feat(tasks): round-based grouping — FAB shows current round only

- New round starts when all tasks complete before next TaskCreate
- FAB counts only current round (e.g. 0/4 instead of 20/24)
- Bottom sheet: current round on top, collapsible "Previous tasks" history
- O(1) Set lookup for history filtering

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/stores/task-aggregator.ts

@@ -1,9 +1,9 @@
 /**
  * Pure aggregator: processes tool_use blocks (TaskCreate, TaskUpdate, TodoWrite)
- * and produces a unified AggregatedTask[] snapshot.
+ * and produces a unified AggregatedTask[] snapshot with round-based grouping.
  *
- * Stateful — call processToolUse() for each relevant tool call in order.
- * Call getSnapshot() to read current state (cached, invalidated on changes).
+ * A new "round" starts when all tasks were completed and a new TaskCreate arrives.
+ * The snapshot exposes both the current round (for FAB) and all tasks (for sheet history).
  */
 
 export interface AggregatedTask {
@@ -15,12 +15,22 @@ export interface AggregatedTask {
   blockedBy?: string[];
   blocks?: string[];
   source: 'task-api' | 'todo-write';
+  round: number;
 }
 
 export interface TaskSnapshot {
+  /** All tasks across all rounds */
   tasks: AggregatedTask[];
+  /** Current round tasks only (for FAB display) */
+  currentRound: AggregatedTask[];
+  /** Completed count in current round */
   completed: number;
+  /** Total count in current round */
   total: number;
+  /** Current round number (0-based) */
+  round: number;
+  /** Whether there are previous rounds (for sheet "history" section) */
+  hasHistory: boolean;
 }
 
 /** Tool names that produce task state changes. */
@@ -32,11 +42,19 @@ export class TaskAggregator {
   private taskApiTasks = new Map<string, AggregatedTask>();
   private todoWriteTasks = new Map<string, AggregatedTask>();
   private cachedSnapshot: TaskSnapshot | null = null;
+  private currentRound = 0;
+  private allCompletedBeforeCreate = true; // tracks if all tasks were done before last TaskCreate
 
   /** Process a single tool_use block. Returns true if state changed. */
   processToolUse(toolName: string, input: Record<string, unknown>, resultText?: string): boolean {
     switch (toolName) {
       case 'TaskCreate': {
+        // Start a new round if all previous tasks were completed
+        if (this.taskApiTasks.size > 0 && this.allCompletedBeforeCreate) {
+          this.currentRound++;
+        }
+        this.allCompletedBeforeCreate = false;
+
         const match = resultText?.match(/Task #(\d+)/);
         const id = match?.[1] || String(this.taskApiTasks.size + 1);
         this.taskApiTasks.set(id, {
@@ -46,6 +64,7 @@ export class TaskAggregator {
           activeForm: (input.activeForm as string) || undefined,
           status: 'pending',
           source: 'task-api',
+          round: this.currentRound,
         });
         this.cachedSnapshot = null;
         return true;
@@ -59,6 +78,7 @@ export class TaskAggregator {
         if (input.status === 'deleted') {
           this.taskApiTasks.delete(taskId);
           this.cachedSnapshot = null;
+          this.updateCompletionState();
           return true;
         }
         const updated: AggregatedTask = { ...existing };
@@ -74,10 +94,16 @@ export class TaskAggregator {
         }
         this.taskApiTasks.set(taskId, updated);
         this.cachedSnapshot = null;
+        this.updateCompletionState();
         return true;
       }
 
       case 'TodoWrite': {
+        // TodoWrite always starts a new round (replaces entire todo list)
+        if (this.todoWriteTasks.size > 0 || this.taskApiTasks.size > 0) {
+          const allDone = this.allTasksCompleted();
+          if (allDone) this.currentRound++;
+        }
         this.todoWriteTasks.clear();
         const tasks = (input.tasks || input.todos || []) as Array<{
           id: string;
@@ -90,9 +116,11 @@ export class TaskAggregator {
             subject: t.content || '',
             status: (t.status as AggregatedTask['status']) || 'pending',
             source: 'todo-write',
+            round: this.currentRound,
           });
         }
         this.cachedSnapshot = null;
+        this.updateCompletionState();
         return true;
       }
 
@@ -107,8 +135,16 @@ export class TaskAggregator {
       ...this.taskApiTasks.values(),
       ...this.todoWriteTasks.values(),
     ];
-    const completed = tasks.filter(t => t.status === 'completed').length;
-    this.cachedSnapshot = { tasks, completed, total: tasks.length };
+    const currentRound = tasks.filter(t => t.round === this.currentRound);
+    const completed = currentRound.filter(t => t.status === 'completed').length;
+    this.cachedSnapshot = {
+      tasks,
+      currentRound,
+      completed,
+      total: currentRound.length,
+      round: this.currentRound,
+      hasHistory: this.currentRound > 0,
+    };
     return this.cachedSnapshot;
   }
 
