diff --git a/modules/backend b/modules/backend
index 76c75ce5..741da4a0 160000
--- a/modules/backend
+++ b/modules/backend
@@ -1 +1 @@
-Subproject commit 76c75ce50c0ccf8b9bb26f28ba7c29c13220b7d9
+Subproject commit 741da4a0b6c8d8e5b665789bda33f65ed3471a0e
diff --git a/tests/integration/multi-instance/multi_instance_test.go b/tests/integration/multi-instance/multi_instance_test.go
index f5952860..7c9f30fc 100644
--- a/tests/integration/multi-instance/multi_instance_test.go
+++ b/tests/integration/multi-instance/multi_instance_test.go
@@ -42,9 +42,6 @@ const (
 	aliceOwner = "mi_alice"
 	alicePass0 = "mi-alice-pass-0"
 	alicePass  = "mi-alice-pass-1"
-	bossOwner  = "mi_boss"
-	bossPass0  = "mi-boss-pass-0"
-	bossPass   = "mi-boss-pass-1"
 	httpWait   = 15 * time.Second
 )
 
@@ -462,34 +459,12 @@ func (e *env) loginAlice(t *testing.T) *userClient {
 		apiB:    &http.Client{Timeout: httpWait, Transport: bearerRT{key: key}},
 		streamB: &http.Client{Transport: bearerRT{key: key}}, // SSE 无整体超时；chan 背压控制
 	}
-	// --mock 只写 OwnerDefault 的设置；alice 是独立租户，须显式开 mock
-	// （selectConversationRunner 按 EffectiveSettings 分流），否则 run 走
-	// LLMRunner 且无模型配置直接失败。P2 受管：runtime.mock 是系统受管项且
-	// 本环境 --auth on，须由管理员经系统面开启（对全部租户生效）；alice
-	// 保持普通租户身份不变。
-	e.enableMockViaSystemAdmin(t)
+	// P2 受管（Backend #190）：--mock 启动选项播种系统层（runtime.mock 为
+	// 系统受管项），对全部租户生效——alice 无需再显式开启 mock；
+	// selectConversationRunner 按 EffectiveSettings 分流到 MockRunner。
 	return uc
 }
 
-// enableMockViaSystemAdmin 用一次性管理员会话经系统面开启 mock（P2 后的
-// 正规路径：受管项写入面要求 isAdmin；新账号须先过改密门才能走业务接口）。
-func (e *env) enableMockViaSystemAdmin(t *testing.T) {
-	t.Helper()
-	e.cli(t, "user", "create", "--dsn", e.dbDSN, "--owner", bossOwner, "--name", "Boss", "--password", bossPass0, "--role", "admin")
-	jar, err := cookiejar.New(nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	sess := &http.Client{Timeout: httpWait, Jar: jar}
-	e.do(t, sess, "POST", "/api/auth/login", map[string]any{
-		"owner": bossOwner, "password": bossPass0,
-	}, nil)
-	e.do(t, sess, "POST", "/api/auth/password", map[string]any{
-		"current": bossPass0, "next": bossPass,
-	}, nil)
-	e.do(t, sess, "PUT", "/api/settings/system", map[string]any{"runtime": map[string]any{"mock": true}}, nil)
-}
-
 // bearerRT 为所有请求附加 Authorization: Bearer <key>。
 type bearerRT struct{ key string }