Louis Mandarini III worked college summers on the construction sites of TD Garden, then known as the FleetCenter, and the Big Dig during the highway project’s salad days, before costs rose to $24 billion.

He grew up in a union family on the North Shore, with his grandfather, the first Louis Mandarini, having served as business manager of Laborers Local 22, when it was based in the North End. Louis Mandarini Jr. followed in his father’s footsteps, taking that job, as well as other top union posts in Massachusetts.

His 46-year-old son, the third to carry the family name, became a union lawyer and went to work for Segal Roitman, the Chinatown-based law firm, and later took a job as the executive director of an entity handling employee benefits funds for laborers, headquartered in Burlington. He cites as his labor movement hero the controversial West Coast longshoreman Harry Bridges, who led a union during World War II, battled the Roosevelt Administration over the internment of Japanese Americans, and worked to end an anti-miscegenation law (criminalizing interracial marriages) in Nevada in the 1950s.

Now Mandarini is sitting inside Boston City Hall, on the management side of the table, across from public sector labor leaders, several of whom are based in Dorchester. In April, he joined Mayor Michelle Wu’s administration as a senior labor policy adviser, an appointment that was not broadly announced but that comes at a critical time for the young administration.

When Wu came into office eight months ago, contracts with more than two dozen municipal unions had expired, from the public safety unions to the bus drivers and teachers. The administration has settled several major contracts, most recently with the school bus drivers, and has a tentative accord in place with the Boston Teachers Union.

“She genuinely wants to do something new under the sun with respect to collective bargaining in the city,” Mandarini said of Wu. Their stance is this: City officials and union workers have historically engaged in talks that are not only unnecessarily contentious, but in a mode that’s antiquated.

For decades, City Hall’s collective bargaining with its workers has been adversarial, drawn out, inefficient, and disrespectful to the employees, Mandarini said. Doing it differently doesn’t mean giving away the store, adds Mandarini, who contends the Wu administration can get reforms for the city while unions get reasonable raises.

The city’s workers, numbering at roughly 18,000, “take pride in what they do and they believe in the city,” Mandarini said. “If you are not tapping into that knowledge and that commitment, you are missing a wealth of knowledge of how the city can work better. They are the ones who make the city run.”

That temperature-lowering attitude goes against the typical back-and-forth seen in public sector contract fights, with the banging of heads and tables, verbal punches and counterpunches, and even spitting. (In a 2001 incident still talked about within Boston’s political circles, a firefighter protesting Mayor Thomas Menino’s State of the City address spat on Menino’s wife.) Marty Walsh, a Dorchester state lawmaker and labor leader who came out of the building trades and succeeded Menino in 2013, had his own clashes with city workers.

During the 2021 mayoral race, police and fire unions, which have historically resisted reforms while demanding higher pay, funneled money into outside groups that aired ads attacking Wu while seeking to boost her rival, Dorchester’s Annissa Essaibi George.

After the election, the public safety unions quickly crossed swords with Wu over a worker vaccine mandate, leading to a court battle even as the vast majority of city workers got vaccinated.

Sam Dillon, who became president of Local 718 in June, said the firefighters union, which is based in Florian Hall and has 1,600 active members, has not yet engaged city officials in formal contract talks. “Every administration is different,” he said. “There’s no set timeline to go off of. It basically just boils down to when the time is right and we do get to the formal process. We look forward to negotiating a fair and just contract for our members.”

Dillon appreciates Mandarini’s conflict-avoidance attitude. “I think any approach that’s geared towards working in fairness and cooperation to avoid conflict is a terrific approach,” he said.

Historically, both City Hall and the public worker unions are to blame for the adversarial legacy, according to Mandarini. His desire for a different tack comes from his background in the building trades where there’s more cooperation between labor and private sector management. He argues that there’s no reason it can’t be that way in the public sector.

“If he can impart that attitude on the people in city government, then I think those negotiations will be much more friendly and much more reasonable on both sides,” said James Grosso, of the law firm O'Reilly, Grosso, Gross, and Jones.

Grosso is a management-side lawyer for all three of the laborers’ benefit funds — health insurance, pension and annuity — that had Mandarini as executive director until April. The entity is overseen by both management and union trustees.

Grosso knew Mandarini’s father, and recalls talking to him about his son as fathers do, since Grosso has a daughter who is the same age. Grosso first met the younger Mandarini when he was an attorney at Segal Roitman, which bills itself as the oldest and largest law firm in the region focusing on labor unions.

Grosso noted that at the laborers benefit funds, Mandarini, as the administrator, answered to trustees, but he ran the show, overseeing a staff that handled medical claims, pensions and annuities, and an information technology operation set up to keep track of 15,000 people and the contributions being made on their behalf.

When it came time to negotiate with staff, Mandarini found himself on the management side of the bargaining table. “He was focused, he was calm, he didn’t get excited,” Grosso said. “We worked it out at the table with their representative, their steward. It was fun to watch.”

According to Grosso, Mandarini looked at negotiations an employer would, dealing with each demand on its face. “Usually when unions are asking for their demands, they’re off the wall,” Grosso said. “You have to whittle them down.” The union was reasonable, and Mandarini was reasonable in how he responded, he added.

Last winter, Mandarini reached out to Grosso as he mulled joining the Wu administration. He and Wu have known each other for a decade, and both worked on Elizabeth Warren’s first run for US Senate in 2012.

“I wish him well,” Grosso said. “I know he has the capability to do the right thing and I’m sure he will.”

Four months after arriving, Mandarini has already parachuted into negotiations, including the one with the Boston Teachers Union (BTU), which represents 10,000 educators. The tentative agreement, announced July 14, overhauls special education within the school district and includes a compounded 9.5 percent wage increase, which involves a retroactive raise since the union was without a contract for 11 months.

Jessica Tang, the BTU’s president, said once Mandarini got involved, the negotiating teams got more done in two months than they had the previous year. “I think his role was really pushing us all to get it done,” she said.

He was part of a team that included School Committee chair Jeri Robinson and outgoing superintendent Brenda Cassellius, who all “really wanted to get it done,” Tang said. “Obviously we did too, so all of these factors together helped all of us to get to a final agreement.”

Outside of City Hall, a resurgent US labor movement serves as a backdrop to the city’s approach to labor matters. On a recent Monday, Wu joined the picket line outside a Starbucks on Commonwealth Avenue. Hours later, she appeared on the radio station WBUR, whose offices are a few doors down. “We have to reject old, tired ways of framing the conversation, that it’s either about protecting workers or having a successful business,” she said. “In fact what we saw during the pandemic and what continues to be reinforced is that to be a successful business, you have to take care of your workers, and, in fact, that then feeds right back into the productivity, the public goodwill, and the support you’ll be able to have as an entity and neighbor in our city.”

She noted that her administration is attempting to settle all of its expired contracts, one by one. “I can’t ever go out there and preach what we’re not willing to do ourselves. So we’re trying to model that as a city as well,” she said.

Mandarini agrees. “There’s never been in my lifetime greater ferment and churn in terms of workers standing up for themselves, engaging in activism,” he said. “What we’re doing in the city — in terms of having more respect for the workforce and making bargaining more efficient — squares with what’s happening in the world. We’re very much in sync with what’s happening.”