> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-docs-add-b20-spec.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Working with base-std

> Install base-std and use StdPrecompiles, B20Constants, interfaces, and helper libraries for B20 development.

`base-std` is the Solidity source of truth for B20 interfaces, constants, factory encoders, and test mocks.

## Install

```bash theme={null}
forge install base/base-std
```

Add remappings for source and test helpers:

```toml foundry.toml theme={null}
remappings = [
  "base-std/=lib/base-std/src/",
  "base-std-test/=lib/base-std/test/"
]
```

Interfaces target `>=0.8.20 <0.9.0`. Reference implementations and tests in `base-std` pin Solidity `0.8.30`.

## Use StdPrecompiles

`StdPrecompiles.sol` exposes fixed precompile addresses and typed handles.

```solidity theme={null}
import {StdPrecompiles} from "base-std/StdPrecompiles.sol";
import {IB20Factory} from "base-std/interfaces/IB20Factory.sol";

address predicted = StdPrecompiles.B20_FACTORY.getB20Address(
    IB20Factory.B20Variant.ASSET,
    deployer,
    salt
);
```

## Use canonical constants

Use `B20Constants.sol` instead of redefining role and scope hashes.

```solidity theme={null}
import {B20Constants} from "base-std/lib/B20Constants.sol";

bytes32 mintRole = B20Constants.MINT_ROLE;
bytes32 mintScope = B20Constants.MINT_RECEIVER_POLICY;
```

## Where things live

| Path                        | Purpose                                                        |
| --------------------------- | -------------------------------------------------------------- |
| `src/StdPrecompiles.sol`    | Fixed precompile addresses and typed handles                   |
| `src/interfaces/`           | Solidity interfaces for B20, variants, factory, and registries |
| `src/lib/B20Constants.sol`  | Role, policy-scope, feature, decimal, and supply-cap constants |
| `src/lib/B20FactoryLib.sol` | Pure encoders for factory params and initCalls                 |
| `test/lib/mocks/`           | Solidity mocks for stock Foundry tests                         |

## What not to do

* Do not hardcode precompile addresses in application code when `StdPrecompiles` is available.
* Do not copy interface files into your repo; import them to avoid version skew.
* Do not assume explorer verification exists for B20 precompile token addresses.
* Do not use stock `forge` alone when your test expects live precompile behavior.

<CardGroup cols={2}>
  <Card title="Testing against precompiles" href="/base-chain/specs/upgrades/beryl/b20/specification/implementation/testing-against-precompiles" />

  <Card title="Constants & addresses" href="/base-chain/specs/upgrades/beryl/b20/specification/reference/constants-and-addresses" />
</CardGroup>