I study a dynamic principal agent model in which the effort cost of the agent is unknown to the principal. The principal is ambiguity averse, and designs a contract which is robust to the worst case effort cost process. Ambiguity divides the contract into two regions. After sufficiently high...

I study a continuous-time principal-agent model in which the principal is ambiguity averse about the agent's effort cost. The robust contract generates a seemingly excessive pay-performance sensitivity. The worst-case effort cost is high after good performance, but low after bad performance,...