> For the complete documentation index, see [llms.txt](https://docs.osero.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.osero.com/osero-sdk/core-concepts/supported-chains.md).

# Supported Chains

`@osero/client` maintains a registry of all supported chains, token addresses, and PSM contract addresses. These are exported from the package root and can be used directly in your application.

***

## Supported chains

| Chain            | Chain ID | PSM contract                                | Status |
| ---------------- | -------- | ------------------------------------------- | ------ |
| Ethereum Mainnet | 1        | Spark `UsdsPsmWrapper` (wraps Sky Lite PSM) | Live   |
| OP Mainnet       | 10       | Spark PSM3                                  | Live   |
| Unichain         | 130      | Spark PSM3                                  | Live   |
| Base             | 8453     | Spark PSM3                                  | Live   |
| Arbitrum One     | 42161    | Spark PSM3                                  | Live   |

Additional chains (Avalanche and others) will be added in future `@osero/client` releases once Sky/Spark deploy their PSM stack to them. Adding a chain requires an SDK upgrade — `SUPPORTED_CHAIN_IDS`, the chain registry, the token registry, and `PSM_ADDRESSES` are all source-of-truth inside the package.

***

## Routing by chain

The SDK routes differently depending on the target chain:

**Ethereum Mainnet** uses Sky's `UsdsPsmWrapper`, which is a wrapper around the original Maker/Sky PSM. Minting sUSDS on mainnet is a two-phase operation: USDC → USDS via the wrapper, then USDS → sUSDS via the ERC-4626 sUSDS vault.

**All L2 chains** use the Spark PSM3, which supports direct USDC → sUSDS swaps in a single operation. This makes L2 minting and redemption simpler and cheaper in terms of transaction count.

***

## Accessing chain and contract data

All addresses are re-exported from the package root:

```typescript
import {
  SUPPORTED_CHAIN_IDS,
  CHAINS,
  PSM_ADDRESSES,
  getToken,
} from '@osero/client';

// List of all supported chain IDs
console.log(SUPPORTED_CHAIN_IDS);
// [1, 10, 130, 8453, 42161]

// PSM contract address on Base
console.log(PSM_ADDRESSES[8453].psm);

// sUSDS token address on Ethereum Mainnet
console.log(getToken(1, 'sUSDS').address);

// USDC token address on Arbitrum One
console.log(getToken(42161, 'USDC').address);
```

***

## Token decimals reference

| Token | Decimals | Notes                                         |
| ----- | -------- | --------------------------------------------- |
| USDC  | 6        | Input token for all mint actions              |
| USDS  | 18       | Output of `mintUsds`; input of `redeemUsds`   |
| sUSDS | 18       | Output of `mintSUsds`; input of `redeemSUsds` |

Always use `parseUnits` and `formatUnits` from viem (or equivalent) when converting between human-readable amounts and the raw `bigint` values the SDK expects.

```typescript
import { parseUnits, formatUnits } from 'viem';

// Preparing an input amount
const amount = parseUnits('100', 6); // 100 USDC → 100_000_000n

// Formatting an output amount for display
const humanReadable = formatUnits(rawSUsdsBalance, 18);
```

***

## Chain-specific notes

### Ethereum Mainnet (Chain ID: 1)

* Routes through Sky's `UsdsPsmWrapper` contract
* `mintSUsds` is a four-transaction, two-phase `MultiStepExecution`
* `redeemSUsds` is a three-transaction, two-phase `MultiStepExecution`
* Higher gas costs than L2s; consider user experience implications

### Base (Chain ID: 8453)

* Routes through Spark PSM3
* All operations are two-transaction `Erc20ApprovalRequired` plans
* Recommended chain for most consumer-facing integrations due to low fees and fast finality

### Arbitrum One (Chain ID: 42161)

* Routes through Spark PSM3
* Two-transaction plans for all operations
* Low fees; suitable for both retail and institutional use cases

### OP Mainnet (Chain ID: 10)

* Routes through Spark PSM3
* Two-transaction plans for all operations

### Unichain (Chain ID: 130)

* Routes through Spark PSM3
* Two-transaction plans for all operations


---

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