The evidence layer for the agent economy.

Settlement for AI agents shipped open and free. Proof didn't.

Every log an agent keeps about itself is testimony from an interested party — and the one thing no self-issued record can manufacture is a second signature from someone with nothing to win. Tersign is that second signature: a neutral ledger counter-signs every receipt, action and verdict into per-seller hash-chains and anchors the commitment to Bitcoin. Every record on this page is verifiable by anyone, and every counter is served raw from a public endpoint. Check them yourself — that is the entire point.

EU AI ACT ART 50 APPLIES FROM 2026-08-02 · IT SETS THE DUTY TO DISCLOSE — NOT HOW YOU DEMONSTRATE YOU DID

The living ledger · chain of custody, live from production — this strip updates itself

Record

0xe5874f1f…3fc4

signed by the seller's agent at transaction time

Counter-signature

0x9d38BA84…FDa6

a neutral ledger signs it into a numbered chain — a party can't be its own sequencer

Chain commitment

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an accumulator over every counter-signed link — the anchored commitment binds every record before it, so a gap is arithmetically visible

Bitcoin

anchoring…

the commitment is re-anchored within six hours of any change — the live head state, the latest anchor, and the cron's own heartbeat are all public (/v1/stats); compare them yourself · existence provable with public tools forever; completeness from the anchored commitment over the counter-signed sequence

anchor one record and you prove that record existed · anchor the chain's commitment at every change and every record is committed under its next anchor — timestamped no later than it — and gaps in the counter-signed sequence are visible to anyone

Live census · the machine-payable economy, probed around the clock

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Chained observations

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Seller endpoints tracked

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Serving valid signed offers

An autonomous prober works the live agent-commerce catalog in 5-minute ticks — 50 targets per tick, ~14,400 probes a day — and hash-chains what it saw: prices, payTo keys, uptime, offer-signature validity. The run counter and last-run time are served raw; poll the endpoint across a tick boundary and watch them move. History accumulates forward only: no later entrant can reconstruct it.

The ledger · every counter published raw, from record one

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Receipts counter-signed

$—

Receipted GMV · USD

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Evidence records

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Disputes decided (deterministic rulebook)

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Sellers on ledger

These counters are served raw from /v1/stats, from record one — anti-vanity by design. Nothing here is a headline number you have to take on faith: each record behind them is independently verifiable. Deployment smoke-test traffic is excluded, by a rule published in the response itself (organic_filter); those records stay in the chain and stay verifiable, because each is counter-signed at its own sequence number and committed under every later anchor; removing one would break the sequence completeness this ledger exists to prove.

Anchored to Bitcoin · latest ledger-wide anchor

Anchored commitment—

Status—Proof—

Verify it yourselfots info proof.ots · offline, stock OpenTimestamps tooling — prints the attested Bitcoin block; cross-check that block's merkle root in any explorer. With a local Bitcoin node, the stronger form: ots verify -d <anchoredDigest> proof.ots

Three doors

You hold the liability

Prove your agents disclosed.

Where record-keeping duties bind — SEC 17a-4(f) for broker-dealers, FINRA 4511-class rules, HK IRO s.51C — records must be preserved, time-stamped and reproducible today, and disclosure regimes such as EU AI Act Art 50 add the duty to disclose. Nothing in those rules makes your own attestation checkable by the party challenging it. When the record is challenged — by a counterparty, an auditor, or a regulator — self-kept logs are testimony; counter-signed, anchored chains are evidence. Control and evidence for your agents, without your own word carrying the proof. Export packs (beta): Art 50 · VAT 226b · HK s.51C · MAS SAFR alignment. Pay by card, provisioned by an agent, running in minutes.

Evidence tiers →

You build

One dependency, evidence-grade receipts.

npm i tersign pip install tersign npx tersign verify 0xe5874f1ffe87f0a6dd9eb157730f67b86ee4538b125fe30fcc4e165213dd3fc4 --ledger https://tersign.ai

Node for issuing: EIP-712 codecs, RFC 8785 canonical digests, idempotency, refunds, disputes. Python for checking: zero dependencies, no network, no account — it verifies a receipt, a chain or a whole evidence bundle from the bytes alone, which is the version to hand an auditor. Both MIT. The record schema and its two-sided conformance vectors (independence, completeness, existence, phase) are open under Apache-2.0, and three independent engines are checked against them — so verification never depends on Tersign.

github.com/tersignhq/tersign-js →

You are an agent

GET /llms.txt
GET /.well-known/ai-catalog.json
GET /v1/stats · /v1/anchors
MCP io.github.tersignhq/evidence

This page is also machine-readable. You are welcome here.

ledger counter-signing key …