brainy/RELEASES.md

# @soulcraft/brainy — Release Notes for Consumers

This file is the **quick reference for downstream sessions** tracking Brainy changes.
Full auto-generated changelog: `CHANGELOG.md` · Releases: https://github.com/soulcraftlabs/brainy/releases

**How to use:** Brainy is the underlying data engine for downstream applications. Read this when:
- Upgrading `@soulcraft/brainy` in your application
- Debugging data, query, or storage behaviour
- A new Brainy feature is available that you want to adopt

---

## v8.3.2 — 2026-07-14 (honest counters — the recount + removal-without-re-reading)

Completes 8.3.1's delete-hygiene story at the counter layer, from a production proof chain reported
by a downstream deployment: persisted entity totals were permanently **inflated** — deletes whose
count decrement was silently skipped — and because paginated `totalCount` serves
`Math.max(persistedTotal, scanned)`, the inflated number always won and **no disk cleanup could ever
lower it**.

- **A removal's count decrement no longer requires re-reading the record being removed.** The
  decrement was sourced from re-reading the entity's metadata inside the delete; if that read
  returned `null` (a replace race, or a ghost left by a pre-8.3.1 partial delete) the decrement was
  silently skipped while the paired add had counted — minting drift on every write→delete→re-create
  cycle. The caller's pre-delete read now rides through the whole delete path
  (`remove()`/`removeMany()` → the delete operation → `deleteNoun`/`deleteVerb` →
  `deleteNounMetadata`/`deleteVerbMetadata`, both sides symmetric): a null internal read falls back
  to the known prior record instead of skipping. The `StorageAdapter` signatures gain an optional
  `priorMetadata` parameter (additive; existing adapters unaffected).

- **`repairIndex()` is the sanctioned counter recount — unconditional, and it actually persists.**
  `rebuildTypeCounts()` previously rebuilt only the type-statistics arrays and computed the total
  *just to log it* — the persisted scalar (`counts.json`) survived every "rebuild" untouched, so an
  already-inflated brain could never be corrected. One canonical walk now rebuilds **every** counter
  rollup — scalar totals, per-type maps, and type statistics — and persists them, and `repairIndex()`
  runs it unconditionally (not only when orphan directories are found: counters can be inflated over
  perfectly clean shelves). Brains with delete history should run `brain.repairIndex()` once after
  upgrading; the correction survives reopen.

No API breaks (optional-parameter additions only). Regression tests cover the drift cycle, the
null-read decrement fallback, and the persisted recount across reopen.

## v8.3.1 — 2026-07-14 (full-removal deletes + family-scoped migration gate)

Two production-reported fixes in the write/index spine, plus an operator repair path. No API changes;
all behavior changes make previously-wrong states honest.

- **Deleting an entity now removes it completely — no more "ghost" leftovers on disk.** A canonical
  noun delete removed the metadata (content) leg but left the entity's `vectors.json` and its `<id>/`
  directory behind. Consequences observed in a production deployment: deleted rows were
  indistinguishable on disk from damage scars, enumerated counts inflated monotonically with every
  delete (the leftovers were counted forever), and locator-style reads hit unreadable ghost rows.
  `remove()`/`removeMany()`/`deleteNoun`/`deleteVerb` now remove **both legs and the entity
  container**, with a full two-leg before-image rollback inside the transaction. The generation log
  still holds the delete's before-image, so `asOf()` time-travel reconstructs deleted entities exactly
  as before — this is live-HEAD hygiene, not a history change. This also fixes **duplicate `readdir`
  entries for re-created VFS paths** at the root: with no ghost state, a delete always unposts its
  index rows, so a delete→recreate cycle lists the path exactly once (regression-tested across
  repeated cycles).

- **`repairIndex()` prunes ghost/scar directories left by earlier versions.** Stores that deleted
  entities under ≤8.3.0 may hold orphaned entity directories (a vector-only leg, or an empty dir).
  `brain.repairIndex()` now sweeps them: it removes only containers with **no metadata content leg**
  (never a directory that still holds content), logs every removal, and recomputes type/subtype
  counts afterward so totals stop counting ghosts.

- **Reads no longer hang behind an unrelated index migration (family-scoped gate).** During a native
  provider's one-time background migration, *every* read — including plain `get()`, VFS
  `readdir`/`readFile`, and metadata-only `find({ where })` — blocked on the whole-brain migration
  lock until timeout, even when the migrating index was irrelevant to the read. The gate is now
  scoped to the index families a read actually consults: canonical reads (`get`, `batchGet`, VFS
  content) never wait; a `find` waits only on the families its query shape needs (vector for
  semantic, metadata for `where`/type, graph for `connected`); graph traversals wait only on the
  graph family. Writes and unclassified operations keep the conservative whole-brain wait. A read
  that *does* need the migrating family still blocks (bounded by `migrationWaitTimeoutMs`) and
  surfaces the retryable `MigrationInProgressError` — never a partial result.

No breaking API change. Each fix ships with regression tests.

## v8.3.0 — 2026-07-13 (faster index heals + the cross-layer integrity contract)

Three additive changes. The first is an immediate, standalone performance win; the other two are the
brainy side of the write/index-spine integrity contract, inert until a native accelerator
that implements the matching hooks is present — so this release changes nothing for a JS-only brain
beyond the speedup.

- **Canonical enumeration is up to ~16× faster — the dominant term in an index heal.** The paginated
  entity walk (`getNounsWithPagination`) hydrated each entity's vector + metadata one-at-a-time; since
  every index rebuild enumerates canonical storage, that serial per-item latency dominated multi-minute
  heals. Hydration is now 16-way bounded-concurrency, with the pagination contract (order, cursor
  resume, filters, totalCount) byte-identical to before. New **`getNounIdsWithPagination()`** returns
  ids without hydrating anything (zero per-entity reads when unfiltered) for callers that own their own
  IO schedule.

- **Cross-layer integrity — `validateIndexConsistency()` is no longer blind to native providers.** It
  only ran the JS metadata index's own check, so a native provider whose manifest/segments/counts had
  diverged still read as "healthy". It now feature-detects and aggregates each provider's optional
  `validateInvariants()` self-report, names every failing invariant with its numbers, and exposes the
  per-provider reports. `repairIndex()` now reconciles native derived state from canonical too
  (rebuilding any provider whose failing invariant asks for it). New exported types
  `ProviderInvariantReport` / `InvariantResult` / `InvariantHeal`.

- **Registered-blob families — declared index files are undeletable through the storage layer.** A
  provider can declare a derived-index blob *family* (a set of members that are load-bearing together);
  once declared, `deleteBinaryBlob` / `removeRawPrefix` refuse to remove a member (new exported
  `ProtectedArtifactError`), so a stray in-process sweeper cannot delete a load-bearing index file. The
  declaration persists across reopen; `checkDerivedFamiliesPresent()` names any member missing on open.
  New optional `StorageAdapter` surface (`registerDerivedFamily` / `unregisterDerivedFamily` /
  `listDerivedFamilies` + `DerivedFamilyDeclaration`) and exported `DerivedArtifactMissingError`.

