diff --git a/src/core.rs b/src/core.rs
index 96de648..f29caad 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -18,10 +18,7 @@ pub(crate) trait Core: Send + Sync {
 
 #[derive(Serialize)]
 pub(crate) struct ClientConfig {
-    #[serde(
-        rename = "serviceAccountToken",
-        skip_serializing_if = "String::is_empty"
-    )]
+    #[serde(rename = "serviceAccountToken")]
     pub sa_token: String,
     #[serde(rename = "programmingLanguage")]
     pub language: String,
@@ -41,7 +38,7 @@ pub(crate) struct ClientConfig {
     pub system_os_version: String,
     #[serde(rename = "architecture")]
     pub system_arch: String,
-    #[serde(skip_serializing)]
+    #[serde(rename = "account_name", skip_serializing_if = "Option::is_none")]
     pub account_name: Option<String>,
 }
 
@@ -183,22 +180,23 @@ mod tests {
     }
 
     #[test]
-    fn service_account_config_serializes_token() {
+    fn service_account_config_omits_account_name() {
         let mut config = ClientConfig::new_default();
         config.sa_token = "ops_test".to_string();
 
         let value = serde_json::to_value(&config).unwrap();
         assert_eq!(value["serviceAccountToken"], "ops_test");
+        assert!(value.get("account_name").is_none());
     }
 
     #[test]
-    fn desktop_config_omits_auth_fields_from_core_config() {
+    fn desktop_config_includes_account_name() {
         let mut config = ClientConfig::new_default();
         config.account_name = Some("myaccount".to_string());
 
         let value = serde_json::to_value(&config).unwrap();
-        assert!(value.get("serviceAccountToken").is_none());
-        assert!(value.get("account_name").is_none());
+        assert_eq!(value["serviceAccountToken"], "");
+        assert_eq!(value["account_name"], "myaccount");
     }
 
     struct InvalidUtf8Core;
diff --git a/src/core_shared_lib.rs b/src/core_shared_lib.rs
index 7e5c848..4df2140 100644
--- a/src/core_shared_lib.rs
+++ b/src/core_shared_lib.rs
@@ -37,23 +37,33 @@ struct Request {
 }
 
 /// JSON response envelope received from the shared library.
-/// Go's json.Marshal encodes `[]byte` as a base64 string.
+/// The payload may arrive as either a base64 string (Go's json.Marshal of []byte)
+/// or a raw JSON byte array, depending on the library version.
 #[derive(Deserialize)]
 struct Response {
     success: bool,
-    #[serde(with = "base64_payload")]
+    #[serde(with = "flexible_payload")]
     payload: Vec<u8>,
 }
 
-mod base64_payload {
+mod flexible_payload {
     use base64::Engine;
     use serde::{Deserialize, Deserializer};
 
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    enum BytesOrBase64 {
+        Bytes(Vec<u8>),
+        Base64(String),
+    }
+
     pub fn deserialize<'de, D: Deserializer<'de>>(deserializer: D) -> Result<Vec<u8>, D::Error> {
-        let s = String::deserialize(deserializer)?;
-        base64::engine::general_purpose::STANDARD
-            .decode(&s)
-            .map_err(serde::de::Error::custom)
+        match BytesOrBase64::deserialize(deserializer)? {
+            BytesOrBase64::Bytes(v) => Ok(v),
+            BytesOrBase64::Base64(s) => base64::engine::general_purpose::STANDARD
+                .decode(&s)
+                .map_err(serde::de::Error::custom),
+        }
     }
 }
 
@@ -284,4 +294,17 @@ mod tests {
         assert!(response.success);
         assert_eq!(response.payload, b"payload");
     }
+
+    #[test]
+    fn response_payload_deserializes_from_byte_array() {
+        let response_json = serde_json::json!({
+            "success": false,
+            "payload": [104, 101, 108, 108, 111],
+        })
+        .to_string();
+
+        let response: Response = serde_json::from_str(&response_json).unwrap();
+        assert!(!response.success);
+        assert_eq!(response.payload, b"hello");
+    }
 }