diff --git a/packages/layout-engine/contracts/bunfig.toml b/packages/layout-engine/contracts/bunfig.toml
new file mode 100644
index 0000000000..26aaecdbf6
--- /dev/null
+++ b/packages/layout-engine/contracts/bunfig.toml
@@ -0,0 +1,3 @@
+[test]
+timeout = 5000
+preload = ["./happydom.ts"]
diff --git a/packages/layout-engine/contracts/happydom.ts b/packages/layout-engine/contracts/happydom.ts
new file mode 100644
index 0000000000..099c99efcc
--- /dev/null
+++ b/packages/layout-engine/contracts/happydom.ts
@@ -0,0 +1,13 @@
+import { Window } from 'happy-dom';
+
+const window = new Window();
+
+// Register globals
+Object.assign(globalThis, {
+  window,
+  document: window.document,
+  HTMLElement: window.HTMLElement,
+  Element: window.Element,
+  Node: window.Node,
+  Blob: window.Blob,
+});
diff --git a/packages/layout-engine/contracts/package.json b/packages/layout-engine/contracts/package.json
index 4d6afd8aba..ce9bff2cf7 100644
--- a/packages/layout-engine/contracts/package.json
+++ b/packages/layout-engine/contracts/package.json
@@ -15,6 +15,9 @@
   },
   "scripts": {
     "build": "tsc --project tsconfig.json",
-    "test": "vitest run"
+    "test": "bun test"
+  },
+  "devDependencies": {
+    "happy-dom": "catalog:"
   }
 }
diff --git a/packages/layout-engine/contracts/src/engines/__tests__/image-wrap.test.ts b/packages/layout-engine/contracts/src/engines/__tests__/image-wrap.test.ts
index b71c008152..bc20eaf162 100644
--- a/packages/layout-engine/contracts/src/engines/__tests__/image-wrap.test.ts
+++ b/packages/layout-engine/contracts/src/engines/__tests__/image-wrap.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { computeWrapExclusion, scaleWrapPolygon } from '../image-wrap.js';
 
 describe('engines-image-wrap scaleWrapPolygon', () => {
diff --git a/packages/layout-engine/contracts/src/engines/__tests__/lists.test.ts b/packages/layout-engine/contracts/src/engines/__tests__/lists.test.ts
index bf7981e4a5..b0d1a80c42 100644
--- a/packages/layout-engine/contracts/src/engines/__tests__/lists.test.ts
+++ b/packages/layout-engine/contracts/src/engines/__tests__/lists.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { computeListIndent, formatListLabel } from '../lists.js';
 
 describe('engines-lists formatListLabel', () => {
diff --git a/packages/layout-engine/contracts/src/engines/__tests__/paragraph.test.ts b/packages/layout-engine/contracts/src/engines/__tests__/paragraph.test.ts
index 7235d2537a..5125898c95 100644
--- a/packages/layout-engine/contracts/src/engines/__tests__/paragraph.test.ts
+++ b/packages/layout-engine/contracts/src/engines/__tests__/paragraph.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { resolveSpacingIndent } from '../paragraph.js';
 
 describe('engines-paragraph resolveSpacingIndent', () => {
diff --git a/packages/layout-engine/contracts/src/engines/tabs.test.ts b/packages/layout-engine/contracts/src/engines/tabs.test.ts
index 427d1abc36..fb568f323f 100644
--- a/packages/layout-engine/contracts/src/engines/tabs.test.ts
+++ b/packages/layout-engine/contracts/src/engines/tabs.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { calculateTabWidth, computeTabStops, layoutWithTabs } from './tabs.js';
 
 describe('engines-tabs computeTabStops', () => {
diff --git a/packages/layout-engine/contracts/src/index.test.ts b/packages/layout-engine/contracts/src/index.test.ts
index 4f53d4f237..57a0ad2304 100644
--- a/packages/layout-engine/contracts/src/index.test.ts
+++ b/packages/layout-engine/contracts/src/index.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { extractHeaderFooterSpace } from './index.js';
 import type { FlowBlock, Layout, PainterDOM, PainterPDF } from './index.js';
 
diff --git a/packages/layout-engine/contracts/src/justify-utils.test.ts b/packages/layout-engine/contracts/src/justify-utils.test.ts
index 57943fcdd7..0cc32c505d 100644
--- a/packages/layout-engine/contracts/src/justify-utils.test.ts
+++ b/packages/layout-engine/contracts/src/justify-utils.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import {
   SPACE_CHARS,
   shouldApplyJustify,
diff --git a/packages/layout-engine/contracts/src/pm-range.test.ts b/packages/layout-engine/contracts/src/pm-range.test.ts
index 2b5991cbcd..a5493d67c3 100644
--- a/packages/layout-engine/contracts/src/pm-range.test.ts
+++ b/packages/layout-engine/contracts/src/pm-range.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { computeFragmentPmRange, computeLinePmRange } from './index.js';
 import type { Line, ParagraphBlock } from './index.js';
 