No breaking API change (all additions are optional/new). Each change ships with regression tests.

## v8.2.8 — 2026-07-13 (honest index readiness — no more silently-empty queries on a cold index)

Closes the last of the three spine anti-patterns: the "dishonest readiness proxy," where `size() > 0`
was treated as "this index actually serves queries." On a cold open (fresh boot, restart, crash
recovery) a native index can load its **count** before its **serving structure** — so for a brief
window it has data but cannot answer, and a query returned a silent empty result indistinguishable
from "no such data." Every fix here asks the index whether it can *actually serve*, and if not,
self-heals or fails loudly instead of returning `[]`.

- **Semantic search no longer returns a silent `[]` on a cold vector index.** A pure semantic
  `find({ query })` has no filter, so nothing previously guarded the vector index. A new one-shot
  guard verifies the vector index serves a known persisted vector on the first semantic/proximity
  search — preferring the provider's honest `isReady()` signal, else a known-vector self-match probe.
  It rebuilds from canonical records if the serving structure did not load, and throws the new
  **`VectorIndexNotReadyError`** only if a rebuild still cannot serve — never a silent empty result.

- **Relationship reads fall back to the canonical scan instead of an empty result on a cold graph
  index.** `getVerbsBySource`/`getVerbsByTarget` (used by relationship queries and virtual-filesystem
  traversal) skipped the fast path only on `isInitialized` — which reads true once the manifest loaded
  even if the source→target adjacency did not. They now consult the honest readiness signal and, when
  the adjacency is not serving, take the correct-but-slower canonical shard scan. A one-shot self-heal
  probe covers providers that expose no readiness signal.

- **`getIndexStatus()` tells the truth for readiness probes.** It reported `populated: size>0` only, so
  a Kubernetes readiness check could route traffic to a brain still warming up. It now folds in the
  honest per-index `ready` signal (making `populated` honest), plus the degraded states already
  surfaced by `checkHealth()`/`validateIndexConsistency()` (`rebuildFailed`/`rebuildError` and a
  `degradedIds` count) — so a probe never reports 200-ready over a known-degraded index.

This completes the write/index-spine hardening end to end. New export: **`VectorIndexNotReadyError`**;
`getIndexStatus()` gains additive fields (`rebuildFailed`, `rebuildError?`, `degradedIds`, per-index
`ready?`). No breaking API change. Each fix ships with a dedicated regression test.

## v8.2.7 — 2026-07-13 (loadBinaryBlob fault-propagation — the lockstep completion of 8.2.6)

Completes the Pass-1 spine hardening. `loadBinaryBlob` (the raw-blob read a native accelerator mmaps
for its index files) previously returned `null` on ANY read error, so a real IO fault
(EIO/EACCES/EMFILE) on a present-but-unreadable index blob masqueraded as "the blob is absent" —
driving a needless full rebuild or an empty read. It now distinguishes genuine absence (ENOENT →
`null`, the documented contract) from a real fault (→ throw), so a transient disk fault surfaces
loudly instead of silently degrading the index.

This one change was deliberately held out of 8.2.6 and ships now, in lockstep with the native
accelerator release that hardened its two column-store read sites to handle the throw (a faulted
segment read marks the field unavailable and throws a named error, instead of relying on
null-on-error). A consumer on new brainy + an older accelerator was never at risk: 8.2.6 kept the
prior swallow-on-fault behavior for this method until the accelerator was ready.

No API change. Regression: `tests/unit/storage/blob-save-durability.test.ts` gains the loadBinaryBlob
leg (absent → null; present → bytes; real fault → throws).

## v8.2.6 — 2026-07-13 (write/index-spine hardening — loud errors, never quiet losses)

Durability + integrity hardening across the write and index paths. Every fix converts a place that
could *silently* lose data, serve a partial result, or acknowledge a write that did not land into a
loud, observable failure. No breaking API changes; one new exported error.

- **A durable blob write that stored nothing is no longer acknowledged.** The atomic blob write
  (`saveBinaryBlob`, used for vector/graph index segments and the native index files) uses a unique
  per-writer temp file, so a rename `ENOENT` can only mean *our* temp vanished before the rename —
  the bytes never landed. It previously returned success on that path; it now retries once with a
  fresh temp and, if the temp vanishes again, throws instead of acknowledging a write that persisted
  nothing. A downstream deployment that mmaps these files no longer finds a "successfully written"
  blob missing on the next open.

- **Single-op history durability is enforced, not assumed.** The asynchronous group-commit flush
  that persists single-op generation history previously swallowed a persist failure as a warning
  while writes kept succeeding and their history piled up, undurable, in memory. It now tolerates a
  transient blip (retry with capped backoff) and, after repeated failures, **refuses further writes**
  with the new **`PendingFlushDurabilityError`** rather than promise a durability it cannot deliver.
  Live canonical data is untouched; the latch self-heals the moment a flush succeeds. Callers needing
  hard per-write durability should keep using `transact()` (or `flush()` after a single-op).

- **A degraded derived index is surfaced on reads, not served silently.** When a non-fatal index
  rebuild fails at open, or a write commits via adopt-forward recovery with an incomplete derived
  index, `find()` and `get()` now emit one loud warning per degraded window (reads still return —
  canonical is the source of truth), the state folds into `checkHealth()` /
  `validateIndexConsistency()`, and `repairIndex()` reconciles and clears it.

- **`clear()` removes the full derived footprint.** It previously left raw index blobs, the native
  id-mapper, and column-index manifests on disk, so a cleared brain could re-read stale native state
  on reopen. It now wipes them together as a set.

- **Counts stay honest across deletes.** A delete decremented the per-type breakdown but not the
  scalar total, so the total inflated permanently (and won pagination). Delete now decrements both;
  the invariant `total === Σ per-type` holds across any interleaving of add / visibility-flip /
  delete and across a reopen.

- **Index-maintenance and aggregation failures are loud.** A partial LSM/segment load no longer
  publishes the manifest's full count as if healthy; an HNSW flush that can't persist a node throws
  (`HnswFlushError`) instead of returning a lying count and dropping the node; a corrupt or missing
  manifest-listed column segment throws (`ColumnSegmentLoadError`) instead of silently dropping its
  entities from every query; and aggregation materialization / state-load failures now warn instead
  of vanishing into an empty catch.

New export: **`PendingFlushDurabilityError`** (with `.cause` and `.failedAttempts`). No other public
API change. Each fix ships with a dedicated regression test.

## v8.2.5 — 2026-07-12 (honest response when a transaction rollback can't complete)

Data-integrity fix. When a transaction failed and its rollback then *also* failed to undo a
canonical write (retries exhausted), the old behavior logged, continued, and threw
`TransactionRollbackError` — while the record it couldn't undo stayed durable on disk, and the
transaction even reported its state as `'rolled_back'`. The caller got an error implying the write
was undone; a read-back showed the record. A failed rollback had no truthful response.

