[app-server] add new RawResponseItem v2 event (#8152)

``codex/event/raw_response_item` (v1) -> `rawResponseItem/completed`
(v1).

test client log:
````
< {
<   "method": "codex/event/raw_response_item",
<   "params": {
<     "conversationId": "019b29f7-b089-7140-a535-3fe681562c15",
<     "id": "0",
<     "msg": {
<       "item": {
<         "arguments": "{\"command\":\"sed -n '1,160p' Cargo.toml\",\"workdir\":\"/Users/celia/code/codex/codex-rs\"}",
<         "call_id": "call_DrqbdB2jPxezPWc19YVEEt3h",
<         "name": "shell_command",
<         "type": "function_call"
<       },
<       "type": "raw_response_item"
<     }
<   }
< }
< {
<   "method": "rawResponseItem/completed",
<   "params": {
<     "item": {
<       "arguments": "{\"command\":\"sed -n '1,160p' Cargo.toml\",\"workdir\":\"/Users/celia/code/codex/codex-rs\"}",
<       "call_id": "call_DrqbdB2jPxezPWc19YVEEt3h",
<       "name": "shell_command",
<       "type": "function_call"
<     },
<     "threadId": "019b29f7-b089-7140-a535-3fe681562c15",
<     "turnId": "0"
<   }
< }
```

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -525,6 +525,8 @@ server_notification_definitions! {
     TurnPlanUpdated => "turn/plan/updated" (v2::TurnPlanUpdatedNotification),
     ItemStarted => "item/started" (v2::ItemStartedNotification),
     ItemCompleted => "item/completed" (v2::ItemCompletedNotification),
+    /// This event is internal-only. Used by Codex Cloud.
+    RawResponseItemCompleted => "rawResponseItem/completed" (v2::RawResponseItemCompletedNotification),
     AgentMessageDelta => "item/agentMessage/delta" (v2::AgentMessageDeltaNotification),
     CommandExecutionOutputDelta => "item/commandExecution/outputDelta" (v2::CommandExecutionOutputDeltaNotification),
     TerminalInteraction => "item/commandExecution/terminalInteraction" (v2::TerminalInteractionNotification),

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -860,6 +860,12 @@ pub struct ThreadStartParams {
     pub config: Option<HashMap<String, JsonValue>>,
     pub base_instructions: Option<String>,
     pub developer_instructions: Option<String>,
+    /// If true, opt into emitting raw response items on the event stream.
+    ///
+    /// This is for internal use only (e.g. Codex Cloud).
+    /// (TODO): Figure out a better way to categorize internal / experimental events & protocols.
+    #[serde(default)]
+    pub experimental_raw_events: bool,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
@@ -1581,6 +1587,15 @@ pub struct ItemCompletedNotification {
     pub turn_id: String,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct RawResponseItemCompletedNotification {
+    pub thread_id: String,
+    pub turn_id: String,
+    pub item: ResponseItem,
+}
+
 // Item-specific progress notifications
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]

codex-rs/app-server/src/bespoke_event_handling.rs

@@ -31,6 +31,7 @@ use codex_app_server_protocol::McpToolCallResult;
 use codex_app_server_protocol::McpToolCallStatus;
 use codex_app_server_protocol::PatchApplyStatus;
 use codex_app_server_protocol::PatchChangeKind as V2PatchChangeKind;
+use codex_app_server_protocol::RawResponseItemCompletedNotification;
 use codex_app_server_protocol::ReasoningSummaryPartAddedNotification;
 use codex_app_server_protocol::ReasoningSummaryTextDeltaNotification;
 use codex_app_server_protocol::ReasoningTextDeltaNotification;
@@ -451,6 +452,16 @@ pub(crate) async fn apply_bespoke_event_handling(
                 .send_server_notification(ServerNotification::ItemCompleted(completed))
                 .await;
         }
+        EventMsg::RawResponseItem(raw_response_item_event) => {
+            maybe_emit_raw_response_item_completed(
+                api_version,
+                conversation_id,
+                &event_turn_id,
+                raw_response_item_event.item,
+                outgoing.as_ref(),
+            )
+            .await;
+        }
         EventMsg::PatchApplyBegin(patch_begin_event) => {
             // Until we migrate the core to be aware of a first class FileChangeItem
             // and emit the corresponding EventMsg, we repurpose the call_id as the item_id.
@@ -820,6 +831,27 @@ async fn complete_command_execution_item(
         .await;
 }
 
+async fn maybe_emit_raw_response_item_completed(
+    api_version: ApiVersion,
+    conversation_id: ConversationId,
+    turn_id: &str,
+    item: codex_protocol::models::ResponseItem,
+    outgoing: &OutgoingMessageSender,
+) {
+    let ApiVersion::V2 = api_version else {
+        return;
+    };
+
+    let notification = RawResponseItemCompletedNotification {
+        thread_id: conversation_id.to_string(),
+        turn_id: turn_id.to_string(),
+        item,
+    };
+    outgoing
+        .send_server_notification(ServerNotification::RawResponseItemCompleted(notification))
+        .await;
+}
+
 async fn find_and_remove_turn_summary(
     conversation_id: ConversationId,
     turn_summary_store: &TurnSummaryStore,

codex-rs/app-server/src/codex_message_processor.rs

@@ -1373,9 +1373,13 @@ impl CodexMessageProcessor {
                 };
 
                 // Auto-attach a conversation listener when starting a thread.
-                // Use the same behavior as the v1 API with experimental_raw_events=false.
+                // Use the same behavior as the v1 API, with opt-in support for raw item events.
                 if let Err(err) = self
-                    .attach_conversation_listener(conversation_id, false, ApiVersion::V2)
+                    .attach_conversation_listener(
+                        conversation_id,
+                        params.experimental_raw_events,
+                        ApiVersion::V2,
+                    )
                     .await
                 {
                     tracing::warn!(