The evidence layer for the agent economy.

Settlement for AI agents is finished and free. What never shipped is proof. 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 heads to Bitcoin. Every record on this page is verifiable by anyone, and every counter is served raw from a public endpoint — no trust in us required.

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 head

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one digest commits to every record ever filed; a gap is arithmetically visible

Bitcoin

anchoring…

the head is re-anchored within six hours of any change — existence and completeness in one proof, verifiable with public tools forever

anchor one record and you prove that record existed · anchor the counter-signed head and every record inherits the timestamp — and omissions become visible

Live census · the machine-payable economy, probed hourly

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Chained observations

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Seller endpoints tracked

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Serving valid signed offers

An autonomous prober runs hourly against the live agent-commerce catalog and hash-chains what it saw — prices, payTo keys, uptime, offer-signature validity. 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 adjudicated

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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 they are anchored and removing them would break the sequence completeness this ledger exists to prove.

Anchored to Bitcoin · latest ledger-wide anchor

Anchored head—

Status—Proof—

Verify it yourselfots verify -d <anchoredDigest> proof.ots · stock OpenTimestamps tooling, no account, no Tersign

Three doors

You hold the liability

Prove your agents disclosed.

When a disclosure is challenged — by a counterparty, an auditor, or a regulator — self-kept logs are testimony; counter-signed, anchored chains are evidence. The obligation is yours; the proof shouldn't be your own word. Export packs (beta): Art 50 · VAT 226b · HK s.51C · MAS SAFR. Pay by card, provisioned by an agent, running in minutes.

Evidence tiers →

You build

One dependency, court-grade receipts.

npm i tersign npx tersign verify 0xe5874f1f… --ledger https://tersign.ai

EIP-712 codecs, RFC 8785 canonical digests, idempotency, refunds, disputes. MIT, provenance-attested, two-sided conformance vectors published.

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 …