Rollback now tells the truth, with a two-branch contract:

- **Adopt-forward (safe case).** A single-op write (`add`/`update`/…) whose only damage is a
  durably-present record — the write the caller asked for — is **adopted**: its generation is
  committed, the write returns success, and a loud warning records that the derived index may be
  incomplete for that id until the next rebuild/`repairIndex()`. No error, no double-write; the
  record is immediately durable and retrievable by `get()`.
- **Fail loud + quarantine (unsafe case).** A multi-operation batch, or *any* case where a record
  was lost (a remove/update whose restore-undo failed), throws the new **`StoreInconsistentError`**
  naming every unreconciled record and its disposition (`orphan` vs `loss`), and puts the brain into
  **write-quarantine**: reads keep working, but writes are refused until `repairIndex()` reconciles
  the derived indexes against canonical storage and lifts the quarantine. The generation counter is
  not advanced, and a transaction whose rollback failed is now `'inconsistent'`, never the
  `'rolled_back'` lie.

The decision is made by *observation*, not guesswork: both commit paths already hold byte-identical
before-images, so after a failed rollback the store compares current canonical state to them to
classify exactly which records are orphaned or lost.

New export: `StoreInconsistentError` (with `.records` and `.cause`) and the `UnreconciledRecord` type.
No other API change; `repairIndex()` gains the quarantine-lift behavior. Regression
(`tests/integration/rollback-trapdoor.test.ts`) injects the exact failure (index add throws →
canonical delete-undo fails) and pins adopt-forward (durable, get-able, not quarantined), fail-loud
(`StoreInconsistentError` + quarantine + reads work + `repairIndex()` lifts it), and the error's
record naming.

## v8.2.4 — 2026-07-12 (restore can no longer destroy the store it's recovering)

Recovery-safety fix. `restore()` removed the entire live brain directory and THEN copied the
snapshot in — so any copy failure left the store destroyed with only a partial copy. The sharpest
edge: the copy (`fs.cp`) materialized the holes of sparse mmap blob files, so a snapshot that fits
on disk could balloon and `ENOSPC` mid-copy, and the recovery tool would have just destroyed the
brain it was asked to recover. Reported from a downstream incident's recovery forensics.

Restore is now **non-destructive and crash-resumable**:

- The snapshot is copied into a staging area (`_restore_staging/`) **before any live data is
  touched**. The copy is **sparse-aware** — all-zero regions are left as holes, so a store of
  mostly-hole blobs restores at its true allocated size instead of its apparent size.
- A copy failure (including `ENOSPC`) removes only the half-written staging area and throws; the
  live store is left **exactly as it was**.
- Only after the copy succeeds and a completion marker is `fsync`'d does an **atomic per-entry
  swap** move the staged data into place — same-filesystem renames that cannot fail for disk space.
- A crash mid-swap is finished **forward** on the next open: startup resumes a committed-but-
  incomplete swap, or discards an uncommitted staging area (live data still authoritative).

No API change — `restore(path, { confirm: true })` is unchanged. `persist()` was already safe
(hard-link snapshot). Regression (`tests/integration/restore-nondestructive.test.ts`): a forced
copy failure leaves live data fully intact, a normal restore round-trips, an interrupted-but-
committed restore completes on reopen, an uncommitted staging area is discarded, and the sparse
copy is byte-identical with allocation far below apparent size.

## v8.2.3 — 2026-07-12 (a committed transaction is durable on return)

Durability fix. A `transact()` reported "committed" while its canonical entity writes were still
only in the OS page cache (written via tmp+rename, not yet `fsync`'d), even though the generation
counter and manifest WERE fsync'd. A hard kill (power loss, SIGKILL) in that window could leave the
durable generation counter **ahead of** the persisted entity bytes — so a consumer resuming from the
counter would see "phantom progress": a generation that claims writes the disk never kept. Reported
from a downstream migration's crash-lifecycle forensics.

`commitTransaction` now runs a **durability barrier**: it records every canonical write and delete
the batch's operations make, then `fsync`s that entire footprint (file contents, the rename
directory entries, and the parent directories of any deletes) **before** advancing the generation
counter and manifest. A committed transaction is therefore durable the moment `transact()` returns —
the counter can never outrun the entity bytes.

**Durability contract, now explicit.** `transact()` is durable-on-return (above). A **single-op**
write (`add`/`update`/`remove`/`relate`/…) is Model-B group-commit: its live bytes are written but
become durable at the next `flush()` or `close()`, not the instant the call resolves — the counter
is buffered alongside the data, so a crash loses both together (never a torn counter-ahead-of-state
store). Need per-write durability? Use `transact()` (even for one op), or `flush()` after the write.
This deliberately trades single-op fsync latency (a 3-5x write regression) for throughput.

No API change; no accelerator involvement (the barrier is in the filesystem storage adapter). In-memory
and durable-per-call (cloud object-PUT) adapters treat the barrier as a no-op. Regression:
`tests/integration/transact-durability-barrier.test.ts` proves entity writes fsync in an earlier
batch than the manifest, for single-op and multi-op (add+relate) transactions, and that a
precommit-rejected batch opens no barrier and advances nothing.

## v8.2.2 — 2026-07-11 (P0: a timed-out transaction now rolls back — no torn state)

Data-integrity fix. A transaction that exceeded its time budget **mid-flight** (e.g. a bulk
`transact()` on slower hardware crossing the 30s ceiling) threw a timeout error WITHOUT rolling
back the operations it had already applied. The budget check sat outside the per-operation
rollback path, so only per-operation *failures* rolled back — a timeout stranded the partial
writes in canonical storage while the generation was never stamped, leaving torn, generation-less
state. This was caught by a downstream migration that crossed the ceiling on a large batch.

`Transaction.execute()` now has a **single rollback point**: any error that escapes the operation
loop — an operation failure OR a mid-flight timeout — rolls back every applied operation in
reverse order, then surfaces the original error (a rollback failure supersedes it, loudly, as
before). This restores the invariant the generation-store commit path already depended on: a throw
from execute means the applied operations were undone byte-identically, and the aborted
transaction leaves `generation()` unchanged and storage byte-identical to its pre-transaction
state.

No API change. Regression pins the reported requirement — after a mid-flight timeout,
storage is byte-identical and the transaction ends in the `rolled_back` terminal state
(`tests/unit/transaction/timeout-rollback.test.ts`), plus the operation-failure and
rollback-failure paths through the same single rollback point.

**Note on the 30s ceiling itself** (configurable/scaled timeout, batched embedding precompute,
timeout telemetry) — that ergonomics work is tracked separately; this release fixes only the
correctness bug (a timeout must never leave partial state), independent of where the ceiling sits.

