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

# Perpetual Stable Swap API

> API reference for the Perpetual Stable Swap programmatic order type for automated stablecoin rebalancing.

# Perpetual Stable Swap API

The Perpetual Stable Swap is a programmatic order type that automatically provides liquidity for swapping between two stable tokens at a 1:1 exchange rate. It operates as an automated market maker that dynamically determines which token to sell based on the owner's current holdings.

## Key Parameters

| Parameter               | Description                                                     |
| ----------------------- | --------------------------------------------------------------- |
| `tokenA` / `tokenB`     | The two tokens eligible for perpetual swapping                  |
| `validityBucketSeconds` | Time window width (recommended 1-2 weeks) for order consistency |
| `halfSpreadBps`         | Markup percentage applied to maintain pricing parity            |
| `appData`               | Custom metadata passed during settlement                        |

## Operational Logic

The `getTradeableOrder` function executes the following workflow:

1. Compares owner balances of both tokens after decimal normalization
2. Identifies which token has greater value
3. Creates a sell order for the entire balance of the higher-value token
4. Applies the spread formula:
   ```
   buyAmount = convertedAmount * (10000 + halfSpreadBps) / 10000
   ```
5. Returns tokens to the owner automatically (`receiver = address(0)`)

## Error Handling

Orders fail with "not funded" messaging when the sell amount equals zero, indicating zero balance in the designated selling token.

## Design Considerations

* Orders utilize time-bucketing to prevent orderbook spam
* Remain non-partially-fillable
* Charge zero protocol fees
* The spread parameter prevents order collision unless intentionally set to zero