> ## Documentation Index
> Fetch the complete documentation index at: https://docs.compose.market/llms.txt
> Use this file to discover all available pages before exploring further.

# Multichain Architecture

> Cross-chain Account Abstraction with deterministic Smart Account addresses

Compose.Market supports multiple EVM chains with a unified Smart Account experience. Users get the **same Smart Account address** across all supported chains through deterministic CREATE2 deployment.

***

## Cross-Chain Identity

The key innovation is **universal Smart Account addresses**. A user who creates a Smart Account on Avalanche Fuji will have the **exact same address** on Cronos Testnet.

```mermaid theme={null}
flowchart TB
    subgraph User["User (Social Login)"]
        EOA["EOA Signer<br/>(Email/Google/Passkey)"]
    end
    
    subgraph Fuji["Avalanche Fuji (43113)"]
        F_Factory["AccountFactory<br/>0x4bE0...dceb"]
        F_Account["Smart Account<br/>0xABC...123"]
        F_Entry["EntryPoint v0.7<br/>0x0000...a032"]
        F_Bundler["ThirdWeb Bundler"]
    end
    
    subgraph Cronos["Cronos Testnet (338)"]
        C_Factory["AccountFactory<br/>0x4bE0...dceb"]
        C_Account["Smart Account<br/>0xABC...123"]
        C_Entry["EntryPoint v0.7<br/>0x0000...a032"]
        C_Paymaster["SimplePaymaster<br/>0xA7c8...7D4"]
    end
    
    EOA --> F_Factory
    EOA --> C_Factory
    F_Factory -->|"CREATE2(salt)"| F_Account
    C_Factory -->|"CREATE2(salt)"| C_Account
    F_Account --> F_Entry
    C_Account --> C_Entry
    F_Entry --> F_Bundler
    C_Entry --> C_Paymaster
```

### How It Works

The Smart Account address is derived from:

```
address = CREATE2(factory, keccak256(admin, salt), initCodeHash)
```

Since we deploy the **same AccountFactory** at the **same address** on all chains, users automatically get identical Smart Account addresses.

| Component              | Requirement    | Address                                      |
| :--------------------- | :------------- | :------------------------------------------- |
| AccountFactory         | Universal      | `0x4bE0ddfebcA9A5A4a617dee4DeCe99E7c862dceb` |
| EntryPoint v0.7        | Universal      | `0x0000000071727De22E5E9d8BAf0edAc6f37da032` |
| Account Implementation | Chain-specific | Varies per chain                             |
| Paymaster              | Chain-specific | Varies per chain                             |

***

## Cronos Testnet Deployment

Cronos Testnet lacks a native ERC-4337 bundler, so we deployed the full AA infrastructure ourselves using CREATE2 to match ThirdWeb's universal addresses.

### Deployment Method

We extracted the deployment parameters from the original Ethereum mainnet transaction and replayed them on Cronos:

1. **Find original deployment tx** on Etherscan/Blockscout
2. **Extract CREATE2 salt** (first 32 bytes of input data)
3. **Extract init code** (remaining bytes)
4. **Call Arachnid's CREATE2 deployer** (`0x4e59b44847b379578588920cA78FbF26c0B4956C`)

This produces identical addresses on any EVM chain where Arachnid's deployer exists.

### Deployed Contracts

| Contract               | Address                                      | Notes          |
| :--------------------- | :------------------------------------------- | :------------- |
| EntryPoint v0.7        | `0x0000000071727De22E5E9d8BAf0edAc6f37da032` | Universal      |
| AccountFactory         | `0x4bE0ddfebcA9A5A4a617dee4DeCe99E7c862dceb` | Universal      |
| Account Implementation | `0x94eC38a5d2EDA5A543Ab4c08D998338D4082beb2` | Chain-specific |
| SimplePaymaster        | `0xA7c85b07aBE6eE06Cd2f1268Ea22d7156C7A67D4` | Chain-specific |

***

## Supported Chains

| Chain          | Chain ID | AA Support           | Payment            |
| :------------- | :------- | :------------------- | :----------------- |
| Avalanche Fuji | 43113    | ThirdWeb Bundler     | x402               |
| Cronos Testnet | 338      | Custom (api bundler) | x402 + Facilitator |

***

## Account Registration Flow

When a user connects on Cronos Testnet:

```mermaid theme={null}
sequenceDiagram
    participant User
    participant Frontend
    participant API as API Bundler
    participant Factory as AccountFactory
    participant Paymaster
    participant EntryPoint

    User->>Frontend: Connect wallet (social login)
    Frontend->>Frontend: Get EOA admin address
    Frontend->>API: POST /api/aa/prepare
    API->>Factory: getAddress(admin, "")
    Factory-->>API: Predicted account address
    API-->>Frontend: UserOp + hash to sign
    
    User->>Frontend: Sign UserOpHash
    Frontend->>API: POST /api/aa/submit
    API->>Paymaster: Sign sponsorship
    API->>EntryPoint: handleOps([userOp])
    EntryPoint->>Factory: Deploy if needed
    EntryPoint-->>API: Success
    API-->>Frontend: Transaction hash
```

***

## API Endpoints

### `POST /api/aa/prepare`

Prepare a UserOperation for signing.

### `POST /api/aa/submit`

Submit a signed UserOperation for execution.

### `POST /api/aa/register-cronos`

Deploy a Smart Account on Cronos (if not already deployed).

***

## Key Files

| Component           | Location                              |
| :------------------ | :------------------------------------ |
| UserOp construction | `backend/api/shared/aa/userop.ts`     |
| Paymaster signing   | `backend/api/shared/aa/paymaster.ts`  |
| Frontend AA client  | `app/src/lib/cronos/aa.ts`            |
| Cronos Facilitator  | `backend/api/shared/config/cronos.ts` |

***

## Value for Cronos Ecosystem

This work provides **production-ready ERC-4337 v0.7 infrastructure** for Cronos Testnet:

* **Universal AccountFactory**: Same address as Ethereum, Fuji, and other chains
* **EntryPoint v0.7**: Latest standard with PackedUserOperation support
* **Gasless transactions**: SimplePaymaster for gas sponsorship
* **Cross-chain identity**: Users keep the same Smart Account address

Developers building on Cronos can reuse these contracts or follow the same CREATE2 deployment pattern.