diff --git a/package-lock.json b/package-lock.json
index ca1c611..33cbdcf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -27699,6 +27699,7 @@
       "dependencies": {
         "axios": "^0.27.2",
         "convict": "^6.2.3",
+        "debug": "^4.3.4",
         "env-ci": "^7.3.0",
         "fast-glob": "^3.2.11",
         "sharp": "^0.30.7",
@@ -28469,6 +28470,7 @@
         "@types/convict": "^6.1.1",
         "axios": "^0.27.2",
         "convict": "^6.2.3",
+        "debug": "^4.3.4",
         "env-ci": "^7.3.0",
         "fast-glob": "^3.2.11",
         "msw": "^0.44.2",
diff --git a/package.json b/package.json
index f59da2e..5938082 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
     "build": "cross-env NODE_ENV=production lerna run build",
     "format": "prettier --write .",
     "lint": "prettier --check . && eslint .",
-    "test": "jest",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest && lerna run test",
     "release": "npm run build && lerna publish --conventional-commits"
   },
   "engines": {
diff --git a/packages/core/.swcrc b/packages/core/.swcrc
index 7bea9e0..cfb1703 100644
--- a/packages/core/.swcrc
+++ b/packages/core/.swcrc
@@ -1,11 +1,7 @@
 {
   "$schema": "https://json.schemastore.org/swcrc",
-  "env": {
-    "targets": {
-      "node": "16"
-    }
-  },
   "jsc": {
+    "target": "es2021",
     "parser": {
       "syntax": "typescript"
     }
diff --git a/packages/core/integration/run-upload.cjs b/packages/core/integration/run-upload.cjs
new file mode 100644
index 0000000..afef731
--- /dev/null
+++ b/packages/core/integration/run-upload.cjs
@@ -0,0 +1,26 @@
+const { join } = require("node:path");
+
+/**
+ * Run upload command.
+ * @param {typeof import('../src/index').upload} implementation
+ * @param {string} name
+ */
+const runUpload = async (implementation, name) => {
+  try {
+    const result = await implementation({
+      cwd: join(__dirname, "../__fixtures__/screenshots"),
+      token: process.env.ARGOS_TOKEN,
+      name,
+    });
+    console.log(result);
+  } catch (err) {
+    if (err.response) {
+      console.error("Status: %s", err.response.status);
+      if (err.response?.data?.message) {
+        console.error(err.response?.data?.message);
+      }
+    }
+    process.exit(1);
+  }
+};
+exports.runUpload = runUpload;
diff --git a/packages/core/integration/upload.cjs b/packages/core/integration/upload.cjs
new file mode 100644
index 0000000..9713557
--- /dev/null
+++ b/packages/core/integration/upload.cjs
@@ -0,0 +1,4 @@
+const { upload } = require("@argos-ci/core");
+const { runUpload } = require("./run-upload.cjs");
+
+runUpload(upload, "@argos/core--cjs");
diff --git a/packages/core/integration/upload.mjs b/packages/core/integration/upload.mjs
new file mode 100644
index 0000000..d517a86
--- /dev/null
+++ b/packages/core/integration/upload.mjs
@@ -0,0 +1,4 @@
+import { upload } from "@argos-ci/core";
+import { runUpload } from "./run-upload.cjs";
+
+runUpload(upload, "@argos/core--mjs");
diff --git a/packages/core/jest.config.cjs b/packages/core/jest.config.cjs
index c39d5a3..381f402 100644
--- a/packages/core/jest.config.cjs
+++ b/packages/core/jest.config.cjs
@@ -2,4 +2,5 @@ module.exports = {
   transform: {
     "^.+\\.(t|j)sx?$": ["@swc/jest"],
   },
+  extensionsToTreatAsEsm: [".ts"],
 };
diff --git a/packages/core/package.json b/packages/core/package.json
index 442b237..7b30063 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -4,14 +4,17 @@
   "version": "0.0.0",
   "scripts": {
     "prebuild": "rm -rf dist",
-    "build": "rollup -c"
+    "build": "rollup -c",
+    "test": "node ./integrations/upload.cjs && node ./integrations/upload.mjs"
   },
   "type": "module",
+  "main": "./dist/index.cjs",
   "exports": {
     ".": {
+      "require": "./dist/index.cjs",
       "import": "./dist/index.mjs",
       "types": "./dist/index.d.ts",
-      "default": "./dist/index.mjs"
+      "default": "./dist/index.cjs"
     },
     "./package.json": "./package.json"
   },
@@ -40,6 +43,7 @@
   "dependencies": {
     "axios": "^0.27.2",
     "convict": "^6.2.3",
+    "debug": "^4.3.4",
     "env-ci": "^7.3.0",
     "fast-glob": "^3.2.11",
     "sharp": "^0.30.7",
diff --git a/packages/core/rollup.config.js b/packages/core/rollup.config.js
index 7a65b32..572ec1e 100644
--- a/packages/core/rollup.config.js
+++ b/packages/core/rollup.config.js
@@ -2,9 +2,11 @@ import dts from "rollup-plugin-dts";
 import swc from "rollup-plugin-swc3";
 
