Audit chain - AtlaSent

Every call to /v1/evaluate — regardless of outcome — writes one entry to the audit chain. The chain is:

Append-only. No UPDATE, no DELETE. Enforced at the database layer.
Hash-linked. Each entry contains prev_hash = SHA-256(previous entry). Any tampering mid-chain breaks the link and is visible at verify time.
Signed. Periodic chain heads are signed with AtlaSent’s Ed25519 key.
Exportable. Ship the chain + the detached signature + the public key to any auditor. They can verify it with our open-source CLI on an air-gapped machine.

Entry shape

Each row matches the AuditEvent schema in the OpenAPI specification. decision and the decision-linking decision_id are top-level columns; other per-decision detail (matched policy, permit token, deny reason) is carried in the payload object so the chain shape stays uniform across event types.

{
  "id": "aud_01HX6Z8FK2...",
  "org_id": "org_01HX...",
  "type": "evaluation.completed",
  "decision": "allow",
  "decision_id": "req_01HX6Z8...",
  "actor_id": "agent-001",
  "resource_type": "ehr_record",
  "resource_id": "patient-42",
  "payload": {
    "action_type": "ehr:write",
    "reason": "RACI rule ehr:write permits role=clinical_agent",
    "permit_token": "pt.v4.g6EBOKGBWCC4wNi5vZmZzZXQ..."
  },
  "previous_hash": "b6f9a1e8c4...",
  "hash": "41d73c8b2e...",
  "sequence": 84217,
  "occurred_at": "2026-04-19T14:02:18.112Z"
}

What it satisfies

Requirement	How
21 CFR §11.10(c) — protection of records	Append-only + hash linking = tamper-evident
21 CFR §11.10(e) — secure audit trails	Computer-generated on every call, immutable
EU Annex 11 §9 — audit trails	Timestamped, attributed, contemporaneous
ALCOA+	Attributable (actor), Legible (JSON), Contemporaneous (ts), Original (not a copy), Accurate (server-generated)

Verifying offline

atlasent-audit-verify --chain <export> --keys atlasent-audit-key.pem --require-signatures

atlasent-audit-verify is the open-source, offline verifier. Get the public key from Audit signing key. See also Quickstart → Export the audit bundle.