`count_empty_sessions` / `delete_empty_sessions` — the dashboard's
"Delete empty (N)" affordance — defined "empty" as `sessions.message_count
= 0`. That column is a denormalized counter over the LIVE (`active = 1`)
rows only, and two production transcript-rewrite paths reset it on purpose
while keeping every dropped turn on disk as `active = 0`:
* `replace_messages(..., archive_dropped=True)` — the rewind / edit /
regenerate mode added in #82756 so a taken-back turn stays recoverable.
* `archive_and_compact` — in-place compaction, which archives the
pre-compaction transcript under the same session id (#38763).
A chat rewound to its first turn, or compacted with an empty live set,
therefore reports `message_count = 0` while still holding its entire
history — and those soft-archived rows are the only copy. A gateway reload
is what makes the row eligible: it stamps `ended_at` on every detached
session (`end_reason='ws_orphan_reap'`), satisfying the sweep's
`ended_at IS NOT NULL` gate. The next sweep then hard-deleted the session
row AND `DELETE FROM messages`, destroying the transcript silently.
Every other emptiness test in `hermes_state` already defends the counter
with a real `EXISTS (SELECT 1 FROM messages ...)` probe
(`delete_session_if_empty`, `prune_empty_ghost_sessions`,
`list_never_active_keyed_sessions`, `find_recoverable_session`). This
sweep was the only destructive path that trusted the counter alone. It now
uses the same probe, via one `_EMPTY_SESSION_WHERE` selector shared by the
count and the delete so the button's N and the sweep it triggers can never
disagree again. The counter stays as a cheap prefilter; `EXISTS` is the
authority.
Genuinely message-less rows are still swept — the feature is unchanged for
the case it was built for.
Fixes#95868
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011zTDHnWcBvQsJSX1fBLhuv
0bfe715e4d