## v8.2.1 — 2026-07-11 (transact forward references work on the native accelerator)

Parity fix. `transact()` has always promised atomic forward references — `add` an entity and
`relate` to it in one batch — but the transaction planner resolved relationship endpoint ids at
**plan** time, before the batch's adds had applied. Asking the id mapper about an entity that
doesn't exist yet made the accelerator's (correctly strict) native mapper throw in
`EntityIdMapper.getOrAssign`, so `transact([{op:'add', id:X}, {op:'relate', to:X}])` failed on
native deployments while the permissive JS mapper masked the bug — and silently leaked an id
assignment whenever a batch was later rejected by a commit precondition.

Endpoint resolution is now **lazy** — evaluated when the graph operation executes inside the
commit, after the batch's adds have applied (the same lazy pattern the operation's generation
stamp already used). Fixed across all transact-planned graph operations: relate (including the
bidirectional reverse edge), remove's relationship cascade, and unrelate. Single-operation writes
are unchanged. Also fixed as a byproduct: a rejected batch no longer pollutes the id mapper.

Regression suite covers the exact reported shape, both-endpoints-in-batch, bidirectional,
add+relate+remove in one batch, and the mapper-cleanliness proof on rejected batches
(`tests/integration/transact-forward-ref-graph.test.ts`). No API changes; no accelerator version
pairing required.

## v8.2.0 — 2026-07-10 (temporal VFS — file content joins the immutability model)

Time travel now covers Virtual Filesystem **content**. Previously the temporal model had a hole
exactly where files were concerned: every entity write was an immutable generation, but the
content *bytes* lived under an eager reference-count GC — deleting a file could physically destroy
bytes that in-window history still referenced, while overwriting never released the old content at
all (an unbounded silent leak that only *accidentally* preserved history). A production consumer's
recovery from a bad deploy succeeded only because a stale field happened to hold the good value —
luck, not a guarantee. Both directions are now fixed by making blob reclamation a **history**
decision instead of a **liveness** decision:

- **Content blobs are retention-protected.** Each blob tracks live references AND history
  references (one per persisted generation record that carries its hash). Deleting/overwriting a
  file drops only the live reference; bytes are physically reclaimed in exactly one place —
  history compaction — once no live reference and no retained generation references the hash.
  Pinned views are exempt automatically (compaction already respects pins). Crash ordering is
  over-count-only (never under-count), so a crash can leak until the built-in scrub recounts, but
  can never reclaim bytes history still needs. Existing stores get a one-time, marker-gated
  backfill on open; cross-file content dedup is handled exactly.
- **`vfs.readFile(path, { asOf })`** — the file's exact bytes as of a generation or `Date`,
  guaranteed present within the retention window.
- **`vfs.history(path)`** — the file's versions (`{ generation, timestamp, hash, size,
  mimeType? }`, ascending). Restore = read the old bytes `asOf` and write them back (a new write;
  history is never rewritten).
- **Overwrites now refresh the file entity's `data`/embedding text** — previously semantic search
  and the `data` field served the FIRST version's text forever.

Lifecycle note: deleting a file no longer frees its bytes immediately — old content lives until
compaction reclaims its generations, under the same `retention` budget as all Model-B history
(`retention: 'all'` keeps every version forever). Guide: the new "Time travel for files" section in
`docs/guides/snapshots-and-time-travel.md`. Native accelerator: unaffected (canonical write path
only) — no version pairing required.

## v8.1.0 — 2026-07-10 (`brain.onChange` — the in-process change feed)

New public API: subscribe to every committed mutation with
`brain.onChange(cb) → unsubscribe`. One event per affected record, for **every**
canonical write regardless of origin — direct calls, batch methods, `transact()`,
imports, and Virtual Filesystem writes all funnel through the same commit point the
feed is emitted from. This is the authoritative in-process signal for live UIs,
cache invalidation, and realtime sync layers (downstream SDKs can forward it over
their own transports to make local and remote brains uniform).

Event shape (`BrainyChangeEvent`, exported): `kind` (`entity`/`relation`/`store`),
`op` (`add`/`update`/`remove`/`relate`/`unrelate`/`updateRelation`/`clear`/`restore`),
the post-commit `entity` or `relation` view (type + full custom metadata), the
committed `generation`, and `timestamp`. Notable properties:

- **Post-commit only** — an aborted write (a losing `ifRev` CAS, a rejected
  transaction) never emits. If you got the event, the write is durable.
- **Deletes fully described** — `remove`/`unrelate` carry the record's last
  committed state (from the commit's own history record), not just an id; batch
  deletes included.
- **Batches emit per item**; a `transact()` batch's events share its single
  generation. Entity deletes also emit `unrelate` for each cascaded relationship.
- **Commit-ordered, asynchronous, isolated** — events arrive in commit order,
  dispatched in a microtask so a slow listener never delays a write and a throwing
  listener never affects the write or other listeners. Zero overhead with no
  subscribers.
- **`kind: 'store'`** events for `clear()`/`restore()` mean "refetch everything".
- Fire-and-forget by design; each event's `generation` composes with
  `asOf()`/`transactionLog()` for catch-up after a gap.

Guide: `docs/guides/reacting-to-changes.md`. No behavior changes for existing code.

## v8.0.17 — 2026-07-08 (count recovery scans the real layout · ~1,100 lines of dead 7.x machinery removed)

A cleanup of the vestigial 7.x "hnsw sharding" machinery that turned up two real fixes.

**1 — Count recovery now scans the layout the database actually uses.** When `counts.json` is
lost or corrupted (container restarts, partial copies), the recovery scan rebuilt the entity/
relationship counters by counting files in `entities/*/hnsw/` — directories the 8.0 write path
never populates — so an established store recovered to **zero counts** on real data: wrong
`getNounCount()`/stats, a "New installation"-style boot log, and a mis-sized rebuild-strategy
decision at open. The scan now counts the canonical `entities/<kind>/<shard>/<id>/` tree.
Regression-tested: delete `counts.json` from a populated store → reopen → exact counts.

**2 — A latent init-time deadlock removed.** The recovery scan's type-distribution sampler called
a guarded accessor (`getNounMetadata` → `ensureInitialized`) from **inside** `init()`, which
re-enters `init()` and hangs the open. It was unreachable before only because the old scan never
found anything to sample; the fix reads the sampled metadata files directly.

**3 — The dead machinery itself is gone (−1,138 lines).** Twenty-three methods with zero callers:
the 7.x hnsw-layout entity/edge CRUD, the sharding-depth prober + depth-migration engine, and an
orphaned streaming paginator. Verified by reachability analysis before deletion; no public API
touched; the full suite is green. New stores no longer carry the always-empty legacy directories'
scan cost, and the boot log keeps the truthful new-vs-established wording from v8.0.13.

