fix(repair): add --mode from-sqlite to recover palaces with corrupt HNSW (#1308)

Both `--mode legacy` and the inline `cli.cmd_repair` rebuild path
call `Collection.count()` as their first read — the same call that
raises `chromadb.errors.InternalError: Failed to apply logs to the
hnsw segment writer` on the corruption class reported in #1308.
Repair would print "Cannot recover — palace may need to be re-mined
from source files" even though the underlying SQLite tables were
fully intact.

The new `--mode from-sqlite` reads `(id, document, metadata)` rows
directly from `chroma.sqlite3` via `segments` → `embeddings` →
`embedding_metadata` joins, never opens a chromadb client against
the corrupt palace, and re-upserts everything into a fresh palace.

  - `--source PATH` extracts from a corrupt palace already moved aside
  - `--archive-existing` handles the in-place case by renaming the
    existing palace to `<palace>.pre-rebuild-<timestamp>` first
  - Partial-rebuild failures raise `RebuildPartialError` with the
    archive path so users can recover; CLI exits non-zero
  - In-place mode calls `SharedSystemClient.clear_system_cache()` to
    drop chromadb's process-wide System registry (cross-palace use
    does not, to limit blast radius for library callers)
  - Source validation runs before any destructive moves

Verified end-to-end recovering a 52,300-row real-world corrupt
palace.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 - **CLI and `fact_checker --stdin` mojibaked non-ASCII content on Windows.** Python defaults `sys.stdin`/`stdout`/`stderr` to the system ANSI codepage (cp1252/cp1251/cp950), so `mempalace search > out.txt` and piped fact_checker invocations corrupted Cyrillic / CJK drawer text at the process boundary. New `mempalace/_stdio.py` helper reconfigures all three streams to UTF-8 on `sys.platform == "win32"`, with per-stream `errors` policy: `surrogateescape` on stdin (preserves bad bytes from redirected files for the consumer's parser), `replace` on stdout/stderr (substitutes U+FFFD instead of `UnicodeEncodeError`-ing mid-print). With this, all three user-facing console_scripts (`mcp_server`, `hooks_cli`, `cli`/`fact_checker`) now reconfigure identically on Windows. (#1282)
 - **MCP knowledge-graph tools forwarded malformed date strings to SQLite.** `tool_kg_query` (`as_of`), `tool_kg_add` (`valid_from`), and `tool_kg_invalidate` (`ended`) accepted any string and produced empty result sets on natural-language inputs like `"March 2026"` or `"yesterday"` — callers (especially LLM agents) could not distinguish "no fact at this time" from "your date format was unrecognized." New `sanitize_iso_date()` validator in `config.py` accepts `YYYY`, `YYYY-MM`, `YYYY-MM-DD` (and passes through `None`/`""`); all three tools call it before values reach the storage layer. **Behavior change:** previously-silent date typos now raise a clear `ValueError` naming the offending field; full ISO-8601 with time (`YYYY-MM-DDTHH:MM:SS`, timezone offsets) is not yet accepted — file an issue if you have a use case. (#1164, #1167)
 - **MCP server's `_kg` was a module-level singleton.** Multi-tenant hosts that rotate `MEMPALACE_PALACE_PATH` between tool calls hit the wrong sqlite file, because the KG was constructed once at import time while the ChromaDB side was already per-call via `_get_client()`. The KG is now resolved per-call through a lazy per-path cache (`_kg_by_path` keyed by `os.path.abspath`, with a double-checked-locking init under `_kg_cache_lock`). `tool_reconnect` drains and `close()`s cached KGs alongside the existing chroma reconnect. A `_call_kg` retry guard catches `sqlite3.ProgrammingError` once after a reconnect race. (#1136, #1160)
+- **`mempalace repair` can now recover palaces whose HNSW segment writer is stuck on `apply_logs`.** Both the existing `--mode legacy` rebuild and the inline `cli.cmd_repair` path call `Collection.count()` as their first read — exactly the call that raises `chromadb.errors.InternalError: Failed to apply logs to the hnsw segment writer` on the corruption class introduced upstream and reported in #1308. Repair would print `Cannot recover — palace may need to be re-mined from source files` even though the underlying SQLite tables were fully intact (the corruption lives in the on-disk index files, not the data layer). New `--mode from-sqlite` reads `(id, document, metadata)` rows directly from `chroma.sqlite3` via a `segments` → `embeddings` → `embedding_metadata` join, never opens a chromadb client against the corrupt palace, and re-upserts everything into a fresh palace at `--palace`. `--source PATH` extracts from a corrupt palace already moved aside; `--archive-existing` handles the in-place case by renaming the existing palace to `<palace>.pre-rebuild-<timestamp>` before reading from it. Documents are re-embedded under the user's configured embedding function (the original HNSW vectors live in the corrupt `data_level0.bin` and cannot be recovered, but the embedding model is deterministic so search results remain semantically equivalent). Verified end-to-end on a 52,300-row real-world corrupt palace. (#1308)
 
