In case there was any doubt about Twitter’s intentions in cutting off the developers of third-party apps, the company has quietly updated its developer agreement to make clear that app makers are no longer permitted to create their own clients.

The “restrictions” section of Twitter’s developer agreement was updated Thursday with a clause banning “use or access the Licensed Materials to create or attempt to create a substitute or similar service or product to the Twitter Applications.” The addition is the only substantive change to the 5,000-word agreement.

The change confirms what the makers of many popular Twitter clients have suspected in recent days: that third-party Twitter services are no longer permitted under Elon Musk’s leadership.

Twitter previously said it was “enforcing long-standing API rules,” but hadn’t cited which rules developers were violating. The company no longer has a communications team, and most staffers working on its developer platform were also cut during the company’s mass layoffs last year.

But the company’s suggestion that the rule was “longstanding” doesn’t line up with its history. Twitter clients have long been a part of Twitter. Twitterrific, one of the most prominent apps affected by the API shut-off last week, was created before Twitter had a native iOS app of its own, and is credited with coining the word “tweet,” as well as other features now commonly associated with Twitter’s app. 

In recent years, clients like Tweetbot and Fenix have had devoted followings due to a lack of ads and other features many longtime users dislike. In fact, Twitter previously changed its developer policies in 2021 to remove a section that discouraged — but didn’t prohibit — app makers from “replicating” its core service. The change was part of a broader shift by Twitter to improve its relationship with developers, including the makers of third-party clients. 

That strategy seems to have officially ended, as the developers whose apps have been cut off have still received no communication from anyone at Twitter about the policy changes. “It’s not totally unexpected, but the lack of communication is a bit insulting,” Matteo Villa, the developer of Fenix, tells Engadget.

Villa has already pulled the Android version of Fenix from the Play Store, but notes that the iOS version of his app still has API access — at least for now. “I’m left with an app working fine on iOS that people are still buying, but I’m wondering if I should pull it too,” he says.

Other developers have also started pulling down their apps. Twitterrific’s Sean Heber confirmed in a blog post that the 16-year-old app has been discontinued. “We are sorry to say that the app’s sudden and undignified demise is due to an unannounced and undocumented policy change by an increasingly capricious Twitter – a Twitter that we no longer recognize as trustworthy nor want to work with any longer,” Heber wrote in an update.

Have a tip about Twitter? Contact the author at karissa.bell@engadget.com or message securely on Signal at +1 628.231.0063.