diff --git a/sdk/plugin.go b/sdk/plugin.go
index ca5e9a6..fa3a89d 100644
--- a/sdk/plugin.go
+++ b/sdk/plugin.go
@@ -111,6 +111,9 @@ type IOInjector interface {
 	InjectInterruptText(source, channel, text string)
 	InjectText(source, channel, text string)
 	InjectTextNoMemory(source, channel, text string)
+	// InjectInputSync injects a text message and synchronously waits for the agent
+	// reply, returning the reply text (empty string if no reply).
+	InjectInputSync(source, channel, text string) string
 }
 
 // EventType identifies the kind of system event.
@@ -367,6 +370,16 @@ func (s *PluginSDK) InjectTextNoMemory(source, channel, text string) {
 	}
 }
 
+// InjectInputSync injects a text message and synchronously waits for the agent reply,
+// returning the reply text (empty if no reply). Use it for request-response flows
+// (e.g. channel plugins forwarding messages and sending the agent's reply back).
+func (s *PluginSDK) InjectInputSync(source, channel, text string) string {
+	if s.io != nil {
+		return s.io.InjectInputSync(source, channel, text)
+	}
+	return ""
+}
+
 // SetAutoRestart 设置插件是否允许内核自动重启（崩溃后自动重载）。
 // 默认 true。如果插件有无法恢复的状态（如外部连接），应设为 false。
 func (s *PluginSDK) SetAutoRestart(enabled bool) { s.autoRestart = enabled }