diff --git a/__pycache__/app.cpython-312.pyc b/__pycache__/app.cpython-312.pyc
new file mode 100644
index 0000000..b73177c
Binary files /dev/null and b/__pycache__/app.cpython-312.pyc differ
diff --git a/app.py b/app.py
index 852fff3..553ef42 100644
--- a/app.py
+++ b/app.py
@@ -4,6 +4,7 @@ Multi-Agent Decision Workshop - 主应用
 """
 import streamlit as st
 import os
+import base64
 from dotenv import load_dotenv
 
 # 加载环境变量
@@ -197,6 +198,23 @@ with st.sidebar:
         on_change=save_current_config
     )
             
+    # 页面背景图片（全局）
+    bg_file = st.file_uploader("页面背景图片（可选）", type=['png', 'jpg', 'jpeg', 'gif'], key='page_bg_uploader')
+    if bg_file:
+        # 保存到 assets 并在 session_state 中保存 data url 用于注入样式
+        saved_path = st.session_state.storage.save_asset(bg_file)
+        st.session_state.bg_image_path = saved_path
+        try:
+            buf = bg_file.getbuffer()
+        except Exception:
+            buf = bg_file.read()
+        # detect mime
+        ext = (bg_file.name.split('.')[-1].lower() if hasattr(bg_file, 'name') and bg_file.name else 'png')
+        mime = 'image/png' if ext == 'png' else ('image/gif' if ext == 'gif' else 'image/jpeg')
+        data_url = f"data:{mime};base64,{base64.b64encode(buf).decode()}"
+        st.session_state.bg_image_data_url = data_url
+        st.success("页面背景已上传并保存")
+
     st.divider()
     
     # 模式选择
@@ -275,9 +293,23 @@ with st.sidebar:
                         del st.session_state.custom_agents[agent_id]
                         st.rerun()
 
+# 注入全局页面背景样式（如果已上传）
+if st.session_state.get("bg_image_data_url"):
+    st.markdown(
+        f"""<style>
+        .stApp {{
+            background-image: url('{st.session_state.get('bg_image_data_url')}');
+            background-size: cover;
+            background-position: center;
+            background-attachment: fixed;
+        }}
+        </style>""",
+        unsafe_allow_html=True
+    )
+
 # ==================== 主界面逻辑 ====================
 
-if mode == "Deep Research":
+if st.session_state.mode == "Deep Research":
     st.title("🧪 Multi-Model Council V4")
     st.markdown("*多模型智囊团：自定义 N 个专家进行多轮对话讨论，最后由最后一位专家决策*")
     
@@ -312,7 +344,6 @@ if mode == "Deep Research":
             })
             
     research_context = st.text_area("补充背景 (可选)", placeholder="任何额外的背景信息...", height=80)
-    research_image = st.file_uploader("上传背景图片（可选）", type=['png', 'jpg', 'jpeg', 'gif'], key='research_bg')
     
     start_research_btn = st.button("🚀 开始多模型协作", type="primary", disabled=not research_topic)
     
@@ -320,16 +351,14 @@ if mode == "Deep Research":
         st.session_state.research_started = True
         st.session_state.research_output = ""
         st.session_state.research_steps_output = []
-        # 如果上传了背景图片，保存到 assets
-        research_bg_path = None
-        if research_image:
-            research_bg_path = st.session_state.storage.save_asset(research_image)
-            if research_bg_path:
-                st.success("背景图片已上传并保存")
-                try:
-                    st.image(research_image, caption="已上传背景图片预览", use_column_width=True)
-                except Exception:
-                    pass
+        # 使用全局页面背景（若已上传）
+        research_bg_path = st.session_state.get("bg_image_path")
+        if st.session_state.get("bg_image_data_url"):
+            try:
+                st.markdown("**页面背景预览**")
+                st.image(st.session_state.get("bg_image_data_url"), use_column_width=True)
+            except Exception:
+                pass
 
         manager = ResearchManager(
             api_key=api_key, 
@@ -418,7 +447,7 @@ if mode == "Deep Research":
                 st.divider()
 
 
-elif mode == "Debate Workshop":
+elif st.session_state.mode == "Debate Workshop":
     # ==================== 原始 Debate UI 逻辑 ====================
     st.title("🎭 多 Agent 决策工作坊")
     st.markdown("*让多个 AI 角色从不同视角辩论，帮助你做出更全面的决策*")
@@ -451,7 +480,7 @@ elif mode == "Debate Workshop":
                 placeholder="提供更多上下文信息，如：\n- 当前状况\n- 已有的资源和限制\n- 相关数据和事实",
                 height=100
             )
-            context_image = st.file_uploader("上传背景图片（可选）", type=['png', 'jpg', 'jpeg', 'gif'], key='debate_bg')
+            # 页面背景请使用侧边栏的“页面背景图片”上传控件进行设置（全局）
         context = context if 'context' in dir() else ""
     
     with col2:
@@ -570,20 +599,14 @@ elif mode == "Debate Workshop":
                         model=ag_model
                     )
 
-            # 如果在界面上传了背景图片，自动保存到 assets
-            debate_bg_path = None
-            try:
-                if 'context_image' in locals() and context_image:
-                    debate_bg_path = st.session_state.storage.save_asset(context_image)
-                    if debate_bg_path:
-                        st.success("背景图片已上传并保存")
-                        try:
-                            st.image(context_image, caption="已上传背景图片预览", use_column_width=True)
-                        except Exception:
-                            pass
-            except Exception:
-                # ignore upload errors but continue
-                debate_bg_path = None
+            # 使用全局页面背景（若已上传）
+            debate_bg_path = st.session_state.get("bg_image_path")
+            if st.session_state.get("bg_image_data_url"):
+                try:
+                    st.markdown("**页面背景预览**")
+                    st.image(st.session_state.get("bg_image_data_url"), use_column_width=True)
+                except Exception:
+                    pass
 
             debate_manager = DebateManager(llm_client)
             
@@ -628,11 +651,7 @@ elif mode == "Debate Workshop":
                         "round": current_round
                     })
                     st.divider()
-                
-                elif event["type"] == "debate_end":
-                    st.session_state.debate_finished = True
-                    st.success("✅ 辩论结束！正在生成决策报告...")
-            
+
             # 生成报告
             if st.session_state.debate_finished:
                 report_generator = ReportGenerator(llm_client)
@@ -661,7 +680,7 @@ elif mode == "Debate Workshop":
                         "rounds": max_rounds,
                         "agents": selected_agents,
                         "language": output_language,
-                        **({"background_image": debate_bg_path} if debate_bg_path else {})
+                        **({"background_image": st.session_state.get("bg_image_path")} if st.session_state.get("bg_image_path") else {})
                     }
                 )
                 st.toast("✅ 记录已保存到历史档案")