waleedlatif1 · Nov 11, 2026 · Nov 11, 2026 · Nov 11, 2026 · Nov 11, 2026
diff --git a/apps/sim/lib/execution/isolated-vm-worker.cjs b/apps/sim/lib/execution/isolated-vm-worker.cjs
@@ -740,6 +740,17 @@ async function executeTask(request, executionId) {
     releaseables.push(textDecodeCallback)
     await jail.set('__textDecode', textDecodeCallback)
 
+    // btoa / atob delegate to Node's native WHATWG implementations, so
+    // libraries that encode base64 through them (docx's Packer.toBase64String,
+    // document protection hashes, data-URI images) behave as in a browser.
+    const btoaCallback = new ivm.Callback((data) => btoa(data))
+    releaseables.push(btoaCallback)
+    await jail.set('__btoa', btoaCallback)
+
+    const atobCallback = new ivm.Callback((data) => atob(data))
+    releaseables.push(atobCallback)
+    await jail.set('__atob', atobCallback)
+
     // Delegate timers to Node's real timer heap via ivm.Reference (the pattern
     // recommended by laverdet/isolated-vm#136). Host-side bookkeeping was
     // hoisted to the function scope above so the finally can always sweep.
@@ -890,6 +901,8 @@ async function executeTask(request, executionId) {
         const __error = globalThis.__error;
         const __textEncode = globalThis.__textEncode;
         const __textDecode = globalThis.__textDecode;
+        const __btoa = globalThis.__btoa;
+        const __atob = globalThis.__atob;
         const __setTimeoutRef = globalThis.__setTimeoutRef;
         const __clearTimeoutRef = globalThis.__clearTimeoutRef;
         const __setIntervalRef = globalThis.__setIntervalRef;
@@ -927,6 +940,9 @@ async function executeTask(request, executionId) {
           }
         };
 
+        globalThis.btoa = function btoa(data) { return __btoa(String(data)); };
+        globalThis.atob = function atob(data) { return __atob(String(data)); };
+
         // setTimeout / setInterval delegate to Node's real timer heap via
         // ivm.Reference. The \`ms\` arg is honored (host clamps to the script
         // timeout window); \`clearTimeout\` / \`clearInterval\` actually cancel.
@@ -1039,7 +1055,7 @@ async function executeTask(request, executionId) {
       const undefined_globals = [
         'Isolate', 'Context', 'Script', 'Module', 'Callback', 'Reference',
         'ExternalCopy', '__dirname', '__filename', '__brokerRef',
-        '__log', '__error', '__textEncode', '__textDecode',
+        '__log', '__error', '__textEncode', '__textDecode', '__btoa', '__atob',
         '__setTimeoutRef', '__clearTimeoutRef', '__setIntervalRef'
       ];
       for (const name of undefined_globals) {

diff --git a/apps/sim/lib/execution/sandbox/bundles/build.ts b/apps/sim/lib/execution/sandbox/bundles/build.ts
@@ -9,7 +9,7 @@
  *
  * Every bundle is evaluated in a bare context before it is written: the
  * bundler can emit a reference to a runtime helper it never defines (Bun does
- * this for docx's inlined CommonJS shim), and nothing else loads these files
+ * this for an inlined CommonJS shim), and nothing else loads these files
  * before a production document generation does.
  *
  * Run via: `bun run build:sandbox-bundles`.

diff --git a/apps/sim/lib/execution/sandbox/bundles/docx.cjs b/apps/sim/lib/execution/sandbox/bundles/docx.cjs
diff --git a/apps/sim/lib/execution/sandbox/bundles/isolate-polyfills.ts b/apps/sim/lib/execution/sandbox/bundles/isolate-polyfills.ts
@@ -10,9 +10,9 @@
  * Beyond aliasing `global -> globalThis` for UMD-style fallbacks inside the
  * bundles, this file only answers the one name the bundler can leave dangling
  * (see below). All other runtime surface (`console`, `TextEncoder`,
- * `TextDecoder`, timers) is installed by the worker via `ivm.Callback` /
- * `ivm.Reference` bridges to Node's native implementations — no hand-rolled
- * polyfill logic lives in the isolate.
+ * `TextDecoder`, `btoa`, `atob`, timers) is installed by the worker via
+ * `ivm.Callback` / `ivm.Reference` bridges to Node's native implementations —
+ * no hand-rolled polyfill logic lives in the isolate.
  */
 
 const g: typeof globalThis & {
@@ -24,11 +24,10 @@ if (typeof g.global === 'undefined') g.global = globalThis
 
