ai2human Onus

The burden of proof is on the evidence.

An open verification layer for AI agents. One call turns a claim plus evidence into approved / rejected / needs_review — and a receipt anyone can replay.

▶ Watch the full 50-second film · Quickstart · How it works · Measured on live Jev · Known limitations

You run a giveaway: "Reply to our post, get $1." Overnight you get 1,000 replies. Half are gm, ads, bots, copy-paste.

An LLM review is slow and pricey. Doing it by hand takes all day. Paying out on self-reported proof means paying the fakers first.

Onus is the layer in between. It grades the evidence, asks a judge only what a judge is good at, and keeps the decision in code.

from a2h_onus import verify_claim

verify_claim(claim, evidence, acceptance_criteria, value_usd, nonce)
# -> {"verdict": "approved", "evidence_grade": "E3", "receipt": {...}}

Why this exists

Agents produce claims all day — "tests pass", "the post is live", "the payment cleared". Something has to decide whether each claim is true before code acts on it. Today that is either brittle hand-written rules, or an expensive model call that still gets forged evidence wrong.

Onus makes verification a primitive. It uses Jev for the semantic judgment, and it is built around the fact that Jev will sometimes be confidently wrong:

1. "Zero hallucination" is a wording trick. Jev cannot return an option outside your schema. It can confidently pick the wrong valid one. A 0.95 wrong verdict is still wrong.

2. Don't let a model compute what code can. Nonce checks, timestamps, hash dedup — deterministic code, never the model.

3. Confidence cannot rescue weak evidence. Forged-image detection tops ~80% even for frontier models, so evidence below a binding threshold never auto-passes, no matter the score.

4. No single closed API is load-bearing. The judge is swappable: Jev, kev (local, free), or a model you train on your own logs.

Related MCP server: AgentGround Cross-Check Verifier

How it works

Four layers, each with one job. Only two of them can decide anything, and neither is a model.

verify_claim(claim, evidence)
        │
        ▼
┌─────────────────────────────────────────────┐
│ L1  Provenance   — pure code, no model       │
│     nonce present? identity bound?           │
│     hash seen before? timestamp in window?   │
│     → assigns evidence grade E0–E4           │
├─────────────────────────────────────────────┤
│ L2  Perception   — (not in this release)     │
│     VLM extracts structured facts from images│
├─────────────────────────────────────────────┤
│ L3  Judgment     — Jev / kev (pluggable)     │
│     typed questions → probability + confidence│
│     only answers "is this genuine / does it  │
│     meet the criteria" — never touches money │
├─────────────────────────────────────────────┤
│ L4  Policy       — pure code, the only layer │
│     that decides. grade < E3 → never auto-   │
│     pass. (posterior, value, grade) → verdict│
└─────────────────────────────────────────────┘
        │
        ▼
  verdict + confidence + replayable receipt

The design rules, one line each:

• Provenance in code, semantics in the model. What a string match or a chain query can settle, the model never sees.

• Judgment ≠ settlement. The model outputs probabilities. Code decides the money.

• The grade gate is absolute. Evidence below E3 never auto-passes, however confident the judge is.

• The backend is pluggable. Speak "System One compatible", not "Jev".

• Every verdict ships a receipt. Grade, model version, full distribution, hash.

Quickstart

git clone https://github.com/richard7463/a2h-onus
cd a2h-onus
python3 -m venv .venv && source .venv/bin/activate
pip install -e .

# runs offline out of the box with a mock judge (no key, no server):
JUDGMENT_BACKEND=mock python examples/verify_x_post.py
JUDGMENT_BACKEND=mock python examples/verify_onchain.py   # E4, no model call
JUDGMENT_BACKEND=mock python examples/grade_gate_demo.py  # E1 @0.99 → review

To run a real Jev judgment, point it at TypeSafe and pin the model version:

export JUDGMENT_BACKEND=jev
export TYPESAFE_API_KEY=...        # your own key; never commit it
export JEV_MODEL=jev-1.13.0        # pinned; never 'latest'
python examples/jev_smoke.py

Full walkthrough — key, first raw call, first real receipt: docs/connect-jev.md.

Call it from an agent

Onus is MCP-native. Any MCP client — Claude, Codex, and others — can call verify_claim directly; no account, no REST schema to read.

pip install -e ".[mcp]"
python -m a2h_onus.mcp_server

Two tools are exposed: verify_claim for one claim, verify_batch for many. Batch mode returns per-item verdicts plus auto_approve_rate, review_rate and reject_rate — the numbers a dashboard needs.

Verify a gitlawb record

Onus reads gitlawb, the decentralized agent-native git network, as an evidence source. Public repositories are readable over the node's HTTP API with no keypair and no registration, so a signed push record can be settled in code without asking a model at all.

gitlawb signs every push. That raises an obvious question the certificate list answers directly: who pushed it? Each ref-update certificate carries a pusher_did separately from the repository's owner DID — so "a signed record exists" and "the owner is accountable for it" are two different checks, and most pipelines only do the first.

