diff --git a/internal/plugin/registry.go b/internal/plugin/registry.go
index 2903270..75a387d 100644
--- a/internal/plugin/registry.go
+++ b/internal/plugin/registry.go
@@ -672,6 +672,33 @@ func (r *Registry) IsBuiltinPlugin(name string) bool {
 	return ok
 }
 
+// pluginInstalled 判断插件是否已安装（可用于禁用/启用等操作前的存在性校验）。
+// 命中任一即视为已安装：
+//  1. 已加载（plugins map 中）
+//  2. 已注册工厂（内置插件，通过 init() 自注册，无需物理目录）
+//  3. 插件目录 plgDir/<name> 存在（外部插件的安装目录）
+func (r *Registry) pluginInstalled(name string) bool {
+	if r == nil || name == "" {
+		return false
+	}
+	r.mu.RLock()
+	_, loaded := r.plugins[name]
+	_, isFactory := r.factories[name]
+	r.mu.RUnlock()
+	if loaded || isFactory {
+		return true
+	}
+	if _, ok := globalFactories.Load(name); ok {
+		return true
+	}
+	if r.plgDir != "" {
+		if fi, err := os.Stat(filepath.Join(r.plgDir, name)); err == nil && fi.IsDir() {
+			return true
+		}
+	}
+	return false
+}
+
 func (r *Registry) ListLoadedPlugins() []string { return r.List() }
 
 func (r *Registry) ListDisabledPlugins() []sdk.DisabledPluginInfo {
@@ -692,6 +719,11 @@ func (r *Registry) ListDisabledPlugins() []sdk.DisabledPluginInfo {
 func (r *Registry) IsPluginDisabled(name string) bool { return r.isDisabled(name) }
 
 func (r *Registry) DisablePlugin(name, by string) error {
+	// 插件不存在（未安装）：拒绝并返回错误，避免把不存在的插件写进 disabled_plugins。
+	// 判断标准：已加载 / 已注册工厂（内置）/ 插件目录存在，任一命中视为已安装。
+	if !r.pluginInstalled(name) {
+		return fmt.Errorf("plugin %s not installed", name)
+	}
 	// Check not disabling self if running
 	if r.cfgReg != nil {
 		// If already disabled, no-op
@@ -731,7 +763,6 @@ func (r *Registry) DisablePlugin(name, by string) error {
 }
 
 func (r *Registry) EnablePlugin(name string) error { return r.Enable(name) }
-
 // StopAndUnload 停止并从注册表移除插件，但保留其配置表（config_<name>）。
 // 供插件更新/升级流程使用：换 so/文件不动配置，重装后配置原样生效。
 // 不执行 onRemove 回调（那是删除专用语义）。目录由调用方管理。
diff --git a/internal/plugin/registry_disable_test.go b/internal/plugin/registry_disable_test.go
new file mode 100644
index 0000000..8664eff
--- /dev/null
+++ b/internal/plugin/registry_disable_test.go
@@ -0,0 +1,74 @@
+package plugin
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	sdk "gitcode.com/JianFeeeee/HomeAgent/internal/sdk"
+)
+
+// TestDisablePluginNotInstalled 验证 DisablePlugin 对未安装插件的拒绝：
+// 修复前会把任意名字写进 disabled_plugins 表（脏数据），修复后应直接报错。
+func TestDisablePluginNotInstalled(t *testing.T) {
+	r := &Registry{
+		plugins:       make(map[string]sdk.Plugin),
+		factories:     make(map[string]NativeFactory),
+		knownDisabled: make(map[string]bool),
+		plgDir:        t.TempDir(),
+	}
+	err := r.DisablePlugin("nonexistent_test_xyz", "test")
+	if err == nil {
+		t.Fatal("DisablePlugin should reject a plugin that is not installed")
+	}
+	if err.Error() != "plugin nonexistent_test_xyz not installed" {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if r.knownDisabled["nonexistent_test_xyz"] {
+		t.Fatal("knownDisabled must not contain a non-installed plugin")
+	}
+}
+
+// TestPluginInstalledFactory 内置插件（工厂注册，无物理目录）应视为已安装。
+func TestPluginInstalledFactory(t *testing.T) {
+	r := &Registry{
+		plugins:       make(map[string]sdk.Plugin),
+		factories:     map[string]NativeFactory{"builtin_demo": nil},
+		knownDisabled: make(map[string]bool),
+		plgDir:        t.TempDir(),
+	}
+	if !r.pluginInstalled("builtin_demo") {
+		t.Fatal("factory-registered builtin plugin should be considered installed")
+	}
+	if r.pluginInstalled("no_such_plugin") {
+		t.Fatal("unknown plugin should not be considered installed")
+	}
+}
+
+// TestPluginInstalledDir 外部插件按 plgDir/<name> 目录存在判定已安装。
+func TestPluginInstalledDir(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "external_demo"), 0o755); err != nil {
+		t.Fatalf("mkdir: %v", err)
+	}
+	r := &Registry{
+		plugins:       make(map[string]sdk.Plugin),
+		factories:     make(map[string]NativeFactory),
+		knownDisabled: make(map[string]bool),
+		plgDir:        dir,
+	}
+	if !r.pluginInstalled("external_demo") {
+		t.Fatal("plugin with an existing directory should be considered installed")
+	}
+	// 同名普通文件（非目录）不算已安装
+	if err := os.WriteFile(filepath.Join(dir, "just_a_file"), []byte("x"), 0o644); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	if r.pluginInstalled("just_a_file") {
+		t.Fatal("a regular file must not count as an installed plugin")
+	}
+	// 空名兜底
+	if r.pluginInstalled("") {
+		t.Fatal("empty plugin name must not be considered installed")
+	}
+}
diff --git a/internal/plugins/webui/handler.go b/internal/plugins/webui/handler.go
index 0719aeb..95ecde6 100644
--- a/internal/plugins/webui/handler.go
+++ b/internal/plugins/webui/handler.go
@@ -2600,7 +2600,16 @@ func (h *Handler) handlePluginByID(w http.ResponseWriter, r *http.Request) {
 					return
 				}
 				if err := h.pluginMgr.DisablePlugin(name, "webui"); err != nil {
-					writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+					// 未安装 → 404；已禁用 → 409；其余为真实内部错误
+					status := http.StatusInternalServerError
+					msg := err.Error()
+					switch {
+					case strings.HasSuffix(msg, "not installed"):
+						status = http.StatusNotFound
+					case strings.HasSuffix(msg, "already disabled"):
+						status = http.StatusConflict
+					}
+					writeJSON(w, status, map[string]string{"error": msg})
 					return
 				}
 				writeJSON(w, http.StatusOK, map[string]string{"status": "disabled"})
@@ -2616,7 +2625,12 @@ func (h *Handler) handlePluginByID(w http.ResponseWriter, r *http.Request) {
 					return
 				}
 				if err := h.pluginMgr.EnablePlugin(name); err != nil {
-					writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+					// 启用失败多数是“插件不存在/加载失败” → 404 更贴切
+					status := http.StatusInternalServerError
+					if strings.Contains(err.Error(), "failed") {
+						status = http.StatusNotFound
+					}
+					writeJSON(w, status, map[string]string{"error": err.Error()})
 					return
 				}
 				writeJSON(w, http.StatusOK, map[string]string{"status": "enabled"})