A plugin owning a standalone open/close bracket cannot tell a dead marker
from a live one: an unmatched `compact/start` reads identically whether the
previous writer died mid-compaction or a compaction is running now.
`Session.firstLiveSeq` already holds that answer exactly, but only in memory.
Append the log-only `session/inherited` event at that seq from the seeded
constructor — the single waist all six seeded-start paths pass through
(resume, configured startup on a persisted id, `sessions.fork()`, a subagent
fork child, `adopt()`'s live prefix, and a bare seeded `create`). Read it
through the new `isInheritedSeq(events, seq)`.
The constructor placement means persistence needs no changes: the marker is
already in `events` when a backend captures the creation seed, so it rides
the ordinary seed path with no load-time write. It also covers fork, where
the inherited bracket's owner may still be running — the case a
persistence-layer boundary could not reach.
Activity ordering excludes the boundary through `lastActivityTime()`, since
lazy resume makes browsing a pickup and the three call sites would otherwise
float every opened session to the top of a picker or list.
The simplification deletes sandbox_mode and approval_policy from the parent branch's SQLite layouts. Restoring master's older version numbers would violate the monotonic schema contract and could make a database created by the parent look current under a different layout.
Advance durable session persistence from schema 11 to 12 and the disposable session-query index from 6 to 7. The former rejects the incompatible parent layout; the latter resets its derived tables through the existing version-mismatch path.
JSONL shares SESSION_FORMAT_VERSION 0 during pre-release, so explicitly reject the retired sandboxMode and approvalPolicy header fields instead of silently dropping the only inherited policy facts from a parent-produced child log. New logs carry those facts as ordinary seeded events.
Focused JSONL, SQLite persistence, and SQLite query suites cover all affected source lines and branches.
Master removed the stdio demo (#702c8cc30) — accept the deletion; this
branch's packChunks passthrough survives in acp-demo (auto-merged), and
cli-demo/tui-demo arrived from master without one (the follow-up snapshot
PR decides which demos expose the switch). Generated catalogs regenerated
over merged sources; the hand-written session.md durability paragraph
re-weaves this branch's lossless-encoding wording with master's invariant-
companion sentence.
Master's Zstandard physical encoding (#416) and this branch's packed chunk
rows compose as orthogonal layers: packChunks shapes the logical storage
records, compression shapes the physical bytes. The backend keeps both
config keys; eventLines(events, packChunks) replaces master's singular
eventLine helper and feeds encodeMaterialization/encodeEventBatch so packed
rows flow through either encoding. Demo apps carry both passthroughs. The
packed-row layout tests pin compression: 'none' (they assert textual line
tags) and read through rawLogPath; zstd spec fixtures inline
JSON.stringify for verbatim lines.
Conflicts: the two generated catalog docs (regenerated over merged sources)
and the jsonl backend README storage-layout bullets — master's required
delegationDepth header field weaves with this branch's storage-record/packed
row wording.
Identity validation must reject a header id that cannot derive a path, and only ENOENT may mean that storage is absent. Other root or per-path failures must remain visible instead of becoming an empty list or false miss.
Exercise those branches with narrow storage-mechanics cases, preserving per-file 100% coverage without restoring the flat-layout or multi-writer tests removed from the replacement design.