 /**
  * A library that inlines a CommonJS dependency ships esbuild's `__require`
- * helper around it (docx >= 9.7.1 does this for JSZip's UMD build). Bun's
- * browser/iife build rewrites the bare `require` references inside that helper
- * to its own `__require` runtime helper and then never emits it, so the bundle
- * throws `ReferenceError: __require is not defined` while it is still being
- * evaluated. The isolate has no `require` at all, so the only correct answer
+ * helper around it. Bun's browser/iife build rewrites the bare `require`
+ * references inside that helper to its own `__require` runtime helper and
+ * then never emits it, so the bundle throws `ReferenceError: __require is not
+ * defined` while it is still being evaluated. The isolate has no `require` at all, so the only correct answer
  * to a dynamic require is the one esbuild's helper gives when `require` is
  * absent: throw. Defining it here keeps every bundle self-contained; `build.ts`
  * evaluates each bundle in a bare context so a new variant of the defect fails

diff --git a/apps/sim/lib/execution/sandbox/bundles/verify.test.ts b/apps/sim/lib/execution/sandbox/bundles/verify.test.ts
@@ -1,7 +1,13 @@
 import { readFileSync } from 'node:fs'
+import vm from 'node:vm'
+import JSZip from 'jszip'
 import { describe, expect, it } from 'vitest'
-import { evaluateSandboxBundle } from '@/lib/execution/sandbox/bundles/verify'
+import {
+  createBareSandboxContext,
+  evaluateSandboxBundle,
+} from '@/lib/execution/sandbox/bundles/verify'
 import type { SandboxBundleName } from '@/lib/execution/sandbox/types'
+import { docxGenerateTask } from '@/sandboxes/docx-generate'
 
 function loadCheckedInBundle(name: SandboxBundleName): Record<string, unknown> {
   const source = readFileSync(new URL(`./${name}.cjs`, import.meta.url), 'utf-8')
@@ -23,6 +29,57 @@ describe('sandbox bundles', () => {
     expect(typeof docx.Paragraph).toBe('function')
   })
 
+  it('docx-generate packs a document with the checked-in bundle in a bare context', async () => {
+    const context = createBareSandboxContext()
+    evaluateSandboxBundle(
+      readFileSync(new URL('./docx.cjs', import.meta.url), 'utf-8'),
+      'docx',
+      context
+    )
+    const runAsync = (body: string) => vm.runInContext(`(async () => { ${body} })()`, context)
+
+    await runAsync(docxGenerateTask.bootstrap)
+    await runAsync(
+      "addSection({ children: [new docx.Paragraph({ children: [new docx.TextRun('R&D <ok>')] })] })"
+    )
+    const bytes: unknown = await runAsync(docxGenerateTask.finalize)
+
+    expect(ArrayBuffer.isView(bytes)).toBe(true)
+    const zip = await JSZip.loadAsync(bytes as Uint8Array)
+    expect(await zip.file('word/document.xml')?.async('string')).toContain('R&amp;D &lt;ok&gt;')
+  })
+
+  it('docx encodes and decodes base64 through the btoa/atob the worker provides', async () => {
+    const context = createBareSandboxContext()
+    evaluateSandboxBundle(
+      readFileSync(new URL('./docx.cjs', import.meta.url), 'utf-8'),
+      'docx',
+      context
+    )
+    const pngBase64 =
+      'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8DwHwAFBQIAX8jx0gAAAABJRU5ErkJggg=='
+
+    const packed: unknown = await vm.runInContext(
+      `(async () => {
+        const docx = globalThis.__bundles.docx;
+        const doc = new docx.Document({
+          protection: { type: 'readOnly', password: 'secret' },
+          sections: [{ children: [new docx.Paragraph({ children: [
+            new docx.ImageRun({ type: 'png', data: 'data:image/png;base64,${pngBase64}', transformation: { width: 10, height: 10 } }),
+          ] })] }],
+        });
+        return docx.Packer.toBase64String(doc);
+      })()`,
+      context
+    )
+
+    const zip = await JSZip.loadAsync(packed as string, { base64: true })
+    expect(await zip.file('word/settings.xml')?.async('string')).toMatch(
+      /<w:documentProtection[^>]*w:hash="[^"]+"/
+    )
+    expect(zip.file('word/media/image1.png')).not.toBeNull()
+  })
+
   it('pdf-lib evaluates in a bare context and exposes the pdf-generate surface', () => {
     const pdfLib = loadCheckedInBundle('pdf-lib')
     expect(typeof pdfLib.PDFDocument).toBe('function')

diff --git a/apps/sim/lib/execution/sandbox/bundles/verify.ts b/apps/sim/lib/execution/sandbox/bundles/verify.ts
@@ -2,15 +2,12 @@ import vm from 'node:vm'
 import type { SandboxBundleName } from '@/lib/execution/sandbox/types'
 
