diff --git a/web/js/package.json b/web/js/package.json
index 539105da..e5546d02 100644
--- a/web/js/package.json
+++ b/web/js/package.json
@@ -11,6 +11,7 @@
     "dev:lux": "vite --open /usdlux.html",
     "dev:webgpu": "vite --open /materialx-webgpu.html",
     "dev:webgpu-raw": "vite --open /mtlx-webgpu.html",
+    "dev:progress": "vite --open /progress-demo.html",
     "build": "vite build",
     "preview": "vite preview",
     "cli": "vite-node load-test-node.js",
@@ -25,7 +26,8 @@
     "test:colorspace": "vite-node tests/colorspace-test.js",
     "benchmark:exr": "vite-node benchmark-exr.js",
     "generate:exr": "vite-node generate-test-exr.js",
-    "test:exr-decoder": "vite-node test-exr-decoder.js"
+    "test:exr-decoder": "vite-node test-exr-decoder.js",
+    "test:progress": "node test-progress-cli.js"
   },
   "devDependencies": {
     "@types/bun": "latest",
diff --git a/web/js/test-progress-cli.js b/web/js/test-progress-cli.js
new file mode 100644
index 00000000..34eff39c
--- /dev/null
+++ b/web/js/test-progress-cli.js
@@ -0,0 +1,341 @@
+#!/usr/bin/env node
+// SPDX-License-Identifier: Apache 2.0
+// Test EM_JS synchronous progress callbacks in Node.js CLI
+//
+// This test verifies that progress callbacks are called synchronously
+// from C++ during Tydra scene conversion via EM_JS.
+
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+// ============================================================================
+// Progress Tracking State
+// ============================================================================
+
+const progressState = {
+  callbackCount: 0,
+  lastMeshCurrent: 0,
+  lastMeshTotal: 0,
+  stages: new Set(),
+  meshNames: [],
+  completeInfo: null,
+  errors: []
+};
+
+function resetProgressState() {
+  progressState.callbackCount = 0;
+  progressState.lastMeshCurrent = 0;
+  progressState.lastMeshTotal = 0;
+  progressState.stages = new Set();
+  progressState.meshNames = [];
+  progressState.completeInfo = null;
+  progressState.errors = [];
+}
+
+// ============================================================================
+// Synthetic USD Generation
+// ============================================================================
+
+/**
+ * Generate a simple USDA file with multiple meshes
+ */
+function generateSyntheticUSDA(meshCount = 3) {
+  let usda = `#usda 1.0
+(
+    defaultPrim = "Root"
+    metersPerUnit = 1
+    upAxis = "Y"
+)
+
+def Xform "Root"
+{
+`;
+
+  for (let i = 0; i < meshCount; i++) {
+    const y = i * 2.5;
+    usda += `
+    def Mesh "Mesh_${String(i).padStart(3, '0')}"
+    {
+        float3[] extent = [(-1, -1, -1), (1, 1, 1)]
+        int[] faceVertexCounts = [4, 4, 4, 4, 4, 4]
+        int[] faceVertexIndices = [0, 1, 3, 2, 2, 3, 5, 4, 4, 5, 7, 6, 6, 7, 1, 0, 1, 7, 5, 3, 6, 0, 2, 4]
+        point3f[] points = [
+            (-1, ${y - 1}, 1), (1, ${y - 1}, 1), (-1, ${y - 1}, -1), (1, ${y - 1}, -1),
+            (-1, ${y + 1}, -1), (1, ${y + 1}, -1), (-1, ${y + 1}, 1), (1, ${y + 1}, 1)
+        ]
+        uniform token subdivisionScheme = "none"
+    }
+`;
+  }
+
+  usda += `}
+`;
+
+  return usda;
+}
+
+/**
+ * Generate USDA with mixed geometry types (mesh, cube, sphere)
+ */
+function generateMixedGeometryUSDA() {
+  return `#usda 1.0
+(
+    defaultPrim = "Root"
+    metersPerUnit = 1
+    upAxis = "Y"
+)
+
+def Xform "Root"
+{
+    def Mesh "CustomMesh"
+    {
+        float3[] extent = [(-1, -1, -1), (1, 1, 1)]
+        int[] faceVertexCounts = [3, 3, 3, 3]
+        int[] faceVertexIndices = [0, 1, 2, 0, 2, 3, 0, 3, 1, 1, 3, 2]
+        point3f[] points = [(0, 1, 0), (-1, -1, 1), (1, -1, 1), (0, -1, -1)]
+        uniform token subdivisionScheme = "none"
+    }
+
+    def Cube "SimpleCube"
+    {
+        double size = 2
