A turn writing against a session already closed by compression died with
session_persistence_failed and a misleading "this is often a full disk"
dialog, even though the store was healthy and a live continuation existed
(#82001). Depth-1 recovery (find_live_compression_child) could not resolve
lineages with >=2 compression hops (root -> mid -> tip), reproduced
independently on two- and three-hop chains.
- run_agent.py flush chokepoint: on CompressionSessionClosedError, resolve
tip = db.get_compression_tip(old_id) (canonical bounded transitive walk),
adopt only when tip != old_id AND the tip row is live, retry the flush
exactly once (adoption budget); otherwise fail closed.
- gateway/session.py append_to_transcript: replace the depth-1 live-child
lookup with the same tip + liveness contract, so gateway transcript
reroutes follow full chains.
- agent/conversation_compression.py _adopt_live_compression_child: turn-start
recovery preflight now resolves via get_compression_tip with the same
liveness check, closing the last depth-1 consumer in this family.
- classify_persistence_error: new "compression_closed" bucket; the turn-end
explanation names compression rotation and tells the client to refresh the
session id instead of blaming a full disk.
Tests: depth-1 adoption, multi-hop chain adoption (agent + gateway), fail
closed with no continuation / stale-closed (ws_orphan_reap) tip, exactly-once
adoption budget, and error-wording guards (compression-closed never mentions
disk; real disk failures keep disk guidance).
Closes#82001
Co-authored-by: Al3xand3r1987 <125030427+Al3xand3r1987@users.noreply.github.com>
Co-authored-by: yuzilongleif-collab <235949691+yuzilongleif-collab@users.noreply.github.com>
Teknium