## v8.0.16 — 2026-07-08 (concurrency fast-follow: atomic `ifAbsent`/`upsert` + exact blob reference counts)

Closes the two remaining check-then-act races found in the sweep that followed v8.0.15's CAS fix
(disclosed in that release's notes). Same bug class — a check performed before the serialization
point that guards the apply — same cure.

**1 — `add({ ifAbsent })` and `add({ upsert })` are now atomic.** The absence check ran before the
commit mutex, so N concurrent same-id creates could all pass it and all write — the second
silently overwriting the first, violating ifAbsent's "returns the existing id **without writing**"
contract and upsert's "merge, never clobber" contract. The insert leg now carries a must-be-absent
precondition (the same conditional-commit primitive as `ifRev`), verified under the commit mutex:
exactly one concurrent create wins; every other caller takes its documented resolution — ifAbsent
returns the existing id with zero writes, upsert merges into the now-existing entity (with a
bounded retry if a concurrent delete intervenes). Verified: 8 concurrent `ifAbsent` creates
advance the store by exactly ONE generation; 8 concurrent upserts on an absent id produce one
create + seven merges (`_rev` lands at exactly 8). Note: `transact()`'s batch-level
ifAbsent/upsert keep planning-time semantics (the batch converges to a valid entity; the window is
documented, not silent).

**2 — Blob reference counts are exact under concurrency.** The content-addressed blob store's
`write()` (dedup: exists → add a reference, absent → create) and `delete()` (decrement → remove at
zero) were unserialized read-modify-writes over the blob's metadata. Concurrent writes of
identical content could lose references — making a later delete remove bytes **another file still
referenced** (data loss), or leak unreferenced blobs. All reference-count-bearing mutations are
now serialized per content hash (distinct content never contends): N concurrent identical writes
yield exactly N references, and a blob is physically removed only when the true last reference
drops. Verified with concurrent write/delete storms.

Both fixes are in-process complete by construction — storage enforces single-writer-per-directory,
so the process is the whole concurrency domain. No API changes.

## v8.0.15 — 2026-07-08 (`ifRev` CAS is now atomic — exactly one winner under concurrency)

Correctness fix for optimistic concurrency, reported from a production cutover rehearsal. N
**concurrent** `update({ ifRev })` calls carrying the same expected revision ALL succeeded — zero
`RevisionConflictError`s, last-writer-wins, the other N−1 writes silently lost. (Sequential calls
conflicted correctly.) The revision check ran before the commit mutex, so interleaved callers all
passed it before any apply landed — breaking the exactly-one-winner semantics the
[optimistic-concurrency guide](docs/guides/optimistic-concurrency.md) promises, which advisory
locks and per-entity ledgers/counters build on.

The fix makes the check-and-apply a **conditional commit**: the generation store's commit paths
accept a precondition that runs under the commit mutex against the just-read authoritative
before-images — the per-record analogue of `ifAtGeneration`, which always ran there. `update()`
and `transact()` per-op `ifRev` both re-verify at that point (the earlier check remains as a cheap
fast-fail). A conflict aborts atomically: nothing staged, nothing applied, the same
`RevisionConflictError` as before. Two adjacent behaviors also became honest:

- **`_rev` is now monotonic under concurrency.** The winner's stamp derives from the
  authoritative before-image, so N concurrent plain updates advance `_rev` by N (previously they
  could all stamp the same stale value).
- **CAS against a concurrently-deleted entity** now throws `EntityNotFoundError` instead of
  silently resurrecting it (plain updates keep their last-writer-wins re-create semantics).

Verified with a concurrency regression suite: 8 parallel same-rev updates → exactly 1 winner + 7
conflicts; the documented read→CAS→retry ledger loop converges exactly (8 workers, 8 decrements,
0 lost) — `tests/integration/ifrev-concurrent-cas.test.ts`. If you serialized writes in your own
adapter as a workaround, it can come out after this upgrade.

## v8.0.14 — 2026-07-07 (7→8 migration preserves branch-scoped non-entity state instead of deleting it)

Defense-in-depth for the one-time 7→8 layout migration. The migration rescues the head branch's
entities (`branches/<head>/entities/*` → `entities/*`) and then drained the whole `branches/<head>/`
directory. If a 7.x engine had written durable state under the head branch *outside* `entities/`
(a branch-scoped index, blob area, or field registry), that drain would have silently deleted it —
the same failure class as the VFS content blobs a 7.x store kept in `_cow/`. The migration now drains
the branch only when nothing but the moved entities remains; if any non-entity object survives, it
**preserves the branch** (no delete) and logs a loud warning naming the leftover keys, so the state is
recoverable rather than lost. No effect on a normal migration (a clean branch still drains); purely a
guard against silent data loss.

Cosmetic boot-log fix. Every persisted 8.0 store logged `📁 New installation: using depth 1
sharding` on **every** open — even established brains holding thousands of entities — which is
alarming to read during a restart or incident. Cause: 8.0 stores nouns in the canonical
`entities/nouns/<shard>/<id>/vectors.json` layout, but the legacy sharding probe inspected the
`entities/nouns/hnsw/` directory, which the 8.0 write path never populates, so it always concluded
"new". The new-vs-existing decision now consults the layout the database actually reads and writes
(plus the known noun count), so an established store logs `📁 Using depth 1 sharding (N entities)`
and only a genuinely empty store reports a new installation. No behavior change beyond the log line —
it never triggered a rebuild or migration; entities were always read correctly.

## v8.0.12 — 2026-07-07 (7→8 VFS-content recovery · zero-rebuild cold open · strict query operators)

Three consumer-facing fixes.

**1 — A 7→8 upgrade recovers Virtual Filesystem content automatically (data-integrity).**
7.x stored VFS file content as blobs in the branch system's copy-on-write area (`_cow/`). 8.0
removed that system and stores content blobs in the content-addressed store (`_cas/`), but the
one-time layout migration only moved entities — it never adopted the `_cow/` content blobs. On a
store that used the VFS (for example, a CMS with published pages), that left every VFS-backed read
throwing `Blob metadata not found` and the pages 500ing. **8.0.12 adds an on-open recovery pass**
that adopts every orphaned `_cow/` blob into `_cas/` — copying both the bytes and the metadata,
idempotently and **non-destructively** (the `_cow/` originals are never deleted). It heals both a
fresh 7→8 upgrade and a store **already** upgraded by an earlier 8.0.x that stranded them, with no
operator action: just open the store under 8.0.12. An explicit force path is exposed as
`brain.vfs.adoptOrphanedBlobs()` (returns `{ cowBlobs, adopted, alreadyPresent, incomplete }`). The
automatic pre-upgrade backup is now **retained** if any blob can't be fully adopted
(`incomplete > 0`) instead of being removed on entity-migration "success" alone. Affects any 7.x
store that used the VFS; native-8.0 and non-VFS stores no-op on a cheap existence check. Full guide:
`docs/guides/upgrading-7-to-8.md`.

