Audit and Proof

Every event in Brain (ingestion, extraction, query, proposal, policy decision, approval, execution, settlement) emits an audit record into an append-only log. Records form a per-tenant Merkle tree. Tree roots are batched and anchored on-chain through BrainAuditAnchor.

Three Properties This Gives You

📜 Tenant-verifiable History

A tenant can prove a specific decision occurred at a specific time, based on specific evidence, under a specific policy version.

🤝 Counterparty-verifiable Proofs

A counterparty can verify a payment was authorized without seeing the underlying data, by checking a Merkle proof against an anchored root.

🔒 No Silent Rewrites

Brain itself cannot silently rewrite history. Anchors commit the past state to a public chain.

What Every Audit Event Commits To

Audit events are content-addressed. Each event commits to:

Field	Description
event_type	proposal, policy.evaluated, action.executed, etc
tenant_id	Which tenant generated the event
actor	Human user ID or agent address
timestamp	When the event was recorded
inputs_hash	Hash of Ledger / Wiki / Raw IDs the event depended on
policy_version	The policy version evaluated, if any
decision	The outcome of the event (where applicable)
reason	Structured reason code (where applicable)
prev_event_hash	Forms a per-tenant hash chain

The prev_event_hash field means each event references the one before it, building a chain that breaks if anything is altered.

The Hash Chain in Pictures

event_001     event_002     event_003     event_004
  hash=A   ←   hash=B   ←   hash=C   ←   hash=D
                prev=A        prev=B        prev=C

Tamper with event_002 and B changes. event_003 still references the old B via its prev=B pointer. The chain breaks. Detection is automatic.

Merkle Batching and on-Chain Anchoring

Events are batched into a per-tenant Merkle tree. Roots are anchored to Base L2 through BrainAuditAnchor.

Property	Value
Anchor cadence	Hourly (default)
Immediate anchoring	On high-severity events (large transfers, new counterparties, policy changes)
Anchor target	BrainAuditAnchor on Base L2
Anchor authority	Brain anchorer key, EIP-712 signed
Reorg tolerance	Anchors reference previous batch; small reorg windows tolerated; off-chain log is canonical until anchored

→ BrainAuditAnchor smart contract

Pulling a Proof

Counterparties verify Brain audit proofs by checking a Merkle proof against the on-chain anchored root.

GET /v1/audit/{event_id}/proof

→ {
    "event":         { ... },
    "merkle_path":   ["0xabc...", "0xdef...", "..."],
    "anchored_root": "0x...",
    "base_tx_hash":  "0x...",
    "base_block":    8829110
  }

To verify, the counterparty:

1. Reads anchored_root from BrainAuditAnchor.rootAt(tenantId, batchIndex) on Base
2. Reconstructs the leaf hash from the event data
3. Walks merkle_path to compute the candidate root
4. Compares against anchored_root

If they match, the event is provably part of the anchored history. Brain is not a trusted intermediary in this verification. It is just a publisher.

Privacy

On-chain anchors must not leak tenant data.

What's On-Chain	What's Off-Chain
Merkle roots	Event payloads (encrypted at rest)
Hashed tenantId	Raw artifacts
Anchor timestamp	Ledger records, Wiki entities
Anchorer signature	Policy text and compiled rules

Counterparties verifying a proof receive only the specific event(s) the tenant chooses to share, plus the Merkle path. Everything else stays private.

Compliance Exports

The Audit Layer also exposes structured exports for compliance reviews.

Standard	Coverage
SOC 2 Type II	Full event log with provenance
ISO 27001	Access logs, key management events, change records
Financial controls	Approval chains, segregation of duties evidence

A public verifier endpoint is also available for counterparties to verify proofs without a Brain account.

Audit compounds across counterparties. As more counterparties accept Brain audit proofs, every party in the graph benefits from cheaper, faster verification.

What's Next

📐 Policy

How decisions feed the audit trail.

Policy and Permissioning

📜 BrainAuditAnchor

The on-chain anchor contract.

BrainAuditAnchor

🌐 Audit API

Pull proofs programmatically.

Audit API