Petal Screen Sharing: The Free, Open-Source CoScreen Successor Built With AI in Under 8 Weeks

Petal screen sharing is a new free and open-source pair programming tool from four members of the original CoScreen team. It launched on Hacker News in October 2026, after Datadog shut down CoScreen on July 31. The striking part: CoScreen took almost six years to build, while the first version of Petal took under eight weeks, with frontier AI models like Fable and Astra doing a lot of the work.

Key Takeaways

What it is: a low-latency, multi-window screen sharing app for small engineering syncs (typically 3 to 8 people).
Who built it: four people from the original CoScreen team, including co-founder Jason Thomas.
Price: completely free and open source (Apache-2.0). The team says it is not monetizing Petal.
Platforms: macOS 13+ (signed and notarized), Windows (early, unsigned installer), plus a browser client.
Self-hosting: run your own LiveKit server and Petal’s stateless backend, then build the app pointing at it.
AI angle: the first version took under eight weeks, versus almost six years for CoScreen.

What Is Petal?

Petal is a screen sharing app built for pairing sessions, code review, debugging together and design reviews. Its core idea is different from Zoom-style tools: when you share a window, it does not appear as a video tile in a grid. It arrives as a real, movable, resizable, borderless native window on each participant’s desktop.

That means you can drag a teammate’s shared editor next to your own editor, stack it behind other windows, or resize it, just like any app running on your machine.

Why the team built it

The founders describe a pattern that keeps repeating in this market:

Screenhero was loved for pairing. Slack bought it in 2015 and shut down the standalone app in December 2017.
CoScreen was acquired by Datadog in 2022. Datadog sunset the service on July 31, 2026.
Around was bought by Miro and shut down in March 2025.
Multi (formerly Remotion) was acqui-hired by OpenAI in 2024 and shut down about a month later.

In the team’s words, a small team builds something people love, a platform buys it, and the standalone product does not survive. Petal is their answer: free, open source and not monetized. If the team loses interest, you can self-host or fork it, “and nobody can sunset it on you.”

Petal Features

Feature	What it does
Native shared windows	Shared windows appear as real windows on your desktop, not grid tiles
Multi-user sharing	Several people can share windows at the same time
Labeled cursors	Everyone gets a labeled cursor on every shared window
Remote control	Click into a shared window to type and scroll, with explicit consent by default
Persistent rooms	Create rooms like “eng-sync” and join with one click, no links to send
Browser client	People without the app can join from a browser by code or invite link
Optional AI chat	Talk with Gemini Live about a shared window, if the host enables it

Video and audio run over LiveKit, an open-source real-time media server (an SFU, which routes video between participants).

How AI Helped Build Petal

This is why Petal matters for AI watchers. According to the founders, CoScreen took almost six years to build. The first version of Petal took under eight weeks, from scratch, “with frontier models like Fable and Astra doing a lot of the work.”

The team says real-time video and window capture is some of the most unforgiving code they have ever written, so they did not expect that speed. They have promised a proper writeup on what worked and what did not.

Petal Pricing

Option	Cost
Petal app (macOS, Windows, browser)	Free
Source code	Free, Apache-2.0 license
Hosted instance by the Petal team	Free, zero config
Self-hosted	Free software; you pay for your own servers
Optional AI chat (self-hosted)	Billed to whoever owns the Gemini API key

Watch out: the Petal name and logo are not covered by the open-source license. If you fork it, you need your own branding.

How to Self-Host Petal

You can use the team’s hosted instance with zero setup. If you want traffic to stay on your own network, the official self-hosting guide describes three pieces.

1. Run a LiveKit server

Set up a LiveKit server reachable over wss:// with a DNS name and a trusted TLS certificate. Create one API key and secret in its config, for example:

keys:
  petal_key: replace-with-a-long-random-secret

keys:
  petal_key: replace-with-a-long-random-secret

Open the network, firewall, media ports and TURN as LiveKit’s own deployment guide requires. livekit-server --dev on ws://localhost:7880 is only for local development.

2. Deploy Petal’s backend

Petal’s backend/ folder is a stateless service that mints short-lived room tokens. It needs no database or Redis. Vercel is the supported target:

cd backend
npm install
vercel --prod

cd backend
npm install
vercel --prod

Set three server-side environment variables, matching your LiveKit config:

LIVEKIT_URL=wss://livekit.example.com
LIVEKIT_API_KEY=petal_key
LIVEKIT_API_SECRET=replace-with-a-long-random-secret

LIVEKIT_URL=wss://livekit.example.com
LIVEKIT_API_KEY=petal_key
LIVEKIT_API_SECRET=replace-with-a-long-random-secret

Add PETAL_ALLOWED_ORIGINS if you host your own browser client. Add GEMINI_API_KEY only if you want AI chat; leaving it unset turns AI chat off.

3. Build the desktop app

The backend URL is baked into the app at build time:

cd apps/desktop
PETAL_BACKEND_URL=https://petal-backend.example.com npm run tauri build

cd apps/desktop
PETAL_BACKEND_URL=https://petal-backend.example.com npm run tauri build

There is no hosted default. A release build without PETAL_BACKEND_URL refuses to compile, so your build never quietly uses someone else’s service. Builds from a plain clone also never phone home: auto-update, crash reporting and analytics are off unless you configure them.

Build note for macOS: Petal runs on macOS 13+, but building it needs the macOS 26 SDK (Xcode 26.x).

Is Petal Worth It?

Pros

Free and open source, with no business model that could lead to a shutdown.
Shared windows behave like real windows, which fits pair programming better than a grid.
Several people can share at once, with labeled cursors and remote control.
Self-hostable, with no hidden calls home in source builds.

Cons

Pre-1.0: interfaces change and remote control is still early.
Windows support is early, buggy and the installer is unsigned (it may trigger SmartScreen).
Linux is not supported yet; the team says it is next.
Self-hosting takes real work: LiveKit, a backend deployment and your own app build.

The verdict: if your team misses Screenhero or CoScreen and uses macOS, Petal is worth trying today on the hosted instance. Self-host once you are sure it fits.

Petal FAQ

Is Petal free?
Yes. Petal is completely free and open source under Apache-2.0, and the team says it is not monetizing it.

Is Petal a CoScreen alternative?
Yes. It was built by four members of the original CoScreen team after Datadog shut CoScreen down on July 31, 2026.

Does Petal work on Linux?
Not yet. It runs on macOS and Windows plus a browser client. The team says Linux is next.

Can I self-host Petal?
Yes. You need your own LiveKit server, a deployment of Petal’s backend (Vercel is supported), and a desktop build with PETAL_BACKEND_URL set.

Was Petal built with AI?
According to the founders, the first version took under eight weeks with frontier models like Fable and Astra doing a lot of the work, versus almost six years for CoScreen.

Sources

Last updated: October 15, 2026