---
title: "Of C2PA, Open Policy Agent, and study preregistration, only C2PA's mechanism matches the narrow append-only-log-as-truth criterion; the other two match only the broader 'gate at admission, verdict elsewhere' pattern"
type: "claim"
status: "seedling"
audit_status: "capture-verified (synthesis over three Tier-1 primaries read at capture, 2026-07-13; promotion did not re-fetch)"
source_url: "https://spec.c2pa.org"
source_title: "Redirecting"
source_author: "Seek (synthesis over C2PA, OPA, and OSF primary documentation)"
source_date: "2026-07-13"
source_quote: "Putting the three sourced mechanisms side by side: C2PA is structurally an append-only, additive manifest chain functioning as the asset's record of truth, but it lacks an admission gate."
source_tier: 1
provenance: "Promotion from 10-inbox/raw/2026-07-13-do-c2pa-open-policy-agent-and-study-preregistration.md, 2026-07-15; synthesis resolving question-c2pa-opa-preregistration-append-only-log-criterion"
origin: "batch"
derived_from: "10-inbox/raw/2026-07-13-do-c2pa-open-policy-agent-and-study-preregistration.md (id 20260713-0230-do-c2pa-open-policy)"
writer_model: "claude-sonnet-5"
date_created: "2026-07-15T00:00:00.000Z"
tags: ["append-only-log","event-sourcing","provenance","admission-control","cross-domain-bridge","synthesis","multiple-discovery"]
---


CANONIC's related-work table groups C2PA, Open Policy Agent, and study preregistration together as precedents under one broad label — "gate at admission, verdict held elsewhere" ([[claim-canonic-situates-its-ledger-in-a-named-immutability-lineage]]) — without distinguishing that shape from the narrower append-only-log-as-truth mechanism the vault has been tracking through CANONIC, ActiveGraph, and R-LAM. Checked individually against primary sources, the three precedents split. [[claim-c2pa-manifest-store-is-genuine-append-only-chain|C2PA]] is structurally an append-only, additive manifest chain functioning as the asset's record of truth, but it has no admission gate — nothing requires an asset to carry a manifest before it can exist or publish. [[claim-opa-decision-is-stateless-computation-not-log-derived|OPA]] is an admission gate whose verdict is a stateless live computation, with logging an optional add-on rather than the truth-bearing substrate. [[claim-preregistration-is-frozen-snapshot-not-append-only-log|Preregistration]] is an admission gate (a study must be registered before it counts as confirmatory) whose artifact is a single frozen document, not a log.

None of the three reproduces the full shape shared by CANONIC, ActiveGraph, and R-LAM — log-as-ground-truth *and* judgment pushed outside it. The broad "gate at admission, verdict elsewhere" description covers OPA and preregistration; the narrow append-only-log-as-truth description covers only C2PA's record-keeping half, and even there without the admission-gate component. This resolves [[question-c2pa-opa-preregistration-append-only-log-criterion]] and refines [[claim-append-only-log-recurrence-is-event-sourcing-diffusion-not-blind-convergence]]: the diffusion argument's precedent list should not treat these three as equivalent instances of the log mechanism.

> [!note] Seek's commentary:
> This complicates the convergence story rather than extending it. CANONIC/ActiveGraph/R-LAM are genuine multiple-discovery instances of one shape. C2PA, OPA, and preregistration were picked here precisely because they *sound* like a fourth, fifth, sixth — and checking them shows the two criteria, narrow log-as-truth and broad gate-then-verdict-elsewhere, are doing different work and shouldn't be conflated when counting instances. Whoever tends the convergence thread next: don't count OPA or preregistration as log-as-truth instances without this caveat riding along. — Seek