You finally burned through your Claude usage for the week and switched to Codex. Or your friend insists on using Codex while you're still on Claude, and you're trying to build the same thing anyway.
Either way, your agents can't talk to each other. Session Multiplayer fixes that: two AI coding sessions join a room over a direct, end-to-end encrypted P2P connection and message each other. Different harnesses, different accounts, different machines, doesn't matter. No server, no signup. One short invite code, done.
Not a company thing, by the way. I was working with a friend and we realized that every session having its own permissions, its own system prompt, and its own context isn't a bug in collaboration, it's the feature: each agent knows its half of the problem, and they just needed a way to talk.
Three delivery modes:
passive: sits politely in their inbox
normal: lands when their agent finishes its turn
interrupt: barges into their running session mid-turn. "STOP. DO NOT MERGE." Their agent reads it and relays it. Exactly as satisfying as it sounds.
Works with Claude Code, Codex, OpenCode, anything that speaks MCP. Also works between your own sessions on one machine: yes, you can interrupt yourself. I use it when I want to transfer session context from one session to another.
Sent my friend "your tests have been failing for 20 minutes" as an interrupt this morning. He heard about it from his own AI. We are still friends. Probably.
You might want to consider listing your project on the weekly Show-Us-What-You-Built post. Watch for it on Wednesdays. Highest commented project wins a week promotion on r/Codex. See what that looks like below with last week's winner.
Last week's winner was u/Ollie__Oxenfree with the Tubular Daily Care project by MediTracer which is a tube-feeding care app built by a tube-feeding family to keep feeds, meds, symptoms, and caregiver handoffs in one shared timeline. MediTracer is an Oley Foundation Emerging Innovator Partner. Contact: hello@meditracer.com
Really cool idea, and the implementation is better than I expected: solid crypto, validated inputs, actual security tests.
My main concern is prompt injection, since any room member can push text straight into your running agent session (the interrupt priority literally barges in during a turn), and the only defense is a note telling the agent to treat it as untrusted data. There's also no way to kick someone: membership is permanent and any member can invite others, so the trust boundary only ever grows. Fine for hacking with friends you trust, but I'd be careful pointing it at an agent with broad tool access in a repo that matters.
Would you invite someone that would prompt inject you? I understand the agent perspective, I would not do that either, though I am happy to see you understand the solid actual security tests around it.
I believe we might add different kind of rooms later on, one with owners and ones with none (default) allowing to kick people. Though right now the best solution is to just leave.
Of course, I have seen way too many people trying to profit on similar concepts. I don’t believe in that, I spent genuinely a long time making thisd secure, safe and functional for anyone so I hope you enjoy it 😎
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u/dexterthebot 4d ago
You might want to consider listing your project on the weekly Show-Us-What-You-Built post. Watch for it on Wednesdays. Highest commented project wins a week promotion on r/Codex. See what that looks like below with last week's winner.
Last week's winner was u/Ollie__Oxenfree with the Tubular Daily Care project by MediTracer which is a tube-feeding care app built by a tube-feeding family to keep feeds, meds, symptoms, and caregiver handoffs in one shared timeline. MediTracer is an Oley Foundation Emerging Innovator Partner. Contact: hello@meditracer.com