feat: add compaction event (#7289)

codex-rs/app-server/README.md

@@ -257,6 +257,7 @@ Today both notifications carry an empty `items` array even when item events were
 - `fileChange` — `{id, changes, status}` describing proposed edits; `changes` list `{path, kind, diff}` and `status` is `inProgress`, `completed`, `failed`, or `declined`.
 - `mcpToolCall` — `{id, server, tool, status, arguments, result?, error?}` describing MCP calls; `status` is `inProgress`, `completed`, or `failed`.
 - `webSearch` — `{id, query}` for a web search request issued by the agent.
+- `compacted` - `{threadId, turnId}` when codex compacts the conversation history. This can happen automatically.
 
 All items emit two shared lifecycle events:
 - `item/started` — emits the full `item` when a new unit of work begins so the UI can render it immediately; the `item.id` in this payload matches the `itemId` used by deltas.

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

@@ -14,6 +14,7 @@ use codex_app_server_protocol::CommandExecutionOutputDeltaNotification;
 use codex_app_server_protocol::CommandExecutionRequestApprovalParams;
 use codex_app_server_protocol::CommandExecutionRequestApprovalResponse;
 use codex_app_server_protocol::CommandExecutionStatus;
+use codex_app_server_protocol::ContextCompactedNotification;
 use codex_app_server_protocol::ErrorNotification;
 use codex_app_server_protocol::ExecCommandApprovalParams;
 use codex_app_server_protocol::ExecCommandApprovalResponse;
@@ -249,6 +250,15 @@ pub(crate) async fn apply_bespoke_event_handling(
                 .send_server_notification(ServerNotification::AgentMessageDelta(notification))
                 .await;
         }
+        EventMsg::ContextCompacted(..) => {
+            let notification = ContextCompactedNotification {
+                thread_id: conversation_id.to_string(),
+                turn_id: event_id.clone(),
+            };
+            outgoing
+                .send_server_notification(ServerNotification::ContextCompacted(notification))
+                .await;
+        }
         EventMsg::ReasoningContentDelta(event) => {
             let notification = ReasoningSummaryTextDeltaNotification {
                 item_id: event.item_id,