diff --git a/src/main/kotlin/org/zhavoronkov/tokenpulse/settings/Account.kt b/src/main/kotlin/org/zhavoronkov/tokenpulse/settings/Account.kt
index 65a66b4..8a57235 100644
--- a/src/main/kotlin/org/zhavoronkov/tokenpulse/settings/Account.kt
+++ b/src/main/kotlin/org/zhavoronkov/tokenpulse/settings/Account.kt
@@ -73,13 +73,13 @@ enum class AuthType(val displayName: String) {
  * @property keyPreview Masked preview of the API key for display purposes.
  */
 data class Account(
-    val id: String = UUID.randomUUID().toString(),
-    val name: String = "",
-    val connectionType: ConnectionType = ConnectionType.CLINE_API,
-    val authType: AuthType = AuthType.CLINE_API_KEY,
+    var id: String = UUID.randomUUID().toString(),
+    var name: String = "",
+    var connectionType: ConnectionType = ConnectionType.CLINE_API,
+    var authType: AuthType = AuthType.CLINE_API_KEY,
     var isEnabled: Boolean = true,
     /** Masked preview of the API key, e.g. "sk-or-…91bc". Stored for display only, not sensitive. */
-    val keyPreview: String = ""
+    var keyPreview: String = ""
 ) {
     /** Human-readable label shown in the accounts table. */
     fun displayLabel(): String {
diff --git a/src/test/kotlin/org/zhavoronkov/tokenpulse/settings/AccountTest.kt b/src/test/kotlin/org/zhavoronkov/tokenpulse/settings/AccountTest.kt
index 3600e74..955e723 100644
--- a/src/test/kotlin/org/zhavoronkov/tokenpulse/settings/AccountTest.kt
+++ b/src/test/kotlin/org/zhavoronkov/tokenpulse/settings/AccountTest.kt
@@ -63,6 +63,66 @@ class AccountTest {
 
         assertEquals("OpenAI: Codex CLI", label)
     }
+
+    @Test
+    fun `Account fields are mutable (var not val) for XStream serialization`() {
+        val account = Account(
+            id = "test-id",
+            name = "Test",
+            connectionType = ConnectionType.OPENROUTER_PROVISIONING,
+            authType = AuthType.OPENROUTER_PROVISIONING_KEY,
+            keyPreview = "sk-or-…91bc"
+        )
+
+        // Verify all fields can be modified (var not val)
+        account.id = "new-id"
+        account.name = "New Name"
+        account.connectionType = ConnectionType.XIAOMI_API
+        account.authType = AuthType.XIAOMI_API_KEY
+        account.isEnabled = false
+        account.keyPreview = "new-preview"
+
+        assertEquals("new-id", account.id)
+        assertEquals("New Name", account.name)
+        assertEquals(ConnectionType.XIAOMI_API, account.connectionType)
+        assertEquals(AuthType.XIAOMI_API_KEY, account.authType)
+        assertFalse(account.isEnabled)
+        assertEquals("new-preview", account.keyPreview)
+    }
+
+    @Test
+    fun `Account copy preserves all fields`() {
+        val original = Account(
+            id = "test-id",
+            name = "Test",
+            connectionType = ConnectionType.XIAOMI_TOKEN_PLAN,
+            authType = AuthType.XIAOMI_TOKEN_PLAN_KEY,
+            isEnabled = false,
+            keyPreview = "tp-…1234"
+        )
+
+        val copy = original.copy()
+
+        assertEquals(original.id, copy.id)
+        assertEquals(original.name, copy.name)
+        assertEquals(original.connectionType, copy.connectionType)
+        assertEquals(original.authType, copy.authType)
+        assertEquals(original.isEnabled, copy.isEnabled)
+        assertEquals(original.keyPreview, copy.keyPreview)
+    }
+
+    @Test
+    fun `Account connectionType and authType are preserved after copy`() {
+        val original = Account(
+            connectionType = ConnectionType.NEBIUS_BILLING,
+            authType = AuthType.NEBIUS_BILLING_SESSION
+        )
+
+        val copy = original.copy(name = "Updated")
+
+        assertEquals(ConnectionType.NEBIUS_BILLING, copy.connectionType)
+        assertEquals(AuthType.NEBIUS_BILLING_SESSION, copy.authType)
+    }
 }
 
 /**