The evidence layer for the agent economy.
_{Venues rotate. The transcript endures.}

Agents now buy from agents. When a deal goes wrong, a chat log is a story — a counter-signed receipt is evidence. Tersign is a neutral, hash-chained ledger for agent commerce: sellers sign EIP-712 receipts (the x402 offer-receipt extension), the ledger counter-signs and chains every record, and each entry exports as an evidence envelope for the venue that will actually hear it — Internet Court, Kleros, UMA.

npx tersign verify 0xe5874f1ffe87f0a6dd9eb157730f67b86ee4538b125fe30fcc4e165213dd3fc4 --ledger https://tersign.ai

ledger: counter-signed OK (seller tersign-first, seq 1 …) VALID

_{Genesis receipt, seq 1, on the production chain. Local EIP-712 signature recovery plus a public chain check. No account. No API key.}

flowchart LR
    subgraph L["neutral ledger · counter-signed secp256k1 · per-seller hash chain"]
        direction LR
        P["seq n-1"] --> N["seq n"] --> Q["seq n+1"]
    end
    T["agent ⇄ agent<br/>x402 transaction"] --> R["EIP-712 receipt<br/>seller-signed"]
    R --> D["keccak256<br/>canonical digest"]
    D --> L
    L --> V["venue envelope<br/>Internet Court · Kleros ERC-1497 · UMA"]

Party statements ride along structurally segregated behind an UNVERIFIED marker — prompt injection does not get to testify.

• Census — 2,500+ hash-chained observations across 1,100+ x402 seller endpoints, probed hourly and autonomously; live count
• Compliance — EU Art-226b minimal tier · EN 16931 full tier · HK IRO s.51C retention · ActionRecordV1 agent action records mapped to EU AI Act Art 50 (binding 2026-08-02) · compliance-fields extension proposed upstream (x402#2853)
• Conformance — RFC 8785 (JCS) canonical serialization · keccak256 digests · published byte-level cross-implementation vectors: reproduce the bytes and your implementation is conformant, in any language · evidence-record suite: the layer criteria as runnable two-sided vectors
• Lifecycle — refunds chained via refundOf · disputes v0 with objective reason codes · idempotency stores (memory + Cloudflare D1) · evidence packs (format=art50, format=safr beta) · Internet Court envelopes fit the 5,000-char slot
• Discovery — ARD catalog served per the 11-vendor June 2026 spec · llms.txt

_{Counter-signed. Hash-chained. On the record.}