# Upgrade Guide — vNEXT

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## What Changed

The Multi-Machine Session Pool gains its activation wiring (still DARK): the SessionRouter
is now constructed at boot and consulted on the inbound message path — but ONLY when the
rollout stage is advanced past 'dark'. A single-machine, un-activated agent behaves exactly
as before (the interception is gated off on three independent conditions and fails safe to
local dispatch).

## What to Tell Your User

Nothing changes yet — this is the plumbing that lets the session pool actually move
conversations between machines once it's staged on. It stays off until explicitly activated.

## Summary of New Capabilities

| Area | Capability |
| --- | --- |
| Multi-machine | The inbound dispatch can route a topic's message to the machine that owns the session (gated; dark by default). |

## Evidence

- `tests/unit/session-pool-activation-wiring.test.ts` pins the safety invariants: gated on a
  non-dark stage, fail-safe to local dispatch, real-deps construction, module-ref sharing.
