The pending new bill reaches across a range of topics, including ghost guns, firearm licensing, dealer inspections, protected areas, the state’s so-called red flag law and more.

The final bill text had not yet been filed with the House clerk’s office just before 4:20 p.m. Wednesday, but top Democrats in both branches said they agree on its contents and plan to advance the measure quickly.

House Speaker Ronald Mariano (D-Quincy) said he will bring the final legislation forward for a vote Thursday, calling it “the most significant gun safety legislation that Massachusetts has seen in a decade.” The Senate has a formal session planned Thursday to take up a health care bill, so it’s possible that the gun bill could emerge for a vote in that branch, depending on the timing of the House vote.

“This bill is the culmination of a multi-year process that began after the Supreme Court’s conservative supermajority issued their disastrous Bruen decision, which weakened the Commonwealth’s gun safety laws and endangered our residents,” Mariano said in a statement.

A spokesperson for Senate President Karen Spilka said the Senate will take up the bill “shortly after we receive it from the House.” The Ashland Democrat praised the legislation as a way to “save lives while respecting the rights of law abiding gun owners.”

“While there is no appropriate measure of the pain and heartbreak that gun violence has caused in our Commonwealth and across the nation, I am proud that Massachusetts has always been a leader in gun violence prevention,” Spilka said in a statement. “The agreement that we have reached on a gun safety bill today builds on that leadership.”

Republicans were nearly united in their opposition to the bills that formed the basis of the consensus bill. Every member of the House GOP voted against it, as did several House Democrats, and three of the Senate’s four Republicans opposed the measure. Senate Minority Leader Bruce Tarr was the lone Republican in either chamber to back a version of the bill.

Hoping to slow the proliferation of ghost guns, the legislation would require all firearms — including individual frames and receivers — to be stamped with a serial number. It would also craft new penalties for possession, creation and transfer of untraceable firearms.

Public safety officials, including Attorney General Andrea Campbell, have grown increasingly concerned about a rise in ghost guns used in crimes. Many of those weapons are assembled at home by people not licensed to carry firearms, officials have said.

The bill would expand the list of areas where state law forbids people from carrying firearms to include schools, polling places and government buildings. Current and retired law enforcement professionals would be exempt, and cities and towns could also choose to allow firearms in their municipal buildings.

Courts would gain the ability to order removal of firearms, licenses and permits when they issue a harassment prevention order to prevent abuse, and the bill would also expand the 2018 “red flag” law. The existing law allows family members and law enforcement to petition a court to temporarily take firearms away from someone deemed a threat to themselves or others, and the bill would extend that petitioning power to school administrators and licensed health care providers.

“The tack we took as a body, as a legislative body, is to make sure that those who interact with individuals on a regular basis have the right to go in and petition that that individual should be removed from the right of carrying a firearm because they’re in a crisis,” said Rep. Michael Day, the lead House negotiator. “So we took health care professionals who have treated individuals in the last six months, law enforcement officers who have treated or interacted with that individual in the last 30 days, school administrators who see these kids every day, and family members can now go in and petition.”

The final compromise drops the House push to extend that ability to employers as well.

Other parts of the bill would consolidate the licensing process, update the definition of assault-style firearms, more tightly regulate modifications and parts that can convert semi-automatic firearms into automatic firearms, boost data reporting about firearms, and align standards for carrying a firearm or hunting while intoxicated with driving under the influence.

The bill also creates a new criminal offense for firing a gun and striking an occupied building or dwelling, and strengthens existing penalties for firing within 500 feet of a dwelling without the owner’s consent.

Under existing law, Bay Staters can acquire a firearms license at 18 years old, which allows them to purchase semi-automatic rifles. The bill would require a license to carry — which is only available to people 21 and older — to buy a semi-automatic rifle.

Day and lead Senate negotiator Cynthia Creem announced their agreement just before 1:30 p.m., saying in a joint statement that the bill “delivers meaningfully on our promise to align our statutes with the challenges gun violence poses to our communities today and incorporates the perspectives of firearm owners, law enforcement, community leaders and those impacted directly by gun violence.”

“We gave law enforcement the tools to target producers of unregistered and serialized ghost guns. We did things on the red flag [law]. We did data collection, things that the activists and everybody wanted us to do. I think it’s a great bill,” Creem told reporters. “I think Massachusetts was number one in protecting everybody, and I think we’ve kind of fallen back. I think this is an opportunity for us to once again be in the forefront.”

Massachusetts experienced 3.7 firearms deaths per 100,000 people in 2022, the second-lowest rate in the nation behind Rhode Island’s 3.1 deaths per 100,000 people, according to the most recent data from the U.S. Centers for Disease Control.

Supporters have long argued that policymakers still need to do more to keep that rate low, especially given disparities that plague lower-income areas and communities of color with a disproportionate burden from gun violence.

“Largely the goal here was to make sure that Massachusetts was safer, that residents were safer, that gun owners were safer, that the general public is safer,” Day, a Stoneham Democrat who co-chairs the Joint Judiciary Committee, said. “We’ve got the lowest incidents of gun violence in the country. That’s going to be even lower, is our intent and our goal with this law. So we protect the interests and rights of lawful gun owners right now, and we make sure that we’re going after those guns that are unserialized, people who have ghost guns that are on the streets and flooding into our streets right now.”

Gun owners groups lambasted both the House and Senate versions of the bills as they moved through the process over the past year, criticizing them as an infringement on Second Amendment rights.

“It’s simply a tantrum because of the Supreme Court case in Bruen,” Jim Wallace, executive director of the Gun Owners Action League, said in an interview Wednesday. “The powers that be that support this garbage basically couldn’t handle being told they’re wrong and went on a fit, and that’s what this represents.”

Wallace also slammed lawmakers for the short window of time between the compromise bill’s emergence and the expected vote. “The Legislature won’t even know what they’re voting on,” he said.

Mariano called it a “game-changing bill.”

“The importance of this bill can’t be stressed enough. We’re taking a leadership position,” the speaker told reporters after a House Democratic Caucus meeting. It’s “a bill that should be a leader in this country and common-sense gun reform,” he added.

The announcement of a breakthrough came four days after the attempted assassination of former President Donald Trump by a 20-year-old with an AR-15 style rifle in Pennsylvania. Day said the shooting did not play a role in expediting the Beacon Hill negotiations.

“I think it highlights the dangers we have out there,” Day said about the Pennsylvania shooting. “That individual could have purchased that semi-automatic himself. Just happened that his father had 20 lawfully registered licensed guns, and he grabbed one and went out and committed that horrific act. Here in Massachusetts, that can’t happen. And if this law passes, that can’t happen. Because if you’ve got a semi-automatic weapon, you’re not allowed to purchase one if you’re under 21.”

Ruth Zakarin, executive director of the Massachusetts Coalition to Prevent Gun Violence, told the News Service Wednesday morning that a “bunch” of advocates planned to wear orange throughout the State House in the next two weeks to signal support for an accord.

“We’re just trying to connect with people and express the urgency of taking action because it’s been a rough month in the commonwealth for gun violence,” Zakarin said. “We’ve seen multiple incidents of gun violence – not just in Boston, but Brockton, and Springfield, and Lynn and other communities. We’ve had a high rate of domestic violence murders in the commonwealth this year.”

[Alison Kuznitz contributed reporting.]