Comparison
Poly vs Mosaic for sharing AI coding sessions across a team
Mosaic shares what everyone's agents did. Poly shares the agent while it works.
Mosaic and Poly both make AI coding a team activity, at different moments. Mosaic (mosaic.inc, YC) is a macOS command-line tool that syncs a team's Claude Code, Codex and Cursor sessions into one shared, read-only place any agent can read, so a teammate can fork your session into their own agent or have one handed to them. Poly (usepoly.co) is a browser room where a team steers one AI together while it works: every member prompts in one timeline, approves each change before it happens and gets a receipt per turn. Mosaic suits teams already running many personal agents who want shared context without changing how anyone works. Poly suits a group that wants to build together live.
| Poly | Mosaic | |
|---|---|---|
| What the team shares | One live AI session | Everyone's sessions, read-only |
| Several people steer one agent | Yes | No; fork or hand off |
| Approve before the AI acts | Yes, per change, any member | Each person's own agent settings |
| Runs on | Any browser | macOS 14 or later, command line |
| Agents | Claude Code and Codex, hosted | Your own Claude Code, Codex, Cursor |
| Price | Free start; $20 or $50 per AI user | Not published |
What Mosaic does
Mosaic, from Shubham Patil and Dorsa Rohani in San Francisco, launched on Y Combinator on August 24, 2026 as shared memory for teams and coding agents: "Everyone's AI coding sessions, in one place." A background sync copies each person's sessions into a shared folder that any agent can read. mosaic fork continues a teammate's session in your own agent, and mosaic handoff assigns one to a teammate. Mosaic doesn't install or modify coding agents or their hooks. It runs on macOS 14 or later, with open sign-up through GitHub or Google and no published pricing. A different YC company, Mosaic at mosaic.so, makes video agents.
Where Mosaic is stronger
- Works with what people already use. Claude Code, Codex and Cursor, unchanged.
- No new habit. The sync runs in the background.
- The team's history. Every agent can read what everyone's agents did, past sessions included.
Where Poly is stronger
- Live, together. In Poly the room steers one AI while it works. Mosaic shares sessions between people; nobody steers one session together.
- A say before it acts. Any Poly member can approve a change before it happens. Mosaic adds no approvals of its own.
- Any device. A Poly room opens in any browser. Mosaic is a macOS command-line tool.
- Models included, with receipts, and built for people who don't code.
Which should you pick?
- A team of engineers already running their own agents who want those agents to share context: Mosaic.
- A group that wants to build together live, approve changes and see who spent what: Poly.
More options are in Multiplayer AI tools.
Common questions
Is Mosaic a multiplayer Claude Code?
Not a live one. Mosaic shares sessions between people's own work: anyone's agent can read the team's sessions, and a session can be forked or handed off. Nobody steers one session together. Poly is the live version.
Which Mosaic is this?
Mosaic at mosaic.inc, the YC company that shares coding-agent sessions. A different YC company, Mosaic at mosaic.so, makes video agents.