Top Senate Democrats released a long-promised gun reform bill Thursday that updates state ghost gun laws, codifies Massachusetts’ existing ban on assault weapons, and makes illegal devices that convert semi-automatic firearms into fully automatic weapons.

Senate President Karen Spilka pitched the legislation as an omnibus proposal that “would help make residents safer,” cracks down on untraceable firearms, and builds on Massachusetts’ “strong record” of gun safety and violence prevention.

“This fact is not by accident,” Spilka said at the State House. “It’s because we have been vigilant in updating … our gun laws to prevent those who wish to do harm from being able to access and use deadly weapons. We believe Massachusetts is, and should continue to be, a model for the nation when it comes to gun safety laws.”

The proposal sets up a dispute with House lawmakers, who passed their own firearms bill in October that drew opposition from the Massachusetts Chiefs of Police Association. The association decided to instead support the Senate proposal.

Massachusetts Chiefs of Police Association President Chief Eric Gillis said members decided to back the Senate proposal because of “the ability to collaborate with Senate leadership.”

The Agawam police chief declined to say if there were any specific policy differences between the House and Senate that made the Senate proposal more appetizing.

“I can say that what we find in the Senate bill makes sense. It’s concise. At the end of the day, it has to be enforceable. Whatever this body does, has to be carried out by people in our sphere. And when it’s distilled down and simple and makes sense, it’s going to work. So that’s what works for us,” he said during a press conference hosted by the Senate.

The two competing efforts to reform Massachusetts’ gun laws draw one difference in their length. The House version clocks in at 126 pages while the Senate attempts to rework state gun laws in 35 pages.

A spokesperson for House Speaker Ron Mariano, a 14-term Quincy Democrat, said the branch “looks forward” to reviewing the Senate proposal.

“We look forward to reviewing the Senate’s proposal, keeping in mind the critical nature of the reforms included in the House’s proposal, and the urgency around the issue of gun violence generally,” the spokesperson said in a statement.

Senate leadership wants to change Massachusetts’ definition of a firearm to align with federal standards.

The definition currently in place only applies to a fully assembled weapon that is capable of discharging a bullet, which means if a person has parts or components of a weapon but has not put them together, they are not in possession of a firearm.

“Massachusetts gun laws are currently inadequate at preventing the unlawful possession of guns, and particularly the growing phenomenon of untraceable ghost guns. This bill will track these unlicensed weapons the same as any other gun and keep them out of the hands of people who are not licensed to carry,” Senate Majority Leader Cindy Creem said.

Glock switches, selector switches, and auto sears that turn a semi-automatic firearm into a fully automatic weapon are banned under the bill, with Senate lawmakers arguing the devices are commonly used in mass shootings and make firearms more dangerous.

Creem pointed to a shooting at Boston’s J’ouvert celebrations in August that left eight people with non-life-threatening injuries as an effect of the devices.

“Their goal is the same, to make a gun more dangerous by shooting it rapidly,” the Newton Democrat said.

The bill bars someone from carrying a firearm into a government administrative building and courthouse, though it makes exceptions for law enforcement officers and, in a difference from the House, allows municipalities to opt-out of the provision.

The Senate’s proposal does not limit the carrying of firearms onto private residences of others nor does it address bringing weapons onto school properties, which Creem said were already covered under existing laws.

“We didn’t want to touch that. It is now law that you can’t have a gun in a school so we didn’t need to redo what was done,” she said. “But this applies to government buildings, administrative buildings and courthouses.”

In a departure from the House, the Senate pitched allowing firearm licensing authorities to have access to information about an applicant’s history of involuntary mental hospitalizations due to posing a serious harm.

The Senate requires a law enforcement agency that is involved in a temporary involuntary hospitalization of an individual with a mental health condition to submit information about the incident to the Department of Criminal Justice Information Services.

Creem said there are “appropriate safeguards to guarantee privacy and due process.”

The bill allows health care professionals to petition courts to remove firearms and licenses from patients who pose a risk to themselves or others, an update to Massachusetts’ red flag law and extreme risk protection orders.

Attorney General Andrea Campbell said the legislation is a “much needed step.”

“There is no question that the time to act is now. We must have gun laws that reflect the changes in technology, the personal tragedies caused by gun violence and its shattering impact on communities,” Campbell said in a statement provided by the Senate.