diff --git a/js/cjs.test.ts b/js/cjs.test.ts
new file mode 100644
index 0000000..7aa4916
--- /dev/null
+++ b/js/cjs.test.ts
@@ -0,0 +1,45 @@
+import { execSync } from "child_process";
+import { existsSync } from "fs";
+import { describe, expect, test, beforeAll } from "vitest";
+
+describe("CJS compatibility", () => {
+  beforeAll(() => {
+    // Ensure the build exists
+    if (!existsSync("./jsdist/index.js")) {
+      execSync("pnpm run build", { stdio: "inherit" });
+    }
+  });
+
+  test("can require the CJS bundle", () => {
+    // Test that CJS require works, including dependencies like linear-sum-assignment (#152)
+    const result = execSync(
+      `node -e "const m = require('./jsdist/index.js'); console.log(JSON.stringify(Object.keys(m).sort()))"`,
+      { encoding: "utf-8" },
+    );
+    const exports = JSON.parse(result.trim());
+
+    // Verify key exports are present
+    expect(exports).toContain("Factuality");
+    expect(exports).toContain("ListContains");
+    expect(exports).toContain("ContextRelevancy");
+    expect(exports).toContain("Levenshtein");
+  });
+
+  test("ListContains works in CJS (uses linear-sum-assignment)", () => {
+    // ListContains uses linear-sum-assignment internally, which was ESM-only (#152)
+    const result = execSync(
+      `node -e "
+        const { ListContains } = require('./jsdist/index.js');
+        ListContains({ output: ['a', 'b'], expected: ['a', 'c'] }).then(r => {
+          console.log(JSON.stringify({ score: r.score, name: r.name }));
+        });
+      "`,
+      { encoding: "utf-8" },
+    );
+    const parsed = JSON.parse(result.trim());
+
+    expect(parsed.name).toBe("ListContains");
+    expect(parsed.score).toBeGreaterThanOrEqual(0);
+    expect(parsed.score).toBeLessThanOrEqual(1);
+  });
+});
diff --git a/tsup.config.js b/tsup.config.js
index 8b49d50..59d3c8d 100644
--- a/tsup.config.js
+++ b/tsup.config.js
@@ -9,5 +9,7 @@ export default defineConfig([
     loader: {
       ".yaml": "text",
     },
+    // Bundle ESM-only dependencies to ensure CJS compatibility (#152)
+    noExternal: ["linear-sum-assignment"],
   },
 ]);