 /**
- * Evaluates a built sandbox bundle the way the isolated-vm worker will: as a
- * classic script in a context that has timers, `console`, and the text codecs
- * but no `require`, `process`, or `Buffer` of its own. Returns the export the
- * bundle registered on `globalThis.__bundles`, or throws with the bundle's own
- * error, so a bundle that references a helper the bundler never emitted fails
- * at build time and in the test suite instead of on the first document
- * generated in production.
+ * A context shaped like the isolated-vm worker's task mode: timers, `console`,
+ * the text codecs, and `btoa`/`atob`, but no `require`, `process`, or `Buffer`
+ * of its own. Code that reaches for any other Node or browser global fails here
+ * the same way it fails inside the isolate.
  */
-export function evaluateSandboxBundle(source: string, name: SandboxBundleName): unknown {
+export function createBareSandboxContext(): vm.Context {
   const context: Record<string, unknown> = {
     setTimeout,
     clearTimeout,
@@ -20,9 +17,26 @@ export function evaluateSandboxBundle(source: string, name: SandboxBundleName):
     console,
     TextEncoder,
     TextDecoder,
+    btoa,
+    atob,
   }
   context.globalThis = context
-  vm.createContext(context)
+  return vm.createContext(context)
+}
+
+/**
+ * Evaluates a built sandbox bundle the way the isolated-vm worker will: as a
+ * classic script in a {@link createBareSandboxContext} context. Returns the
+ * export the bundle registered on `globalThis.__bundles`, or throws with the
+ * bundle's own error, so a bundle that references a helper the bundler never
+ * emitted fails at build time and in the test suite instead of on the first
+ * document generated in production.
+ */
+export function evaluateSandboxBundle(
+  source: string,
+  name: SandboxBundleName,
+  context: vm.Context = createBareSandboxContext()
+): unknown {
   vm.runInContext(source, context, { filename: `sandbox/${name}.cjs` })
 
   const bundles = context.__bundles

diff --git a/apps/sim/lib/microsoft-word/document.server.test.ts b/apps/sim/lib/microsoft-word/document.server.test.ts
@@ -91,8 +91,6 @@ describe('buildDocxFromContent', () => {
   })
 
   it('strips control characters that would make the package unopenable', async () => {
-    // The docx package writes run text into the XML verbatim, so a forbidden
-    // character reaching it produces invalid XML 1.0 rather than a rendering bug.
     const buffer = await buildDocxFromContent(`before${String.fromCharCode(8)}after`)
     const xml = await readDocumentXml(buffer)
 

diff --git a/apps/sim/lib/microsoft-word/document.server.ts b/apps/sim/lib/microsoft-word/document.server.ts
@@ -83,11 +83,10 @@ function parseInlineRuns(line: string): ContentRun[] {
 function parseContentBlocks(content: string): ContentBlock[] {
   const blocks: ContentBlock[] = []
 
-  // Stripped once here rather than per run: the `docx` package writes run text
-  // into the XML verbatim, so a stray control character from an upstream block
-  // would produce a package Word refuses to open. Tab, newline, and carriage
-  // return are legal XML and are outside the class, so the split below is
-  // unaffected.
+  // Stripped before the Markdown patterns run, so a stray control character
+  // from an upstream block can't hide a heading or bullet marker. Tab, newline,
+  // and carriage return are legal XML and outside the class, so the split below
+  // is unaffected.
   for (const rawLine of stripInvalidXmlChars(content).replace(/\r\n?/g, '\n').split('\n')) {
     const line = rawLine.trimEnd()
     if (line.trim().length === 0) continue

@@ -211,7 +211,7 @@
     "date-fns": "4.4.0",
     "decimal.js": "10.6.0",
     "diff": "9.0.0",
-    "docx": "^9.6.1",
+    "docx": "^9.15.2",
     "docx-preview": "^0.4.1",
     "drizzle-orm": "^0.45.4",
     "echarts": "6.1.0",

diff --git a/apps/sim/sandboxes/docx-generate.ts b/apps/sim/sandboxes/docx-generate.ts
@@ -78,8 +78,6 @@ export const docxGenerateTask = defineSandboxTask<SandboxTaskInput>({
       }));
     };
   `,
-  // JSZip's browser build doesn't support nodebuffer output, so we go through
-  // base64 and decode back to bytes inside the isolate (avoids DataURL / Blob).
   finalize: `
     let doc = globalThis.doc;
     if (!doc && globalThis.__docxSections.length > 0) {
@@ -91,23 +89,7 @@ export const docxGenerateTask = defineSandboxTask<SandboxTaskInput>({
     if (!doc) {
       throw new Error('No document created. Use addSection({ children: [...] }) for chunked writes, or set globalThis.doc = new docx.Document({...}) for a single write.');
     }
-    const b64 = await globalThis.docx.Packer.toBase64String(doc);
-    const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
-    const lookup = new Uint8Array(128);
-    for (let i = 0; i < alphabet.length; i++) lookup[alphabet.charCodeAt(i)] = i;
-    const clean = b64.replace(/=+$/, '');
-    const out = new Uint8Array(Math.floor((clean.length * 3) / 4));
-    let pos = 0;
-    for (let i = 0; i < clean.length; i += 4) {
-      const c0 = lookup[clean.charCodeAt(i)];
-      const c1 = lookup[clean.charCodeAt(i + 1)];
-      const c2 = lookup[clean.charCodeAt(i + 2)];
-      const c3 = lookup[clean.charCodeAt(i + 3)];
-      out[pos++] = (c0 << 2) | (c1 >> 4);
-      if (i + 2 < clean.length) out[pos++] = ((c1 & 0x0f) << 4) | (c2 >> 2);
-      if (i + 3 < clean.length) out[pos++] = ((c2 & 0x03) << 6) | c3;
-    }
-    return out.subarray(0, pos);
+    return new Uint8Array(await globalThis.docx.Packer.toArrayBuffer(doc));
   `,
   toResult: (bytes) => Buffer.from(bytes),
 })