**2 — A cold open no longer re-derives durable indexes it can just load.**
Opening a persisted store rebuilt the vector, graph, and metadata indexes from the canonical
records even when the durable index state was present and loadable — an O(N) cost paid on every
boot (measured at ~48 s on an ~11k-entity store). The rebuild gate now consults an honest
per-provider durability signal (`init()` / `isReady()`) instead of an in-memory size heuristic, so
a provider that has loaded (or can cheaply demand-load) its persisted index is not rebuilt. The
built-in JS indexes keep today's behavior (a rebuild *is* their load path); the live query-time
guards that self-heal a genuinely lost index are unchanged. **The zero-rebuild boot activates when
the accelerator exposes the durability signal (`@soulcraft/cor@3.0.5`);** on earlier accelerator
versions 8.0.12 falls back to the previous behavior safely — no regression, just no speedup yet.

**3 — Unknown query operators now throw instead of silently returning nothing.**
`find({ where })` had two gaps: the in-memory matcher (used for egress re-validation and historical
reads) was missing several documented operators (`in`, `greaterThanOrEqual`, `lessThanOrEqual`), so
it silently disagreed with the index path; and an unknown operator key (a typo, or `notIn` written
where `not: { in }` was meant) was treated as a nested-object field and silently matched nothing.
8.0.12 aligns the matcher to the full documented operator set and **validates the `where` filter
up front**, throwing a typed `BrainyError('INVALID_QUERY')` naming the bad operator. Dotted paths
remain the supported form for nested fields. If you relied on an unknown key silently returning `[]`,
it now throws — the fix is to use the documented operator or dot-notation.

## v8.0.11 — 2026-07-02 (no script shape can hang on brainy's internals)

Completes v8.0.10's exit fix for every operation class. Two further mechanisms found and fixed:
the `beforeExit` auto-flush hook looped forever on any script that never reaches `close()` (Node
re-emits `beforeExit` after each event-loop drain and the async flush schedules new work — it now
self-deregisters before its single flush, which still lands your buffered data before exit), and
every background-maintenance interval (graph auto-flush, LSM compaction, metadata write-buffer,
VFS/path-cache maintenance, statistics debounce) is now unref'd at creation. Verified against the
published package: an `add + relate` script exits cleanly both with `close()` (~0.5 s) and with no
teardown at all — with the data confirmed durable on reopen. A per-operation-class sweep test now
asserts no ref'd timer survives `close()`, so this bug class stays closed.

## v8.0.10 — 2026-07-02 (a bare script exits cleanly after `close()`)

A minimal `init → add → close` script used to hang forever after `close()` returned — brainy held
four process keep-alives it never released: the global SIGTERM/SIGINT shutdown hooks (never
removed; now deregistered when the last live instance closes), an internal cache-fairness interval
(unclearable by construction; now unref'd), and the VFS/PathResolver maintenance intervals
(`close()` never shut the VFS down; now wired). Verified against the published package: the same
script now exits ~1 ms after `close()` resolves. No API change; servers and long-running processes
are unaffected.

## v8.0.9 — 2026-07-02 (guarded plugin auto-detection — the "install it and it's on" contract)

With the default config (`plugins` unset), brainy now **auto-detects the first-party accelerator**:
installing `@soulcraft/cor` is the opt-in. The detection is guarded — everything except "not
installed" fails loud:

- Not installed → plain brainy, silently (the free path — zero noise, zero cost).
- Installed and healthy → it loads and announces itself (`[brainy] Plugin activated`).
- Installed but broken (unresolvable, invalid shape, failed activation, version mismatch) →
  **`init()` throws.** An installed accelerator never silently vanishes behind the JS engines.
- `plugins: []` / `false` = explicit opt-out; `plugins: ['@soulcraft/cor']` pins the exact list
  (unchanged semantics).

Also new: if a plugin activates but registers **zero** native providers (e.g. a licensing gate
declining to engage), brainy warns loudly instead of leaving you to discover every query is running
on the JS engines.

> This supersedes v8.0.8's "plugins are explicit opt-in" wording, which documented the pre-GA
> loader accurately but contradicted the published product contract ("add the package and it
> activates"). 8.0.9 makes the contract true — with the loud-failure guarantees intact.

## v8.0.8 — 2026-07-02 (docs-only patch on the GA)

Corrects the README's scale-up section: the native provider is **not** auto-detected — plugins are
**explicit opt-in** (`new Brainy({ plugins: ['@soulcraft/cor'] })`; brainy never auto-imports a
package you didn't list, and a listed plugin that fails to load throws rather than silently falling
back to the JS engines). Also fixes the stale `plugins` config comment in the public types and one
phrase in the plugin-author guide. No code change.

## v8.0.7 — 2026-07-02 (GA, npm tag `latest`)

> **Why 8.0.7:** npm permanently retires unpublished version numbers, and `8.0.0`–`8.0.6` were
> consumed by a January development cycle (published and immediately unpublished). `8.0.7` is
> the first stable release of the 8.x line; there are no earlier stable 8.0.x releases.

**8.0.7 is the first stable major on the u64-id core.** It ships in lockstep with the optional
native provider's `3.0` (the billion-scale path). Everything below works standalone on the open-core
JS engine — a native provider is feature-detected and only changes the scale ceiling, never the API.

**Upgrading from 7.x: nothing to script.** The first time 8.0 opens a 7.x brain it upgrades itself —
an automatic, observable, **coordinated migration lock** rebuilds every derived index from your
canonical records while Brainy **blocks and queues** reads and writes, so no operation ever touches a
half-built index and no write is ever lost. Budget seconds-to-minutes per brain at large sizes; small
brains rebuild inline on open. A pre-upgrade hard-link **backup** is taken automatically (removed on
success, kept on failure for rollback). Observe it via `getIndexStatus().migration`; a caller that
hits the window gets a typed, retryable **`MigrationInProgressError`** (catch → HTTP 503 +
`Retry-After`). Bounded by `migrationWaitTimeoutMs` (default 30 s — it bounds *your wait*, not the
rebuild). Opt out of the backup with `migrationBackup: false`.

### Headline changes

- **The cold-open silent-`[]` class is gone.** On a cold reopen, filtered finds (`find({ where })`)
  and graph reads (`find({ connected })` / `neighbors()` / `related()`) never silently return `[]`
  for data that is actually present. With a native provider the durable indexes cold-serve every
  filter and edge with zero rebuild; the open-core engine adds belt-and-suspenders guards that
  self-heal from canonical data or throw a loud, typed error — never a silent empty result. Two new
  exported errors: **`MetadataIndexNotReadyError`**, **`GraphIndexNotReadyError`**.

- **Faster vector search (open-core).** The JS distance functions are allocation-free loops instead
  of `reduce`: **~6× cosine, ~1.4× euclidean** (MEASURED — `tests/benchmarks/distance-microbench.mjs`,
  384-dim, median of 41). Numerically identical, so recall is unchanged. Exact metadata-filter
  pushdown and scale-aware search width keep `find()` recall-correct as data grows.

