Sdílení chatu s externím hostem na hostovaném Prostředí (guest links bez T3 Connect, na několik dní) #193

Use case

An integrator builds a light installation for a client and has it running as a simulation in the browser (a page served from the integrator's Environment, driven by the same animation program as the real installation). Next week (16.–20. 11. 2026) the client's IT technician wants to tune the animations with us: he describes what he wants in a chat, the agent changes the animations, he immediately sees the result in the simulation, and once he is happy the integrator publishes the change to the real installation.

What the integrator needs from Lazurio T3 Code:

1. Share one chat thread with an external person, without an account in the Organization, from a hosted Environment: their own Pracovní Prostředí or a Týmové Prostředí set up for this client.
2. The guest writes, the owner stays in control. The guest's messages wait until the owner sends or dismisses them (upstream guest links already do this). Publishing to the real installation stays with the owner, never the guest.
3. The guest sees the result. At minimum the agent's replies with images. Ideally also the simulation page the agent shows (html_render or a preview tab), or a separate link to the simulation next to the chat.
4. It works for a few sessions over several days. Not just one 24-hour browser session.

What already exists

Upstream guest links have been in the fork since the rebases (docs/user/guest-links.md, apps/server/src/guest/*, GuestShareControls.tsx): Share with guest on a thread, the guest page, sending or dismissing guest messages, guest attachments, beta in Settings → Labs.

What is missing on a hosted Lazurio Environment

• T3 Connect. Guest links need T3 Connect, because the link points at the machine's T3 Connect address. A hosted Environment runs behind its own external origin (T3CODE_EXTERNAL_ORIGIN). It must be decided whether the guest page is served over that origin (the same family of problems as Behind an external origin, copied thread links point at app.t3.codes and external-origin links are not chips #175, links built from app.t3.codes), or whether T3 Connect will be supported on Environments.
• Who may share. Who may share a thread and from which kind of Environment (Pracovní, Týmové). A guest link exposes everything the agent read or printed in the thread, so it must stay an explicit owner action, and an Organization should be able to turn it off by policy.
• Link lifetime. 24 hours and a single browser are too short for tuning across several days. Proposal: a longer lifetime the owner chooses, or renewal without a new thread.
• Previews. Guests do not see previews or the agent's browser. For this use case it is enough when the guest sees the images the agent sends and has a separate link to the simulation, which must not require logging in to Lazurio.

Goal

Ready for next week: a host on a hosted Environment can open a guest link, write to the agent, and the owner approves their messages. Decisions that only the Lazurio owner can make (T3 Connect vs. own origin, who may share) should be raised early as questions on this issue.

Agent: environment f9d55fe8-4ee8-4ad9-b472-1729a4d78eab · T3 thread c01032df-68c8-4239-be10-8ee77024f16f