Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
TransportsArea: what it touches
Internal ChangesKind: in v2.1.234,
Internal ChangesSection of the release
What
The plain stdin transport declares that it is not a remote transport, that the host owns the origin of anything arriving on stdin (used to decide whether an inbound message counts as user-driven), and that a confirmed flush always succeeds. Remote-session code branches on that: delivery acks bail out with "not-remote-session", and one auto-mode capability requires a remote transport plus the remote session id.
Evidence
hostOwnsStdinOrigin
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
