When /compress rotates the session, the handler repointed the live
session entry onto the new (empty) continuation session_id and _save()d
that BEFORE writing the compressed transcript — and rewrite_transcript
swallowed DB write failures at DEBUG. A transient write failure (SQLite
lock under concurrent writes, ENOSPC, disk/IO error) left the session
pointing at an empty id while the handler still reported a cheerful
'Compressed: N → M' success. The active conversation vanished from view.
- gateway/session.py: rewrite_transcript now returns bool (True on write
success or no-DB, False on canonical write failure). /retry, /undo, and
yuanbao recall ignore the result, so their behavior is unchanged.
- gateway/slash_commands.py: _handle_compress_command persists the
compressed transcript FIRST and treats a write failure as fatal (raises
into the outer handler's 'compress failed' banner). Only repoints +
_save()s the session on a successful write. Widened beyond the original
rotation case to also cover in-place compaction (#38763): a failed
in-place write would otherwise leave the DB untouched while still
reporting success.
- tests: regression tests for both the rotation and in-place write-failure
paths — assert a failure banner, unchanged session_id, and no _save().
Co-authored-by: Hermes Agent <agent@nousresearch.com>
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