 ---
 

mempalace/cli.py

@@ -673,6 +673,48 @@ def cmd_repair(args):
         )
         return
 
+    if getattr(args, "mode", "legacy") == "from-sqlite":
+        from .migrate import confirm_destructive_action
+        from .repair import RebuildPartialError, rebuild_from_sqlite
+
+        source_path = getattr(args, "source", None)
+        source_path = (
+            os.path.abspath(os.path.expanduser(source_path)) if source_path else palace_path
+        )
+        archive_existing = getattr(args, "archive_existing", False)
+
+        # Gate any path that touches the user's existing palace dir
+        # behind confirm_destructive_action. The legacy mode already
+        # gates; from-sqlite needs the same protection because:
+        # (a) --archive-existing renames the existing palace,
+        # (b) --source PATH writes into --palace dir which the user
+        #     may not realize is also a palace.
+        # No prompt when source != dest AND dest does not exist (pure
+        # extract-into-fresh-dir case is non-destructive to existing
+        # palaces).
+        is_destructive_to_dest = source_path == palace_path or os.path.exists(palace_path)
+        if is_destructive_to_dest and not confirm_destructive_action(
+            "Rebuild from SQLite", palace_path, assume_yes=getattr(args, "yes", False)
+        ):
+            return
+
+        try:
+            rebuild_from_sqlite(
+                source_palace=source_path,
+                dest_palace=palace_path,
+                archive_existing_dest=archive_existing,
+            )
+        except RebuildPartialError as exc:
+            # The error itself was already printed by rebuild_from_sqlite
+            # with recovery instructions; surface a non-zero exit so
+            # scripts and CI gates see the failure.
+            print(
+                "\n  Rebuild partial — see message above. "
+                f"Failed in collection: {exc.failed_collection}"
+            )
+            sys.exit(1)
+        return
+
     db_path = os.path.join(palace_path, "chroma.sqlite3")
 
     if not os.path.isdir(palace_path):
@@ -1213,11 +1255,31 @@ def main():
     )
     p_repair.add_argument(
         "--mode",
-        choices=["legacy", "max-seq-id"],
+        choices=["legacy", "max-seq-id", "from-sqlite"],
         default="legacy",
         help=(
-            "legacy: full-palace rebuild (default). "
+            "legacy: full-palace rebuild via the chromadb client (default). "
             "max-seq-id: un-poison max_seq_id rows corrupted by the legacy 0.6.x shim. "
+            "from-sqlite: rebuild by reading rows directly from chroma.sqlite3, "
+            "bypassing the chromadb client. Use when legacy mode bails because the "
+            "chromadb client cannot open the collection."
+        ),
+    )
+    p_repair.add_argument(
+        "--source",
+        default=None,
+        help=(
+            "Source palace path for --mode from-sqlite (defaults to --palace). "
+            "Use when extracting from an archived corrupt palace into a new location."
+        ),
+    )
+    p_repair.add_argument(
+        "--archive-existing",
+        action="store_true",
+        help=(
+            "For --mode from-sqlite when --source equals --palace: rename the "
+            "existing palace to <palace>.pre-rebuild-<timestamp> before "
+            "rebuilding so the corrupt copy is preserved."
         ),
     )
     p_repair.add_argument(

mempalace/repair.py

@@ -34,14 +34,21 @@ import os
 import shutil
 import sqlite3
 import time
+from collections import defaultdict
 from datetime import datetime
-from typing import Optional
+from typing import Iterator, Optional
 
 from .backends.chroma import ChromaBackend, hnsw_capacity_status
 
 
 COLLECTION_NAME = "mempalace_drawers"
 
+# Collections rebuilt by ``rebuild_from_sqlite``. Order matters for the
+# upsert pass — drawers carry the bulk of the data, closets are the AAAK
+# index layer and reference drawer IDs by string in their documents (no
+# foreign-key validation, so ordering is informational, not load-bearing).
+RECOVERABLE_COLLECTIONS = ("mempalace_drawers", "mempalace_closets")
+
 
 def _get_palace_path():
     """Resolve palace path from config."""
@@ -436,6 +443,355 @@ def rebuild_index(palace_path=None, confirm_truncation_ok: bool = False):
     print(f"\n{'=' * 55}\n")
 
