Kanye West's created a monster ... a super-fashionable one, who's taking every opportunity -- including her son's first birthday -- to show off her couture wardrobe.
Julia Fox jumped into fashion runway mode when photogs showed up outside Lucien in NYC's SoHo neighborhood -- posing her ass off (don't worry she's got plenty) in a head-to-toe black ensemble that included a black hoodie ... one of Ye's fave looks.
She was also rocking a black leather trench along with black leather pants and boots. Fact is, Julia's been draped in high fashion designs like Balenciaga -- often at Ye's behest -- ever since they hooked up on New Year's Eve.
Anyone walking past her sidewalk catwalk act Monday in SoHo would never have imagined this was all for a 1-year-old's party!
Yes, Mama Fox was there celebrating her baby boy Valentino's birthday.
We'll say this, her co-parenting seems to be going smoother than her BF's. As you know, Kanye was pissed over the weekend, claiming Kim Kardashian kept the location of their daughter Chicago's birthday party secret from him.
TMZ broke the story ... our Kim sources say she simply thought Ye was throwing a separate 4th birthday party for Chi.
In any event, Julia's baby daddy, Peter Artemiev, was at their kid's party ... and the exes even posed together for pics with their son.