> ## 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

> Automatic rebalancing between two stablecoins by continuously trading whichever token has higher balance.

# Perpetual Stable Swap

This programmatic order type enables automatic rebalancing between two stablecoins by continuously trading whichever token you hold more of. The mechanism adds a configurable spread to generate profit from rebalancing activities.

## Core Mechanism

The contract examines your holdings of both tokens and creates sell orders for whichever asset represents the larger balance. The trade targets balance equilibrium while applying a half-spread markup to the exchange rate.

## Configuration Parameters

| Parameter               | Description                                                                                                                  |
| ----------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| `tokenA` / `tokenB`     | The two assets for swapping, typically stablecoins like USDC and DAI                                                         |
| `validityBucketSeconds` | Controls order validity duration by bucketing time into fixed windows. Recommended: 604800 (one week) or 1209600 (two weeks) |
| `halfSpreadBps`         | Basis point markup above 1:1 parity. 10 = 0.1% markup, 100 = 1% markup                                                       |
| `appData`               | IPFS hash associated with the order                                                                                          |

### Validity Bucket Calculation

```
validTo = ((currentTime / validityBucketSeconds) * validityBucketSeconds) + validityBucketSeconds
```

### Buy Amount Formula

```
buyAmount = convertAmount(sellAmount) * (10000 + halfSpreadBps) / 10000
```

## Operational Logic

### Balance Assessment and Token Selection

The contract retrieves both token balances, normalizes them to a common decimal standard, then determines which token exceeds the other. The excess token becomes the sell asset.

### Decimal Handling

Different token decimals receive automatic conversion. For example, converting 1000 USDC (6 decimals) to DAI (18 decimals):

```
1000 * 10^6 * 10^(18-6) = 1000 * 10^18
```

### Key Order Characteristics

* Orders are always sell-type (`KIND_SELL`)
* Partial fills are disabled
* No protocol fees apply
* Receiver defaults to `address(0)`, which routes tokens back to the owner

## Validation

The system rejects orders where `NOT_FUNDED` occurs -- meaning zero sell amount due to missing balance of the required token.

## Practical Applications

### Liquidity Provision

Maintain equal stablecoin amounts while automatically rebalancing as supplies deplete, earning spread on each trade.

### Yield Capture

Exploit minor stablecoin peg deviations with modest spreads (0.1-0.5%) while maintaining original position exposure.

### Portfolio Diversification

Distribute holdings across multiple stablecoins with automatic equilibration to mitigate single-asset depeg risk.

## Implementation Note

The validity bucket system ensures identical `orderUid` values when queried within the same time window, preventing orderbook spam on CoW Protocol.