Symbiosis Core Smart Contracts Overview
Symbiosis Core Smart Contracts: Overview
The Symbiosis Core Smart Contracts implement the on-chain logic for cross-chain operations. These smart contracts are deployed across all blockchain networks supported by Symbiosis and are fine-tuned to handle requests specific to each network. When the smart contracts process a request, they generate events called Oracle requests. These events contain all the necessary data to execute the next steps of cross-chain operations on other chains and are key triggers for the relayers’ activity.
The Symbiosis protocol has two slightly different sets of smart contracts: Scheme 1.

Let's see what each contract does:
- The MetaRouterGateway contract secures the interactions of the MetaRouter contract with users’ ERC20 tokens. Users’ ERC20 tokens should only be approved for this contract. 
- The MetaRouter contract manages calls to other Symbiosis contracts on one blockchain within a cross-chain operation. 
- The Portal contract locks and unlocks users' stablecoins during cross-chain operations. 
- The BridgeV2 contract is a proxy between the Symbiosis Relayers Network and the Synthesis/Portal contracts. 
- The Synthesis contract mints and burns sTokens during cross-chain operations. 
- A Symbiosis Octopool is an AMM liquidity pool containing several types of tokens of the same nominal value. For more information, see Symbiosis Octopools. 
- The MulticallRouter contract manages calls to Symbiosis contracts on on the Symbiosis Host Chain within a cross-chain operation, when the Symbiosis Host Chain isn't the source or destination blockchain of the cross-chain operation. 
Symbiosis Routing Contracts document explains how the Core Smart Contracts interact during cross-chain operations.
More Information
- sTokens (sStable tokens, sWETH, sWBTC, etc.) are explained here: Symbiosis sTokens and Supported Chains. 
- Here is an explanation of how the Symbiosis Protocol handles cross-chain operations Symbiosis Routing Contracts. 
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