diff --git a/static/admin/agent.js b/static/admin/agent.js
index 9ae532c..082de5e 100644
--- a/static/admin/agent.js
+++ b/static/admin/agent.js
@@ -184,9 +184,11 @@ function listenStream(runId){
     const cards = msgEl.querySelector('.agent-toolcards');
     const card = document.createElement('div');
     card.className = 'agent-toolcard';
+    const argsTxt = typeof d.args === 'string' ? d.args
+                    : JSON.stringify(d.args || {});
     card.innerHTML = '<span class="dot"></span>'
       + '<code style="color:var(--teal)">' + esc(d.tool||'') + '</code>'
-      + '<span class="text-muted">' + esc(d.args||'') + '</span>';
+      + '<span class="text-muted">' + esc(argsTxt) + '</span>';
     if(d.image){
       const img = document.createElement('img');
       img.src = 'data:image/jpeg;base64,' + d.image;
@@ -242,11 +244,13 @@ function stopLive(){
   document.getElementById('agent-live-empty').style.display = 'block';
   document.getElementById('agent-live-serial').textContent = '';
 }
-function followSerialFromArgs(argsStr){
-  try{
-    const a = JSON.parse(argsStr || '{}');
-    if(a.serial) showLive(a.serial);
-  }catch(e){}
+function followSerialFromArgs(args){
+  // 工具 args（后端 SSE 已序列化为对象；兼容历史字符串格式）
+  let a = args;
+  if(typeof args === 'string'){
+    try{ a = JSON.parse(args); }catch(e){ return; }
+  }
+  if(a && a.serial) showLive(a.serial);
 }
 function watchDevice(serial){
   if(!serial){ stopLive(); return; }
diff --git a/web/agent_api.py b/web/agent_api.py
index 4781f81..1750915 100644
--- a/web/agent_api.py
+++ b/web/agent_api.py
@@ -594,8 +594,10 @@ def _agent_thread(run_id, prompt, serial, cfg):
         tool_seq = []   # 本轮工具序列（经验提炼用）
 
         def on_tool(step):
+            # args 保留对象（json.dumps 序列化）——前端要解析 serial 做画面跟随；
+            # 之前 str() 成 Python repr（单引号）导致前端 JSON.parse 失败、跟随失效
             rec = {"tool": step.get("tool"),
-                   "args": str(step.get("args"))[:200]}
+                   "args": step.get("args") or {}}
             if step.get("image"):
                 rec["image"] = _shrink_image(step["image"])
             q.put(("step", rec))