fix: TaskStore snapshot を compact 後 history の末尾に置いて retained 中の TaskCreate 重複を防ぐ

crates/pod/src/pod.rs

@@ -1395,7 +1395,12 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             .filter(|i| i.is_user_message())
             .count();
 
-        // Build new history: [summary, ...auto-read, task snapshot, TaskList result, references, ...retained].
+        // Build new history: [summary, ...auto-read, references, ...retained, task snapshot, TaskList synthetic call/result].
+        // The TaskStore snapshot trails the retained items so that, on resume,
+        // `replay_history` walks any pre-compact Task* calls preserved verbatim
+        // in retained_items first and the trailing snapshot's `replace_with`
+        // is the final word — pre-compact `TaskCreate` calls cannot leak as
+        // duplicate entries.
         let mut new_history = Vec::with_capacity(
             1 + auto_read_messages.len()
                 + 3
@@ -1406,6 +1411,10 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             "[Compacted context summary]\n\n{summary_text}"
         )));
         new_history.extend(auto_read_messages);
+        if let Some(msg) = reference_message {
+            new_history.push(msg);
+        }
+        new_history.extend(retained_items);
         new_history.push(Item::system_message(format!(
             "[Session TaskStore snapshot]\n\n{task_snapshot_text}\n\n\
              This is the complete session task list preserved across compaction. \
@@ -1417,10 +1426,6 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             tools::task::snapshot_overview(&self.task_store.list()),
             task_snapshot_text.clone(),
         ));
-        if let Some(msg) = reference_message {
-            new_history.push(msg);
-        }
-        new_history.extend(retained_items);
 
         // Persist as a new compacted session.
         let old_session_id = self.session_id;

crates/tools/src/task.rs

@@ -609,4 +609,37 @@ mod tests {
         assert_eq!(tasks[1].taskid, 2);
         assert_eq!(tasks[1].subject, "new");
     }
+
+    #[test]
+    fn trailing_snapshot_supersedes_pre_compact_taskcreates_in_retained() {
+        // Mirrors the post-compact layout: pre-compact `TaskCreate` calls are
+        // preserved verbatim in retained_items, and the snapshot trails them.
+        // The trailing snapshot must reset the store to the captured state so
+        // pre-compact `TaskCreate`s do not surface as duplicates.
+        let snapshot = "[Session TaskStore snapshot]\n\nTaskStore: 2 task(s) (pending: 0, inprogress: 1, completed: 1, deleted: 0)\n\n- taskid: 1\n  status: completed\n  subject: A\n  description: A-desc\n\n- taskid: 2\n  status: inprogress\n  subject: B\n  description: B-desc\n";
+        let history = vec![
+            Item::tool_call("c1", "TaskCreate", r#"{"subject":"A","description":"A-desc"}"#),
+            Item::tool_call("u1", "TaskUpdate", r#"{"taskid":1,"status":"completed"}"#),
+            Item::tool_call("c2", "TaskCreate", r#"{"subject":"B","description":"B-desc"}"#),
+            Item::tool_call("u2", "TaskUpdate", r#"{"taskid":2,"status":"inprogress"}"#),
+            Item::system_message(snapshot),
+            Item::tool_call("compact-tasklist", "TaskList", "{}"),
+            Item::tool_call(
+                "c3",
+                "TaskCreate",
+                r#"{"subject":"C","description":"after compact"}"#,
+            ),
+        ];
+        let store = TaskStore::from_history(&history);
+        let tasks = store.list();
+        assert_eq!(tasks.len(), 3);
+        assert_eq!(tasks[0].taskid, 1);
+        assert_eq!(tasks[0].subject, "A");
+        assert_eq!(tasks[0].status, TaskStatus::Completed);
+        assert_eq!(tasks[1].taskid, 2);
+        assert_eq!(tasks[1].subject, "B");
+        assert_eq!(tasks[1].status, TaskStatus::Inprogress);
+        assert_eq!(tasks[2].taskid, 3);
+        assert_eq!(tasks[2].subject, "C");
+    }
 }