MetaHarness

Mint a custom AI agent harness from any repo.

npx metaharness · open the Studio →

(Repo: ruvnet/agent-harness-generator · CLI: metaharness · Library: @ruvnet/agent-harness-generator)

What this is

Every serious repo deserves its own agent. A repo-aware CLI, a repo-aware coding agent, a local MCP server, memory scoped to the project, skills generated from the actual file layout, governance policy, release verification, witness-signed provenance.

metaharness mints those, on demand, from a GitHub URL or a blank slate. It is not another agent framework. It is a factory for agent frameworks.

The model is replaceable. The harness is the product.

What it gives you

In under 60 seconds, in your browser, with nothing leaving your machine:

• A custom AI agent harness for your repo (or any repo)
• Recommended agents, skills, slash commands, MCP tools
• A scoped memory namespace + governance policy
• Witness-signed provenance + release gates
• Drops into Claude Code, OpenAI Codex, pi.dev, Hermes, OpenClaw, or RVM — pick one or all

Output is an npm-publishable .zip with your name on it, your branding, your npx <your-name> CLI.

New

• Score any repo before you build it. npx metaharness score <repo> reads the repo (never runs it) and prints a one-screen report card — how well a harness fits, how likely it is to build, how safe the tools are, and the rough cost per run — so you know what you'll get before scaffolding.
• Pick the cheapest model that's good enough. @metaharness/router routes each request to the right model from your own results — same quality, far less spend. Works out of the box with zero native deps; train it on your data for a sharper fit (npm i @metaharness/router). Add the optional @ruvector/tiny-dancer to train a fast native model instead — same training data, no API change.
• Let your harness improve itself. Every scaffold now ships with Darwin Mode (@metaharness/darwin) wired in — run npm run evolve and the harness mutates its own config, tests each change in a sandbox, and keeps only what measurably improves. The model stays frozen; the harness evolves. Safe by default (no network, no API key; pure refactor/tuning behind a safety gate). Validated on real SWE-bench Lite bug-fixing. --no-darwin to skip.
• Distil the cheap tier instead of escalating to a frontier model. Weight-EFT (@metaharness/weight-eft, metaharness weight-eft) takes the complementary lever to Darwin's gradient-free evolution: it exports the harness's gold-resolved archive into standard SFT/DPO sets and LoRA-tunes the open cheap tier (GLM/Qwen), so the cost-cascade escalates to Opus/GPT less often. It attacks cost (fewer $0.50 escalations), not the frontier ceiling — and stays honest about it. Strict train/eval-disjointness + reward-hacking filters keep the lift real; the tune is a gene Darwin can prune if it overfits. See ADR-198. ($0 / GPU-gated.)

Tune it to your project — then ship it as your own npm

A generated harness is a starting point you own, not a fixed framework. Open it and make it yours:

• Keep only what your repo needs. Delete the agents, skills, slash commands, and MCP servers you won't use — the scaffold ships a recommended set, but a payments service and a docs site want very different harnesses. A smaller, targeted harness is faster, cheaper, and easier to reason about. harness doctor / harness validate keep it healthy as you trim.
• Optimize the model routing for your work. Swap the per-task model tiers, tighten the governance policy, point the memory namespace at your domain. The harness is config you control, not a black box.
• Publish it as your own package for the whole org. Rename it, set your scope, and npm publish — now anyone on your team runs npx @your-org/your-harness and gets the same repo-tuned agent. One command, org-wide, versioned like any other dependency. (The 19 @metaharness/* examples are exactly this pattern, published live.)

Make older, cheaper models punch like frontier ones. The right harness isn't a pile of extra steps bolted onto an expensive model — it's putting the right model on each task and getting out of the way. Our DRACO benchmark proves it: a small, cheap model delivers frontier-quality research at roughly one-tenth the cost, and a smart router squeezes out the rest. Stop paying frontier prices for work a $0.10 model does just as well.

That router ships as @metaharness/router — route(query) returns the cheapest model predicted to clear your quality bar, learned from your own eval logs. npm i @metaharness/router.

Try it in 30 seconds

# In the browser — zero install, nothing leaves the page
open https://ruvnet.github.io/agent-harness-generator/

# Or in the terminal — the same harness (behaviourally equivalent output)
npx metaharness my-bot --template vertical:coding --host claude-code
cd my-bot && npx . --help

Don't know what to pick? Run the wizard:

npx metaharness --wizard

Already have a repo you want a harness for?

harness analyze-repo .                       # local — deterministic analysis only
harness analyze-repo . --scaffold my-bot     # materialise the recommended harness

No repository code is executed. Inferred build/test commands are emitted as trust: inferred · execution: disabled.

📖 Read the plain-language user guide →

Hosts

The same harness output runs on nine agent hosts — eight interactive, plus GitHub Actions (CI/CD):

See ADR-004 — Host integration model and ADR-033 — GitHub Actions host.

MCP — modular, default-deny

MCP is included as a first-class adapter surface, not the identity. It is gated and default-deny (ADR-022):

• Modes: off · local (stdio) · remote (HTTPS + auth)
• Emits src/mcp/{server,tools,resources,prompts,policy,audit}.ts + a scannable .harness/mcp-policy.json
• Safe defaults: no network, no shell, no file-write, approve-dangerous, 30s timeout, 8 calls/turn, audit on
• harness mcp-scan <path> — "npm audit for agent tools": static-only scan flagging shell/network grants, missing audit/timeouts, wildcard permissions, unguarded secrets, unpinned deps. Exits 1 on any HIGH.

Verticals (19 quick-start templates)

npx metaharness --list
npx metaharness my-bot --template vertical:coding

Each ships bespoke domain agents (with system prompts), skills, commands, and per-host settings — all default-deny.

One-command examples

Don't want to pick flags? Each host and vertical has a dedicated @metaharness/* wrapper — published, one npx away, no template/