diff --git a/packages/layout-engine/contracts/vitest.config.mjs b/packages/layout-engine/contracts/vitest.config.mjs
deleted file mode 100644
index 29bb879cd9..0000000000
--- a/packages/layout-engine/contracts/vitest.config.mjs
+++ /dev/null
@@ -1,11 +0,0 @@
-import { defineConfig } from 'vitest/config';
-import baseConfig from '../../../vitest.baseConfig';
-
-export default defineConfig({
-  ...baseConfig,
-  test: {
-    // Use happy-dom for faster tests (set VITEST_DOM=jsdom to use jsdom)
-    environment: process.env.VITEST_DOM || 'happy-dom',
-    include: ['src/**/*.test.ts']
-  }
-});
diff --git a/packages/layout-engine/geometry-utils/bunfig.toml b/packages/layout-engine/geometry-utils/bunfig.toml
new file mode 100644
index 0000000000..554f6fb8f2
--- /dev/null
+++ b/packages/layout-engine/geometry-utils/bunfig.toml
@@ -0,0 +1,2 @@
+[test]
+timeout = 5000
diff --git a/packages/layout-engine/geometry-utils/package.json b/packages/layout-engine/geometry-utils/package.json
index fbb768d626..b86c219657 100644
--- a/packages/layout-engine/geometry-utils/package.json
+++ b/packages/layout-engine/geometry-utils/package.json
@@ -10,10 +10,9 @@
   },
   "scripts": {
     "build": "tsc --project tsconfig.json --noEmit",
-    "test": "vitest run"
+    "test": "bun test"
   },
   "devDependencies": {
-    "typescript": "catalog:",
-    "vitest": "catalog:"
+    "typescript": "catalog:"
   }
 }
diff --git a/packages/layout-engine/geometry-utils/src/index.test.ts b/packages/layout-engine/geometry-utils/src/index.test.ts
index 6e89685be0..5faebbb0a6 100644
--- a/packages/layout-engine/geometry-utils/src/index.test.ts
+++ b/packages/layout-engine/geometry-utils/src/index.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import {
   applyMatrix,
   calculateRotatedBounds,
diff --git a/packages/layout-engine/geometry-utils/vitest.config.mjs b/packages/layout-engine/geometry-utils/vitest.config.mjs
deleted file mode 100644
index 2368bd9853..0000000000
--- a/packages/layout-engine/geometry-utils/vitest.config.mjs
+++ /dev/null
@@ -1,10 +0,0 @@
-import { defineConfig } from 'vitest/config';
-import baseConfig from '../../../vitest.baseConfig';
-
-export default defineConfig({
-  ...baseConfig,
-  test: {
-    environment: 'node',
-    include: ['src/**/*.test.ts']
-  }
-});
diff --git a/packages/layout-engine/style-engine/bunfig.toml b/packages/layout-engine/style-engine/bunfig.toml
new file mode 100644
index 0000000000..554f6fb8f2
--- /dev/null
+++ b/packages/layout-engine/style-engine/bunfig.toml
@@ -0,0 +1,2 @@
+[test]
+timeout = 5000
diff --git a/packages/layout-engine/style-engine/package.json b/packages/layout-engine/style-engine/package.json
index 0ec8a00212..fc89ed4b48 100644
--- a/packages/layout-engine/style-engine/package.json
+++ b/packages/layout-engine/style-engine/package.json
@@ -17,14 +17,13 @@
   },
   "scripts": {
     "build": "tsc --project tsconfig.json --noEmit",
-    "test": "vitest run"
+    "test": "bun test"
   },
   "dependencies": {
     "@superdoc/contracts": "workspace:*",
     "@superdoc/font-utils": "workspace:*"
   },
   "devDependencies": {
-    "typescript": "catalog:",
-    "vitest": "catalog:"
+    "typescript": "catalog:"
   }
 }
diff --git a/packages/layout-engine/style-engine/src/cascade.test.ts b/packages/layout-engine/style-engine/src/cascade.test.ts
index b9940714ee..470d3e705e 100644
--- a/packages/layout-engine/style-engine/src/cascade.test.ts
+++ b/packages/layout-engine/style-engine/src/cascade.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import { combineProperties, combineRunProperties, combineIndentProperties } from './cascade.js';
 
 describe('cascade - combineProperties', () => {
diff --git a/packages/layout-engine/style-engine/src/index.test.ts b/packages/layout-engine/style-engine/src/index.test.ts
index f21034729c..1188a62646 100644
--- a/packages/layout-engine/style-engine/src/index.test.ts
+++ b/packages/layout-engine/style-engine/src/index.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it, beforeEach } from 'vitest';
+import { describe, expect, it, beforeEach } from 'bun:test';
 import { resolveSdtMetadata, clearSdtMetadataCache } from './index.js';
 