+        double3 xformOp:translate = (3, 0, 0)
+        uniform token[] xformOpOrder = ["xformOp:translate"]
+    }
+
+    def Sphere "SimpleSphere"
+    {
+        double radius = 1
+        double3 xformOp:translate = (-3, 0, 0)
+        uniform token[] xformOpOrder = ["xformOp:translate"]
+    }
+}
+`;
+}
+
+// ============================================================================
+// Test Runner
+// ============================================================================
+
+async function runTest(testName, usdData, filename = 'test.usda') {
+  console.log(`\n${'='.repeat(60)}`);
+  console.log(`Test: ${testName}`);
+  console.log('='.repeat(60));
+
+  resetProgressState();
+
+  // Dynamic import to allow callbacks to be set
+  const createTinyUSDZ = (await import('./src/tinyusdz/tinyusdz.js')).default;
+
+  // Initialize WASM module with EM_JS callbacks
+  const tinyusdz = await createTinyUSDZ({
+    onTydraProgress: (info) => {
+      progressState.callbackCount++;
+      progressState.lastMeshCurrent = info.meshCurrent;
+      progressState.lastMeshTotal = info.meshTotal;
+      progressState.stages.add(info.stage);
+      if (info.meshName) {
+        progressState.meshNames.push(info.meshName);
+      }
+
+      // Print progress
+      const pct = info.meshTotal > 0
+        ? Math.round((info.meshCurrent / info.meshTotal) * 100)
+        : Math.round(info.progress * 100);
+      const meshInfo = info.meshTotal > 0
+        ? `${info.meshCurrent}/${info.meshTotal}`
+        : '';
+      const meshName = info.meshName ? path.basename(info.meshName) : '';
+
+      console.log(`  [Progress] ${pct}% | ${info.stage} | ${meshInfo} ${meshName}`);
+    },
+    onTydraStage: (info) => {
+      console.log(`  [Stage] ${info.stage}: ${info.message || ''}`);
+    },
+    onTydraComplete: (info) => {
+      progressState.completeInfo = info;
+      console.log(`  [Complete] ${info.meshCount} meshes, ${info.materialCount} materials, ${info.textureCount} textures`);
+    }
+  });
+
+  // Create native loader
+  const loader = new tinyusdz.TinyUSDZLoaderNative();
+
+  // Convert string to binary
+  const encoder = new TextEncoder();
+  const binary = encoder.encode(usdData);
+
+  console.log(`\nLoading ${filename} (${binary.length} bytes)...`);
+  console.log('-'.repeat(40));
+
+  const startTime = performance.now();
+  const ok = loader.loadFromBinary(binary, filename);
+  const elapsed = performance.now() - startTime;
+
+  console.log('-'.repeat(40));
+
+  if (!ok) {
+    console.log(`\n❌ FAILED: ${loader.error()}`);
+    progressState.errors.push(loader.error());
+    return false;
+  }
+
+  console.log(`\n✅ SUCCESS in ${elapsed.toFixed(1)}ms`);
+  console.log(`   Callback count: ${progressState.callbackCount}`);
+  console.log(`   Stages seen: ${[...progressState.stages].join(', ')}`);
+  console.log(`   Unique meshes: ${new Set(progressState.meshNames).size}`);
+
+  if (progressState.completeInfo) {
+    console.log(`   Final counts: ${progressState.completeInfo.meshCount} meshes`);
+  }
+
+  // Cleanup
+  loader.delete();
+
+  return true;
+}
+
+async function runFileTest(filePath) {
+  console.log(`\n${'='.repeat(60)}`);
+  console.log(`Test: Load from file - ${filePath}`);
+  console.log('='.repeat(60));
+
+  if (!fs.existsSync(filePath)) {
+    console.log(`⚠️  SKIPPED: File not found`);
+    return null;
+  }
+
+  const data = fs.readFileSync(filePath);
+  const filename = path.basename(filePath);
+
+  resetProgressState();
+
+  const createTinyUSDZ = (await import('./src/tinyusdz/tinyusdz.js')).default;
+
+  const tinyusdz = await createTinyUSDZ({
+    onTydraProgress: (info) => {
+      progressState.callbackCount++;
+      progressState.lastMeshCurrent = info.meshCurrent;
