Bipartisan congressional skepticism over the June 2026 U.S.-Iran Memorandum of Understanding has shaped trader expectations that no final nuclear or comprehensive agreement will secure legislative approval this year. Lawmakers from both parties raised concerns about sanctions relief, a potential $300 billion reconstruction fund, limited verifiable constraints on Iran's nuclear program, and enforcement gaps, prompting repeated calls for review under the Iran Nuclear Agreement Review Act alongside war powers resolutions limiting executive action. The 60-day negotiating window expired in mid-August without a final deal, amid mutual violations, resumed tensions, and fresh military exchanges that further eroded momentum for diplomacy requiring congressional endorsement. Administration efforts to sidestep or delay formal submission have reinforced the view that any binding pact faces steep procedural and political barriers on Capitol Hill.