diff --git a/docs/integration/heicode-desktop-client-api.md b/docs/integration/heicode-desktop-client-api.md
index d1d2ac55..a1071c64 100644
--- a/docs/integration/heicode-desktop-client-api.md
+++ b/docs/integration/heicode-desktop-client-api.md
@@ -241,7 +241,12 @@ signature = base64( ed25519_sign( device_priv, sha256(canonical) ) )
       "status": "Pending",                        // Pending | running | failed | stopped …
       "runtime_id": "dep-4bb07dc1e376",           // AM 侧运行时 id
       "created_at": "2026-06-04T09:04:15Z",
-      "updated_at": "2026-06-04T09:04:15Z"
+      "updated_at": "2026-06-04T09:04:15Z",
+      "security": {                                // ★ #55 A2A 直连安全元数据
+        "scheme": "http",                          //   http | https
+        "security_profile": "none",                //   none | tls | mtls
+        "secure": false                            //   = security_profile != none
+      }
     }
   ],
   "total": 1
@@ -327,6 +332,8 @@ signature = base64( ed25519_sign( device_priv, sha256(canonical) ) )
 > ⚠️ **连之前先确认 agent 就绪**:新建后 `status=Pending`(还在拉起)。等 `GET /api/heicode/agents/{id}/status` 变 `running`、或 `GET {subdomain}/health` 返 200 再连。**2026-06-04 复测:数秒即 `running`,`/health` 200、`/message/send` 带令牌任务 `completed`,直连已通。**
 >
 > ⚠️ 当前 AM 侧两点(待加固,不影响调通):① **令牌校验尚未真正生效**——无 `X-Agent-Access-Token` 也被放行;客户端仍应规范地每请求都带,等 AM 开启校验即自动生效。② 子域名目前 `http://` 明文,令牌/`api_key` 会明文传输,等 AM 上 HTTPS。
+>
+> 🔒 **传输安全门(#55)**:agent 对象回传 `security`(`scheme` http/https、`security_profile` none/tls/mtls、`secure` 布尔)。客户端据此在生产强制 HTTPS(`HEICODE_AGENT_REQUIRE_SECURE=1`):`secure=false`(当前明文)→ 拒绝直连并提示。AM 上线 HTTPS/mTLS listener 后 `security_profile` 自动变 tls,客户端无需改包。HM 保守口径:无法确证 TLS 即标 `none`。
 
 - **同步**:`POST {subdomain}/message/send`
 - **流式**:`POST {subdomain}/message/stream`(返回 `text/event-stream`)
diff --git a/heicode/controller/agent_endpoint_security_test.go b/heicode/controller/agent_endpoint_security_test.go
new file mode 100644
index 00000000..712220b1
--- /dev/null
+++ b/heicode/controller/agent_endpoint_security_test.go
@@ -0,0 +1,24 @@
+package controller
+
+import "testing"
+
+// #55: agent endpoint 安全级别推断 —— 明文/裸主机 = none(客户端生产可拒),显式 https = tls。
+func TestAgentEndpointSecurity(t *testing.T) {
+	cases := []struct {
+		in            string
+		scheme, prof  string
+		secure        bool
+	}{
+		{"https://dep-x.agents.example", "https", "tls", true},
+		{"http://dep-x.agents.example", "http", "none", false},
+		{"dep-x.taijiagnet.com", "http", "none", false}, // 裸主机:AM 当前明文
+		{"  HTTPS://Dep.Example  ", "https", "tls", true},
+		{"", "http", "none", false},
+	}
+	for _, c := range cases {
+		sc, pr, se := agentEndpointSecurity(c.in)
+		if sc != c.scheme || pr != c.prof || se != c.secure {
+			t.Errorf("agentEndpointSecurity(%q) = (%s,%s,%v), want (%s,%s,%v)", c.in, sc, pr, se, c.scheme, c.prof, c.secure)
+		}
+	}
+}
diff --git a/heicode/controller/agent_template_handlers.go b/heicode/controller/agent_template_handlers.go
index ec2f4390..21e010b5 100644
--- a/heicode/controller/agent_template_handlers.go
+++ b/heicode/controller/agent_template_handlers.go
@@ -111,6 +111,7 @@ func templateAgentResponse(row model.AgentDeployment) gin.H {
 	if strings.TrimSpace(row.BindingIDsJSON) != "" {
 		_ = common.UnmarshalJsonStr(row.BindingIDsJSON, &bindingIDs)
 	}
+	scheme, profile, secure := agentEndpointSecurity(row.Subdomain)
 	return gin.H{
 		"agent_id":     row.DeploymentID,
 		"template_id":  row.TemplateID,
@@ -121,6 +122,30 @@ func templateAgentResponse(row model.AgentDeployment) gin.H {
 		"runtime_id":   row.RuntimeDeploymentID,
 		"created_at":   row.CreatedAtText,
 		"updated_at":   row.UpdatedAtText,
+		// #55: A2A 直连安全元数据。客户端据此在生产强制 HTTPS(HEICODE_AGENT_REQUIRE_SECURE):
+		// scheme=http/https,security_profile=none/tls,secure=profile!=none。AM 启用 HTTPS/
+		// mTLS listener 是 AM(azgy)的事;HM 只如实回传当前子域安全级别,明文 http →
+		// security_profile=none,客户端可拒绝并提示(元数据不含任何 secret_ref)。
+		"security": gin.H{
+			"scheme":           scheme,
+			"security_profile": profile,
+			"secure":           secure,
+		},
+	}
+}
+
+// agentEndpointSecurity 从子域字符串推断 A2A 直连的安全级别(#55)。纯函数,可单测。
+// 显式 https:// → (https, tls, true);显式 http:// 或裸主机(AM 当前默认明文) → (http, none, false)。
+// 保守口径:无法确证 TLS 即视为 none,宁可让客户端在生产拒绝,也不回传"看似安全"的明文端点。
+func agentEndpointSecurity(subdomain string) (scheme, profile string, secure bool) {
+	s := strings.TrimSpace(strings.ToLower(subdomain))
+	switch {
+	case strings.HasPrefix(s, "https://"):
+		return "https", "tls", true
+	case strings.HasPrefix(s, "http://"):
+		return "http", "none", false
+	default:
+		return "http", "none", false // 裸主机:AM 当前明文 HTTP,保守标 none
 	}
 }