MILAN — The pieces of the Dior puzzle are expected to start falling into place today when sources say Valentino will reveal that Maria Grazia Chiuri is exiting the Rome-based fashion house.

As reported, the designer is expected to become Dior’s seventh couturier. WWD first reported last November that Chiuri could be in the frame to succeed Raf Simons at Dior, and reported on May 31 that she was among three finalists for the job. The Italian designer is to show her first collection for Dior this fall, for the spring 2o17 ready-to-wear season.

The development will come a day after Valentino showed its couture collection in Paris. Chiuri’s departure marks the end of her fruitful collaboration with Pierpaolo Piccioli, which has spanned more than two decades. Piccioli is expected to be appointed sole creative director of Valentino upon Chiuri’s departure.

The two first worked together at Fendi for 10 years and are credited with contributing to the design of the Baguette bag. Couturier Valentino Garavani handpicked the designers to boost his brand’s accessories category, which they did, rejuvenating that division. They were promoted to creative directors of accessories at Valentino when Alessandra Facchinetti was assigned the same title for rtw after Garavani retired in 2007. In 2008, they succeeded Facchinetti as creative directors of the brand.

Accessories continue to be a commercial pillar for Valentino, accounting for 50 percent of sales last year. The designers famously launched the Rockstud collection and Camouflage sneakers, balancing punk and streetwear edge with bourgeois style.

Sources speculate Dior may have zeroed in on Chiuri to further grow its own accessories division.

Chiuri and Piccioli are longtime friends, and are known to speak in unison during interviews. But speculation about friction between them has recently intensified. Sources also speculated at the time that Gucci had contacted Chiuri to succeed Frida Giannini, before Alessandro Michele was promoted to the top creative role.

Speaking at the WWD CEO Summit last year, the designers said their creative process is collaborative. “We have an idea, we think about it and we have a mood board,” Chiuri said. “Day by day, we work on it and we pick out different ideas,” Piccioli added. “At the end, what comes out is really something from two people who share the same vision.” Do they fight? “Of course,” Chiuri said. “Nothing is a fairy tale.”

At the summit, Chiuri talked about her affinity for high fashion: “It’s a culture of couture. It’s very close with craftsmanship and quality, but also the tradition that’s part of our past, like Italian. In Rome, you feel that really strongly. In any case, it’s very close with the heart, with the idea that the profession is something artistic, something has a human touch and we really believe that has made a difference in our brand.”

While their initial collections for Valentino were seen as somewhat referential, the duo gradually developed their own style for the brand, anchored by a romantic silhouette with high-necked, long-sleeved dresses with A-line skirts. Over the last few years, they and Stefano Sassi, the company’s chief executive officer, have turned Valentino into one of the hottest and fastest-growing designer brands. Last year, the firm surpassed the $1 billion revenue threshold, posting a 48 percent jump in sales.

Chiuri’s speculated exit comes ahead of Valentino’s possible initial public offering, expected to take place not before 2017. “It doesn’t seem like a good year to list,” said Sassi last month of 2016.

Chiuri and Piccioli’s clear aesthetic has drawn a new generation of customers to the brand. They have often culled inspiration from Rome, last year exceptionally showing their couture show in the Italian capital and staging the “Mirabilia Romae” exhibit as a tribute to the city. They have recently branched out with collections referencing Africa and the world of dance, and often refer to the arts — the Renaissance, in particular — music and culture.

The designers have succeeded in transforming a heritage brand into a modern and influential couture, rtw and accessories luxury label. All this while its founder remains a constant presence on the fashion scene and attends most of their shows. Together the trio most recently worked on the costumes for “La Traviata” directed by Sofia Coppola, which bowed in Rome in May.

Valentino is owned by Qatar’s Mayhoola for Investments, which just bought Balmain and also controls Pal Zileri and has a stake in Anya Hindmarch.