How can I guarantee capital in an interest-based (mudarabah) project, knowing that guaranteeing capital is unlawful and void?

Losses in companies, such as Mudarabah (definition) (commenda), are borne by the capital. It is not permissible to stipulate a guarantee of capital except in cases of transgression or negligence on the part of the partner. In a Mudarabah company, the loss is borne solely by the capital provider, and the عامل (laborer/manager) bears nothing, because it is a reduction in the capital owned by the capital provider. As for other companies, losses are distributed among all partners according to each one's capital. It is permissible for an independent third party to voluntarily guarantee the capital in Mudarabah to compensate for losses, provided that their commitment is independent of the Mudarabah contract.