The default (legacy) repair path ignored --dry-run and ran the real
rebuild: it deleted any existing <palace>.backup, copied the live palace
over it, re-filed the drawers collection through a staged temp copy, then
rebuilt FTS5 and VACUUMed. #2095 and #2133 fixed this for
--mode from-sqlite only.
The preview now returns before ChromaBackend() is constructed. Opening a
chromadb client is itself a write to chroma.sqlite3, so a preview that
reached one could not be inert; the row count comes from
sqlite_drawer_count instead, the read-only SQLite ground truth
check_extraction_safety already trusts. Staying off the chromadb layer
also keeps a dry run clear of the layer repair is separately reported to
segfault in on a large palace (#2113).
resolve_repair_preflight_errors() decides what a dry run does about the
FTS5 autoheal. The autoheal is a write, so a preview must not run it, but
skipping it routed an isolated inverted-index error into the abort banner
and exit 1 - telling the operator to run offline sqlite3 .recover on a
palace a real run heals by itself (#1596). The dry run now classifies the
errors with the same _errors_are_isolated_fts5 predicate the real path
gates on and continues; broader corruption still aborts in both modes.
It is worded as an attempt rather than a promise, because the real heal
still gives up when another process holds the mine lock, when the rebuild
raises, or when quick_check is still dirty afterwards.
The plan describes the real run in execution order. It names the
live-collection delete the rebuild performs, since "re-file via a staged
temp copy" alone reads as additive; it warns when an existing backup
would be deleted; and it reports a no-op instead of a rebuild when the
collection holds no rows. It states the #1208 truncation guard that can
abort the run, and reports that guard as disabled when
--confirm-truncation-ok is set, because check_extraction_safety returns
immediately then and the promised abort would not happen. An unreadable
count fails closed with a non-zero exit, for parity with the from-sqlite
preview.
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