diff --git a/core/functions/result_handler.py b/core/functions/result_handler.py
index 4d98b53..a84b6ec 100644
--- a/core/functions/result_handler.py
+++ b/core/functions/result_handler.py
@@ -3,8 +3,18 @@ import json
 import csv
 import os
 import time
+import dataclasses
 from typing import Any, Dict, List
 
+
+class _InferenceResultEncoder(json.JSONEncoder):
+    """將 dataclass 推論結果物件轉為可序列化的 dict。"""
+    def default(self, o):
+        if dataclasses.is_dataclass(o) and not isinstance(o, type):
+            return dataclasses.asdict(o)
+        return super().default(o)
+
+
 class ResultSerializer:
     """
     Serializes inference results into various formats.
@@ -12,8 +22,10 @@ class ResultSerializer:
     def to_json(self, data: Dict[str, Any]) -> str:
         """
         Serializes data to a JSON string.
+        Dataclass objects (ObjectDetectionResult, ClassificationResult, etc.)
+        are automatically converted to dicts via _InferenceResultEncoder.
         """
-        return json.dumps(data, indent=2)
+        return json.dumps(data, indent=2, cls=_InferenceResultEncoder)
 
     def to_csv(self, data: List[Dict[str, Any]], fieldnames: List[str]) -> str:
         """
diff --git a/main.py b/main.py
index 623238c..4615529 100644
--- a/main.py
+++ b/main.py
@@ -233,10 +233,10 @@ class SingleInstance:
 
 def setup_application():
     """Initialize and configure the QApplication."""
-    # Enable high DPI support BEFORE creating QApplication
-    QApplication.setAttribute(Qt.AA_EnableHighDpiScaling, True)
-    QApplication.setAttribute(Qt.AA_UseHighDpiPixmaps, True)
-    
+    # High DPI attributes must be set before QApplication is created.
+    # They are set in main() before the first QApplication instantiation.
+    # Do NOT set them here — QApplication already exists at this point.
+
     # Create QApplication if it doesn't exist
     if not QApplication.instance():
         app = QApplication(sys.argv)
diff --git a/ui/dialogs/deployment.py b/ui/dialogs/deployment.py
index efd3544..13cd1f9 100644
--- a/ui/dialogs/deployment.py
+++ b/ui/dialogs/deployment.py
@@ -1163,22 +1163,22 @@ Stage Configurations:
     def update_terminal_output(self, terminal_text: str):
         """Update the terminal output display with new text."""
         try:
-            # Use append() instead of setPlainText() for better performance and no truncation
             self.terminal_output_display.append(terminal_text.rstrip('\n'))
-            
+
             # Auto-scroll to bottom
             scrollbar = self.terminal_output_display.verticalScrollBar()
             scrollbar.setValue(scrollbar.maximum())
-            
-            # Optional: Limit total lines to prevent excessive memory usage
-            # Only trim if we have way too many lines (e.g., > 1000)
+
+            # Limit total lines to prevent excessive memory usage.
+            # Use toPlainText/setPlainText to avoid QTextCursor cross-thread warnings.
             document = self.terminal_output_display.document()
             if document.lineCount() > 1000:
-                cursor = self.terminal_output_display.textCursor()
-                cursor.movePosition(cursor.Start)
-                cursor.movePosition(cursor.Down, cursor.KeepAnchor, 200)  # Select first 200 lines
-                cursor.removeSelectedText()
-            
+                lines = self.terminal_output_display.toPlainText().split('\n')
+                trimmed = '\n'.join(lines[-800:])  # Keep last 800 lines
+                self.terminal_output_display.setPlainText(trimmed)
+                # Restore scroll to bottom after setPlainText resets it
+                scrollbar.setValue(scrollbar.maximum())
+
         except Exception as e:
             print(f"Error updating terminal output: {e}")