This article investigates agreement in Persian sentences with a specificational copular clause embedded under the epistemic modal tavānestan ‘can’. We argue that this structure is a raising structure. It exhibits agreement on both the embedded and modal verbs. Crucially, while the subject fails to control agreement in the embedded clause, it successfully controls agreement on the modal. We argue that the subject’s failure to form an Agree relation in the embedded specificational clause is due to its defective feature structure, resulting in agreement with the lower noun phrase instead, this being an accessible goal as well. In the matrix clause, the lower noun phrase is inaccessible, due to the presence of an intervening domain boundary. This triggers probe reduction, a process that impoverishes the feature structure of the probe, expanding the set of possible goals to include the subject. We extend this analysis to subject agreement in simple specificational clauses in languages like English.