Cross-Server Session Access via T3 Connect

[sunjay-dev]

Suppose I have multiple cloud VPS instances, each running T3 Code and connected through T3 Connect. How can one server interact with or control sessions running on another server? Is cross-server session access supported?

[shurkanTwo]

Not as a built-in server-to-server link. Each T3 server owns its own threads and runs their agents locally; T3 Connect makes every server reachable for clients (desktop, web, mobile), but the servers don't federate with each other.

What you can do in v0.1.0:

Control all of them from one client. Sign in to the same T3 Connect account on your desktop/web/phone and every VPS shows up as its own environment. If your projects are grouped across environments, Settings → Connections → Load balancing can even pick the machine for new threads (remote access docs). Existing threads stay on the server they started on.

Let an agent on server A drive threads on server B. Every environment exposes an MCP server at <environment-address>/mcp, and agents T3 didn't start can use it to read projects and threads and to start, message and stop threads (outside agents docs). On server A, register server B's MCP endpoint with the provider CLI that A's agents use:

# Claude Code (user scope, so agents T3 starts in any project see it)
claude mcp add --scope user --transport http t3-server-b https://<server-b-address>/mcp
claude mcp login t3-server-b --no-browser

# or Codex
codex mcp add t3-server-b --url https://<server-b-address>/mcp
codex mcp login t3-server-b --no-browser

Get the exact URL from Settings → Connections → (server B's menu) → Copy MCP URL. Use B's T3 Connect address if A can't reach it over a LAN or tailnet. Approve the sign-in with a pairing code from t3 auth pairing create on server B. Read only is the default; choose Supervised or Full access if A should be allowed to start or message threads on B. A thread started that way can't run with more permissions than the mode you pick.

After that, an agent in a thread on A can call B's tools (list threads, read one, send a message, start a new one), which is the closest thing to cross-server session access right now. Revoke it any time under Settings → Connections on B; the sign-in expires after 30 days.