 
+class RebuildPartialError(Exception):
+    """Raised when ``rebuild_from_sqlite`` fails partway through upserts.
+
+    Carries enough state for the user (or CLI) to recover: the
+    per-collection counts that succeeded, the collection that failed,
+    the dest path holding the partial palace, and the archive path
+    (when an in-place rebuild had moved the original aside). Re-raises
+    the underlying chromadb error as ``__cause__``.
+    """
+
+    def __init__(
+        self,
+        message: str,
+        *,
+        partial_counts: dict[str, int],
+        failed_collection: str,
+        dest_palace: str,
+        archive_path: Optional[str],
+    ):
+        super().__init__(message)
+        self.message = message
+        self.partial_counts = partial_counts
+        self.failed_collection = failed_collection
+        self.dest_palace = dest_palace
+        self.archive_path = archive_path
+
+
+def _rebuild_one_collection(
+    *,
+    backend: ChromaBackend,
+    source_palace: str,
+    dest_palace: str,
+    collection_name: str,
+    batch_size: int,
+    archive_path: Optional[str],
+    counts_so_far: dict[str, int],
+) -> int:
+    """Stream rows for one collection from SQLite and upsert into a
+    freshly-created collection at ``dest_palace``. Returns rows
+    upserted. Raises :class:`RebuildPartialError` (with the underlying
+    chromadb exception as ``__cause__``) on any upsert failure so the
+    caller can stop the loop and print recovery instructions instead of
+    silently shipping a partial palace.
+    """
+    col = backend.create_collection(dest_palace, collection_name)
+
+    ids: list[str] = []
+    docs: list[str] = []
+    metas: list[dict] = []
+    upserted = 0
+
+    def _flush() -> int:
+        nonlocal upserted
+        if not ids:
+            return upserted
+        col.upsert(ids=list(ids), documents=list(docs), metadatas=list(metas))
+        upserted += len(ids)
+        print(f"    upserted {upserted}")
+        ids.clear()
+        docs.clear()
+        metas.clear()
+        return upserted
+
+    try:
+        for emb_id, doc, meta in extract_via_sqlite(source_palace, collection_name):
+            ids.append(emb_id)
+            docs.append(doc or "")
+            # chromadb 1.5.x rejects None entries in the metadatas list
+            # but accepts empty dicts. Mempalace drawers always carry at
+            # least wing/room, so this branch is defensive — corruption
+            # in embedding_metadata could yield an emb_id with no rows.
+            metas.append(meta if meta else {})
+            if len(ids) >= batch_size:
+                _flush()
+        _flush()
+    except Exception as exc:  # noqa: BLE001 — chromadb raises many shapes
+        partial = dict(counts_so_far)
+        partial[collection_name] = upserted
+        msg_parts = [
+            f"Upsert failed in collection {collection_name!r} after {upserted} rows: {exc!r}",
+            f"Partial palace left at: {dest_palace}",
+        ]
+        if archive_path is not None:
+            msg_parts.append(f"Original palace archived at: {archive_path}")
+            msg_parts.append(
+                "  Recover by removing the partial dest and re-running with "
+                f"--source {archive_path}"
+            )
+        else:
+            msg_parts.append("  Source palace is unchanged. Remove the partial dest and re-run.")
+        message = "\n  ".join(msg_parts)
+        print(f"\n  ERROR: {message}")
+        raise RebuildPartialError(
+            message,
+            partial_counts=partial,
+            failed_collection=collection_name,
+            dest_palace=dest_palace,
+            archive_path=archive_path,
+        ) from exc
+
+    return upserted
+
+
+def extract_via_sqlite(palace_path: str, collection_name: str) -> Iterator[tuple[str, str, dict]]:
+    """Yield ``(embedding_id, document, metadata)`` for every row in
+    ``collection_name``'s metadata segment by reading ``chroma.sqlite3``
+    directly.
+
+    Bypasses the chromadb client entirely — never opens a
+    ``PersistentClient``, never imports hnswlib, never invokes the
+    HNSW segment writer. This is the recovery path for palaces where
+    ``Collection.count()`` / ``Collection.get()`` raise ``InternalError``
+    because the compactor cannot apply WAL logs to the HNSW segment
+    (#1308). The drawer rows are still on disk in
+    ``embeddings`` + ``embedding_metadata``; the corruption lives in the
+    on-disk index files, not the SQLite tables.
+
+    Resolution rule for chromadb's typed metadata columns: each
+    ``embedding_metadata`` row stores its value in exactly one of
+    ``string_value`` / ``int_value`` / ``float_value`` / ``bool_value``;
+    we pick the first non-NULL column in that order. Rows where every
+    typed column is NULL are dropped (chromadb never writes that shape).
+    The ``chroma:document`` key is removed from the metadata dict and
+    returned as the document; this matches how chromadb itself stores
+    ``add(documents=...)``.
+
+    Silent on missing palace, missing ``chroma.sqlite3``, or unknown
+    collection name — yields nothing. Callers that need to distinguish
+    "empty collection" from "collection not present" should query
+    :func:`sqlite_drawer_count` first.
+    """
+    sqlite_path = os.path.join(palace_path, "chroma.sqlite3")
+    if not os.path.isfile(sqlite_path):
+        return
+
+    conn = sqlite3.connect(f"file:{sqlite_path}?mode=ro", uri=True)
+    try:
+        seg_row = conn.execute(
+            """
+            SELECT s.id FROM segments s
+            JOIN collections c ON s.collection = c.id
+            WHERE c.name = ? AND s.scope = 'METADATA'
+            """,
+            (collection_name,),
+        ).fetchone()
+        if not seg_row:
+            return
+        segment_id = seg_row[0]
+
+        per_id: dict[str, dict] = defaultdict(dict)
+        order: list[str] = []
+        for emb_id, key, sv, iv, fv, bv in conn.execute(
+            """
+            SELECT e.embedding_id, em.key, em.string_value, em.int_value,
+                   em.float_value, em.bool_value
+            FROM embedding_metadata em
+            JOIN embeddings e ON em.id = e.id
+            WHERE e.segment_id = ?
+            ORDER BY em.id
+            """,
+            (segment_id,),
+        ):
+            if emb_id not in per_id:
+                order.append(emb_id)
+            if sv is not None:
+                per_id[emb_id][key] = sv
+            elif iv is not None:
+                per_id[emb_id][key] = iv
+            elif fv is not None:
+                per_id[emb_id][key] = fv
+            elif bv is not None:
+                per_id[emb_id][key] = bool(bv)
+
+        for emb_id in order:
+            kv = per_id[emb_id]
+            doc = kv.pop("chroma:document", "")
+            yield emb_id, doc, kv
+    finally:
+        conn.close()
+
+
+def rebuild_from_sqlite(
+    source_palace: str,
+    dest_palace: str,
+    *,
+    archive_existing_dest: bool = False,
+    batch_size: int = 1000,
+) -> dict[str, int]:
+    """Rebuild a palace by reading drawers from ``source_palace``'s
+    ``chroma.sqlite3`` and upserting them into a fresh palace at
+    ``dest_palace``.
+
+    Recovery path for the #1308 failure mode: the chromadb client raises
+    ``InternalError: Failed to apply logs to the hnsw segment writer``
+    on every operation that touches the index (``count``, ``get``,
+    ``query``), but the underlying SQLite tables are intact. Both the
+    legacy ``rebuild_index`` and the inline ``cli.cmd_repair`` path call
+    ``Collection.count()`` as their first read — exactly the call that
+    fails — so neither can recover this class of corruption. This
+    function bypasses the chromadb read path entirely via
+    :func:`extract_via_sqlite`.
+
+    Re-embeds documents at upsert time using the configured embedding
+    function; the original HNSW vectors are not preserved (they live in
+    the corrupt ``data_level0.bin`` / ``link_lists.bin``, not in
+    SQLite). Acceptable for a corruption-recovery flow because the
+    embedding model is deterministic — same model + same document text
+    yields semantically equivalent search results.
+
+    ``archive_existing_dest`` controls behavior when ``dest_palace``
+    already exists:
+
+    * ``False`` (default) — refuse with a clear message. Callers must
+      manually move the existing palace aside first.
+    * ``True`` — rename ``dest_palace`` to
+      ``<dest_palace>.pre-rebuild-<timestamp>`` and read from there
+      instead. Used by the in-place CLI flow where ``--source`` defaults
+      to the same path as ``--palace``.
+
+    Returns a ``{collection_name: row_count}`` dict so callers (CLI,
+    tests) can verify the per-collection rebuild count without parsing
+    stdout. Returns ``{}`` on validation failures (missing source,
+    refusing to overwrite). Raises :class:`RebuildPartialError` if a
+    chromadb upsert fails partway through; the dest palace is left in
+    place so the user can inspect what landed, and the in-place archive
+    (when applicable) is reported in the error so the user can re-run
+    against it.
+
+    .. warning::
+
+       In-place mode (``source_palace == dest_palace`` with
+       ``archive_existing_dest=True``) calls
+       ``chromadb.api.client.SharedSystemClient.clear_system_cache()`` to
+       drop chromadb's process-wide System registry — required because
+       an existing cached System built against the original palace will
+       refuse ``create_collection`` after the dir is renamed (chromadb
+       still thinks the collections exist). This invalidates any
+       PersistentClient instances held elsewhere in the same process for
+       *any* palace, not just this one. Do not call this function from
+       inside a long-running mempalace process (MCP server, daemon)
+       while other callers hold live ``PersistentClient`` references —
+       use the CLI in a separate process instead. Cross-palace use
+       (``source != dest``) does not touch the cache.
+
+    Note on metadata fidelity: the resolution rule
+    (``string_value`` → ``int_value`` → ``float_value`` → ``bool_value``)
+    matches the precedent in :mod:`mempalace.migrate`. ChromaDB 0.4.x
+    occasionally wrote booleans as ``int_value=0/1``; those will
+    round-trip as ``int`` rather than ``bool`` after this rebuild. This
+    is a known divergence and matches the existing migrate-path
+    behavior.
+    """
+    source_palace = os.path.abspath(os.path.expanduser(source_palace))
+    dest_palace = os.path.abspath(os.path.expanduser(dest_palace))
+
+    src_db = os.path.join(source_palace, "chroma.sqlite3")
+
+    in_place = source_palace == dest_palace
+
+    print(f"\n{'=' * 55}")
+    print("  MemPalace Repair — Rebuild from SQLite")
+    print(f"{'=' * 55}\n")
+    print(f"  Source: {source_palace}")
+    print(f"  Dest:   {dest_palace}")
+
+    # Validate source BEFORE any destructive moves. An earlier draft
+    # archived the dest first and surfaced the missing-chroma.sqlite3
+    # error after — leaving the user with a renamed dir to manually undo
+    # when the archive itself was empty. Validate first so a user error
+    # (--source pointing at a non-palace dir) bails cleanly.
+    if in_place:
+        if not archive_existing_dest:
+            print(
+                "\n  Source and dest are the same path. Pass "
+                "archive_existing_dest=True (CLI: --archive-existing) to move "
+                "the existing palace aside, or pass a different source_palace= "
+                "(CLI: --source)."
+            )
+            return {}
+        if not os.path.isfile(src_db):
+            print(f"\n  Source palace has no chroma.sqlite3 at {src_db}")
+            return {}
+    else:
+        if not os.path.isfile(src_db):
+            print(f"\n  Source palace has no chroma.sqlite3 at {src_db}")
+            return {}
+        if os.path.exists(dest_palace):
+            print(
+                f"\n  Refusing to rebuild into existing path: {dest_palace}\n"
+                "  Move it aside, pass a different dest, or set "
+                "archive_existing_dest=True if rebuilding in place "
+                "(source_palace == dest_palace)."
+            )
+            return {}
+
+    archive_path: Optional[str] = None
+    if in_place:
+        ts = datetime.now().strftime("%Y%m%d-%H%M%S")
+        archive_path = f"{dest_palace}.pre-rebuild-{ts}"
+        print(f"  Archiving {dest_palace} → {archive_path}")
+        shutil.move(dest_palace, archive_path)
+        source_palace = archive_path
+        src_db = os.path.join(source_palace, "chroma.sqlite3")
+
+        # In-place only: drop chromadb's process-wide System registry so
+        # the new client at dest_palace builds a fresh System. Without
+        # this, ``create_collection`` raises "Collection already exists"
+        # because the cached System still holds the pre-rename schema.
+        # Cross-palace mode does not need this and would needlessly
+        # invalidate other callers' clients (see docstring warning).
+        try:
+            from chromadb.api.client import SharedSystemClient
+
+            SharedSystemClient.clear_system_cache()
+        except Exception as exc:  # noqa: BLE001
+            print(
+                f"  Warning: could not clear chromadb system cache ({exc!r}); "
+                "in-place rebuild may fail with 'Collection already exists'."
+            )
+
+    os.makedirs(dest_palace, exist_ok=True)
+
+    backend = ChromaBackend()
+    counts: dict[str, int] = {}
+
+    for cname in RECOVERABLE_COLLECTIONS:
+        print(f"\n  [{cname}]")
+        upserted = _rebuild_one_collection(
+            backend=backend,
+            source_palace=source_palace,
+            dest_palace=dest_palace,
+            collection_name=cname,
+            batch_size=batch_size,
+            archive_path=archive_path,
+            counts_so_far=counts,
+        )
+        counts[cname] = upserted
+        if upserted == 0:
+            print(f"    no rows found for {cname} in source palace")
+        else:
+            print(f"    done: {upserted} rows in {cname}")
+
+    print(f"\n  Rebuild complete. {sum(counts.values())} total rows.")
+    if archive_path is not None:
+        print(f"  Original palace archived at: {archive_path}")
+    print(f"{'=' * 55}\n")
+    return counts
+
+
 def status(palace_path=None) -> dict:
     """Read-only health check: compare sqlite vs HNSW element counts.
 

