A mid-conversation model/provider switch rebuilds the agent runtime. The
rebuilt runtime emits session.info (and all later events) under a NEW
explicit session_id while the pane still holds the dead one as its
active id — isActiveEvent is false for the same conversation from that
moment on, so view-scoped updates stop and the chat freezes until a
full resume (#93942 scenario B; backend even logs 'client should resume
the stored session', but the client never does).
Fix: when a session.info event lineage-matches the selected conversation
(sessionMatchesStoredId over stored_session_id) but carries a different
runtime id, adopt the new runtime id as the active session id — keeping
the durable selection untouched — so every subsequent isActiveEvent gate
keeps matching without a resume. Guarded: the old runtime must show no
live turn (not busy/awaiting/streaming) or the adoption is refused, so
an overlapping manual switch can never split one conversation across
two panes.
The existing compression-rotation path does not cover this case: it
fires when the SAME runtime's stored id rotates, while a rebuild
produces a NEW runtime with a NEW stored id.
Together with #94255 (tile reconcile on sessions.changed), closes
#93942.
Regression tests verified failing pre-fix on 41447a6d70.
beplee
ec8ca8f2cb