> [!IMPORTANT]
> **This is a minor release.** Two changes alter default behavior compared to `1.0.3`. Please read this section before upgrading. Everything else is additive (new features, fixes, deps).

## ⚠️ Notable behavior changes

### 1. `experimental.lazyBarrel` is now enabled by default (#9632)

**What changed.** `experimental.lazyBarrel` now defaults to `true`. When a barrel module is recognized as side-effect-free, Rolldown skips compiling the re-exported modules that are never actually used.

**Impact.** For codebases with large barrel files (component libraries such as Ant Design, `@mui/icons-material`, etc.) this is a meaningful build-time speedup, and for the vast majority of projects the emitted output is unchanged. In rare cases where a barrel is *incorrectly* treated as side-effect-free, the optimization could drop a module that was being relied on for its side effects.

**How to opt out (backward compatible).**

```js
// rolldown.config.js
export default {
  experimental: { lazyBarrel: false },
}
```

> Note: this opt-out flag is planned to be removed in a future release. If you have a case where you must turn it off, please open an issue so we can fix the underlying detection instead.

---

### 2. `tsconfig` project-reference resolution now aligns with TypeScript

Upgrading `oxc_resolver` (`11.19.1` → `11.20.0` in #9549, then `→ 11.21.0` in #9634) changes how a *solution-style* `tsconfig.json` (one that only lists `references` and delegates the real settings to `tsconfig.app.json` / `tsconfig.node.json`, as Vite scaffolds) is resolved, bringing it **in line with how TypeScript (`tsc`) itself behaves**:

- **Reference match priority** (oxc-resolver [#1151](oxc-project/oxc-resolver#1151)): when the root has `references`, a referenced project that includes the file now **takes precedence over the root**, instead of the root matching it first (this is what TypeScript already does). So that project's `compilerOptions.paths` now apply.
- **`allowJs`** (oxc-resolver [#1198](oxc-project/oxc-resolver#1198)): whether a `.js`/`.jsx`/`.mjs`/`.cjs` file is included is now decided by **each referenced project's own** `allowJs`, not the root's (again matching TypeScript). So `tsconfig.app.json` with `allowJs: true` + `paths` now resolves aliases for `.js` files even when the root doesn't set `allowJs`.

For most projects this is a fix (the standard Vite `paths` aliases now resolve, closes #8468), but it **is** a behavior change if you relied on the previous behavior, where the root's `paths` / `allowJs` took precedence.

**If you relied on the old "root wins" behavior.** There is no exact toggle back, because the old behavior was the bug being fixed. The recommended path is to align your config with TypeScript: declare the `paths` / `allowJs` on the referenced project that actually owns the files.

If you must keep the old precedence while still using `references`: a referenced project's match wins, and **the first matching `references` entry takes priority** (the root is only a fallback when no reference claims the file). So extract the old root settings into their own config and list it **first**:

```jsonc
// tsconfig.json (solution root)
{
  "files": [],
  "references": [
    { "path": "./tsconfig.base.json" }, // old root paths/allowJs — listed first, so it wins
    { "path": "./tsconfig.app.json" },
    { "path": "./tsconfig.node.json" }
  ]
}
```

`tsconfig.base.json` should carry the `paths` you previously declared on the root, plus `allowJs: true` if it needs to claim `.js` files (the extension is checked against each config's own `allowJs`). With no `include`, it defaults to `**/*` under its directory and claims every file first.

Alternatively, bypass reference resolution entirely by pointing the top-level `tsconfig` option at a single config: `export default { tsconfig: './tsconfig.app.json' }`.

---

## [1.1.0] - 2026-06-03

### 🚀 Features

- enable `experimental.lazyBarrel` by default (#9632) by @shulaoda
- `import.meta.glob` support `caseSensitive` option (#9594) by @btea
- add `SOURCEMAP_BROKEN` warning for renderChunk hook (#9601) by @sapphi-red
- add `SOURCEMAP_BROKEN` warning for transform hook (#9600) by @sapphi-red
- add `@__NO_SIDE_EFFECTS__` hint for invalid `@__PURE__` before function declarations (#9505) by @Copilot
- code-splitting: support group-local `includeDependenciesRecursively` (#9587) by @hyf0

### 🐛 Bug Fixes

- report TSCONFIG_ERROR instead of UNHANDLEABLE_ERROR for a missing tsconfig file (#9633) by @shulaoda
- browser: add missing exports and ensure consistency with `rolldown` package (#9629) by @sapphi-red
- should build test-dev-server when test-node (#9610) by @situ2001
- chunk-optimizer: refuse asymmetric merge for cyclic dynamic entries (#9320) (#9322) by @aminpaks
- dev: handle the remaining errors in dev (#9570) by @h-a-n-a
- handle slash-normalized ids with preserveModulesRoot (#9595) by @IWANABETHATGUY
- json: preserve .default access on JSON default imports (#9568) by @IWANABETHATGUY
- testing: remove unintended trigger_full_build from test harness (#9573) by @hyf0

### 🚜 Refactor

- js-regex: use regress native replace/replace_all (#9607) by @IWANABETHATGUY
- remove never-constructed `ImportStatus` variants (#9606) by @Boshen

### 📚 Documentation

- clarify that `RolldownBuild::close` method should be called in most cases (#9619) by @sapphi-red

### ⚡ Performance

- avoid unnecessary intermediate sourcemaps (#9599) by @sapphi-red

### 🧪 Testing

- add unit test for collapsing module sourcemap (#9626) by @sapphi-red
- cover vite-alias regex capture-group expansion (#9602) (#9608) by @IWANABETHATGUY

### ⚙️ Miscellaneous Tasks

- deps: update oxc_resolver to 11.21.0 (#9634) by @shulaoda
- update invalid option diagnostic link to point to Rolldown docs (#9631) by @sapphi-red
- deps: update vite+ to v0.1.24 (#9628) by @renovate[bot]
- deps: update oxc resolver to v11.20.0 (#9549) by @renovate[bot]
- deps: update dependency vite-plus to v0.1.24 (#9470) by @renovate[bot]
- deps: update npm packages (#9614) by @renovate[bot]
- deps: upgrade oxc to 0.134.0 (#9625) by @shulaoda
- deps: update crate-ci/typos action to v1.47.0 (#9620) by @renovate[bot]
- deps: update rollup submodule for tests to v4.61.0 (#9623) by @rolldown-guard[bot]
- deps: update github actions (#9613) by @renovate[bot]
- deps: update pnpm to v11.4.0 (#9616) by @renovate[bot]
- deps: update rust crates (#9615) by @renovate[bot]
- deps: update test262 submodule for tests (#9624) by @rolldown-guard[bot]
- deps: update dependency @napi-rs/cli to v3.7.0 (#9588) by @renovate[bot]
- deps: update dependency rust to v1.96.0 (#9596) by @renovate[bot]
- re-enable WASI testing with proper infrastructure (#9397) by @Boshen

### ❤️ New Contributors

* @aminpaks made their first contribution in [#9322](#9322)

Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>