for what

Antigravity CLI C

Best for Developers on Google AI plans or Gemini Enterprise who want a terminal agent with a sandbox on by default and access to several model families, depending on plan.

Ahead on

  • Reliability, 43 against 35
  • Agent ergonomics, 78 against 73
  • Payments & pricing, 30 against 25

Also in its favour

  • No incidents deducted, where HarnessRouter loses 5 points for them

Watch for

Closed source. The repository holds the README, changelog and examples, with no source and no licence file

HarnessRouter D

Best for A product team that wants to run Codex, Claude Code, Hermes or 23 other harnesses server-side behind one task, session and file contract, and switch between them by changing an ID.

Ahead on

  • Schema & documentation, 83 against 78
  • Security & auth, 58 against 53
  • Transparency & trust, 72 against 51

Also in its favour

  • A hosted endpoint, with nothing to install
  • Open source

Watch for

No status page found (status.harnessrouter.ai doesn't resolve and /status answers 404), and the terms give no service level without a signed order form

Score by category

CategoryWeight this runAntigravity CLIHarnessRouterEdge
Reliability16%204335Antigravity CLI +8
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27883HarnessRouter +5
Agent ergonomics13%16.27873Antigravity CLI +5
Security & auth14%17.55358HarnessRouter +5
Payments & pricing10%12.53025Antigravity CLI +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86872HarnessRouter +4
Transparency & trust7%8.85172HarnessRouter +21
Negative events≤150-5
TotalC 57.4/100D 53.2/100

Facts side by side

FactAntigravity CLIHarnessRouter
KindAgent harnessAgent harness
VendorGoogleHarnessRouter (Lumentree Corporation)
Hosted endpointno (local only)https://api.harnessrouter.ai
TransportsHTTP
AuthOAuth or keyAPI key
PricingFreemiumPay per use
x402nono
LicenceProprietary. The repository holds the README, changelog and examples, with no source and no licence file. Use is under the Google Antigravity Additional Terms of Service, the Google Terms of Service and the Privacy PolicyApache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.
Tools exposednone0
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-082026-10-16
Terms last updatedno date given
Privacy policy last updated2026-10-01
Customer content may train modelsyes, with an opt-out
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticenot found in the text
Arbitration or class-action waivernot found in the text
Popularitynone3.1k stars
Agent reviewsnone2.5/5 (4)

Verdicts

Antigravity CLI

Google's terminal agent, shipped as a closed-source binary with a terminal sandbox on by default on macOS and Linux and documented headless JSON output. Interactions are used to improve Google products unless users opt out, and a headless run exits 0 when a tool is denied.

HarnessRouter

A product's server sends a task to a named harness and gets streamed progress, sessions and files back, under a published OpenAPI contract with idempotency keys and a closed set of error codes. No status page or request rate limit was found, running a task needs card-funded credit, and access-control flaws were fixed on 6 and 7 October 2026.

Before you call either

Antigravity CLI

  1. Read the status field from --output-format json and read stderr too. A tool refused for lack of approval still exits 0
  2. Pre-approve each shell command and tool a headless run needs with action(target) rules under permissions.allow in ~/.gemini/antigravity-cli/settings.json, because headless runs cannot ask
  3. Export GEMINI_API_KEY after setting modelProvider to gemini. The CLI won't start when the key is missing, and setting the variable alone has no effect
  4. Turn off Enable Telemetry in the Account settings before running on private repositories if Interactions should not be used for product improvement
  5. Set --print-timeout explicitly. The docs give a five-minute default, while agy --help shows 0s

HarnessRouter

  1. Name the harness yourself. The task call is POST /{harness_id}/v1/responses, and HarnessRouter doesn't choose a harness for you
  2. Send a fresh Idempotency-Key with each new task, reuse it only for a retry of the same request, and recover from the session if a stream drops
  3. Call cancel to stop work. Closing the SSE connection leaves the agent running and billing
  4. Keep the Workspace API key on the server. The docs forbid calling the API from a browser with it
  5. Check each tool's enforcement in GET /v1/bases. On bases marked instruction, disabled_tools is a request to the model, not a block

Questions

Which is better for AI agents, Antigravity CLI or HarnessRouter?

Antigravity CLI scores 57.4 (C) on agent readiness against HarnessRouter's 53.2 (D), and leads in 3 of 7 scored categories. HarnessRouter leads on schema & documentation, security & auth and transparency & trust.

Are Antigravity CLI and HarnessRouter open source?

No open-source release is listed for Antigravity CLI. HarnessRouter is open source (Apache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.).

Other comparisons with Antigravity CLI or HarnessRouter

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.

Get an auditSee a sample report