feat(node): persistent index cache, visible scan progress, adaptive reconcile, and delta sync

Indexer performance work, in four parts:

- Persistent (path, size, mtime) -> hash cache (indexer/cache.py) so a node
  restart no longer re-hashes every file — measured at 23 minutes for a
  114 GB library on a slow disk before this, near-instant after. Hashing
  is deliberately kept sequential (max_workers=1): it was never actually
  concurrent despite the pool size, and two interleaved reads seek-thrash
  a spinning disk instead of going faster.

- Byte-based scan progress (IndexProgress), surfaced via the loopback
  index-status route, the handshake ack, and a periodic INDEX_PROGRESS
  push to connected peers — drives a progress bar in the Create Group
  wizard and "add a directory" in Settings, and an animated presence dot.
  Guaranteed to settle back to idle via try/finally and a final push on
  the scanning->false transition.

- The reconcile backstop's directory walks now run in the executor
  instead of blocking the daemon's event loop; its interval defaults to
  10 min (was 60s) with adaptive backoff to 2h when nothing changes,
  reset on a real change or a peer connecting, and is now a per-group
  operator setting (signed op + group Settings UI).

- INDEX_DELTA wired up (protocol support existed, nothing called it):
  _on_index_change now sends additions/deletions instead of rebuilding
  the full entries list, coalesced over a short window so a burst of
  file events produces one push, and the hub swarm registration for
  public groups only (re-)registers newly added hashes.

Also fixes several bugs found while testing the above against real
libraries (a 114 GB and a 100+ GB group on a USB HDD):

- /api/reload blocked until the reload — including a brand-new group's
  full initial scan — finished, which the Electron bridge's fixed 30s
  call timeout turned into a hard failure on any real library. The route
  now fires the reload without waiting (ops.start_reload), matching
  add_root/remove_root's existing pattern; the wizard's own step order
  was fixed to wait for the group to actually appear hosted before the
  steps that need it (extra roots, GEK), with retries for the residual
  race between that and the daemon's own bookkeeping.
- transport.js's hand-rolled msgpack codec had no case for uint64/int64
  (0xcf/0xd3) and crashed decoding any message containing one — hit by
  IndexProgress.scanned_bytes/total_bytes for any group over ~4.3 GB.
  Verified against real msgpack-encoded bytes from the Python side.
- chat_hist_resp, and this change's own index_progress and
  set_scan_settings_ack pushes, were not routed by message type and
  could be handed to an unrelated pending request by the transport's
  "oldest pending" fallback, stalling it until its own 30s timeout and
  corrupting whatever received the wrong reply in its place.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016SF6RKNBKg9qejmoMJ9ybA

1 files changed, 95 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/indexer/cache.py b/packages/meshbay-node/src/meshbay_node/indexer/cache.py
new file mode 100644
index 0000000..c26ddf1
--- /dev/null
+++ b/packages/meshbay-node/src/meshbay_node/indexer/cache.py
@@ -0,0 +1,95 @@
+"""
+MeshBay Node — persistent (path, size, mtime) -> hash cache, one per group.
+
+Without this, every node restart re-reads and re-hashes every file in every
+root, even when nothing changed — measured at 23 minutes for a 114 GB library
+on a USB hard drive. This cache lets a scan skip the read entirely for a file
+whose size and mtime still match what was hashed last time.
+
+It is a path-keyed accelerator only. The GroupIndex itself stays keyed by
+content hash (see indexer.py's note on why two identical files are one
+entry) — this cache never changes that, it only avoids recomputing a hash
+that has not changed.
+"""
+
+import logging
+from dataclasses import dataclass
+from pathlib import Path
+
+import aiosqlite
+
+log = logging.getLogger(__name__)
+
+_SCHEMA = """
+CREATE TABLE IF NOT EXISTS files (
+    path      TEXT PRIMARY KEY,
+    mtime     REAL NOT NULL,
+    size      INTEGER NOT NULL,
+    hash      TEXT NOT NULL,
+    type      TEXT NOT NULL,
+    added_at  INTEGER NOT NULL
+);
+"""
+
+
+@dataclass
+class CachedEntry:
+    hash: str
+    type: str
+    added_at: int
+
+
+class IndexCache:
+    """Async SQLite (path, size, mtime) -> hash cache for one group."""
+
+    def __init__(self, db_path: Path):
+        self._db_path = db_path
+        self._db: aiosqlite.Connection | None = None
+
+    async def open(self) -> None:
+        self._db_path.parent.mkdir(parents=True, exist_ok=True)
+        self._db = await aiosqlite.connect(str(self._db_path))
+        await self._db.executescript(_SCHEMA)
+        await self._db.commit()
+
+    async def close(self) -> None:
+        if self._db:
+            await self._db.close()
+            self._db = None
+
+    async def __aenter__(self):
+        await self.open()
+        return self
+
+    async def __aexit__(self, *_):
+        await self.close()
+
+    async def lookup(self, path: str, size: int, mtime: float) -> CachedEntry | None:
+        """
+        A cache hit requires an EXACT match on both size and mtime. A mtime
+        touched without a content change is a false negative (an unnecessary
+        rehash) — accepted, since the alternative (trusting a stale hash) is
+        a silent wrong answer instead of an occasional wasted read.
+        """
+        async with self._db.execute(
+                "SELECT hash, type, added_at FROM files "
+                "WHERE path = ? AND size = ? AND mtime = ?",
+                (path, size, mtime)) as cur:
+            row = await cur.fetchone()
+        return CachedEntry(hash=row[0], type=row[1], added_at=row[2]) if row else None
+
+    async def put(self, path: str, size: int, mtime: float, hash: str,
+                  type: str, added_at: int) -> None:
+        """
+        Written only once a file has been hashed in full — never partway
+        through — so a crash mid-hash leaves no stale/partial row behind: the
+        next scan simply finds no cache entry and hashes the file again.
+        """
+        await self._db.execute(
+            "INSERT INTO files (path, mtime, size, hash, type, added_at) "
+            "VALUES (?, ?, ?, ?, ?, ?) "
+            "ON CONFLICT(path) DO UPDATE SET "
+            "mtime = excluded.mtime, size = excluded.size, hash = excluded.hash, "
+            "type = excluded.type, added_at = excluded.added_at",
+            (path, mtime, size, hash, type, added_at))
+        await self._db.commit()