diff --git a/codex-rs/core/src/protocol.rs b/codex-rs/core/src/protocol.rs
index cf6e8b51..1a6313db 100644
--- a/codex-rs/core/src/protocol.rs
+++ b/codex-rs/core/src/protocol.rs
@@ -278,8 +278,9 @@ pub struct Event {
 }
 
 /// Response event from the agent
-#[derive(Debug, Clone, Deserialize, Serialize)]
+#[derive(Debug, Clone, Deserialize, Serialize, Display)]
 #[serde(tag = "type", rename_all = "snake_case")]
+#[strum(serialize_all = "lowercase")]
 pub enum EventMsg {
     /// Error while executing a submission
     Error(ErrorEvent),
diff --git a/codex-rs/mcp-server/src/outgoing_message.rs b/codex-rs/mcp-server/src/outgoing_message.rs
index a1eea65f..e4af1f78 100644
--- a/codex-rs/mcp-server/src/outgoing_message.rs
+++ b/codex-rs/mcp-server/src/outgoing_message.rs
@@ -83,11 +83,26 @@ impl OutgoingMessageSender {
         let params = Some(serde_json::to_value(event).expect("Event must serialize"));
         let outgoing_message = OutgoingMessage::Notification(OutgoingNotification {
             method: "codex/event".to_string(),
+            params: params.clone(),
+        });
+        let _ = self.sender.send(outgoing_message).await;
+
+        self.send_event_as_notification_new_schema(event, params)
+            .await;
+    }
+    // should be backwards compatible.
+    // it will replace send_event_as_notification eventually.
+    async fn send_event_as_notification_new_schema(
+        &self,
+        event: &Event,
+        params: Option<serde_json::Value>,
+    ) {
+        let outgoing_message = OutgoingMessage::Notification(OutgoingNotification {
+            method: event.msg.to_string(),
             params,
         });
         let _ = self.sender.send(outgoing_message).await;
     }
-
     pub(crate) async fn send_error(&self, id: RequestId, error: JSONRPCErrorError) {
         let outgoing_message = OutgoingMessage::Error(OutgoingError { id, error });
         let _ = self.sender.send(outgoing_message).await;
diff --git a/codex-rs/mcp-server/tests/common/mcp_process.rs b/codex-rs/mcp-server/tests/common/mcp_process.rs
index b27a96eb..528a4015 100644
--- a/codex-rs/mcp-server/tests/common/mcp_process.rs
+++ b/codex-rs/mcp-server/tests/common/mcp_process.rs
@@ -270,27 +270,49 @@ impl McpProcess {
     pub async fn read_stream_until_configured_response_message(
         &mut self,
     ) -> anyhow::Result<String> {
+        let mut sid_old: Option<String> = None;
+        let mut sid_new: Option<String> = None;
         loop {
             let message = self.read_jsonrpc_message().await?;
             eprint!("message: {message:?}");
 
             match message {
                 JSONRPCMessage::Notification(notification) => {
-                    if notification.method == "codex/event" {
-                        if let Some(params) = notification.params {
+                    if let Some(params) = notification.params {
+                        // Back-compat schema: method == "codex/event" and msg.type == "session_configured"
+                        if notification.method == "codex/event" {
                             if let Some(msg) = params.get("msg") {
-                                if let Some(msg_type) = msg.get("type") {
-                                    if msg_type == "session_configured" {
-                                        if let Some(session_id) = msg.get("session_id") {
-                                            return Ok(session_id
-                                                .to_string()
-                                                .trim_matches('"')
-                                                .to_string());
-                                        }
+                                if msg.get("type").and_then(|v| v.as_str())
+                                    == Some("session_configured")
+                                {
+                                    if let Some(session_id) =
+                                        msg.get("session_id").and_then(|v| v.as_str())
+                                    {
+                                        sid_old = Some(session_id.to_string());
                                     }
                                 }
                             }
                         }
+                        // New schema: method is the Display of EventMsg::SessionConfigured => "SessionConfigured"
+                        if notification.method == "sessionconfigured" {
+                            if let Some(msg) = params.get("msg") {
+                                if let Some(session_id) =
+                                    msg.get("session_id").and_then(|v| v.as_str())
+                                {
+                                    sid_new = Some(session_id.to_string());
+                                }
+                            }
+                        }
+                    }
+
+                    if sid_old.is_some() && sid_new.is_some() {
+                        // Both seen, they must match
+                        assert_eq!(
+                            sid_old.as_ref().unwrap(),
+                            sid_new.as_ref().unwrap(),
+                            "session_id mismatch between old and new schema"
+                        );
+                        return Ok(sid_old.unwrap());
                     }
                 }
                 JSONRPCMessage::Request(_) => {