# Slippage Tolerance Distribution in Cross-Chain Swaps

Generally, a cross-chain swap consists of **three transactions** executed on the **source**, **host**, and **destination** chains.

There can be on-chain swaps within a cross-chain swap:

* **(A) Source chain** — An on-chain swap is **optional** and performed if the source token differs from the transit token used on the source chain.
* **(B) Host chain** — An on-chain swap is **always performed** to exchange synthetic tokens issued for the source and destination chains.
* **(C) Destination chain** — An on-chain swap is **optional** and performed if the destination token differs from the transit token used on the destination chain.

**Example**

Consider a swap: ETH (Ethereum) → BNB (BNB Chain)\
This cross-chain swap includes three on-chain swaps:

* **(A) Ethereum:** ETH → USDC
* **(B) Symbiosis Chain:** sUSDC (issued for Ethereum) → sUSDC (issued for BNB Chain)
* **(C) BNB Chain:** USDC → BNB

## Slippage Tolerance Value

The Symbiosis API accepts slippage tolerance values ranging from 0.2% to 10%. The specified slippage tolerance value applies to the entire cross-chain swap.

The following describes how this value is divided between chains.

Let the specified slippage tolerance be **Y**.

**Slippage Tolerance Allocation Summary**

| <p>A: ✗ B: ✓ C: ✗<br></p><p>Swap example:<br>USDC (Ethereum) -> USDC (BNB)</p> | <ul><li>B (host): 0.2%</li><li>Remaining slippage ignored</li></ul>                                                                                                                                                                |
| ------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| <p>A: ✓ B: ✓ C: ✗<br><br>Swap example:<br>ETH (Ethereum) -> USDC (BNB)</p>     | <p>if Y/2 > 0.2%</p><ul><li>B (host): 0.2</li><li>A (source): Y − 0.2</li></ul><p>Else</p><ul><li>B (host): Y/2</li><li>A (source): Y/2</li></ul>                                                                                  |
| <p>A: ✗ B: ✓ C: ✓<br></p><p>Swap example:<br>USDC (Ethereum) -> BNB (BNB)</p>  | <p>if Y/2 > 0.2%</p><ul><li>B (host): 0.2%</li><li>C (destination): Y - 0.2</li></ul><p>Else</p><ul><li>B (host): Y/2</li><li>C (destination): Y/2</li></ul>                                                                       |
| <p>A: ✓ B: ✓ C: ✓<br></p><p>Swap example:<br>ETH (Ethereum) -> BNB (BNB)</p>   | <p>if Y/3 > 0.2%</p><ul><li>B (host): 0.2%</li><li>A (source): (Y - 0.2) / 2</li><li>C (destination): (Y - 0.2) / 2</li></ul><p>else</p><ul><li>B (host): Y / 3</li><li>A (source): Y / 3</li><li>C (destination): Y / 3</li></ul> |

**Note:**

* A maximum of 0.2 % is reserved for the host-chain on-chain swap (B).

**Example:**

ETH (Ethereum) -> BNB (BNB), Y = 1.5%

* **A (source):** 0.65%
* **B (host):** 0.2%
* **C (destination):** 0.65%

### Auto Slippage Mode

{% hint style="info" %}
This feature is currently under development. Detailed parameters and calculation logic will be documented after release.
{% endhint %}

If the slippage tolerance value is not specified for a cross-chain swap, Symbiosis will apply an auto slippage mode.

In this mode, the slippage tolerance is determined dynamically based on the current on-chain market conditions and liquidity depth for each leg of the swap.

<br>


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