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

# tools.tsChecker

- **Type:** `Object | Function`
- **Default:**

```js
const defaultOptions = {
  typescript: {
    // avoid OOM issue
    memoryLimit: 8192,
    // use tsconfig of user project
    configFile: tsconfigPath,
    // use TypeScript Go checker by default
    tsgo: true,
    // use TS-Go native preview of user project
    typescriptPath: require.resolve('typescript/package.json'),
  },
  issue: {
    exclude: [
      { file: '**/*.(spec|test).ts' },
      { file: '**/node_modules/**/*' },
    ],
  },
  logger: {
    log() {
      // do nothing
      // we only want to display error messages
    },
    error(message: string) {
      console.error(message.replace(/ERROR/g, 'Type Error'));
    },
  },
},
```

By default, the [@rsbuild/plugin-type-check](https://github.com/rstackjs/rsbuild-plugin-type-check) is enabled for type checking. You can use `output.disableTsChecker` config to disable it.

## Example

### Object Type

When the value of `tsChecker` is an object, it will be deeply merged with the default configuration.

```ts
export default {
  tools: {
    tsChecker: {
      issue: {
        exclude: [({ file = '' }) => /[\\/]some-folder[\\/]/.test(file)],
      },
    },
  },
};
```

### Function Type

When the value of `tsChecker` is a function, the default configuration will be passed as the first argument. You can directly modify the configuration object or return an object as the final configuration.

```ts
export default {
  tools: {
    tsChecker(options) {
      options.async = false;
      return options;
    },
  },
};
```

> Please refer to [@rsbuild/plugin-type-check](https://github.com/rstackjs/rsbuild-plugin-type-check) for more details.

## TypeScript Go by Default

Type checking runs on [TypeScript Go](https://github.com/microsoft/typescript-go) (`tsgo`) by default in this fork. The capability is provided by [`ts-checker-rspack-plugin`](https://github.com/rstackjs/ts-checker-rspack-plugin), which is integrated by [`@rsbuild/plugin-type-check`](https://github.com/rstackjs/rsbuild-plugin-type-check), and reduces type-checking time by about 5-10x.

Modern.js prefers the project's stable `typescript` package when it is TypeScript 7 or newer, and falls back to `@typescript/native-preview` for projects still on the preview lane. To pin stable TypeScript 7, install it in your project:


```sh [npm]
npm install typescript -D
```

```sh [yarn]
yarn add typescript -D
```

```sh [pnpm]
pnpm add typescript -D
```

```sh [bun]
bun add typescript -D
```

```sh [deno]
deno add npm:typescript -D
```

When `tsgo` is enabled, the default `typescript.typescriptPath` resolves to `typescript/package.json` for TypeScript 7 projects. If you manually set `typescript.typescriptPath`, it must be an absolute path to `typescript/package.json` or `@typescript/native-preview/package.json`.

To fall back to the classic TypeScript checker, set `typescript.tsgo` to `false` and make sure `typescript` is installed in your project:

```ts
export default {
  tools: {
    tsChecker: {
      typescript: {
        tsgo: false,
      },
    },
  },
};
```

For supported options and limitations, please refer to [ts-checker-rspack-plugin - TypeScript Go support](https://github.com/rstackjs/ts-checker-rspack-plugin#typescript-go-support).