> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt.

# tools.bundlerChain

- **Type:**

```ts
type BundlerChainFn = (
  chain: RspackChain,
  utils: ModifyBundlerChainUtils,
) => Promise<void> | void;
```

- **Default:** `undefined`

You can modify the Rspack configuration by configuring `tools.bundlerChain` which is type of `Function`. The function receives two parameters, the first is the original bundler chain object, and the second is an object containing some utils.

:::tip What is BundlerChain

Bundler chain is a chainable configuration tool implemented based on the Rspack configuration API, which you can use to modify Rspack configuration.

Configurations modified via bundler chain will work on Rspack builds.

:::

> `tools.bundlerChain` is executed earlier than tools.rspack and thus will be overridden by changes in tools.rspack.

For more information, please refer to [Rsbuild#tools.bundlerChain](https://v2.rsbuild.rs/config/tools/bundler-chain).