tests/test_repair.py

@@ -682,3 +682,294 @@ def test_max_seq_id_rollback_on_verification_failure(tmp_path, monkeypatch):
     # A backup file is still present — caller can roll back from it.
     leftover = [fn for fn in os.listdir(palace) if "max-seq-id-backup-" in fn]
     assert leftover
+
+
+# ── extract_via_sqlite + rebuild_from_sqlite (#1308) ──────────────────
+#
+# These tests build real chromadb palaces in tmp_path rather than mocking
+# the SQLite layer. The bug class they guard against is "extraction sees
+# different rows than chromadb stored" — the only honest check is to let
+# chromadb actually write rows and then read them back via the SQLite
+# bypass. Mocking the SQLite cursor would defeat the test.
+
+
+def _seed_palace(palace_path, collection_name, rows):
+    """Build a real chromadb palace at ``palace_path`` and add ``rows``.
+
+    ``rows`` is a list of ``(id, document, metadata)`` tuples. Returns
+    the populated collection so callers can assert on the writer's view
+    of state before the SQLite read.
+    """
+    from mempalace.backends.chroma import ChromaBackend
+
+    backend = ChromaBackend()
+    col = backend.create_collection(str(palace_path), collection_name)
+    col.upsert(
+        ids=[r[0] for r in rows],
+        documents=[r[1] for r in rows],
+        metadatas=[r[2] for r in rows],
+    )
+    return col
+
+
+def test_extract_via_sqlite_returns_all_rows_with_metadata(tmp_path):
+    """Round-trip: a chromadb palace with N upserted rows returns those
+    same N rows when read via the SQLite bypass.
+
+    Catches: anyone who breaks the segments/embeddings/embedding_metadata
+    JOIN, swaps the metadata vs vector segment, or changes how the
+    document is stored under the ``chroma:document`` key.
+    """
+    rows = [
+        (f"drawer_{i:03d}", f"document body {i}", {"wing": "test_wing", "room": f"r{i % 3}"})
+        for i in range(25)
+    ]
+    _seed_palace(tmp_path, "mempalace_drawers", rows)
+
+    extracted = list(repair.extract_via_sqlite(str(tmp_path), "mempalace_drawers"))
+
+    assert len(extracted) == 25
+    by_id = {emb_id: (doc, meta) for emb_id, doc, meta in extracted}
+    assert set(by_id) == {r[0] for r in rows}
+    for emb_id, doc, meta in rows:
+        got_doc, got_meta = by_id[emb_id]
+        assert got_doc == doc, f"document mangled for {emb_id}"
+        assert got_meta == meta, f"metadata mangled for {emb_id}: {got_meta!r}"
+
+
+def test_extract_via_sqlite_preserves_typed_metadata(tmp_path):
+    """Chromadb stores int / float / bool / string in distinct typed
+    columns. Extraction must round-trip the original type, not coerce
+    everything to string.
+
+    Catches: a regression where the SELECT order changes and ints come
+    back as None, or where the column-resolution rule prefers the wrong
+    column.
+    """
+    rows = [
+        (
+            "drawer_typed",
+            "doc",
+            {
+                "wing": "w",
+                "chunk_index": 7,  # int
+                "score": 0.42,  # float
+                "is_active": True,  # bool
+            },
+        ),
+    ]
+    _seed_palace(tmp_path, "mempalace_drawers", rows)
+
+    extracted = list(repair.extract_via_sqlite(str(tmp_path), "mempalace_drawers"))
+    assert len(extracted) == 1
+    _, _, meta = extracted[0]
+
+    assert meta["chunk_index"] == 7 and isinstance(meta["chunk_index"], int)
+    assert meta["score"] == 0.42 and isinstance(meta["score"], float)
+    assert meta["is_active"] is True
+    assert meta["wing"] == "w"
+
+
+def test_extract_via_sqlite_unknown_collection_yields_nothing(tmp_path):
+    """Asking for a collection that isn't in the palace must return an
+    empty iterator, not silently fall back to another collection's
+    metadata segment. Seeds two real collections and queries for a third
+    name so a regression that drops the WHERE c.name=? filter would leak
+    rows from the seeded collections rather than passing.
+    """
+    _seed_palace(tmp_path, "mempalace_drawers", [("d1", "doc", {"wing": "w"})])
+    _seed_palace(tmp_path, "mempalace_closets", [("c1", "abbrev", {"wing": "w"})])
+    assert list(repair.extract_via_sqlite(str(tmp_path), "not_a_real_collection")) == []
+
+
+def test_extract_via_sqlite_missing_palace_yields_nothing(tmp_path):
