Dozens of lawmakers, shouting, "We want a vote!" left the House chamber in protest of an apparent filibuster by pro-gay rights lawmakers.
"Anarchy. Anarchy," said Democratic Sen. Jarrett Barrios, an openly gay lawmaker and one of the most visible critics of the constitutional ban.
Thousands of miles away, meanwhile, in an open challenge to California law, the mayor of San Francisco helped perform scores of same-sex weddings and issued a stack of marriage licenses to gay and lesbian couples.
"Today a barrier to true justice has been removed," said Gavin Newsom, newly elected mayor of the city considered the capital of gay America.
No state legally sanctions gay marriage, and it remains unclear what practical value the marriage licenses will have.
The weddings violate a ballot measure California voters approved in 2000 that defines marriage as a union between a man and a woman.
The protesting Boston lawmakers returned shortly, but their brief exit reflected the deep frustrations of a legislature that has been grappling with one of the most-watched social issues in the nation since the state's highest court ordered gay marriages to begin in mid-May.
The constitutional convention was recessed soon afterward, but reconvened about 11:20 p.m.
Three other amendments have been defeated during the course of the constitutional convention. Senate and House leaders had expressed hope earlier Thursday that a new mix of words would muster a majority and bring the Statehouse spectacle to an end.
"It's so clear that the legislators need time to think. It's so clear that they're exhausted, they're confused about the amendments, they're uncertain about the issues and they're desperately asking time to sort this out," said Arline Isaacson, co-leader of the Massachusetts Gay and Lesbian Political Caucus.
"And right now, before they take more votes and make more mistakes, it's not unreasonable to let them have some time to sort this out."