Adversarial review of the salvaged recovery found a reachable fail-open:
compression continuations inherit the rotated agent's model_config
verbatim (publish_compression_child callers pass
agent._session_init_model_config), so a delegate subagent's continuation
carries _delegate_from=<the delegate's own parent>. The marker-PRESENCE
filters in reopen_orphaned_compression_session and
find_live_compression_child misclassified such a REAL continuation as a
delegate child:
- reopen: parent 'orphaned' -> reopened while a live continuation exists
-> two live heads in one lineage (verified with a live repro)
- find_live: adoption misses the continuation (fail-closed, masked the
fork pre-PR; the PR made it active)
Fix: markers only disqualify a child when they point at the queried
parent (shared _NON_CONTINUATION_CHILD_FILTER_SQL fragment, also
resolving the duplicated-SQL drift risk flagged by the reuse reviewer).
Both directions regression-tested: reopen fails closed on an
inherited-marker continuation; find_live adopts it.
Also from review: reopen-failure log raised debug->warning (the failure
hard-fails the turn moments later), commit-semantics hardening comment
on the lease DELETE path, blank-line nit.
The three read-only projection walks (get_compression_tip,
list_sessions_rich chain, resume walk) share the marker-presence shape
but fail closed (skip a continuation -> resume shows the parent), and
the fixed adoption path self-heals that case at turn start; left as-is.