+    """No chroma.sqlite3 → empty iterator, no exception. Callers depend
+    on this when probing speculatively."""
+    empty = tmp_path / "no_palace_here"
+    empty.mkdir()
+    assert list(repair.extract_via_sqlite(str(empty), "mempalace_drawers")) == []
+
+
+def test_rebuild_from_sqlite_roundtrips_via_real_chromadb(tmp_path):
+    """End-to-end: seed source palace, rebuild into a fresh dest, then
+    open dest with a fresh ChromaBackend and verify ``count()`` and
+    metadata filters return the original rows. Also asserts a closet
+    document round-trips so a future regression that re-embeds with the
+    wrong EF or swaps drawer/closet content would fail here.
+
+    This is the single most important regression guard. If
+    ``rebuild_from_sqlite`` silently drops rows or mangles metadata, no
+    other test in this file would catch it because they all stop at the
+    extraction layer.
+    """
+    from mempalace.backends.chroma import ChromaBackend
+
+    source = tmp_path / "source"
+    dest = tmp_path / "dest"
+
+    rows = [
+        (f"drawer_{i:03d}", f"body {i}", {"wing": "alpha" if i % 2 else "beta", "room": "r0"})
+        for i in range(40)
+    ]
+    _seed_palace(source, "mempalace_drawers", rows)
+    _seed_palace(
+        source,
+        "mempalace_closets",
+        [("closet_x", "abbrev pointer →drawer_001", {"wing": "alpha"})],
+    )
+
+    counts = repair.rebuild_from_sqlite(str(source), str(dest))
+    assert counts == {"mempalace_drawers": 40, "mempalace_closets": 1}
+
+    backend = ChromaBackend()
+    drawers = backend.get_collection(str(dest), "mempalace_drawers")
+    assert drawers.count() == 40
+    alpha = drawers.get(where={"wing": "alpha"})
+    assert len(alpha["ids"]) == 20
+
+    # Spot-check that document text round-trips for one specific drawer
+    # — protects against a regression where extraction or upsert order
+    # silently swaps document bodies between IDs.
+    one = drawers.get(ids=["drawer_007"], include=["documents", "metadatas"])
+    assert one["documents"] == ["body 7"]
+    assert one["metadatas"][0]["wing"] == "alpha"
+
+    # Closets: the AAAK index layer. Re-embedded with the same EF so a
+    # known closet ID and its document body must come back intact.
+    closets = backend.get_collection(str(dest), "mempalace_closets")
+    assert closets.count() == 1
+    closet_row = closets.get(ids=["closet_x"], include=["documents", "metadatas"])
+    assert closet_row["documents"] == ["abbrev pointer →drawer_001"]
+    assert closet_row["metadatas"][0] == {"wing": "alpha"}
+
+
+def test_rebuild_from_sqlite_refuses_existing_dest(tmp_path):
+    """Refuse to write into a directory that already exists when source
+    and dest differ. Without this, an unattended re-run would silently
+    interleave a partial rebuild with whatever's already at dest.
+    """
+    source = tmp_path / "source"
+    dest = tmp_path / "dest"
+    _seed_palace(source, "mempalace_drawers", [("d1", "doc", {"wing": "w"})])
+    dest.mkdir()
+    # Drop a marker file so we can prove the dir wasn't touched.
+    (dest / "marker.txt").write_text("preexisting")
+
+    counts = repair.rebuild_from_sqlite(str(source), str(dest))
+    assert counts == {}
+    assert (dest / "marker.txt").read_text() == "preexisting"
+    assert not (dest / "chroma.sqlite3").exists()
+
+
+def test_rebuild_from_sqlite_in_place_archives_when_opted_in(tmp_path):
+    """In-place rebuild (source == dest) with ``archive_existing_dest=True``
+    must move the original aside to ``<dest>.pre-rebuild-<ts>`` and read
+    from the archive — the original drawer rows must survive in the new
+    palace, AND the archive itself must still contain the original rows.
+
+    Catches: a refactor that moves the original out but then reads from
+    the now-empty original location, producing an empty rebuild; also
+    catches a swap that empties the archive after reading.
+    """
+    palace = tmp_path / "palace"
+    rows = [(f"d{i}", f"body {i}", {"wing": "w", "room": "r"}) for i in range(15)]
+    _seed_palace(palace, "mempalace_drawers", rows)
+
+    counts = repair.rebuild_from_sqlite(str(palace), str(palace), archive_existing_dest=True)
+    assert counts["mempalace_drawers"] == 15
+
