> For the complete documentation index, see [llms.txt](https://docs.lumia.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lumia.org/ecosystem/lumia/architecture/polygon-cdk-and-agglayer/how-lumia-settles-and-bridges-to-ethereum.md).

# How Lumia settles and bridges to Ethereum

**Who this is for:** developers and issuers who want to know what cross-chain settlement and bridging Lumia gets from Polygon, beyond its own chain. **You should already know:** [What Lumia's chain is built with](https://app.gitbook.com/s/chmhPiVNAafGw48c4oU2/ecosystem/lumia/architecture/polygon-cdk-and-agglayer/what-the-lumia-chain-is-built-with).

### The shared settlement hub

Lumia settles and bridges to Ethereum as a member of AggLayer, a shared settlement-and-bridge hub on Ethereum that a number of Polygon CDK chains register with. Rather than each CDK chain deploying and maintaining its own bridge and settlement contracts in isolation, member chains share one canonical bridge contract and one aggregated exit-root structure on Ethereum.

```mermaid
flowchart TD
  L["Lumia"] -->|"deposits and withdrawals"| BR["Canonical bridge contract"]
  C2["Other AggLayer member chains"] --> BR
  L -->|"exit data"| EX["Aggregated exit root"]
  C2 --> EX
  subgraph ETH["Shared hub on Ethereum, governed by Polygon"]
    BR
    EX
  end
  EX -. "chain-to-chain transfer: a capability,<br/>not a description of current volume" .-> C2
```

### What membership gives Lumia

**A standardized bridge to Ethereum, rather than a bespoke one.** Lumia deposits and withdraws through the same shared, unified bridge contract that other AggLayer member chains use, rather than a one-off Lumia-specific bridge. Wallets, explorers, and bridge aggregators that already integrate with that shared bridge model need little to no custom work to support Lumia. The bridge also inherits the scrutiny of code shared across many chains rather than a single, unreviewed deployment.

**A path to native cross-chain transfers with other member chains.** Every member chain's exit data feeds into one aggregated structure on Ethereum, which is what lets an asset leave one member chain and be claimed on another without a separate third-party bridge or a wrapped-asset intermediary.

**Shared infrastructure cost.** The hub's core contracts are deployed once and shared; a member chain isn't paying to deploy or maintain that shared core, only its own periodic settlement transactions against it.

### The honest caveat

{% hint style="warning" %}
The AggLayer hub itself (the shared contracts Lumia registers into) is governed by Polygon, not by Lumia. Lumia controls its own chain's keys and configuration, but the shared hub's upgrade path is a standing dependency on Polygon regardless of how independent Lumia's own operations become.
{% endhint %}