- **Per-write immutable history.** Every write is generation-stamped; `now()` / `asOf()` /
  `transact()` read a consistent point in time, and a retention knob bounds history growth. Single
  writes participate in the same immutable timeline as transactions.

- **Billion-scale resident memory.** Nothing is O(N)-resident on the write or time-travel path —
  per-id caches removed, the committed-generation ledger is an interval set, per-id history chains
  are bounded (hot-window + LRU). Resident memory is independent of entity count.

- **Deterministic, round-trip-free writes.** Supply your own ids, forward-reference not-yet-written
  entities inside a `transact()`, `ifAbsent` upsert, and `brain.newId()` (uuidv7) — write graphs
  without a write→wait→get round-trip.

### Breaking changes (summary — the full migration guide follows below)

- **Runtime floor: Node ≥ 22 / Bun ≥ 1.1** (Bun recommended). Compiler target ES2023; the DOM lib is
  dropped — 8.0 is a Node/Bun/Deno engine with no browser path.
- **`neural()` removed** and **`Db.search` removed** — use `find()` on the brain.
- **Storage config is one `path` key.** Removed aliases now throw with a message pointing at `path`.
- **`get()` omits the vector by default** — pass `{ includeVectors: true }` when you need it.
- **Export/import type is `PortableGraph`** (was `BackupData`; wire tag `brainy-backup` →
  `brainy-portable-graph`). Re-export any snapshots you version outside Brainy.
- **Reserved `visibility` field** (`public` / `internal` / `system`) on nouns and verbs; `internal`
  and `system` are excluded from normal reads by default.
- **4 deprecated query operators removed** (`is`/`isNot`/`greaterEqual`/`lessEqual`) and reserved
  keys in a `metadata` bag now **throw** by default — details in the rc notes below.

> Post-rc.9 hardening folded into GA (no on-disk or provider-contract change vs `8.0.0-rc.9`):
> the metadata cold-read guard, the auto pre-upgrade backup (with an `_id_mapper/*` mmap byte-copy
> correctness fix), and a CI fix so a fresh clone builds green.

### RC history (rc.1 → rc.9, npm tag `rc`)

> **rc.9 changes (2026-07-01):**
> - **Whole-brain auto-upgrade is now a coordinated, observable LOCK — supersedes rc.8's no-freeze
>   approach.** When a large brain's derived-index format changes (7.x→8.0), the native provider
>   rebuilds the indexes from the canonical records **in place** while Brainy **blocks and queues**
>   reads and writes — so no operation ever touches a half-built index. This is a clean *blocking
>   upgrade to a known-good state* (vs rc.8's online background swap): unknown/halfway states are
>   more dangerous than a bounded wait. Small brains still rebuild inline on open. New surface, all
>   additive: a typed, exported, retryable **`MigrationInProgressError`** (catch it → HTTP 503 +
>   `Retry-After`); `getIndexStatus()` gains **`migrating` + `migration`** progress (never gated —
>   the readiness-probe signal); a **`migrationWaitTimeoutMs`** config (default 30 s — it bounds the
>   *caller's wait*, NOT the rebuild, which is unbounded); `health()` / `checkHealth()` report the
>   upgrade without blocking. No effect without a native provider.
> - **Faster vector search (open-core).** The JS distance functions are rewritten from `reduce` to
>   allocation-free loops — **~6× cosine, ~1.4× euclidean** (MEASURED, `tests/benchmarks/distance-microbench.mjs`,
>   384-dim, median of 41). Numerically identical → recall unchanged.
> - **Runtime floor + Bun.** Engines are now **Node ≥22 / Bun ≥1.1** (fixes a Node-24 `EBADENGINE`);
>   compiler target ES2023 with DOM dropped from the type lib (8.0 is Node/Bun/Deno-only, no browser
>   path). **Bun is recommended as a runtime** (`bun add` / `bun run`); the single-binary
>   `bun build --compile` is not a supported target (native addon can't embed + a Bun 1.3.10 codegen
>   regression). `.d.ts` stays TS-5.x-parseable.

> **rc.8 additions (2026-06-30) — additive, no breaking change:**
> - **No-freeze (online) whole-brain auto-upgrade.** When a derived-index format changes, a large
>   brain upgrades **without blocking** — the native provider rebuilds the new indexes in the
>   background and serves correct reads from the canonical records meanwhile, then atomically swaps;
>   no minutes-long freeze on the first open/query. (Small brains still auto-rebuild inline on open.)
>   New surface: an optional provider `isMigrating()` deference signal, a public `brain.stampBrainFormat()`
>   the provider calls once its swap verifies, and a `@soulcraft/brainy/brain-format` export so the
>   provider shares the `indexEpoch` constant. No effect without a native provider.

> **rc.7 additions (2026-06-30) — additive, no breaking change:**
> - **8.0 cold-graph self-heal.** `find({ connected })` / `neighbors()` / `related()` never
>   silently return `[]` on a cold open where the graph adjacency loaded its membership but not
>   its source→target edges — it self-heals (rebuild from storage) or throws a loud
>   `GraphIndexNotReadyError`, never empty-for-persisted-data. (The 8.0 equivalent of the 7.33.4
>   fix 7.x consumers already have; gates on the native provider's honest `isReady()` edge-readiness
>   signal.)
> - **Billion-scale RAM — nothing O(N)-resident on the write/time-travel path.** Eliminated the
>   per-id storage caches (per-type counts now sourced from the record), made the
>   committed-generation ledger an interval set, and bounded the per-id time-travel history chains
>   (hot-window + LRU, with lock-light reconstruction so historical reads never stall writers).
>   Resident memory is now independent of entity count.
> - **Whole-brain version handshake.** A `_system/brain-format.json` marker + `brain.formatInfo()`
>   + a shared, lockstep `indexEpoch`: a future derived-index format change auto-rebuilds the
>   indexes from the canonical records on open (non-destructively) — the foundation for
>   whole-brain auto-upgrade with the native provider. No effect on an unchanged brain.

> **rc.6 additions (2026-06-29) — additive, no breaking change:**
> - **Open-core perf**: HNSW delete is now O(in-degree) (was O(N²) for bulk delete) via a
>   reverse-adjacency index; the negation/absence operators (`ne`/`exists:false`/`missing:true`)
>   are served as a roaring-bitmap difference instead of materializing the whole corpus.
> - **Native provider contract** (cor lockstep, optional/feature-detected — no effect without a
>   native provider): a cold-open `probeConsistency()` self-heal hook, and a `getIdsForFilter`
>   page bound so the native index can early-stop the unsorted `find({ type, where, limit })` path.
> - **Test hygiene**: re-homed previously-unrun test suites into CI + a guard so a test file can
>   never silently fall outside every config again. No source/API change from these.