 const bundle = (config) => ({
-  ...config,
   input: "src/index.ts",
-  external: (id) => !/^[./]/.test(id),
+  external: (id) => {
+    return id === "./index.mjs" || !/^[./]/.test(id);
+  },
+  ...config,
 });
 
 export default [
@@ -15,6 +17,14 @@ export default [
     },
     plugins: [swc()],
   }),
+  bundle({
+    input: "src/index.cjs.ts",
+    output: {
+      file: `dist/index.cjs`,
+      format: "es",
+    },
+    plugins: [swc()],
+  }),
   bundle({
     plugins: [dts()],
     output: {
diff --git a/packages/core/src/api-client.ts b/packages/core/src/api-client.ts
index 936452f..4661cee 100644
--- a/packages/core/src/api-client.ts
+++ b/packages/core/src/api-client.ts
@@ -69,9 +69,6 @@ export const createArgosApiClient = (
       });
       return response.data;
     } catch (error) {
-      if (axios.isAxiosError(error)) {
-        console.log(error.response?.data);
-      }
       throw error;
     }
   };
diff --git a/packages/core/src/config.ts b/packages/core/src/config.ts
index 9af01f7..8d8d3f0 100644
--- a/packages/core/src/config.ts
+++ b/packages/core/src/config.ts
@@ -30,7 +30,7 @@ const mustBeArgosToken = (value: any) => {
 const schema = {
   apiBaseUrl: {
     env: "ARGOS_API_BASE_URL",
-    default: "https://api.argos-ci.com",
+    default: "https://api.argos-ci.com/v2/",
     format: mustBeApiBaseUrl,
   },
   commit: {
diff --git a/packages/core/src/debug.ts b/packages/core/src/debug.ts
new file mode 100644
index 0000000..87d7c6e
--- /dev/null
+++ b/packages/core/src/debug.ts
@@ -0,0 +1,3 @@
+import createDebug from "debug";
+
+export const debug = createDebug("@argos-ci/core");
diff --git a/packages/core/src/discovery.test.ts b/packages/core/src/discovery.test.ts
index e8fcbef..74bf425 100644
--- a/packages/core/src/discovery.test.ts
+++ b/packages/core/src/discovery.test.ts
@@ -1,41 +1,35 @@
-import path from "path";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
 import { discoverScreenshots } from "./discovery";
 
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
 describe("#discoverScreenshots", () => {
   it("finds all images", async () => {
     const screenshots = await discoverScreenshots(["**/*.{png,jpg,jpeg}"], {
-      cwd: path.join(__dirname, "../__fixtures__/screenshots"),
+      cwd: join(__dirname, "../__fixtures__/screenshots"),
     });
     expect(screenshots).toEqual([
       {
         name: "penelope.jpg",
-        path: path.resolve(
-          __dirname,
-          "../__fixtures__/screenshots/penelope.jpg"
-        ),
+        path: join(__dirname, "../__fixtures__/screenshots/penelope.jpg"),
       },
       {
         name: "nested/alicia.jpg",
-        path: path.resolve(
-          __dirname,
-          "../__fixtures__/screenshots/nested/alicia.jpg"
-        ),
+        path: join(__dirname, "../__fixtures__/screenshots/nested/alicia.jpg"),
       },
     ]);
   });
 
   it("ignores files using `ignore` option", async () => {
     const screenshots = await discoverScreenshots(["**/*.{png,jpg,jpeg}"], {
-      cwd: path.join(__dirname, "../__fixtures__/screenshots"),
+      cwd: join(__dirname, "../__fixtures__/screenshots"),
       ignore: ["**/alicia.jpg"],
     });
     expect(screenshots).toEqual([
       {
         name: "penelope.jpg",
-        path: path.resolve(
-          __dirname,
-          "../__fixtures__/screenshots/penelope.jpg"
-        ),
+        path: join(__dirname, "../__fixtures__/screenshots/penelope.jpg"),
       },
     ]);
   });
diff --git a/packages/core/src/hashing.test.ts b/packages/core/src/hashing.test.ts
index 484beb9..a6ff2fe 100644
--- a/packages/core/src/hashing.test.ts
+++ b/packages/core/src/hashing.test.ts
@@ -1,6 +1,9 @@
 import { join } from "node:path";
+import { fileURLToPath } from "node:url";
 import { hashFile } from "./hashing";
 
