The person spoke on condition of anonymity because the deal cannot become official until March 12, when the NFL's new business year begins. Another person familiar with the swap said the 49ers will get a second-round pick in April's draft, No. 34 overall, and a conditional pick in the 2014 draft.
After spending his first eight up-and-down years with the 49ers, Smith will get a new start. The Chiefs will get the proven play-caller they hope can help turn things around under a new coach much the way Smith did under Jim Harbaugh in San Francisco.
"You never know when your opportunity's going to come," Smith said late in the season. "The good ones are ready when they do come."
Moving Smith was hardly unexpected. He realized it once Colin Kaepernick emerged as a capable starter over the season's final two months, and Smith all but said goodbye with his first pro team when he played briefly in the regular-season finale against Arizona to cheers of "Let's Go, Alex!" and "Alex! Alex!" from the Candlestick Park crowd.
With Smith now headed for Kansas City, Matt Cassel is likely headed out of town. And Reid will enter his first draft as Chiefs coach in April no longer needing to search for a quarterback.
The Chiefs' problems at quarterback are the single biggest reason they went 2-14 last season and secured the No. 1 pick in the draft for the first time in franchise history.
Even memorable names such as Steve Bono, Elvis Grbac, Damon Huard, Tyler Thigpen and Tyler Palko haven't fared well with this franchise. And then there's Cassel.
He was acquired by recently fired general manager Scott Pioli, and has two years left on a $63 million, six-year deal. He will likely be cut once Smith is acquired.
Cassel was benched last season in favor of Brady Quinn, who also is a free agent after going 1-7 as the starter.
If Smith can bring the steady form that defined his last two years, the Chiefs might be able to establish a much-needed consistency under center. They also found themselves a team-first player who led the 49ers through workouts during the 2011 lockout.
Under the three-year contract he signed last March, Smith is guaranteed $1 million from the 49ers, and that would have become $8.5 million guaranteed his 2013 salary if he was still on their roster April 1.
Smith thrived under 49ers coach and former NFL quarterback Harbaugh in one-plus season as the starter. Then, just like that, it all changed after he sustained a concussion.
Last week at the NFL combine, Harbaugh praised Smith and reiterated just how strong San Francisco was with Colin Kaepernick as the starter and someone with Smith's credentials at backup.
Yet everyone knew it was likely the 49ers would do their best to improve Smith's situation considering all he did for the franchise for nearly the past decade.
"Alex is really playing the best football of his career the last two years," Harbaugh said. "We think we got the best quarterback situation in the National Football League, feel strongly about that. Again, that'll be a process that plays out. Alex Smith continuing to be a 49er or if a trade occurs in the next weeks or months. Those are the two possibilities, most likely possibilities."
Smith acknowledged when he lost the job to Kaepernick back in November that he had done nothing wrong but get hurt. Not only had he completed 26 of his previous 28 passes 18 of 19 for 232 yards and three touchdowns without an interception and a 157.1 passer rating in a Monday Night Football win at Arizona on Oct. 29 Smith had just earned NFC Offensive Player of the Week honors after that victory in the desert.
He then sustained a concussion in the second quarter of a 24-24 tie against St. Louis on Nov. 11 acknowledging later he threw a touchdown pass with blurry vision. Smith sat out the next game as Kaepernick dazzled in his debut as an NFL starter, beating the Bears handily at home on Monday Night Football.
After that, Harbaugh vowed to stick with the "hot hand," as he regularly put it, while complicating matters by still referring to Smith as a starter.
Smith's most poignant response to the situation was, "I feel like the only thing I did to lose my job was get a concussion."
As strong-armed second-year pro, Kaepernick led the 49ers to the NFC championship and a 34-31 loss to Baltimore in the Super Bowl in which the 49ers missed several chances in the waning moments. The 49ers are now looking for a backup for him.
The 28-year-old Smith struggled for most of his career in San Francisco, plagued as much by coaching and constant coordinator changes as by his own indecisiveness. But when Harbaugh became coach in January 2011, Smith blossomed under the former QB's guidance. He was among the league leaders in passer rating (104.1) with a 70.2 completion percentage when he got hurt last season.
Fox Sports first reported the deal Wednesday.