Show Codex background task counts

server/src/session/codex/translate.rs

@@ -64,11 +64,19 @@ impl Translator {
     /// Translates one multiplexed app-server record. `prefix` contains image
     /// events extracted by the driver and must precede the item's ToolEnd in
     /// whichever transcript owns the record.
-    pub(super) fn translate_with_prefix(
-        &mut self,
-        line: &Value,
-        mut prefix: Vec<Event>,
-    ) -> Vec<Event> {
+    pub(super) fn translate_with_prefix(&mut self, line: &Value, prefix: Vec<Event>) -> Vec<Event> {
+        let before = self.background_task_count();
+        let mut events = self.translate_inner(line, prefix);
+        let after = self.background_task_count();
+        if after != before
+            && let Some(count) = after
+        {
+            events.push(Event::BackgroundTasks { count });
+        }
+        events
+    }
+
+    fn translate_inner(&mut self, line: &Value, mut prefix: Vec<Event>) -> Vec<Event> {
         let method = line.get("method").and_then(Value::as_str);
         let body = method.and_then(|_| line.get("params")).unwrap_or(line);
         let kind = method.or_else(|| line.get("type").and_then(Value::as_str));
@@ -109,6 +117,12 @@ impl Translator {
         prefix
     }
 
+    fn background_task_count(&self) -> Option<usize> {
+        self.subagents
+            .as_ref()
+            .map(|subagents| subagents.open_count())
+    }
+
     fn translate_line(&mut self, kind: Option<&str>, body: &Value, line: &Value) -> Vec<Event> {
         match kind {
             Some("thread.started") => {
@@ -1222,10 +1236,13 @@ mod tests {
             translator.translate(&line(
                 r#"{"method":"item/completed","params":{"threadId":"parent-thread","turnId":"turn-1","item":{"id":"spawn-1","type":"subAgentActivity","kind":"started","agentThreadId":"child-thread","agentPath":"/root/history_boundaries"}}}"#
             )),
-            vec![Event::ToolEnd {
-                id: "spawn-1".to_string(),
-                output: String::new()
-            }]
+            vec![
+                Event::ToolEnd {
+                    id: "spawn-1".to_string(),
+                    output: String::new()
+                },
+                Event::BackgroundTasks { count: 1 }
+            ]
         );
         let rows = subagents.list(true);
         assert_eq!(rows.len(), 1);
@@ -1265,9 +1282,12 @@ mod tests {
             translator.translate(&line(
                 r#"{"method":"item/completed","params":{"threadId":"parent-thread","turnId":"turn-1","item":{"id":"subagent-completed-1","type":"subAgentActivity","kind":"completed","agentThreadId":"child-thread","agentPath":"/root/history_boundaries"}}}"#
             )),
-            vec![Event::Status {
-                state: SessionStatus::Idle
-            }]
+            vec![
+                Event::Status {
+                    state: SessionStatus::Idle
+                },
+                Event::BackgroundTasks { count: 0 }
+            ]
         );
 
         let child = subagents.get("child-thread").expect("child");
@@ -1289,6 +1309,50 @@ mod tests {
         );
     }
 
+    #[test]
+    fn codex_reports_each_change_to_its_live_background_count() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let subagents = Arc::new(Subagents::new(dir.path().to_path_buf()));
+        let mut translator = Translator::new(
+            Arc::clone(&subagents),
+            Some("parent-thread".to_string()),
+            false,
+        );
+
+        for (call, child, count) in [("spawn-a", "child-a", 1), ("spawn-b", "child-b", 2)] {
+            let events = translator.translate(&json!({
+                "method": "item/completed",
+                "params": {
+                    "threadId": "parent-thread",
+                    "item": {
+                        "id": call,
+                        "type": "subAgentActivity",
+                        "kind": "started",
+                        "agentThreadId": child,
+                        "agentPath": format!("/root/{child}")
+                    }
+                }
+            }));
+            assert_eq!(events.last(), Some(&Event::BackgroundTasks { count }));
+        }
+        for (child, count) in [("child-a", 1), ("child-b", 0)] {
+            let events = translator.translate(&json!({
+                "method": "item/completed",
+                "params": {
+                    "threadId": "parent-thread",
+                    "item": {
+                        "id": format!("completed-{child}"),
+                        "type": "subAgentActivity",
+                        "kind": "completed",
+                        "agentThreadId": child,
+                        "agentPath": format!("/root/{child}")
+                    }
+                }
+            }));
+            assert_eq!(events.last(), Some(&Event::BackgroundTasks { count }));
+        }
+    }
+
     #[test]
     fn codex_collaboration_coordination_has_clean_parent_tool_cards() {
         let mut translator = Translator::default();
@@ -1430,12 +1494,11 @@ mod tests {
             true,
         );
 
-        assert!(
-            translator
-                .translate(&line(
-                    r#"{"method":"item/completed","params":{"threadId":"parent-thread","turnId":"turn-1","item":{"id":"subagent-completed-1","type":"subAgentActivity","kind":"completed","agentThreadId":"child-thread","agentPath":"/root/child"}}}"#
-                ))
-                .is_empty()
+        assert_eq!(
+            translator.translate(&line(
+                r#"{"method":"item/completed","params":{"threadId":"parent-thread","turnId":"turn-1","item":{"id":"subagent-completed-1","type":"subAgentActivity","kind":"completed","agentThreadId":"child-thread","agentPath":"/root/child"}}}"#
+            )),
+            vec![Event::BackgroundTasks { count: 0 }]
         );
         assert_eq!(subagents.list(true)[0].status, SessionStatus::Exited);
     }