+      progressState.lastMeshTotal = info.meshTotal;
+      progressState.stages.add(info.stage);
+      if (info.meshName) {
+        progressState.meshNames.push(info.meshName);
+      }
+
+      const pct = info.meshTotal > 0
+        ? Math.round((info.meshCurrent / info.meshTotal) * 100)
+        : Math.round(info.progress * 100);
+      const meshInfo = info.meshTotal > 0
+        ? `${info.meshCurrent}/${info.meshTotal}`
+        : '';
+      const meshName = info.meshName ? path.basename(info.meshName) : '';
+
+      console.log(`  [Progress] ${pct}% | ${info.stage} | ${meshInfo} ${meshName}`);
+    },
+    onTydraComplete: (info) => {
+      progressState.completeInfo = info;
+      console.log(`  [Complete] ${info.meshCount} meshes, ${info.materialCount} materials, ${info.textureCount} textures`);
+    }
+  });
+
+  const loader = new tinyusdz.TinyUSDZLoaderNative();
+
+  console.log(`\nLoading ${filename} (${data.length} bytes)...`);
+  console.log('-'.repeat(40));
+
+  const startTime = performance.now();
+  const ok = loader.loadFromBinary(data, filename);
+  const elapsed = performance.now() - startTime;
+
+  console.log('-'.repeat(40));
+
+  if (!ok) {
+    console.log(`\n❌ FAILED: ${loader.error()}`);
+    return false;
+  }
+
+  console.log(`\n✅ SUCCESS in ${elapsed.toFixed(1)}ms`);
+  console.log(`   Callback count: ${progressState.callbackCount}`);
+  console.log(`   Stages seen: ${[...progressState.stages].join(', ')}`);
+  console.log(`   Unique meshes: ${new Set(progressState.meshNames).size}`);
+
+  loader.delete();
+
+  return true;
+}
+
+// ============================================================================
+// Main
+// ============================================================================
+
+async function main() {
+  console.log('╔════════════════════════════════════════════════════════════╗');
+  console.log('║     EM_JS Progress Callback Test (Node.js CLI)             ║');
+  console.log('╚════════════════════════════════════════════════════════════╝');
+
+  const results = {
+    passed: 0,
+    failed: 0,
+    skipped: 0
+  };
+
+  // Test 1: Simple synthetic USD with 3 meshes
+  const result1 = await runTest(
+    'Synthetic USDA - 3 Meshes',
+    generateSyntheticUSDA(3),
+    'synthetic-3mesh.usda'
+  );
+  if (result1) results.passed++; else results.failed++;
+
+  // Test 2: Synthetic USD with 10 meshes
+  const result2 = await runTest(
+    'Synthetic USDA - 10 Meshes',
+    generateSyntheticUSDA(10),
+    'synthetic-10mesh.usda'
+  );
+  if (result2) results.passed++; else results.failed++;
+
+  // Test 3: Mixed geometry types
+  const result3 = await runTest(
+    'Mixed Geometry (Mesh + Cube + Sphere)',
+    generateMixedGeometryUSDA(),
+    'mixed-geometry.usda'
+  );
+  if (result3) results.passed++; else results.failed++;
+
+  // Test 4: Load from file (if available)
+  const testFiles = [
+    path.join(__dirname, 'assets/multi-mesh-test.usda'),
+    path.join(__dirname, 'assets/suzanne.usdc'),
+    path.join(__dirname, 'assets/mtlx-normalmap-sphere.usdz')
+  ];
+
+  for (const filePath of testFiles) {
+    const result = await runFileTest(filePath);
+    if (result === true) results.passed++;
+    else if (result === false) results.failed++;
+    else results.skipped++;
+  }
+
+  // Summary
+  console.log('\n' + '═'.repeat(60));
+  console.log('SUMMARY');
+  console.log('═'.repeat(60));
+  console.log(`  ✅ Passed:  ${results.passed}`);
+  console.log(`  ❌ Failed:  ${results.failed}`);
+  console.log(`  ⚠️  Skipped: ${results.skipped}`);
+  console.log('═'.repeat(60));
+
+  if (results.failed > 0) {
+    process.exit(1);
+  }
+}
+
+main().catch(err => {
+  console.error('\n💥 Unhandled error:', err);
+  process.exit(1);
+});