fix: close early dispatch recovery gaps

crates/session-store/src/logged_item.rs

@@ -50,6 +50,9 @@ pub enum LoggedItem {
         role: LoggedRole,
         content: Vec<LoggedContentPart>,
     },
+    AssistantResponseBoundary {
+        response_id: String,
+    },
     ToolCall {
         call_id: String,
         name: String,
@@ -122,6 +125,9 @@ impl From<&Item> for LoggedItem {
                 role: (*role).into(),
                 content: content.iter().map(LoggedContentPart::from).collect(),
             },
+            Item::AssistantResponseBoundary { response_id } => Self::AssistantResponseBoundary {
+                response_id: response_id.clone(),
+            },
             Item::ToolCall {
                 call_id,
                 name,
@@ -185,6 +191,9 @@ impl From<LoggedItem> for Item {
                 content: content.into_iter().map(Into::into).collect(),
                 status: None,
             },
+            LoggedItem::AssistantResponseBoundary { response_id } => {
+                Item::assistant_response_boundary(response_id)
+            }
             LoggedItem::ToolCall {
                 call_id,
                 name,
@@ -343,6 +352,18 @@ mod tests {
         }
     }
 
+    #[test]
+    fn assistant_response_boundary_round_trips_for_provider_projection() {
+        let original = Item::assistant_response_boundary("response-7");
+        let logged: LoggedItem = (&original).into();
+        let json = serde_json::to_string(&logged).unwrap();
+        assert!(json.contains(r#""kind":"assistant_response_boundary""#));
+        assert_eq!(
+            Item::from(serde_json::from_str::<LoggedItem>(&json).unwrap()),
+            original
+        );
+    }
+
     #[test]
     fn round_trip_tool_call() {
         let original = Item::tool_call("call_42", "get_weather", r#"{"city":"Tokyo"}"#)

crates/session-store/src/public_snapshot.rs

@@ -386,8 +386,8 @@ fn project_item(item: &LoggedItem) -> Option<SessionSnapshotEntryData> {
                 })
                 .collect(),
         }),
-        // Hidden model reasoning is never observable.
-        LoggedItem::Reasoning { .. } => None,
+        // Internal response grouping and hidden model reasoning are never observable.
+        LoggedItem::AssistantResponseBoundary { .. } | LoggedItem::Reasoning { .. } => None,
     }
 }