mxaccessgw gives no reply-before-event ordering: the worker completes the STA
command via a RunContinuationsAsynchronously TCS, so the reply is framed on a
thread-pool continuation while the STA already pumps the OnDataChange Advise
queued (drained/framed by a separate loop), and the reply (unary Invoke) and
the event (StreamEvents) are separate HTTP/2 streams. The driver then also
registers handles concurrently with the pump's dispatch loop. MXAccess's
initial value could therefore be dropped as "stale after unsubscribe",
leaving the node at its pre-subscribe value until the next change.
SubscriptionRegistry gains an early-event window: every SubscribeBulk call
site (SubscribeAsync, ResubscribeAllAsync, PerPlatformProbeWatcher) opens
BeginPendingSubscribe() before the RPC and closes it after registering.
Inside the window unknown-handle events are parked (bounded, 100k); the
Register/Rebind that binds a handle promotes them, and the EventPump replays
them on its single dispatch thread before any later event for that handle
(woken by a sentinel when no further event arrives). Closing the last window
discards unclaimed events, so the stale drop is unchanged outside it.
New counters galaxy.events.early_{parked,replayed,overflow}.
Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
Joseph Doherty
1a31e3f584