INGLEWOOD, CALIFORNIA - APRIL 03: Recording artists Calvin Harris (L) and Taylor Swift hug during the iHeartRadio Music Award
Kevin Mazur/Getty Images for iHeartRadio / Turner

Update 2:40 PM ET: Katy Perry's response to all this?

Original: A mere two hours after Taylor Swift's rep confirmed that she co-wrote the Rihanna-featuring "This Is What You Came For" with ex-boyfriend Calvin Harris, the producer is attempting to take her down on Twitter.

News broke on Wednesday that Swift had used a pen name, Nils Sjoberg, to create "This Is What You Came For" so that her name wouldn't take attention away from the single. (You can even hear her singing on the yous at the 1:15 mark.) TMZ suggested that the couple, who were together for 15 months, broke up because he took their secret too far when he wouldn't admit to press that they would collaborate.

Harris has some stuff to say about that:

And then comes the Katy Perry kicker. Of course, you don't need to be terribly invested in pop culture to know that Swift and Perry have one of the most infamous beefs of all time, leading to "Bad Blood":

Here's the full text of his tweets, as we anticipate deletion:

"And she sings on a little bit of it too Amazing lyric writer and she smashed it as usual

I wrote the music, produced the song, arranged it and cut the vocals though. And initially she wanted it kept secret, hence the pseudonym

Hurtful to me at this point that her and her team would go so far out of their way to try and make ME look bad at this stage though

I figure if you're happy in your new relationship you should focus on that instead of trying to tear your ex bf down for something to do

I know you're off tour and you need someone new to try and bury like Katy ETC but I'm not that guy, sorry. I won't allow it

Please focus on the positive aspects of YOUR life because you've earned a great one

God bless everyone have a beautiful day"

Watch Calvin Harris tell Fuse about his collaborative process: