notify_session_compacted closed the old session scope immediately on a
legacy rotating compaction. A compaction can complete while a turn is
still live on the old session; closing then pops the session scope under
the live turn scope, violating the stack's LIFO order — the exact
invariant the rest of the segmentation feature protects.
Now: when the old session has an active turn, set close_pending instead;
that turn's end_turn consumes the flag after its own turn scope pops and
it unregisters from the active-turn table. Sabotage-verified: the new
test fails without the fix.
Continuous gateway sessions keep the Relay session scope open for days;
close-driven export means the session root span and out-of-turn marks
never export until /new or idle-end, and a crash loses the open segment
entirely.
Opt-in segmentation (both defaults OFF => scope lifecycle byte-identical
to today):
gateway.telemetry.session_segments.on_compaction: false
gateway.telemetry.session_segments.max_turns: 0
Rotation closes the current session scope and pushes the next segment
(same session_id attribute, plus hermes.session.segment=N and
segment_reason=compaction|max_turns) ONLY at a turn boundary in
begin_turn — never mid-turn (scope stack is LIFO). Compaction completion
just flags rotate_pending (observer semantics, nothing on the compaction
critical path); legacy rotating compaction closes the orphaned old
session scope so its segment exports. Both native calls ride the
existing bounded scope-op executor: a wedged rotation costs one segment
span, never the agent. Segment bookkeeping advances even on native
failure so a degraded rotation cannot retry every turn.
Teknium
Victor Kyriazakos