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Anchoring is how Lucid makes AI interactions permanently verifiable. Cryptographic receipts are batched into epochs, compressed into a Merkle Mountain Range (MMR) root, and committed on-chain. Anyone can later verify that a specific interaction occurred without trusting Lucid.

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The Receipt-to-Chain Pipeline

AI interaction
  -> Receipt created (SHA-256 of RFC 8785 canonical JSON)
  -> Ed25519 signed by orchestrator
  -> Appended to MMR
  -> Epoch finalized (>100 receipts OR >1 hour)
  -> MMR root committed on-chain (Solana + EVM)
  -> Epoch bundle archived to DePIN storage

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Key Algorithms

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Receipt Hashing

Every receipt is hashed using SHA-256 over RFC 8785 canonical JSON (JCS). This ensures identical receipts produce identical hashes regardless of JSON key ordering or formatting.

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Merkle Mountain Range (MMR)

Receipts are appended to an MMR — an append-only authenticated data structure. The root is computed via SHA-256 with right-to-left peak bagging. Properties:
  • Append-only (no rewriting history)
  • Efficient inclusion proofs (O(log N))
  • Supports batched verification

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Epoch Finalization

An epoch closes when either condition is met:
  • 100+ receipts accumulated
  • 1+ hour since epoch opened

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On-Chain Commitment

The thought_epoch Solana program stores MMR roots on-chain with three instruction variants:
InstructionDescription
commit_epochSingle epoch root (32-byte MMR root)
commit_epochsBatch up to 16 roots in one transaction
commit_epoch_v2Extended metadata: epoch ID, leaf count, timestamp, MMR size
Each commitment is stored in a PDA derived from the authority’s public key.

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Multi-Chain Anchoring

Lucid anchors to both Solana and EVM chains simultaneously. Configure via the ANCHORING_CHAINS environment variable: 
ANCHORING_CHAINS=solana-devnet,base
EVM anchoring uses the EpochRegistry contract, which stores the same root hash, epoch ID, and metadata.

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Gas Costs

OperationCost
iGas (per inference call)1 LUCID
mGas (per epoch root commitment)5 LUCID
Batch commit (16 roots)7 LUCID total

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DePIN Archival

After on-chain commitment, the full epoch bundle (all receipts, MMR state, metadata) is archived to decentralized storage:
ProviderTierUse Case
ArweavePermanentImmutable epoch bundles, passport metadata
LighthouseEvolvingMMR checkpoints, memory snapshots
All DePIN uploads go through the AnchorDispatcher, which handles storage selection, CID tracking, and deduplication.

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Verifying a Receipt

To verify that a specific receipt was included in an anchored epoch: 
# Get an inclusion proof
curl https://api.lucid.foundation/v1/receipts/:id/proof \
  -H "Authorization: Bearer lk_..."

# Verify against on-chain root
curl -X POST https://api.lucid.foundation/v1/receipts/:id/verify \
  -H "Authorization: Bearer lk_..."
The proof contains the receipt hash, the MMR path, and the on-chain epoch root — sufficient for independent verification.