We characterise the optimal demand and supply for favours in a dynamic principal-agent model of joint production, in which heterogenous project opportunities are stochastically generated and publicly observed upon arrival. No transfers are available to distribute the utility from joint projects across periods and there is limited commitment, so that expected future production must provide incentives for current production decisions. Our results characterise those subgame perfect equilibria that maximise the principal’s payoffs, and we establish that the principal's supply of favours (the production of projects that benefit the agent but not the principal) is backloaded, while the principal's demand for favours (the production of projects that benefit the principal but not the agent) is frontloaded. We give an exact characterisation of principal-optimal equilibria when project opportunities follow a Markov process.