Add Tersign Evidence Skill: Counter-Signed, Verifiable Evidence for the Disputes Layer

[wowlegend]

What This Adds

vendored/tersign/tersign-evidence/ — the official Tersign agent skill (pinned from tersignhq/skills @ 8120210), plus a skills-lock.json entry and table rows in the README / vendored README / master SKILL.md routing.

Tersign is a neutral evidence ledger for agent commerce: sellers submit signed artifacts (x402 offer-receipts, agent action records) at transaction time, and the ledger counter-signs each into a per-seller hash chain. Any party — including a jury — can verify a record with no account and no trust in the parties or in Tersign: GET /v1/receipts/{digest}/verify recomputes the chain link and recovers the counter-signature to the published ledger signer.

Why It Belongs in the Stack

Layer 6 adjudicators (GenLayer, Kleros, UMA) consume evidence the parties supply. The dispute guidelines in this repo ask for delivery receipts, timestamped logs, and third-party records — but a self-submitted blob is testimony, not an exhibit. This skill supplies the missing input: evidence that existed, counter-signed by a neutral non-party, before the dispute arose.

The skill produces jury-ready evidence envelopes for the venues already in this stack:

• Internet Court: a self-describing JSON string sized for a ≤5,000-char evidenceDefs slot
• Kleros: ERC-1497 evidence JSON (fileURI = public verify endpoint, fileHash = artifact digest)
• UMA: a compact mechanically-checkable claim string

Envelopes carry digests + a public verify URL, never raw evidence. Party statements travel in a structurally segregated, clearly-labeled unverified field — they can never impersonate ledger-attested content to a human or LLM juror (prompt-injection into adjudicators is in our threat model, and should be in every venue's).

Conventions Followed

• Vendored copy is faithful to the upstream source and pinned by commit + hash in skills-lock.json (computedHash = sha256 of SKILL.md — please recompute with your internal workflow if your recipe covers additional files)
• MIT licensed, LICENSE included in the vendored dir
• Alphabetical placement in the lock file; README rows follow existing table formats
• Like the Kleros entries, this is third-party infrastructure — disclose accordingly

Happy to adjust format, placement, or trigger-description style to match maintainer preferences. If an evidence/attestation working group forms around the "Adjudicated: signed evidence" trust tier, we'd like to participate.

Live surfaces: ledger + dashboard · public verification · SDK: npm install tersign

[wowlegend]

@rasca — a decision on this would help, and a close is as useful to me as a merge.

It has been open since 10 July and still applies cleanly (MERGEABLE, no conflicts). It vendors one skill under vendored/tersign/tersign-evidence/ with its own licence, plus the registration lines that make it visible: skills-lock.json (+15), and one or two lines each in README.md, SKILL.md and vendored/README.md. Two files added, four touched by a total of +19 −2.

If the vendoring shape is wrong for this repo, or evidence tooling is not something you want listed here, say so and I will close it myself — what is not useful is it sitting open as an implied maybe.

Related, and worth a second of your time even if this PR is a no: #8 (the gap issue on the unified evidence schema behind the "Adjudicated: signed evidence" tier) now has a competing answer in #13, which proposes an internet-court/evidence-envelope/1 schema. That is a schema decision for the adjudication table rather than a listing decision, and it will be harder to unwind later than either of these PRs is now.

— Tersign

Drafted with AI assistance.