+    archives = [p for p in tmp_path.iterdir() if p.name.startswith("palace.pre-rebuild-")]
+    assert len(archives) == 1
+    assert (archives[0] / "chroma.sqlite3").exists()
+    # Archive must still hold the same row count via the SQLite bypass —
+    # proves the archive wasn't silently truncated as a side effect.
+    archived_rows = list(repair.extract_via_sqlite(str(archives[0]), "mempalace_drawers"))
+    assert len(archived_rows) == 15
+
+    from mempalace.backends.chroma import ChromaBackend
+
+    rebuilt = ChromaBackend().get_collection(str(palace), "mempalace_drawers")
+    assert rebuilt.count() == 15
+
+
+def test_rebuild_from_sqlite_in_place_refuses_without_archive_flag(tmp_path):
+    """Source == dest without archive flag must abort untouched. The
+    most catastrophic possible regression of this code path is silently
+    deleting the only copy of the user's data."""
+    palace = tmp_path / "palace"
+    _seed_palace(palace, "mempalace_drawers", [("d1", "doc", {"wing": "w"})])
+    sqlite_before = (palace / "chroma.sqlite3").stat().st_size
+
+    counts = repair.rebuild_from_sqlite(str(palace), str(palace))
+    assert counts == {}
+    # Same file, untouched.
+    assert (palace / "chroma.sqlite3").stat().st_size == sqlite_before
+    archives = [p for p in tmp_path.iterdir() if "pre-rebuild" in p.name]
+    assert archives == []
+
+
+def test_rebuild_from_sqlite_source_missing_chroma_db(tmp_path):
+    """Source dir exists but has no chroma.sqlite3 → returns empty,
+    leaves dest untouched."""
+    source = tmp_path / "source"
+    source.mkdir()
+    (source / "stray_file").write_text("not a palace")
+    dest = tmp_path / "dest"
+
+    counts = repair.rebuild_from_sqlite(str(source), str(dest))
+    assert counts == {}
+    assert not dest.exists()
+
+
+def test_rebuild_from_sqlite_in_place_validates_source_before_archiving(tmp_path):
+    """In-place + archive_existing_dest=True with a dir that lacks
+    chroma.sqlite3 must NOT rename the dir before bailing. An earlier
+    revision archived first and validated second, leaving the user with
+    a renamed empty dir to manually undo. Catches that ordering bug.
+    """
+    palace = tmp_path / "palace"
+    palace.mkdir()
+    (palace / "marker.txt").write_text("not a real palace")
+
+    counts = repair.rebuild_from_sqlite(str(palace), str(palace), archive_existing_dest=True)
+    assert counts == {}
+    # No archive created — original dir still in place with its marker.
+    assert palace.exists()
+    assert (palace / "marker.txt").read_text() == "not a real palace"
+    archives = [p for p in tmp_path.iterdir() if "pre-rebuild" in p.name]
+    assert archives == []
+
+
+def test_rebuild_from_sqlite_raises_on_upsert_failure(tmp_path, monkeypatch):
+    """Mid-batch upsert failure must raise ``RebuildPartialError`` and
+    surface the failed collection + archive path so the user can recover.
+    Without this, an unattended script gets exit-code-zero on a partial
+    rebuild and the user discovers the data loss only when search starts
+    returning fewer hits.
+    """
+    palace = tmp_path / "palace"
+    rows = [(f"d{i}", f"body {i}", {"wing": "w", "room": "r"}) for i in range(5)]
+    _seed_palace(palace, "mempalace_drawers", rows)
+
+    # Make the very first upsert raise so we don't depend on batch
+    # boundary behavior. Patching ChromaCollection.upsert (the wrapper
+    # mempalace's backend returns) keeps the failure path realistic.
+    # ``monkeypatch`` is pytest's built-in fixture that auto-restores
+    # the original attribute when the test exits, so we don't need to
+    # undo this manually.
+    from mempalace.backends.chroma import ChromaCollection
+
+    def boom(self, **kwargs):
+        raise RuntimeError("simulated chromadb upsert failure")
+
+    monkeypatch.setattr(ChromaCollection, "upsert", boom)
+
+    with pytest.raises(repair.RebuildPartialError) as excinfo:
+        repair.rebuild_from_sqlite(str(palace), str(palace), archive_existing_dest=True)
+
+    err = excinfo.value
+    assert err.failed_collection == "mempalace_drawers"
+    assert err.partial_counts.get("mempalace_drawers") == 0
+    assert err.archive_path is not None
+    assert os.path.isfile(os.path.join(err.archive_path, "chroma.sqlite3"))
+    assert err.dest_palace == os.path.abspath(str(palace))