Questão jurídica principal
Whether the respondent could rely on an oral cumulative assumption of debt and related set-off arrangement against the appellant.
Decisão extraída
Yes. The cantonal court correctly found a cumulative assumption of debt based on the parties' agreement and related writings, allowing set-off of the retained amounts against the respondent's debt to the appellant.
Fundamentação extraída
The Federal Supreme Court held that the cantonal court applied federal contract law, not evidence-allocation rules, when it interpreted the parties' declarations objectively. A cumulative assumption of debt is allowed by contractual freedom and may arise from an agreement between the creditor and the assuming third party. The challenge that essential terms were missing was unpersuasive because the cantonal court had not treated the arrangement as a guarantee.