diff --git a/pkg/concurrent/slice.go b/pkg/concurrent/slice.go
index 4b44a0724..a45ec5792 100644
--- a/pkg/concurrent/slice.go
+++ b/pkg/concurrent/slice.go
@@ -88,3 +88,10 @@ func (s *Slice[V]) Update(index int, f func(V) V) bool {
 	s.values[index] = f(s.values[index])
 	return true
 }
+
+func (s *Slice[V]) Clear() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.values = nil
+}
diff --git a/pkg/tools/builtin/todo.go b/pkg/tools/builtin/todo.go
index fad5d1b72..c7b340ab1 100644
--- a/pkg/tools/builtin/todo.go
+++ b/pkg/tools/builtin/todo.go
@@ -157,12 +157,32 @@ func (h *todoHandler) updateTodos(_ context.Context, params UpdateTodosArgs) (*t
 		return tools.ResultError(output.String()), nil
 	}
 
+	// Clear all todos if all are completed
+	if h.allCompleted() {
+		h.todos.Clear()
+	}
+
 	return &tools.ToolCallResult{
 		Output: output.String(),
 		Meta:   h.todos.All(),
 	}, nil
 }
 
+func (h *todoHandler) allCompleted() bool {
+	if h.todos.Length() == 0 {
+		return false
+	}
+	allDone := true
+	h.todos.Range(func(_ int, todo Todo) bool {
+		if todo.Status != "completed" {
+			allDone = false
+			return false
+		}
+		return true
+	})
+	return allDone
+}
+
 func (h *todoHandler) listTodos(_ context.Context, _ tools.ToolCall) (*tools.ToolCallResult, error) {
 	var output strings.Builder
 	output.WriteString("Current todos:\n")
diff --git a/pkg/tools/builtin/todo_test.go b/pkg/tools/builtin/todo_test.go
index 899f05566..933e942b5 100644
--- a/pkg/tools/builtin/todo_test.go
+++ b/pkg/tools/builtin/todo_test.go
@@ -167,9 +167,9 @@ func TestTodoTool_UpdateTodos(t *testing.T) {
 func TestTodoTool_UpdateTodos_PartialFailure(t *testing.T) {
 	tool := NewTodoTool()
 
-	// Create a single todo
-	_, err := tool.handler.createTodo(t.Context(), CreateTodoArgs{
-		Description: "Test todo item",
+	// Create two todos so we can complete one without clearing the list
+	_, err := tool.handler.createTodos(t.Context(), CreateTodosArgs{
+		Descriptions: []string{"First todo item", "Second todo item"},
 	})
 	require.NoError(t, err)
 
@@ -185,10 +185,11 @@ func TestTodoTool_UpdateTodos_PartialFailure(t *testing.T) {
 	assert.Contains(t, result.Output, "Updated 1 todos")
 	assert.Contains(t, result.Output, "Not found: nonexistent")
 
-	// Verify the existing todo was updated
+	// Verify the existing todo was updated (list not cleared because todo_2 still pending)
 	todos := tool.handler.todos.All()
-	require.Len(t, todos, 1)
+	require.Len(t, todos, 2)
 	assert.Equal(t, "completed", todos[0].Status)
+	assert.Equal(t, "pending", todos[1].Status)
 }
 
 func TestTodoTool_UpdateTodos_AllNotFound(t *testing.T) {
@@ -206,6 +207,35 @@ func TestTodoTool_UpdateTodos_AllNotFound(t *testing.T) {
 	assert.Contains(t, result.Output, "Not found: nonexistent1, nonexistent2")
 }
 
+func TestTodoTool_UpdateTodos_ClearsWhenAllCompleted(t *testing.T) {
+	tool := NewTodoTool()
+
+	// Create multiple todos
+	_, err := tool.handler.createTodos(t.Context(), CreateTodosArgs{
+		Descriptions: []string{"First todo item", "Second todo item"},
+	})
+	require.NoError(t, err)
+
+	// Complete all todos
+	result, err := tool.handler.updateTodos(t.Context(), UpdateTodosArgs{
+		Updates: []TodoUpdate{
+			{ID: "todo_1", Status: "completed"},
+			{ID: "todo_2", Status: "completed"},
+		},
+	})
+	require.NoError(t, err)
+	assert.Contains(t, result.Output, "Updated 2 todos")
+
+	// Verify all todos were cleared
+	todos := tool.handler.todos.All()
+	assert.Empty(t, todos)
+
+	// Verify Meta is also empty
+	metaTodos, ok := result.Meta.([]Todo)
+	require.True(t, ok, "Meta should be []Todo")
+	assert.Empty(t, metaTodos)
+}
+
 func TestTodoTool_OutputSchema(t *testing.T) {
 	tool := NewTodoTool()