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

# performance

## performance.buildCache [![performance.buildCache](https://assets.rspack.rs/rsbuild/rsbuild-logo.svg)performance.buildCache](https://rsbuild.rs/config/performance/build-cache)

[Added in v0.10.0](https://github.com/web-infra-dev/rstest/releases/tag/v0.10.0)

- **Type:**

```ts
type BuildCacheConfig =
  | boolean
  | {
      cacheDirectory?: string;
      cacheDigest?: Array<string | undefined>;
      buildDependencies?: string[];
    };
```

- **Default:** `false`

Enables Rsbuild persistent build cache for Rstest test builds.

:::tip
Rspack's persistent cache is still experimental and may change across versions, so Rstest does not enable `performance.buildCache` by default.
:::

```ts title="rstest.config.ts"
import { defineConfig } from '@rstest/core';

export default defineConfig({
  performance: {
    buildCache: true,
  },
});
```

When enabled, Rstest applies a few Rstest-specific defaults to keep the cache stable across runs:

- `cacheDirectory` defaults to the `node_modules/.cache/rstest-<project-name>` base directory under the active project root. Rspack stores the cache data under `<cacheDirectory>/<cache.name>`, so projects that share the same root still get isolated caches.
- `cacheDigest` automatically includes Rstest runtime inputs such as command, environment name, browser-vs-node mode.
- `buildDependencies` automatically includes the active Rstest config file, project config files, and discovered `tsconfig` paths when available.

You can customize these fields to override or extend the defaults:

- `cacheDirectory`: **override**. When you provide it, Rstest uses it as the base directory; the final cache location is `<cacheDirectory>/<cache.name>`.
- `cacheDigest`: **extend**. Rstest keeps its own runtime digest entries and appends your custom values after them.
- `buildDependencies`: **extend**. Rstest keeps its own dependency files and appends your custom files after resolving relative paths from the active config file directory.

For example:

```ts title="rstest.config.ts"
import { defineConfig } from '@rstest/core';

export default defineConfig({
  performance: {
    buildCache: {
      cacheDirectory: '.cache/rstest/browser',
      cacheDigest: [process.env.CUSTOM_ENV],
      buildDependencies: ['./scripts/test-env.ts'],
    },
  },
});
```