Ex-CoScreen Team Releases Petal, a Free Open-Source Pair Programming Tool

The code is published at github.com/kiruna-labs/petal. According to the post, shared windows appear on a collaborator's desktop as real windows that can be moved and resized, rather than as tiles in a grid. Several people can share at once, each with a labelled cursor, and any shared window can be clicked into for typing and scrolling. Rooms are persistent, so joining a session named "eng-sync" takes a single click instead of passing a link around.

The app runs on macOS and Windows, with Linux next, and also as a web app. Media is carried over LiveKit. Users can connect to the team's hosted instance with no configuration, or point the client at their own LiveKit server using one docker-compose file if they want traffic to stay on their own network; Thomas wrote that an entirely different video backend can be substituted as well.

Thomas placed the release in the context of similar tools that disappeared after being acquired. Screenhero, which he described as a widely loved pairing tool with multiple cursors and low latency, was bought by Slack in 2015 and its standalone app was shut down in December 2017. He, Till and Max then started CoScreen, which Datadog acquired in 2022. Datadog invested in CoScreen for years while the team adapted its real-time technology into Datadog products, but Thomas wrote that CoScreen proved too tangential to Datadog's customer base and core mission. The team instead built other communication features at Datadog, integrations with video platforms and the company's MCP server.

He cited further examples: Miro bought Around and shut it down in March 2025, and OpenAI acqui-hired Multi, formerly Remotion, in 2024 and shut it down about a month later. Thomas wrote that Petal, by contrast, is completely free, is not being monetized, and can be self-hosted or forked if the team loses interest or is unable to continue, so that no acquirer can sunset it. He described the project as a response to the community that supported CoScreen and an attempt to break what he called a vicious cycle in collaborative screen sharing.

On the engineering side, Thomas said CoScreen took almost six years to build, while the first version of Petal was written from scratch in under eight weeks, with frontier models including Fable and Astra doing much of the work. Real-time video and window capture, he added, is some of the most unforgiving code the team has written, and he said they plan a fuller writeup of what worked and what did not.

The Hacker News submission carried 6 points and 2 comments at the time of posting. Thomas said he, Till, Darren and Max would be answering questions in the thread.