AggSender - Polygon Developer Docs

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.

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.

Certificate Generation

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.

Certificate Lifecycle

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
}

Certificate Sizing Limits

Chain operators can bound certificate size with two AggSender configuration options:

Option	Type	Description
`MaxL2BlockNumber`	`uint64`	Highest L2 block number that a certificate may include. AggSender stops submitting once coverage reaches this block. `0` disables the limit.
`MaxL2BlockRange`	`uint64`	Maximum span (`ToBlock - FromBlock`) of a single certificate. AggSender splits work so that no certificate covers a wider range. `0` disables the limit.

MaxL2BlockNumber caps the absolute end block; MaxL2BlockRange caps the width of each certificate. The two limits compose: AggSender shrinks the current certificate to satisfy whichever is reached first. Both limits apply across Pessimistic Proof, FEP, optimistic, builder, and validator flows. The Validator inherits MaxL2BlockRange from AggSender by default.

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.

​What AggSender Does

​The Trust Problem AggSender Solves

​Certificate Generation

​Epoch-Based Operation

​Certificate Lifecycle

​Certificate Structure

​Certificate Sizing Limits

​Full Certificate Submission Flow