 describe('resolveSdtMetadata', () => {
diff --git a/packages/layout-engine/style-engine/src/ooxml/index.test.ts b/packages/layout-engine/style-engine/src/ooxml/index.test.ts
index d47944ae13..0022013d48 100644
--- a/packages/layout-engine/style-engine/src/ooxml/index.test.ts
+++ b/packages/layout-engine/style-engine/src/ooxml/index.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 import {
   resolveStyleChain,
   getNumberingProperties,
diff --git a/packages/layout-engine/style-engine/vitest.config.mjs b/packages/layout-engine/style-engine/vitest.config.mjs
deleted file mode 100644
index bfc67bf9d0..0000000000
--- a/packages/layout-engine/style-engine/vitest.config.mjs
+++ /dev/null
@@ -1,9 +0,0 @@
-import { defineConfig } from 'vitest/config';
-import baseConfig from '../../../vitest.baseConfig';
-
-export default defineConfig({
-  ...baseConfig,
-  test: {
-    globals: true,
-  },
-});
diff --git a/packages/word-layout/bunfig.toml b/packages/word-layout/bunfig.toml
new file mode 100644
index 0000000000..554f6fb8f2
--- /dev/null
+++ b/packages/word-layout/bunfig.toml
@@ -0,0 +1,2 @@
+[test]
+timeout = 5000
diff --git a/packages/word-layout/package.json b/packages/word-layout/package.json
index e7b46ba4da..2b1d795bbf 100644
--- a/packages/word-layout/package.json
+++ b/packages/word-layout/package.json
@@ -15,9 +15,6 @@
   },
   "scripts": {
     "build": "tsc --project tsconfig.json",
-    "test": "vitest run"
-  },
-  "devDependencies": {
-    "vitest": "catalog:"
+    "test": "bun test"
   }
 }
diff --git a/packages/word-layout/tests/numbering-manager.test.ts b/packages/word-layout/tests/numbering-manager.test.ts
index 606a196670..c913454d99 100644
--- a/packages/word-layout/tests/numbering-manager.test.ts
+++ b/packages/word-layout/tests/numbering-manager.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 
 import { createNumberingManager } from '../src/numbering-manager.js';
 
diff --git a/packages/word-layout/tests/unit-conversions.test.ts b/packages/word-layout/tests/unit-conversions.test.ts
index e23927cb26..d85368c36e 100644
--- a/packages/word-layout/tests/unit-conversions.test.ts
+++ b/packages/word-layout/tests/unit-conversions.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 
 import {
   TWIPS_PER_PIXEL,
diff --git a/packages/word-layout/tests/word-layout.test.ts b/packages/word-layout/tests/word-layout.test.ts
index 1e0de992f5..a6ff75369a 100644
--- a/packages/word-layout/tests/word-layout.test.ts
+++ b/packages/word-layout/tests/word-layout.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it } from 'bun:test';
 
 import { computeWordParagraphLayout, DEFAULT_LIST_HANGING_PX } from '../src/index.js';
 import type { WordParagraphLayoutInput } from '../src/types.js';
diff --git a/packages/word-layout/vitest.config.mjs b/packages/word-layout/vitest.config.mjs
deleted file mode 100644
index 5cb415c834..0000000000
--- a/packages/word-layout/vitest.config.mjs
+++ /dev/null
@@ -1,9 +0,0 @@
-import { defineConfig } from 'vitest/config';
-import baseConfig from '../../vitest.baseConfig';
-
-export default defineConfig({
-  ...baseConfig,
-  test: {
-    globals: true,
-  },
-});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 47811918e3..209362c84e 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -642,16 +642,17 @@ importers:
 
   packages/layout-engine: {}
 
-  packages/layout-engine/contracts: {}
+  packages/layout-engine/contracts:
+    devDependencies:
+      happy-dom:
+        specifier: 'catalog:'
+        version: 20.3.4
 
   packages/layout-engine/geometry-utils:
     devDependencies:
       typescript:
         specifier: 'catalog:'
         version: 5.9.3
-      vitest:
-        specifier: 'catalog:'
-        version: 3.2.4(@types/debug@4.1.12)(@types/node@22.19.2)(happy-dom@20.3.4)(jiti@2.6.1)(jsdom@27.3.0(canvas@3.2.0)(postcss@8.5.6))(tsx@4.21.0)(yaml@2.8.2)
 
   packages/layout-engine/layout-bridge:
     dependencies:
@@ -788,9 +789,6 @@ importers:
       typescript:
         specifier: 'catalog:'
         version: 5.9.3
-      vitest:
-        specifier: 'catalog:'
-        version: 3.2.4(@types/debug@4.1.12)(@types/node@22.19.2)(happy-dom@20.3.4)(jiti@2.6.1)(jsdom@27.3.0(canvas@3.2.0)(postcss@8.5.6))(tsx@4.21.0)(yaml@2.8.2)
 
   packages/layout-engine/tests:
     dependencies:
@@ -1170,11 +1168,7 @@ importers:
         specifier: 'catalog:'
         version: 7.2.7(@types/node@22.19.2)(jiti@2.6.1)(tsx@4.21.0)(yaml@2.8.2)
 
-  packages/word-layout:
-    devDependencies:
-      vitest:
-        specifier: 'catalog:'
-        version: 3.2.4(@types/debug@4.1.12)(@types/node@22.19.2)(happy-dom@20.3.4)(jiti@2.6.1)(jsdom@27.3.0(canvas@3.2.0)(postcss@8.5.6))(tsx@4.21.0)(yaml@2.8.2)
+  packages/word-layout: {}
 
   shared/common:
     devDependencies: