diff --git a/cmd/gui/renderer/app.js b/cmd/gui/renderer/app.js
index c211670..df7f9ef 100644
--- a/cmd/gui/renderer/app.js
+++ b/cmd/gui/renderer/app.js
@@ -43,6 +43,7 @@ const state = {
   pendingTools: [],
   eventSource: null,
   chatFinalIdx: -1,
+  sseLastEventID: "", // 最近一次 SSE 事件 id，断线重连时随 Last-Event-ID 头回传
   lang: localStorage.getItem("ha-lang") || "zh",
   connections: [],
   currentConn: null,
@@ -325,6 +326,29 @@ function toggleAppearance() {
 })();
 
 // ===== Utility =====
+// 安全渲染 markdown：marked 转 HTML 后由 DOMPurify 剥离脚本/事件/危险标签。
+// CDN 加载失败时降级为纯转义文本，绝不把未消毒 HTML 直接写入 innerHTML。
+function renderMd(text) {
+  if (typeof text !== "string") text = String(text || "");
+  var html;
+  if (typeof marked !== "undefined") {
+    try { html = marked.parse(text); }
+    catch (e) { html = escHtml(text); }
+  } else {
+    html = "<pre>" + escHtml(text) + "</pre>";
+  }
+  if (typeof DOMPurify !== "undefined" && typeof DOMPurify.sanitize === "function") {
+    try { return DOMPurify.sanitize(html, { USE_PROFILES: { html: true } }); }
+    catch (e) {}
+  }
+  // 兜底：手动删除 <script> 块 + 危险属性/事件句柄（CDN 加载失败时）
+  return html
+    .replace(/<script[\s\S]*?<\/script>/gi, "")
+    .replace(/\son\w+\s*=\s*"[^"]*"/gi, "")
+    .replace(/\son\w+\s*=\s*'[^']*'/gi, "")
+    .replace(/javascript:/gi, "");
+}
+
 function escHtml(s) {
   return String(s)
     .replace(/&/g, "&amp;")
@@ -459,6 +483,17 @@ function cliMap(path, o) {
   );
 }
 
+// HTTP API 错误对象：携带 status/statusText/body，便于调用方按 HTTP 语义分支处理。
+function ApiError(message, status, statusText, body) {
+  this.name = "ApiError";
+  this.message = message;
+  this.status = status;
+  this.statusText = statusText || "";
+  this.body = body || null;
+  this.stack = (new Error()).stack;
+}
+ApiError.prototype = Object.create(Error.prototype);
+
 async function api(p, o) {
   if (!state.currentConn)
     throw new Error(__("未选择连接", "No connection selected"));
@@ -487,7 +522,7 @@ async function api(p, o) {
   clearTimeout(timer);
   if (r.status === 401) {
     // 认证失败：尝试自动重新登录一次（避免 cookie 过期后界面持续报错）
-    if (window._haReloginLock) throw new Error(__("认证失败", "unauthorized"));
+    if (window._haReloginLock) throw new ApiError(__("认证失败", "unauthorized"), 401, r.statusText, null);
     window._haReloginLock = true;
     try {
       await syncConnAuth();
@@ -497,6 +532,20 @@ async function api(p, o) {
     // 重试一次
     return api(p, o);
   }
+  if (r.status === 408 || r.status === 504) {
+    // 网关超时：API 层直接抛错，调用方可选择提示用户重试或自动降级
+    throw new ApiError(__("请求超时", "Request timeout"), r.status, r.statusText, null);
+  }
+  if (r.status === 429) {
+    // 限流：抛错 + 建议调用方退避
+    var retryAfter = r.headers.get("Retry-After");
+    throw new ApiError(
+      __("请求过于频繁，请稍后重试", "Rate limited, please retry later"),
+      429,
+      r.statusText,
+      retryAfter ? { retryAfterSeconds: parseInt(retryAfter, 10) } : null,
+    );
+  }
   if (opts.raw) return r;
   var body = await r.text();
   // 网关会话过期：返回 200 但内容为登录页 HTML —— 自动重登后重试
@@ -505,7 +554,7 @@ async function api(p, o) {
     body.indexOf("统一门户登录") !== -1 ||
     (body.indexOf("<title>") !== -1 && body.indexOf("login") !== -1)
   ) {
-    if (window._haReloginLock) throw new Error(__("认证失败", "unauthorized"));
+    if (window._haReloginLock) throw new ApiError(__("认证失败", "unauthorized"), r.status, r.statusText, body);
     window._haReloginLock = true;
     try {
       await syncConnAuth();
@@ -514,6 +563,21 @@ async function api(p, o) {
     window._haReloginLock = false;
     return api(p, o);
   }
+  // 非 2xx 状态码：解包 server error + 以 ApiError 抛出，调用方按 status 分支处理
+  if (!r.ok) {
+    var errMsg = body;
+    try {
+      var parsed = JSON.parse(body);
+      if (parsed.error) errMsg = parsed.error;
+      else if (parsed.message) errMsg = parsed.message;
+    } catch (e) {}
+    throw new ApiError(
+      __("请求失败: ", "Request failed: ") + errMsg,
+      r.status,
+      r.statusText,
+      body,
+    );
+  }
   var ct = r.headers.get("content-type") || "";
   if (ct.includes("json")) {
     try {
@@ -562,6 +626,13 @@ function switchView(n) {
 
 // ===== Tab Render Dispatch =====
 async function doRenderAll() {
+  // 如果连接表单正在显示（用户正在编辑），跳过全量刷新，避免擦掉用户输入
+  var connForm = document.getElementById("conn-form");
+  if (connForm && connForm.style.display === "block") {
+    // 仅刷新数据，不重建 DOM
+    await refreshDataOnly();
+    return;
+  }
   await refreshAll();
 }
 
@@ -610,6 +681,86 @@ function renderAll() {
   refreshAll();
 }
 
+async function refreshDataOnly() {
+  // 仅刷新 state 数据，不重建 DOM（用于定时轮询时避免擦掉用户输入）
+  try {
+    var s = await api("/status");
+    state.status = s;
+    state.startedAt = s.startedAt ? new Date(s.startedAt).getTime() : null;
+    updateConnIndicator();
+  } catch (e) {}
+  try {
+    state.kernel = await api("/kernel");
+  } catch (e) {}
+  try {
+    var s = await api("/settings");
+    state.settings = s.settings || {};
+    state.meta = s.meta || {};
+    state.settingsPlugins = s.plugins || ["core"];
+    state.pluginMeta = s.plugin_meta || {};
+    state.disabledPlugins = s.disabled_plugins || [];
+  } catch (e) {}
+  try {
+    state.installedPlugins = await api("/plugins");
+  } catch (e) {}
+  try {
+    await loadTerminals();
+  } catch (e) {}
+  try {
+    await loadCmdHistory();
+  } catch (e) {}
+  try {
+    if (
+      state.currentConn &&
+      state.currentConn.type === "webui" &&
+      state.currentConn.url
+    ) {
+      var d = await api("/device/online");
+      state.devices = (d && d.devices) || [];
+    } else {
+      state.devices = [];
+    }
+  } catch (e) {
+    state.devices = [];
+  }
+  try {
+    try {
+      if (window.homeagent && window.homeagent.displays) {
+        state.displays = (await window.homeagent.displays.list()) || [];
+      }
+    } catch (e) {}
+    try {
+      if (window.homeagent && window.homeagent.audio) {
+        state.audioDevices = (await window.homeagent.audio.list()) || [];
+      }
+    } catch (e) {}
+    if (window.homeagent && window.homeagent.deviceBridge) {
+      var dbinfo = await window.homeagent.deviceBridge.get();
+      state.dbConfig = dbinfo || state.dbConfig;
+      if (dbinfo && dbinfo.enabled) {
+        if (dbinfo.deviceId) {
+          state.selfDeviceId = dbinfo.deviceId;
+          state.selfGateway = dbinfo.address || state.selfGateway;
+        }
+        if (
+          state.devices.length === 0 &&
+          dbinfo.gateway &&
+          window.homeagent &&
+          window.homeagent.device
+        ) {
+          try {
+            var eb = await window.homeagent.device.identity();
+            if (eb && eb.device_id) {
+              state.selfDeviceId = eb.device_id;
+              state.selfGateway = eb.address || dbinfo.gateway;
+            }
+          } catch (e2) {}
+        }
+      }
+    }
+  } catch (e) {}
+}
+
 async function refreshAll() {
   try {
     var s = await api("/status");
@@ -1232,7 +1383,7 @@ function renderChat() {
         if (typeof marked === "undefined") {
           c = "<pre>" + escHtml(c) + "</pre>";
         } else {
-          c = marked.parse(c);
+          c = renderMd(c);
         }
       } else if (role === "system") {
         c = escHtml(c);
@@ -1499,8 +1650,7 @@ function toggleReasoning(el) {
     var idx = parseInt(card.getAttribute("data-idx"), 10) || 0;
     var text =
       (state.messages[idx] && state.messages[idx].reasoning_content) || "";
-    content.innerHTML =
-      typeof marked === "undefined" ? escHtml(text) : marked.parse(text);
+    content.innerHTML = renderMd(text);
   }
   body.style.display = "block";
   card.classList.add("open");
@@ -4617,6 +4767,9 @@ async function connectFetchSSE(url) {
     var headers = {};
     if (state.currentConn && state.currentConn.apiKey)
       headers["X-API-Key"] = state.currentConn.apiKey;
+    // 断线重连时回传 Last-Event-ID，让服务端重放遗漏事件
+    if (state.sseLastEventID)
+      headers["Last-Event-ID"] = state.sseLastEventID;
     var resp = await fetch(url, { headers: headers, cache: "no-store" });
     if (!resp.ok || !resp.body) {
       setTimeout(() => {
@@ -4638,10 +4791,14 @@ async function connectFetchSSE(url) {
       var lines = buffer.split("\n");
       buffer = lines.pop() || "";
       var eventType = "",
-        data = "";
+        data = "",
+        id = "";
       for (var i = 0; i < lines.length; i++) {
         var line = lines[i];
-        if (line.startsWith("event: ")) eventType = line.slice(7).trim();
+        if (line.startsWith("id: ")) {
+          id = line.slice(4).trim();
+          if (id) state.sseLastEventID = id;
+        } else if (line.startsWith("event: ")) eventType = line.slice(7).trim();
         else if (line.startsWith("data: ")) data = line.slice(6).trim();
         else if (line === "" && eventType && data) {
           handleSSEEvent(eventType, data);
@@ -4795,13 +4952,15 @@ async function connectFetchSSE(url) {
       }
       reconnectTimer = setTimeout(() => {
         connectSSE();
-      }, 3000);
+      }, Math.min(1000 * Math.pow(2, Math.min((state._sseRetryAttempts || 0), 5)), 60000));
     }
     pump();
   } catch (e) {
+    var attempts = (state._sseRetryAttempts || 0) + 1;
+    state._sseRetryAttempts = attempts;
     setTimeout(() => {
       connectSSE();
-    }, 5000);
+    }, Math.min(1000 * Math.pow(2, Math.min(attempts - 1, 5)), 60000));
   }
 }
 
@@ -4851,8 +5010,7 @@ function renderChatStreamChunk() {
     var lastParse = el.__lastParse || 0;
     var lastLen = el.__lastLen || 0;
     if (c.length - lastLen > 200 || now - lastParse > 300) {
-      textEl.innerHTML =
-        typeof marked === "undefined" ? escHtml(c) : marked.parse(c);
+      textEl.innerHTML = renderMd(c);
       el.__lastParse = now;
       el.__lastLen = c.length;
     } else {
diff --git a/cmd/gui/renderer/index.html b/cmd/gui/renderer/index.html
index 567f4c0..4123ec5 100644
--- a/cmd/gui/renderer/index.html
+++ b/cmd/gui/renderer/index.html
@@ -18,6 +18,10 @@
       src="https://cdnjs.cloudflare.com/ajax/libs/marked/4.3.0/marked.min.js"
       onerror="console.warn('marked CDN failed')"
     ></script>
+    <script
+      src="https://cdn.jsdelivr.net/npm/dompurify@3.2.4/dist/purify.min.js"
+      onerror="console.warn('DOMPurify CDN failed')"
+    ></script>
     <script>
       setTimeout(function () {
         if (!window.THREE) window._THREE_FAILED = true;
diff --git a/internal/plugins/webui/dashboard.html b/internal/plugins/webui/dashboard.html
index 97acbcb..a62ebd5 100644
--- a/internal/plugins/webui/dashboard.html
+++ b/internal/plugins/webui/dashboard.html
@@ -17,6 +17,10 @@
       src="https://cdnjs.cloudflare.com/ajax/libs/marked/4.3.0/marked.min.js"
       onerror="console.warn('marked CDN failed')"
     ></script>
+    <script
+      src="https://cdn.jsdelivr.net/npm/dompurify@3.2.4/dist/purify.min.js"
+      onerror="console.warn('DOMPurify CDN failed')"
+    ></script>
     <script>
       setTimeout(function () {
         if (!window.THREE) window._THREE_FAILED = true;
@@ -2508,6 +2512,25 @@ background:
       })();
 
       // ===== Utility =====
+      function renderMd(text) {
+        if (typeof text !== "string") text = String(text || "");
+        var html;
+        if (typeof marked !== "undefined") {
+          try { html = marked.parse(text); }
+          catch (e) { html = escHtml(text); }
+        } else {
+          html = "<pre>" + escHtml(text) + "</pre>";
+        }
+        if (typeof DOMPurify !== "undefined" && typeof DOMPurify.sanitize === "function") {
+          try { return DOMPurify.sanitize(html, { USE_PROFILES: { html: true } }); }
+          catch (e) {}
+        }
+        return html
+          .replace(/<script[\s\S]*?<\/script>/gi, "")
+          .replace(/\son\w+\s*=\s*"[^"]*"/gi, "")
+          .replace(/\son\w+\s*=\s*'[^']*'/gi, "")
+          .replace(/javascript:/gi, "");
+      }
       function escHtml(s) {
         return String(s)
           .replace(/&/g, "&amp;")
@@ -3200,11 +3223,7 @@ background:
             var role = m.role || "user";
             var c = m.content || "";
             if (role === "assistant") {
-              if (typeof marked !== "undefined") {
-                c = marked.parse(c);
-              } else {
-                c = "<pre>" + escHtml(c) + "</pre>";
-              }
+              c = renderMd(c);
             } else if (role === "system") {
               c = escHtml(c);
             } else {
@@ -3384,10 +3403,7 @@ background:
       }
 
       function renderReasoningCard(text, isStreaming) {
-        var body =
-          typeof marked !== "undefined"
-            ? marked.parse(text)
-            : escHtml(text);
+        var body = renderMd(text);
         var preview =
           typeof marked !== "undefined"
             ? text.replace(/[\s\n]+/g, " ").slice(0, 60)
diff --git a/internal/plugins/webui/handler.go b/internal/plugins/webui/handler.go
index b2f6399..31635b6 100644
--- a/internal/plugins/webui/handler.go
+++ b/internal/plugins/webui/handler.go
@@ -66,6 +66,51 @@ func init() {
 	}
 }
 
+// sseEventRecord 保存一条 SSE 事件元数据，供断线重连时按 Last-Event-ID 重放遗漏事件。
+type sseEventRecord struct {
+	id        string          // SSE 事件 id 值（如 "1234567890-5"）
+	eventType string          // 事件类型（agent_output, reasoning 等）
+	data      json.RawMessage // 序列化后的 payload JSON
+}
+
+// sseEventRing 是一个固定大小的环状缓冲区，保持最近 cap 条 SSE 事件。
+type sseEventRing struct {
+	mu  sync.Mutex
+	buf []sseEventRecord
+	cap int
+}
+
+func newSSEEventRing(cap int) *sseEventRing {
+	return &sseEventRing{cap: cap}
+}
+
+// Append 追加一条事件，超过容量时丢弃最旧条目。
+func (r *sseEventRing) Append(id, eventType string, data json.RawMessage) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.buf = append(r.buf, sseEventRecord{id: id, eventType: eventType, data: data})
+	if len(r.buf) > r.cap {
+		r.buf = r.buf[len(r.buf)-r.cap:]
+	}
+}
+
+// After 返回所有在指定 id 之后的事件（按写入顺序），若 id 不在缓冲区中则返回全部。
+func (r *sseEventRing) After(id string) []sseEventRecord {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	for i := len(r.buf) - 1; i >= 0; i-- {
+		if r.buf[i].id == id {
+			result := make([]sseEventRecord, len(r.buf)-i-1)
+			copy(result, r.buf[i+1:])
+			return result
+		}
+	}
+	// ID 不在缓冲区（可能是太旧或从未收到），返回全部
+	result := make([]sseEventRecord, len(r.buf))
+	copy(result, r.buf)
+	return result
+}
+
 type Handler struct {
 	sdk        *sdk.PluginSDK
 	supervisor sdk.SupervisorAPI
@@ -85,6 +130,8 @@ type Handler struct {
 	sessionMu sync.Mutex
 	sessions  map[string]time.Time
 
+	sseEvents *sseEventRing // SSE 事件环状缓冲区，Last-Event-ID 重放用
+
 	chatMu      sync.Mutex
 	chatHistory []ChatMsg
 	pendingIdx  int // chatHistory 中正在进行的 assistant 消息索引，-1 表示无
@@ -214,6 +261,7 @@ func NewHandler(s *sdk.PluginSDK) *Handler {
 		termStates: make(map[string]*termState),
 		pendingIdx: -1,
 		chatMsgCache: make(map[string]*chatMsgEntry),
+		sseEvents:    newSSEEventRing(200),
 	}
 	h.loadChatHistory()
 	if s != nil {
@@ -1344,10 +1392,24 @@ func (h *Handler) handleChatEvents(w http.ResponseWriter, r *http.Request) {
 
 	log.Printf("[SSE] handler started, subscribing to events")
 
-	// 解析 Last-Event-ID（断线重连时客户端携带）
-	lastEventID := r.Header.Get("Last-Event-ID")
-	if lastEventID != "" {
+	// 解析 Last-Event-ID（断线重连时客户端携带），重放期间内遗漏的事件。
+	// 注意：本 handler 的 Last-Event-ID 重放仅为 GUI (cmd/gui/renderer/app.js) 服务。
+	// 浏览器原生 EventSource (webui/dashboard.html 使用) 由浏览器自动处理 Last-Event-ID 重连。
+	if lastEventID := r.Header.Get("Last-Event-ID"); lastEventID != "" {
 		log.Printf("[SSE] client reported Last-Event-ID: %s", lastEventID)
+		if h.sseEvents != nil {
+			replayed := h.sseEvents.After(lastEventID)
+			if len(replayed) == 0 {
+				log.Printf("[SSE] replay: nothing after id %s (id not in ring or already at tip)", lastEventID)
+			} else {
+				log.Printf("[SSE] replay: sending %d events after id %s", len(replayed), lastEventID)
+				for _, rec := range replayed {
+					fmt.Fprintf(w, "id: %s\nevent: %s\ndata: %s\n", rec.id, rec.eventType, string(rec.data))
+					flusher.Flush()
+				}
+				log.Printf("[SSE] replay complete, wrote %d events", len(replayed))
+			}
+		}
 	}
 
 	subTypes := []string{"agent_output", "reasoning", "agent_error", "tool_call", "stage", "agent_llm_chain", "terminal_output"}
@@ -1362,8 +1424,13 @@ func (h *Handler) handleChatEvents(w http.ResponseWriter, r *http.Request) {
 			}
 			data, _ := json.Marshal(evt)
 			seq++
+			id := fmt.Sprintf("%d-%d", evt.Timestamp, seq)
+			// 写入环状缓冲区，供断线重连重放
+			if h.sseEvents != nil {
+				h.sseEvents.Append(id, string(evt.Type), data)
+			}
 			select {
-			case writeCh <- fmt.Sprintf("id: %d-%d\nevent: %s\ndata: %s\n", evt.Timestamp, seq, evt.Type, string(data)):
+			case writeCh <- fmt.Sprintf("id: %s\nevent: %s\ndata: %s\n", id, evt.Type, string(data)):
 				if evt.Type == sdk.EventToolCall {
 					toolName, _ := evt.Payload["tool"].(string)
 					log.Printf("[SSE] wrote tool_call to writeCh: tool=%s", toolName)
diff --git a/internal/plugins/webui/handler_sse_test.go b/internal/plugins/webui/handler_sse_test.go
new file mode 100644
index 0000000..e32c3c0
--- /dev/null
+++ b/internal/plugins/webui/handler_sse_test.go
@@ -0,0 +1,96 @@
+package webui
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func TestSSEEventRing_Append_Capacity(t *testing.T) {
+	r := newSSEEventRing(3)
+	data := json.RawMessage(`{"a":1}`)
+	for i := 0; i < 5; i++ {
+		r.Append("id-"+string(rune('0'+i)), "agent_output", data)
+	}
+	// cap=3，只保留 id-2,id-3,id-4
+	if len(r.buf) != 3 {
+		t.Fatalf("expected 3, got %d", len(r.buf))
+	}
+	if r.buf[0].id != "id-2" {
+		t.Fatalf("expected id-2, got %s", r.buf[0].id)
+	}
+}
+
+func TestSSEEventRing_After_Mid(t *testing.T) {
+	r := newSSEEventRing(10)
+	data := json.RawMessage(`{"x":"y"}`)
+	r.Append("id-1", "reasoning", data)
+	r.Append("id-2", "agent_output", data)
+	r.Append("id-3", "tool_call", data)
+
+	after := r.After("id-2")
+	if len(after) != 1 || after[0].id != "id-3" {
+		t.Fatalf("expected [id-3], got %v", after)
+	}
+
+	after = r.After("id-3")
+	if len(after) != 0 {
+		t.Fatalf("expected 0, got %d", len(after))
+	}
+}
+
+func TestSSEEventRing_After_NotFound_ReturnsAll(t *testing.T) {
+	r := newSSEEventRing(3)
+	data := json.RawMessage(`{}`)
+	r.Append("id-1", "agent_output", data)
+	r.Append("id-2", "agent_output", data)
+
+	after := r.After("id-0")
+	if len(after) != 2 {
+		t.Fatalf("expected 2 (fallback to all), got %d", len(after))
+	}
+}
+
+func TestSSEEventRing_After_Last_Tip(t *testing.T) {
+	r := newSSEEventRing(5)
+	data := json.RawMessage(`{"a":1}`)
+	for i := 0; i < 5; i++ {
+		r.Append("id-"+string(rune('0'+i)), "agent_output", data)
+	}
+	after := r.After("id-4")
+	if len(after) != 0 {
+		t.Fatalf("expected 0 after tip, got %d", len(after))
+	}
+}
+
+func TestSSEEventRing_Concurrent(t *testing.T) {
+	r := newSSEEventRing(100)
+	done := make(chan struct{})
+	for i := 0; i < 8; i++ {
+		go func(n int) {
+			defer func() { done <- struct{}{} }()
+			data := json.RawMessage(`{}`)
+			for j := 0; j < 100; j++ {
+				r.Append("w"+string(rune('0'+n))+"/"+string(rune('0'+j)), "agent_output", data)
+			}
+		}(i)
+	}
+	for i := 0; i < 8; i++ {
+		go func() {
+			defer func() { done <- struct{}{} }()
+			for j := 0; j < 100; j++ {
+				_ = r.After("w0/0")
+			}
+		}()
+	}
+	for i := 0; i < 16; i++ {
+		<-done
+	}
+}
+
+func TestSSEEventRecord_Type(t *testing.T) {
+	var got interface{} = sseEventRecord{}
+	if reflect.TypeOf(got).Kind() != reflect.Struct {
+		t.Fatal("sseEventRecord should be a struct")
+	}
+}