fix(proxy): align shadow turns to tail on client history truncation

src-tauri/src/proxy/thinking_rectifier.rs

@@ -52,6 +52,14 @@ pub fn should_rectify_thinking_signature(
         return true;
     }
 
+    // 场景1b: Gemini/第三方渠道返回 "Thought signature is not valid"
+    // 错误示例: "Unable to submit request because Thought signature is not valid"
+    if lower.contains("thought signature")
+        && (lower.contains("not valid") || lower.contains("invalid"))
+    {
+        return true;
+    }
+
     // 场景2: assistant 消息必须以 thinking block 开头
     // 错误示例: "must start with a thinking block"
     if lower.contains("must start with a thinking block") {
@@ -280,6 +288,16 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn test_detect_invalid_thought_signature_message() {
+        assert!(should_rectify_thinking_signature(
+            Some(
+                "Unable to submit request because Thought signature is not valid.. Learn more: https://example.com/help"
+            ),
+            &enabled_config()
+        ));
+    }
+
     #[test]
     fn test_detect_invalid_signature_nested_json() {
         // 测试嵌套 JSON 格式的错误消息（第三方渠道常见格式）
@@ -290,6 +308,15 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn test_detect_invalid_thought_signature_nested_json() {
+        let nested_error = r#"{"error":{"message":"Unable to submit request because Thought signature is not valid.. Learn more: https://example.com/help","type":"upstream_error","param":"","code":400}}"#;
+        assert!(should_rectify_thinking_signature(
+            Some(nested_error),
+            &enabled_config()
+        ));
+    }
+
     #[test]
     fn test_detect_thinking_expected() {
         assert!(should_rectify_thinking_signature(