diff --git a/src/auth/unwrap.ts b/src/auth/unwrap.ts
index 1a894df..7e4f12c 100644
--- a/src/auth/unwrap.ts
+++ b/src/auth/unwrap.ts
@@ -3,7 +3,7 @@ import {
     decryptSealed,
     deriveKEK,
     fromBase64,
-    toBase64URL,
+    toBase64URLPadded,
 } from "../crypto/index.js";
 import type { AuthorizationResponse } from "./types.js";
 
@@ -58,7 +58,10 @@ export const unwrapAuth = async (
         publicKey,
         secretKey,
     );
-    const token = toBase64URL(tokenBytes);
+    // The Ente server validates the token as URL-safe base64 WITH padding,
+    // matching Go's base64.URLEncoding. Using the no-padding form results
+    // in HTTP 401 "invalid token".
+    const token = toBase64URLPadded(tokenBytes);
 
     return { masterKey, secretKey, publicKey, token };
 };
diff --git a/src/crypto/encoding.ts b/src/crypto/encoding.ts
index 6fa886c..beaed1e 100644
--- a/src/crypto/encoding.ts
+++ b/src/crypto/encoding.ts
@@ -6,6 +6,12 @@ export const toBase64 = (b: Uint8Array): string =>
 export const toBase64URL = (b: Uint8Array): string =>
     sodium.to_base64(b, sodium.base64_variants.URLSAFE_NO_PADDING);
 
+// URL-safe base64 WITH padding. Go's base64.URLEncoding produces this form,
+// and the Ente server validates the auth token in this format. Use toBase64URL
+// for general use (JWT-style, no padding); use this for the auth token.
+export const toBase64URLPadded = (b: Uint8Array): string =>
+    sodium.to_base64(b, sodium.base64_variants.URLSAFE);
+
 // Ente uses standard base64 for most fields, URL-safe (with padding stripped)
 // for the auth token. Rather than make callers specify, fromBase64 accepts
 // any of the four variants libsodium understands and returns the bytes.
diff --git a/src/crypto/index.ts b/src/crypto/index.ts
index 0c77196..6cff5f5 100644
--- a/src/crypto/index.ts
+++ b/src/crypto/index.ts
@@ -1,5 +1,10 @@
 export { init } from "./sodium.js";
-export { fromBase64, toBase64, toBase64URL } from "./encoding.js";
+export {
+    fromBase64,
+    toBase64,
+    toBase64URL,
+    toBase64URLPadded,
+} from "./encoding.js";
 export { deriveKEK, deriveLoginSubkey } from "./kdf.js";
 export { decryptBox, decryptSealed } from "./box.js";
 export {
diff --git a/test/auth/unwrap.test.ts b/test/auth/unwrap.test.ts
index 082fb8e..bfdba53 100644
--- a/test/auth/unwrap.test.ts
+++ b/test/auth/unwrap.test.ts
@@ -30,7 +30,7 @@
  *       ▼  sealed_box_open(encryptedToken, publicKey, secretKey)
  *       tokenBytes
  *       │
- *       ▼  toBase64URL
+ *       ▼  toBase64URLPadded
  *       token ───── X-Auth-Token header value
  *
  * No HTTP happens here. The caller is responsible for the round trip
@@ -44,7 +44,7 @@
 
 import sodium from "libsodium-wrappers-sumo";
 import { beforeAll, describe, expect, it } from "vitest";
-import { init, toBase64, toBase64URL } from "../../src/crypto/index.js";
+import { init, toBase64, toBase64URLPadded } from "../../src/crypto/index.js";
 import { unwrapAuth } from "../../src/auth/unwrap.js";
 import type {
     AuthorizationResponse,
@@ -154,7 +154,9 @@ describe("auth.unwrapAuth", () => {
         // Token is returned as URL-safe-no-padding base64 of the bytes
         // sealed by the server. The caller passes this string directly
         // as the X-Auth-Token header.
-        expect(result.token).toBe(toBase64URL(tokenBytes));
+        // Token uses URL-safe base64 WITH padding to match the Go CLI's
+        // base64.URLEncoding and the Ente server's token validation.
+        expect(result.token).toBe(toBase64URLPadded(tokenBytes));
     });
 
     it("rejects a wrong password", async () => {
diff --git a/test/integration/live-login.ts b/test/integration/live-login.ts
new file mode 100644
index 0000000..5780f84
--- /dev/null
+++ b/test/integration/live-login.ts
@@ -0,0 +1,64 @@
+import { init } from "../../src/crypto/index.js";
+import { ApiClient } from "../../src/api/client.js";
+import { beginLogin } from "../../src/auth/login.js";
+import { unwrapAuth } from "../../src/auth/unwrap.js";
+
+// Dev account — not a secret, throwaway account for integration testing.
+const EMAIL = "entedev2026jp@acidhou.se";
+const PASSWORD = "loldongs";
+const RECOVERY_KEY =
+    "deliver have behave collect void chicken boring embrace coast reflect squeeze cotton dish resemble license remain quick dwarf plastic ensure amused cry nasty equip";
+
+void RECOVERY_KEY; // available if needed for account recovery tests
+
+const main = async () => {
+    await init();
+    const api = new ApiClient();
+
+    console.log(`Logging in as ${EMAIL}...`);
+    const challenge = await beginLogin(api, EMAIL, PASSWORD);
+    console.log("beginLogin returned:", challenge.kind);
+
+    let response;
+    if (challenge.kind === "complete") {
+        response = challenge.response;
+    } else if (challenge.kind === "totp") {
+        console.error("Account requires TOTP — disable 2FA for dev testing");
+        process.exit(1);
+    } else if (challenge.kind === "emailOTP") {
+        console.error("Account uses email OTP — SRP not set up?");
+        process.exit(1);
+    } else {
+        console.error("Unexpected challenge:", challenge);
+        process.exit(1);
+    }
+
+    console.log("Got AuthorizationResponse, user ID:", response.id);
+
+    console.log("Unwrapping keys...");
+    const { masterKey, token } = await unwrapAuth(response, PASSWORD);
+    console.log("Master key length:", masterKey.length, "bytes");
+    console.log("Token length:", token.length, "chars");
+
+    api.setAuthToken(token);
+
+    console.log("\nFetching collections...");
+    const { collections } = await api.getJSON<{ collections: unknown[] }>(
+        "/collections/v2",
+        { sinceTime: 0 },
+    );
+    console.log(`Got ${collections.length} collection(s)`);
+    for (const c of collections.slice(0, 5)) {
+        const col = c as Record<string, unknown>;
+        console.log(
+            `  id=${col.id} type=${col.type} updationTime=${col.updationTime}`,
+        );
+    }
+
+    console.log("\nLive login test passed.");
+};
+
+main().catch((err) => {
+    console.error("FAILED:", err);
+    process.exit(1);
+});