System Models

EasyLayer includes built-in models that run automatically alongside your custom models. They handle chain integrity monitoring and mempool state out of the box. You can subscribe to their events and query their state without writing any model code.

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Network Chain Model

The Network Chain Model tracks the state of the blockchain as the crawler sees it. It runs on every crawler instance.

What it does:

• Maintains the current chain tip: block height, hash, and timestamp
• Detects and records blockchain reorganizations as they happen
• Optionally validates block headers using Merkle proofs

Events it emits:

Event	When	Payload
BitcoinNetworkInitializedEvent	Crawler starts	chain info, start height
BitcoinNetworkBlocksAddedEvent	New blocks confirmed	block heights, hashes
BitcoinNetworkReorganizedEvent	Reorg detected and resolved	orphaned blocks, new blocks
EvmNetworkInitializedEvent	EVM crawler starts	chain ID, start block
EvmNetworkBlocksAddedEvent	New EVM blocks confirmed	block numbers, hashes
EvmNetworkReorganizedEvent	EVM reorg detected	orphaned and new blocks

Subscribing:

client.subscribe('BitcoinNetworkBlocksAddedEvent', (event) => {
  console.log('New blocks:', event.payload.blocks.map(b => b.height));
});

client.subscribe('BitcoinNetworkReorganizedEvent', (event) => {
  console.log('Reorg! Orphaned:', event.payload.orphanedBlocks.length, 'blocks');
});

Querying chain state:

const stats = await client.query('GetNetworkStatsQuery');
console.log(stats.currentHeight, stats.syncProgress);

const latest = await client.query('GetNetworkLastBlockQuery');
console.log(latest.height, latest.hash);

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Mempool Model

The Mempool Model is available when mempool monitoring is enabled. It maintains a snapshot of current pending transactions.

What it does:

• Polls the connected node for mempool contents on a configurable interval
• Emits a refresh event on every poll
• Tracks which mempool transactions get confirmed vs dropped

Events it emits:

Event	When	Payload
BitcoinNetworkMempoolRefreshedEvent	Each mempool poll	list of pending transactions
EvmMempoolRefreshedEvent	Each EVM mempool poll	list of pending transactions

Subscribing:

client.subscribe('BitcoinNetworkMempoolRefreshedEvent', (event) => {
  const { transactions } = event.payload;
  console.log(`${transactions.length} unconfirmed transactions in mempool`);
});

See Mempool Monitoring for configuration and custom model integration.

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Merkle Validation (Bitcoin)

Optionally enable Merkle proof validation to cryptographically verify that each block's transactions match its header commitment. Useful for high-integrity deployments where you want to catch any data integrity issues.

BITCOIN_MERKLE_VALIDATION=true

When enabled, the crawler verifies every block before processing it. Invalid blocks are rejected and the crawler reconnects to the provider.

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Using System Events in Your App

System events use the same transport as your custom model events. You subscribe with the same client.subscribe() call. No extra configuration needed.

Common patterns:

• Listen to BlocksAdded to trigger downstream processing in your own service
• Listen to Reorg events to invalidate caches or send alerts
• Poll GetNetworkStatsQuery to display sync progress in a dashboard
• Use GetNetworkLastBlockQuery to check crawler health in a monitoring endpoint

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Related

• Transport Layer — how to subscribe and query
• Mempool Monitoring — detailed mempool configuration
• Event Store — how system events are stored alongside custom events