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What AggSender Does

AggSender is the component responsible for submitting L2 state transitions to Agglayer. It collects bridge events and L1 verification data, packages them into a signed certificate, and submits that certificate to Agglayer on each epoch. Agglayer then uses the certificate to generate a Pessimistic Proof and validate the state transition. Without AggSender, an L2 chain cannot participate in Agglayer’s security guarantees or cross-chain coordination. Every chain connected to Agglayer must run AggSender.

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The Trust Problem AggSender Solves

Agglayer connects multiple independent blockchains, and any of them could theoretically be compromised. The Pessimistic Proof system limits the damage a compromised chain can do, but it needs reliable input data to work correctly. AggSender provides that input. Rather than simply reporting what happened on a chain, it creates a signed certificate that contains:
  • Cryptographic proof that bridge transactions occurred
  • Evidence that the chain has sufficient funds to back those transactions
  • Mathematical verification data that the chain’s state transitions are valid
  • A digital signature committing to all of the above
This allows Agglayer to verify the submission rather than trust it.

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Certificate Generation

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Epoch-Based Operation

AggSender submits certificates on Agglayer epochs rather than per-transaction. On each epoch, it collects all bridge activity since the last certificate, packages it, and submits once. This batching is more efficient than per-transaction submissions and provides comprehensive context about the chain’s activities.

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Certificate Lifecycle

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Certificate Structure

type Certificate struct {
    NetworkID              uint32                // L2 network identifier
    Height                 uint64                // Certificate sequence number
    PrevLocalExitRoot      common.Hash           // Previous Local Exit Root
    NewLocalExitRoot       common.Hash           // New Local Exit Root
    BridgeExits            []BridgeExit          // Outgoing bridge transactions
    ImportedBridgeExits    []ImportedBridgeExit  // Incoming bridge claims
    Signature              []byte                // Cryptographic signature
    Metadata               []byte                // Additional chain-specific data
}

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Full Certificate Submission Flow

Note: AggchainProofGen is only involved when the chain uses the advanced state transition proof system. Chains using basic ECDSA authorization do not require AggchainProofGen.