An open standard for runtime proof of AI.

§ i · definition

What OVERT is.

OVERT defines a compact, cryptographically sealed record — a receipt — that captures what an AI system was asked to do, what it actually did, and under whose policy it was evaluated at that moment. Each receipt is signed by a quorum of witnesses and chained to the previous one, so a history of decisions can be audited as a single tamper-evident ledger.

The specification covers three things: the schema of the receipt itself, the witness semantics that produce it, and the verification rules any third party can use to check it. That is all. OVERT deliberately does not prescribe the model, the policy language, or the enforcement engine — only what gets recorded and how it can be trusted.

§ ii · rationale

Why an open standard.

Attestation is only useful if someone who does not trust the vendor can still verify the claim. A closed, vendor-specific format does not meet that bar — it asks auditors, regulators, and insurers to take the vendor’s word for it. An open specification removes that dependency: any conformant verifier, in any jurisdiction, can check a receipt without GLACIS in the loop.

OVERT is published under terms that allow anyone to implement it, including competitors. The value of a standard grows as more parties adopt it, and we would rather compete on the quality of the runtime than on the walls of the format.

§ iii · scope

What is in v1.0.

• Receipt schema. Required and optional fields covering subject, probe, verdict, policy, witness, content hash, and chain pointer — enough to replay an evaluation and verify its result.
• Witness semantics. Quorum rules for producing a valid receipt (default 3-of-3), signature algorithm profile, and the conditions under which no receipt is written rather than a partial one.
• Verification rules. The exact checks a verifier must perform to accept a receipt as valid, including schema validation, signature verification, and chain integrity.
• Versioning and profiles. How OVERT evolves without breaking older receipts, and how industry-specific profiles layer on top (healthcare, financial services, medical devices).

Spec · overt.is / v1.0.0·April 2026

§ iv · governance

GLACIS’s role.

GLACIS authored the initial draft of OVERT and runs the reference witness fabric. The specification itself is governed through the OVERT IPR policy published on overt.is, with contributions open to any organization operating a production witness.

We think about OVERT the way cryptographers think about signed-log formats and certificate transparency: the value is in the commons. Runtime defense for AI is a category we are building for; the proof format it leaves behind is one we would like to see in every auditor’s toolkit, regardless of whose runtime produced it.