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
 describe("#hashFile", () => {
   it("hashes file", async () => {
     const hash = await hashFile(
diff --git a/packages/core/src/index.cjs.ts b/packages/core/src/index.cjs.ts
new file mode 100644
index 0000000..c8d9600
--- /dev/null
+++ b/packages/core/src/index.cjs.ts
@@ -0,0 +1,7 @@
+import type { UploadParameters } from "./index";
+
+exports.upload = async (params: UploadParameters) => {
+  // @ts-ignore
+  const { upload } = await import("./index.mjs");
+  return upload(params);
+};
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 2da9db2..ab6125a 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -1 +1 @@
-export { upload } from "./upload";
+export * from "./upload";
diff --git a/packages/core/src/optimize.test.ts b/packages/core/src/optimize.test.ts
index 128bb5b..46ed233 100644
--- a/packages/core/src/optimize.test.ts
+++ b/packages/core/src/optimize.test.ts
@@ -1,7 +1,10 @@
 import { join } from "node:path";
-import { stat } from "fs/promises";
+import { fileURLToPath } from "node:url";
+import { stat } from "node:fs/promises";
 import { optimizeScreenshot } from "./optimize";
 
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
 const exists = async (filepath: string) => {
   try {
     await stat(filepath);
diff --git a/packages/core/src/s3.test.ts b/packages/core/src/s3.test.ts
index 873e75d..92ff92e 100644
--- a/packages/core/src/s3.test.ts
+++ b/packages/core/src/s3.test.ts
@@ -1,7 +1,10 @@
 import { join } from "node:path";
+import { fileURLToPath } from "node:url";
 import { setupJest } from "../mocks/server";
 import { upload } from "./s3";
 
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
 setupJest();
 
 describe("#upload", () => {
diff --git a/packages/core/src/upload.test.ts b/packages/core/src/upload.test.ts
index 49a7fdc..d574e70 100644
--- a/packages/core/src/upload.test.ts
+++ b/packages/core/src/upload.test.ts
@@ -1,7 +1,10 @@
 import { join } from "node:path";
+import { fileURLToPath } from "node:url";
 import { upload } from "./upload";
 import { setupJest } from "../mocks/server";
 
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
 setupJest();
 
 describe("#upload", () => {
diff --git a/packages/core/src/upload.ts b/packages/core/src/upload.ts
index 4921fe3..d5606f8 100644
--- a/packages/core/src/upload.ts
+++ b/packages/core/src/upload.ts
@@ -6,8 +6,9 @@ import { optimizeScreenshot } from "./optimize";
 import { hashFile } from "./hashing";
 import { createArgosApiClient } from "./api-client";
 import { upload as uploadToS3 } from "./s3";
+import { debug } from "./debug";
 
-interface UploadParameters {
+export interface UploadParameters {
   files?: string[];
   cwd?: string;
   ignore?: string[];
@@ -85,6 +86,7 @@ export const upload = async (params: UploadParameters) => {
   });
 
   // Create build
+  debug("Creating build");
   const result = await apiClient.createBuild({
     commit: config.commit,
     branch: config.branch,
@@ -94,7 +96,10 @@ export const upload = async (params: UploadParameters) => {
     screenshotKeys: screenshots.map((screenshot) => screenshot.hash),
   });
 
+  debug("Got screenshots", result);
+
   // Upload screenshots
+  debug("Uploading screenshots");
   await Promise.all(
     result.screenshots.map(async ({ key, putUrl }) => {
       const screenshot = screenshots.find((s) => s.hash === key);
@@ -106,6 +111,7 @@ export const upload = async (params: UploadParameters) => {
   );
 
   // Update build
+  debug("Updating build");
   await apiClient.updateBuild({
     buildId: result.build.id,
     screenshots: screenshots.map((screenshot) => ({
diff --git a/packages/core/tsconfig.json b/packages/core/tsconfig.json
index 511df3b..6c5f5f3 100644
--- a/packages/core/tsconfig.json
+++ b/packages/core/tsconfig.json
@@ -2,9 +2,9 @@
   "include": ["./src", "./typings"],
   "exclude": ["node_modules/**"],
   "compilerOptions": {
-    "module": "Node16",
+    "module": "ESNext",
     "moduleResolution": "node",
-    "target": "ES2022",
+    "target": "ES2021",
     "importHelpers": true,
     "declaration": true,
     "sourceMap": true,