Fast Path Preconfirmations

Overview

Fast Path enables significantly faster L1 to L2 deposits by reducing the block finality requirements from full Ethereum finality to just 6 blocks. This feature allows developers to choose between speed and security based on their application's needs.

Confirmation Modes

Fast Path Mode

Finality: 6 L1 blocks (~70 seconds)
Use case: Applications prioritizing user experience and faster deposits
Configuration: LatestBlock/-6

Standard Mode (Default)

Finality: Full Ethereum finality (~15 minutes)
Use case: Applications prioritizing maximum security
Configuration: FinalizedBlock

Trade-offs

Aspect	Fast Path	Standard Mode
L1→L2 Deposit Time	~70 seconds	~15 minutes
Security	Lower (reorg risk)	Maximum
User Experience	Faster	Slower

Reorg Risk: Fast Path mode increases the risk of chain reorganizations affecting bridge state. Evaluate this risk based on your network's requirements.

Configuration

To enable Fast Path mode, ensure you are on v0.8.0 of aggkit or above, then configure both L1InfoTreeSync and BridgeL1Sync block finality settings:

[L1InfoTreeSync]
BlockFinality = "LatestBlock/-6"

[BridgeL1Sync]
BlockFinality = "LatestBlock/-6"

For Standard Mode (default), use:

[L1InfoTreeSync]
BlockFinality = "FinalizedBlock"

[BridgeL1Sync]
BlockFinality = "FinalizedBlock"

Note: This configuration is optional and should be evaluated based on your network's risk tolerance. The default FinalizedBlock setting prioritizes safety over speed.