Is a sin incurred by an engineer who contracts with suppliers and contractors for his company, if the company later violates the terms of the contract and delays payments, knowing that the contract is made in the name of the company owner, and that the engineer was the one who brought them in and agreed with them on the terms? And must he resign immediately, or is it permissible to search for a new job first?

The questioner is an agent, not a principal, in these contracts. The suppliers and contractors know that they are contracting with the company, so the consequences of the contracts do not fall upon him, but rather upon the principal. This is because the rights of the contract are related to the principal, as Al-Bahuti stated in Kashshaf Al-Qina': "The agent in buying is not demanded to pay the price, nor is the agent in selling demanded to deliver the sold item; rather, the principal is demanded with both, because the rights of the contract are related to him." Furthermore, the suppliers' and contractors' knowledge of the delay in payments removes moral embarrassment from the questioner.