diff --git a/AGENTS.md b/AGENTS.md
index b64555fe1a..96014fa1f3 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -48,12 +48,12 @@ website/              # demo site (Vite + TanStack Router)
 - **Light/dark mode** — handled via CSS `light-dark()` + `color-scheme`, not JS.
 - **Accessibility first** — ARIA attributes (e.g. `aria-colindex`, `aria-rowindex`, `aria-selected`, roles) are required. Tests query by role.
 - **Formatting** — oxfmt (not Prettier). **Linting** — ESLint (must pass with zero warnings).
-- **Build** — Rolldown bundles library to `lib/`; `ecij` plugin prefixes classes with `rdg-{version}-` (dots→dashes) to avoid cross-version conflicts.
+- **Build** — tsdown bundles library to `lib/`; `ecij` plugin prefixes classes with `rdg-{version}-` (dots→dashes) to avoid cross-version conflicts.
 
 ## Testing
 
-- Browser tests use `vitest/browser` + Playwright. `test/setupBrowser.ts` configures `page.render()` via `vitest-browser-react` and registers custom locators via `locators.extend()` — prefer `page.getGrid()`, `page.getCell({ name })`, `page.getRow()`, `page.getHeaderCell()`, `page.getSelectedCell()`, etc. over raw `page.getByRole()`.
-- Test helpers in `test/browser/utils.tsx`: `setup()`, `getRowWithCell()`, `getCellsAtRowIndex()`, `validateCellPosition()`, `scrollGrid()`, `tabIntoGrid()`, `testCount()`, `testRowCount()`.
+- Browser tests use `vitest/browser` + Playwright. `test/setupBrowser.ts` configures `page.render()` via `vitest-browser-react` and registers custom locators via `locators.extend()` — prefer `page.getGrid()`, `page.getCell({ name })`, `page.getRow()`, `page.getHeaderCell()`, `page.getActiveCell()`, etc. over raw `page.getByRole()`.
+- Test helpers in `test/browser/utils.tsx`: `setup()`, `getRowWithCell()`, `getCellsAtRowIndex()`, `validateCellPosition()`, `scrollGrid()`, `safeTab()`, `testCount()`, `testRowCount()`.
 - `test/failOnConsole.ts` fails tests on unexpected console warnings/errors.
 - **Never run visual regression tests** — screenshots are environment-dependent so visual regression tests must run in CI only.
 
diff --git a/package.json b/package.json
index da1256623f..9e94431d6b 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "start": "vite serve --clearScreen false",
     "preview": "vite preview",
     "build:website": "vite build",
-    "build": "rolldown -c",
+    "build": "tsdown",
     "test": "vitest run --project browser --project node",
     "test:watch": "vitest watch --project browser --project node",
     "test:ci": "vitest run",
@@ -52,6 +52,7 @@
     "@faker-js/faker": "^10.3.0",
     "@tanstack/react-router": "^1.166.7",
     "@tanstack/router-plugin": "^1.166.7",
+    "@tsdown/css": "^0.21.7",
     "@types/node": "^25.5.0",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
@@ -73,8 +74,7 @@
     "postcss": "^8.5.2",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
-    "rolldown": "1.0.0-rc.5",
-    "rolldown-plugin-dts": "^0.22.5",
+    "tsdown": "^0.21.7",
     "typescript": "~6.0.1-rc",
     "typescript-eslint": "^8.57.0",
     "vite": "^8.0.0",
diff --git a/tsconfig.vite.json b/tsconfig.vite.json
index 54f86f05d6..57b2050a8e 100644
--- a/tsconfig.vite.json
+++ b/tsconfig.vite.json
@@ -4,5 +4,5 @@
     "lib": ["ESNext", "DOM"],
     "skipLibCheck": true
   },
-  "include": ["package.json", "rolldown.config.ts", "vite.config.ts"]
+  "include": ["package.json", "tsdown.config.ts", "vite.config.ts"]
 }
diff --git a/rolldown.config.ts b/tsdown.config.ts
similarity index 50%
rename from rolldown.config.ts
rename to tsdown.config.ts
index 23394ef5af..ac943e1849 100644
--- a/rolldown.config.ts
+++ b/tsdown.config.ts
@@ -1,28 +1,27 @@
-import { isAbsolute } from 'node:path';
 import { ecij } from 'ecij/plugin';
-import { defineConfig } from 'rolldown';
-import { dts } from 'rolldown-plugin-dts';
+import { defineConfig } from 'tsdown';
 
 import pkg from './package.json' with { type: 'json' };
 
 export default defineConfig({
-  input: './src/index.ts',
-  output: {
-    dir: 'lib',
-    cssEntryFileNames: 'styles.css',
-    sourcemap: true,
-    cleanDir: true
-  },
+  outDir: 'lib',
   platform: 'neutral',
-  external: (id) => !id.startsWith('.') && !isAbsolute(id),
+  sourcemap: true,
+  deps: {
+    skipNodeModulesBundle: true
+  },
+  css: {
+    fileName: 'styles.css'
+  },
+  dts: {
+    build: true,
+    tsconfig: './tsconfig.src.json'
+  },
   plugins: [
     ecij({
       // We add the package version as prefix to avoid style conflicts
       // between multiple versions of RDG on the same page
       classPrefix: `rdg-${pkg.version.replaceAll('.', '-')}-`
-    }),
-    dts({
-      tsconfig: './tsconfig.src.json'
     })
   ]
 });