Onus requires both, plus a certificate that names this exact commit:

python examples/verify_gitlawb.py

verify_claim(
    claim="Commit f0b7a571 was pushed to a2h-onus by the repo owner",
    evidence={"type": "gitlawb_commit",
              "content": {"owner": "z6Mk...", "repo": "a2h-onus",
                          "sha": "f0b7a571ec263ac2c99482d5f6688aece484bc99"}},
)
# -> evidence_grade E4, verdict approved, receipt.model_id "deterministic"

Three conditions must all hold before this reaches E4: the hash is in the repository's commit list, a ref-update certificate names that exact hash, and that certificate's pusher_did equals the owner DID. Anything short of the three is downgraded to E1 and routed to review. The check fails closed — any network or parse error means not verified, never verified.

A commit that only ever appeared mid-push has no certificate naming it, so it cannot be owner-attributed from this API and does not reach E4. One push produces one certificate, covering the ref tip.

Endpoints read (all verified against a live node):

What this proves, and what it does not. It proves that the node recorded a signed ref update, by the owner, naming that exact commit. It says nothing about whether the work in the commit is correct, useful, or honest — that is a judgment, and judgments stay in the judge layer one step up.

It also does not prove that the node would have blocked a push from a non-owner. gitlawb's own documentation states that write authorization is not owner-enforced by default (GITLAWB_ENFORCE_OWNER_PUSH defaults to false). That policy is not visible through the public API, so Onus reports it as gitlawb_owner_push_enforced: null — unknown, not assumed.

Measured on live Jev

Model jev-1.13.0, measured 2026-09-23. Every number below was produced by the code in this repository — nothing here is estimated or projected.

The number that matters

Across the 30-case A/B set, the judge on its own let one forgery through. It scored that forgery 0.90 — a confident, schema-valid, wrong answer. The evidence grade behind it was E1, so the gate refused to auto-pass it and routed it to a human instead. 0 / 20 with the gate.

That is the whole argument for this repository: the model is not the safety mechanism. The grade gate is.

On the pass threshold

Genuine submissions score 0.51–0.56, sitting right on the 0.55 bar, so the auto-approve rate is noisy: four consecutive runs gave 2, 3, 4 and 4 genuine approvals out of 10. The fraud figure is stable — 1/20 by the model alone, 0/20 with the gate, in every run. Treat the auto-approve rate as uncalibrated until it has a larger sample.

Known limitations (read before relying on it)

This is an early release. Be clear about what it does not do yet:

• Identity is not verified yet. An account handle in evidence.identity is currently taken as given. A submitter can type any handle. Real binding (OAuth / wallet signature checked against your platform's records) is the next milestone.

• Content is not fetched from the source yet. For x_post and url, the text is whatever the submitter sends. Fetching the post / page ourselves is on the roadmap.

• On-chain checks are stubbed. The E4 path exists, but the RPC lookup is not wired in.

• Duplicate detection is exact-match. Change one character and it's a new hash.

• No image understanding. Screenshots always route to human review.

• gitlawb verification covers records, not quality. The node confirms that a commit exists under an owner; it cannot tell you whether the work is any good. Treat a gitlawb pass as "this happened", not "this was worth paying for".

• gitlawb owner attribution is the closest the API gets, not a guarantee. pusher_did == owner_did is checked, but the node does not enforce owner-only pushes yet, so this establishes who the record credits, not that the node would have rejected anyone else. gitlawb_owner_push_enforced is returned as null for that reason.

• Only ref tips carry a certificate. A commit that was never the tip of a signed push cannot be owner-attributed and is downgraded rather than assumed.

• gitlawb attribution is a snapshot, not a permanent property. The certificate list covers the ref tips the node currently lists. Push again and the previous tip's certificate rolls off, so a commit that verified today may not verify tomorrow. gitlawb_cert_list_is_snapshot is true on every result for exactly this reason — persist the verdict and its receipt when you check it instead of re-deriving it later.

What it is good for today: a cheap first-pass filter — flag off-topic and low-effort submissions, never auto-approve screenshots, and send humans only what is left.

Why the guardrails, specifically

The long version, with the failure each guardrail was built to catch: docs/four-traps.md. It covers the four traps that cost real money to learn — "zero hallucination" as a wording trick, letting the model compute what code can, trusting a confident score on a screenshot, and betting the pipeline on one closed API.

What this is not

• Not a task marketplace and not settlement — it decides whether a claim holds; what you do with the verdict is yours.

• Not an image forensics tool — L2 perception is not in this release; image evidence routes to review.

• Not tied to Jev — kev, NanoJev, or a model you train on your own logs all drop in.

License

MIT. Clone it, gut it, ship your own. The judgment logs you accumulate are the real moat — not this code.