@@ -120,5 +156,22 @@ export class TaskAggregator {
     this.taskApiTasks.clear();
     this.todoWriteTasks.clear();
     this.cachedSnapshot = null;
+    this.currentRound = 0;
+    this.allCompletedBeforeCreate = true;
+  }
+
+  private allTasksCompleted(): boolean {
+    for (const t of this.taskApiTasks.values()) {
+      if (t.status !== 'completed') return false;
+    }
+    for (const t of this.todoWriteTasks.values()) {
+      if (t.status !== 'completed') return false;
+    }
+    return true;
+  }
+
+  /** Update the flag that tracks whether all tasks are done (for round detection). */
+  private updateCompletionState(): void {
+    this.allCompletedBeforeCreate = this.allTasksCompleted();
   }
 }

src/components/TaskBottomSheet.tsx

@@ -85,8 +85,28 @@ function TaskRow({ task, taskMap }: { task: AggregatedTask; taskMap: Map<string,
   );
 }
 
+function HistorySection({ tasks, taskMap }: { tasks: AggregatedTask[]; taskMap: Map<string, AggregatedTask> }) {
+  const [expanded, setExpanded] = useState(false);
+  const completed = tasks.filter(t => t.status === 'completed').length;
+
+  return (
+    <div className="border-t border-border/30 mt-2 pt-2">
+      <button
+        onClick={() => setExpanded(!expanded)}
+        className="flex items-center justify-between w-full text-xs text-text-dim py-1"
+      >
+        <span>Previous tasks ({completed}/{tasks.length})</span>
+        {expanded ? <ChevronUp className="size-3" /> : <ChevronDown className="size-3" />}
+      </button>
+      {expanded && tasks.map(task => (
+        <TaskRow key={`${task.source}:${task.id}`} task={task} taskMap={taskMap} />
+      ))}
+    </div>
+  );
+}
+
 export function TaskBottomSheet({ snapshot, open, onClose }: TaskBottomSheetProps) {
-  const { tasks, completed, total } = snapshot;
+  const { tasks, currentRound, completed, total, hasHistory } = snapshot;
   const pct = total > 0 ? Math.round((completed / total) * 100) : 0;
 
   const taskMap = useMemo(() => {
@@ -95,6 +115,12 @@ export function TaskBottomSheet({ snapshot, open, onClose }: TaskBottomSheetProp
     return map;
   }, [tasks]);
 
+  const historyTasks = useMemo(() => {
+    if (!hasHistory) return [];
+    const currentIds = new Set(currentRound.map(t => `${t.source}:${t.id}`));
+    return tasks.filter(t => !currentIds.has(`${t.source}:${t.id}`));
+  }, [tasks, currentRound, hasHistory]);
+
   return (
     <BottomSheet visible={open} onClose={onClose} className="max-h-[70vh] flex flex-col">
       <div className="flex items-center justify-between px-4 pb-2">
@@ -107,13 +133,17 @@ export function TaskBottomSheet({ snapshot, open, onClose }: TaskBottomSheetProp
       </div>
 
       <div className="flex-1 overflow-y-auto px-4 pb-4">
-        {tasks.map(task => (
+        {currentRound.map(task => (
           <TaskRow
             key={`${task.source}:${task.id}`}
             task={task}
             taskMap={taskMap}
           />
         ))}
+
+        {historyTasks.length > 0 && (
+          <HistorySection tasks={historyTasks} taskMap={taskMap} />
+        )}
       </div>
     </BottomSheet>
   );

src/hooks/useChat.ts

@@ -476,7 +476,14 @@ export function useChat(initialSessionId?: string, cwd?: string, initialAdapter?
         break;
 
       case WS.TASK_STATE:
-        handleTaskState({ tasks: msg.tasks, completed: msg.completed, total: msg.total });
+        handleTaskState({
+          tasks: msg.tasks,
+          currentRound: msg.currentRound,
+          completed: msg.completed,
+          total: msg.total,
+          round: msg.round,
+          hasHistory: msg.hasHistory,
+        });
         break;
     }
   }, [drainQueue, enterStreaming, handleTaskState, resetTasks]);

src/hooks/useTaskState.ts

@@ -3,7 +3,7 @@ import type { AggregatedTask, TaskSnapshot } from '../../server/stores/task-aggr
 
 export type { AggregatedTask, TaskSnapshot };
 
-const EMPTY_SNAPSHOT: TaskSnapshot = { tasks: [], completed: 0, total: 0 };
+const EMPTY_SNAPSHOT: TaskSnapshot = { tasks: [], currentRound: [], completed: 0, total: 0, round: 0, hasHistory: false };
 
 export function useTaskState() {
   const [taskSnapshot, setTaskSnapshot] = useState<TaskSnapshot>(EMPTY_SNAPSHOT);