Let agents cancel open questions; fix snapshots missing same-size edits

internal/agents/inbox.go

@@ -124,10 +124,61 @@ func (m *Manager) ask(ctx context.Context, l *live, raw json.RawMessage) (string
 
 	m.snapshotSoon(l, api.SnapshotTriggerAskHuman)
 
+	cancel := fmt.Sprintf("If the human answers it some other way, such as in a chat message, withdraw it with cancel_question and question_id %q.", id)
 	if *args.Blocking {
-		return fmt.Sprintf("Question %s filed in the human's inbox. It is blocking: end your turn now. The answer will arrive as your next message.", id), nil
+		return fmt.Sprintf("Question filed in the human's inbox. question_id: %s. It is blocking: end your turn now. The answer will arrive as your next message. %s", id, cancel), nil
 	}
-	return fmt.Sprintf("Question %s filed in the human's inbox. Continue with work that doesn't depend on it; the answer will arrive as a later message.", id), nil
+	return fmt.Sprintf("Question filed in the human's inbox. question_id: %s. Continue with work that doesn't depend on it; the answer will arrive as a later message. %s", id, cancel), nil
+}
+
+type cancelArgs struct {
+	QuestionID string `json:"question_id"`
+}
+
+func (m *Manager) cancelQuestionTool(l *live) mcp.Tool {
+	return mcp.Tool{
+		Name: "cancel_question",
+		Description: "Withdraw a question you asked with ask_human that is still waiting in the human's inbox, " +
+			"for example because the human answered it in a chat message instead. It is removed from the inbox and no answer to it will arrive.",
+		InputSchema: json.RawMessage(`{
+			"type": "object",
+			"properties": {
+				"question_id": {"type": "string", "description": "The question_id ask_human returned."}
+			},
+			"required": ["question_id"]
+		}`),
+		Handler: func(ctx context.Context, raw json.RawMessage) (string, error) {
+			return m.cancelQuestion(ctx, l, raw)
+		},
+	}
+}
+
+func (m *Manager) cancelQuestion(ctx context.Context, l *live, raw json.RawMessage) (string, error) {
+	args := cancelArgs{}
+	err := json.Unmarshal(raw, &args)
+	if err != nil {
+		return "", fmt.Errorf("malformed cancel_question call: %w", err)
+	}
+
+	item, err := m.store.GetInboxItem(ctx, args.QuestionID)
+	if errors.Is(err, store.ErrNotFound) {
+		return "", fmt.Errorf("question_id %s does not exist", args.QuestionID)
+	}
+	if err != nil {
+		return "", err
+	}
+	if item.AgentSessionId != l.id || item.Kind != api.Question {
+		return "", fmt.Errorf("question_id %s is not a question you asked", args.QuestionID)
+	}
+
+	err = m.store.WithdrawItem(ctx, item.Id)
+	if errors.Is(err, store.ErrNotOpen) {
+		return "", fmt.Errorf("question %s is already %s; nothing was cancelled", item.Id, item.State)
+	}
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("Question %s withdrawn from the human's inbox.", item.Id), nil
 }
 
 func (m *Manager) validateAsk(ctx context.Context, l *live, args askArgs) error {