diff --git a/package.json b/package.json
index 10af96bd..627af23f 100644
--- a/package.json
+++ b/package.json
@@ -33,9 +33,11 @@
         "build:cjs": "npx tsc -p tsconfig.cjs.json",
         "build:esm": "npx tsc -p tsconfig.esm.json",
         "build:fix-esm": "node scripts/fix-esm-imports.cjs",
+        "build:fix-dts": "node scripts/fix-dts-imports.cjs",
         "build:post": "echo '{\"type\":\"commonjs\"}' > dist/cjs/package.json",
-        "build": "npm-run-all clean build:cjs build:esm build:fix-esm build:post",
-        "integrity-checks": "npm-run-all clean format-check lint-check test build",
+        "build": "npm-run-all clean build:cjs build:esm build:fix-esm build:fix-dts build:post",
+        "attw": "npx @arethetypeswrong/cli --pack --ignore-rules fallback-condition false-esm",
+        "integrity-checks": "npm-run-all clean format-check lint-check test build attw",
         "prepublishOnly": "npm run integrity-checks",
         "prepare": "npm run build"
     },
diff --git a/scripts/fix-dts-imports.cjs b/scripts/fix-dts-imports.cjs
new file mode 100644
index 00000000..2de161d6
--- /dev/null
+++ b/scripts/fix-dts-imports.cjs
@@ -0,0 +1,125 @@
+#!/usr/bin/env node
+
+const fs = require('fs');
+const path = require('path');
+
+/**
+ * Post-build script to fix TypeScript declaration file imports by adding .js extensions.
+ * This is required because when package.json has "type": "module", TypeScript treats
+ * .d.ts files as ESM modules, which require explicit file extensions for relative imports.
+ */
+
+const TYPES_DIR = path.join(__dirname, '../dist/types');
+
+function fixImportsInFile(filePath) {
+    let content = fs.readFileSync(filePath, 'utf8');
+    let modified = false;
+
+    // Fix relative imports - add .js extension if missing
+    content = content.replace(
+        /from\s+['"](\.[^'"]*?)['"];?/g,
+        (match, importPath) => {
+            // Skip if already has extension or is directory import
+            if (path.extname(importPath) || importPath.endsWith('/')) {
+                return match;
+            }
+
+            // Check if this is a directory import (look for index file)
+            const fullPath = path.resolve(path.dirname(filePath), importPath);
+            const indexPath = path.join(fullPath, 'index.d.ts');
+
+            if (fs.existsSync(indexPath)) {
+                // Directory import - add /index.js
+                modified = true;
+                return match.replace(importPath, importPath + '/index.js');
+            } else {
+                // File import - add .js
+                modified = true;
+                return match.replace(importPath, importPath + '.js');
+            }
+        }
+    );
+
+    // Fix export statements as well
+    content = content.replace(
+        /export\s+(?:\*|\{[^}]*\})\s+from\s+['"](\.[^'"]*?)['"];?/g,
+        (match, importPath) => {
+            // Skip if already has extension or is directory import
+            if (path.extname(importPath) || importPath.endsWith('/')) {
+                return match;
+            }
+
+            // Check if this is a directory import (look for index file)
+            const fullPath = path.resolve(path.dirname(filePath), importPath);
+            const indexPath = path.join(fullPath, 'index.d.ts');
+
+            if (fs.existsSync(indexPath)) {
+                // Directory import - add /index.js
+                modified = true;
+                return match.replace(importPath, importPath + '/index.js');
+            } else {
+                // File import - add .js
+                modified = true;
+                return match.replace(importPath, importPath + '.js');
+            }
+        }
+    );
+
+    // Fix dynamic import() type expressions
+    content = content.replace(
+        /import\(['"](\.[^'"]*?)['"]\)/g,
+        (match, importPath) => {
+            // Skip if already has extension or is directory import
+            if (path.extname(importPath) || importPath.endsWith('/')) {
+                return match;
+            }
+
+            // Check if this is a directory import (look for index file)
+            const fullPath = path.resolve(path.dirname(filePath), importPath);
+            const indexPath = path.join(fullPath, 'index.d.ts');
+
+            if (fs.existsSync(indexPath)) {
+                // Directory import - add /index.js
+                modified = true;
+                return match.replace(importPath, importPath + '/index.js');
+            } else {
+                // File import - add .js
+                modified = true;
+                return match.replace(importPath, importPath + '.js');
+            }
+        }
+    );
+
+    if (modified) {
+        fs.writeFileSync(filePath, content, 'utf8');
+        console.log(`Fixed imports in: ${path.relative(process.cwd(), filePath)}`);
+    }
+}
+
+function walkDirectory(dir) {
+    const files = fs.readdirSync(dir);
+
+    for (const file of files) {
+        const filePath = path.join(dir, file);
+        const stat = fs.statSync(filePath);
+
+        if (stat.isDirectory()) {
+            walkDirectory(filePath);
+        } else if (file.endsWith('.d.ts')) {
+            fixImportsInFile(filePath);
+        }
+    }
+}
+
+function main() {
+    if (!fs.existsSync(TYPES_DIR)) {
+        console.log('Types directory does not exist, skipping declaration file fixing');
+        return;
+    }
+
+    console.log('Fixing TypeScript declaration file imports by adding .js extensions...');
+    walkDirectory(TYPES_DIR);
+    console.log('Declaration file import fixing completed');
+}
+
+main();