**Affected products:** every consumer — this is a major release with removed
surfaces, hard renames (no aliases, no deprecation period), and one flipped
default. This entry **is** the migration guide: the find/replace pairs, the
sed snippet, and the upgrade checklist below are the complete story — there is
no separate migration doc. **`8.0.7` is GA on `latest`** — install with
`npm i @soulcraft/brainy@latest`.

> **rc.3–rc.5 additions (2026-06-24):**
> - **Showcase-quality GA hardening (rc.5).** A full readiness audit closed a cold-init
>   version-coupling bug (a matched native provider could be rejected on first open), turned
>   silent storage-read failures into named `BrainyError`s (no more empty-result-on-error),
>   stopped the JS graph LSM from orphaning compacted SSTables, corrected the public docs to
>   the real API, and documented the two headline methods. Plus a dead/deprecated-code sweep.
> - **BREAKING — 4 deprecated query operators removed.** `is`→`eq`, `isNot`→`ne`,
>   `greaterEqual`→`gte`, `lessEqual`→`lte`. The canonical operators and their clean long-form
>   aliases (`equals`/`notEquals`/`greaterThan`/`greaterThanOrEqual`/`lessThan`/`lessThanOrEqual`)
>   are unchanged — only the four redundant spellings are gone. Find/replace if you used them.
> - **`find()` search mode** is now the single `searchMode: SearchMode` option (the redundant,
>   silently-ignored `mode` alias and the unwired `explain` flag were removed from `FindParams`).
> - The phantom index-integrity guard (find() re-validates every result against its predicate)
>   shipped in rc.3; rc.4 added the `accel.isInitialized` gate + #35 at-gen candidate vectors.

> **rc.1 additions (this entry predates them — full writeup lands at GA):** entity-id
> normalization — `brain.newId()` (UUID v7) + v7 default ids, and non-UUID string ids are
> transparently normalized to a stable UUID v5 (original key preserved under `_originalId`);
> `brain.neural()` clustering and `Db.search()` removed (use `find({ vector })` /
> `find()` + aggregation `GROUP BY`); storage config collapsed to one `path` key (the
> pre-8.0 aliases now throw); and `queryAggregate` no longer hangs/staled min-max after a delete.
> **Reserved fields in a `metadata` bag now throw by default** — passing a Brainy-reserved key
> (`confidence`, `weight`, `subtype`, `visibility`, `service`, `createdBy`, `noun`/`verb`, `data`,
> `createdAt`, `updatedAt`, `_rev`) inside `metadata` on `add()`/`update()`/`relate()`/`updateRelation()`
> (untyped/JS callers — TypeScript already blocks it) is rejected with an Error naming the correct
> param, instead of the old silent remap-or-drop. Pass reserved values as their dedicated top-level
> params. Opt back into the legacy behavior with `new Brainy({ reservedFieldPolicy: 'warn' | 'remap' })`.

> **rc.2 additions (2026-06-21):**
> - **Graph performance + the `brain.graph` namespace.** New `brain.graph.subgraph(seeds, opts)`
>   (bounded multi-hop neighborhood → `{ nodes, edges, truncated }`) and `brain.graph.export(opts)`
>   (stream the whole graph in one O(N+E) pass — the right primitive for visualizing all data
>   instead of paging per node). `related({ node })` returns every edge incident to an entity in
>   **both directions** in one O(degree) call. Under the hood: `related({ from/to })` now stays
>   O(degree) under the default visibility filter (was a full scan), and the verb **and** noun
>   pagination walks are cursor-based, so a full edge/node walk is **O(N), not O(N²)** (a consumer
>   measured a 19k-edge whole-graph read drop from ~27s toward a single scan). These transparently
>   use a native graph engine when present (the `@soulcraft/cor` 3.0 acceleration layer) and fall
>   back to pure-TS adjacency otherwise.
> - **Additive ergonomics:** `add({ upsert: true })` (create-or-update in one call — merges into an
>   existing id instead of overwriting), `find({ includeVectors: true })`, and `removeMany`'s batch
>   size is now storage-adaptive (was a hardcoded 10).
> - **Correctness fixes (apply to all consumers, not just graph users):** `related()` results now
>   carry `visibility`; whole-graph/`getNouns` streaming no longer leaks `system`/`internal` entities;
>   and small-page cursor walks over nouns no longer loop. No API change — just correct behavior.

> **rc.3 additions (2026-06-23):**
> - **Graph analytics on the `brain.graph` namespace.** Three intent-level reads that answer
>   whole-graph questions in one call:
>   - **`brain.graph.rank(opts?)`** → `{ id, score }[]` descending — "which entities matter most"
>     (importance / centrality). `topK` to cap.
>   - **`brain.graph.communities(opts?)`** → `{ groups: string[][], count }` — "which things group
>     together". Weakly-connected components by default; `{ directed: true }` returns
>     strongly-connected components.
>   - **`brain.graph.path(from, to, opts?)`** → `{ nodes, relationships, cost } | null` — the best
>     route between two entities. Fewest hops by default; `{ by: 'weight' }` minimizes summed edge
>     weight (the 0–1 connection strength); `direction`, `type`, and `maxDepth` filters apply.
>   These are **intent contracts, not algorithm contracts** — the question is the promise, the
>   algorithm is the engine's choice. They transparently use the native `@soulcraft/cor` 3.0 graph
>   engine when present, and fall back to pure-TS kernels (PageRank, connected components / Tarjan
>   SCC, BFS / Dijkstra) otherwise. Both paths return identical shapes and respect the default
>   visibility filter (opt in with `includeInternal` / `includeSystem`).
> - **Filtered vector search keeps its recall (`allowedIds` pushdown).** A `find({ query, where })`
>   that combines semantic search with a metadata filter now restricts the vector walk to the
>   matching candidates *inside* the search (walk-all, collect-allowed) instead of filtering the
>   top-k afterward — so a query whose nearest vectors are all filtered out still returns the best
>   matches that DO pass the filter, rather than coming back empty. No API change. With the native
>   `@soulcraft/cor` 3.0 stack the matched universe is forwarded as an opaque roaring buffer with
>   zero id materialization in TypeScript; the pure-JS path restricts the beam walk with a string set.
> - **Historical (`asOf`) semantic search can skip the rebuild.** A filtered semantic query at a
>   past generation — `db.asOf(g).find({ query, where })` — no longer always rebuilds an ephemeral
>   in-memory vector index over every at-`g` vector (O(n@G)). When a native versioned vector engine
>   is registered and can serve the pinned generation, Brainy resolves the at-`g` filter universe from
>   its record layer (no rebuild) and routes the vector leg to the engine with the matched ids + the
>   generation; without one it falls back to the materialization (unchanged). The `VectorIndexProvider.search`
>   options gained an optional `generation?: bigint` ("omitted = now") to carry this — additive, the
>   built-in index ignores it. No public API change.
> - **`find({ where, orderBy })` bounds the sort to the page.** A broad filter + `orderBy`
>   returning one page no longer materializes every matching sorted id (it produced the full sorted
>   match set, then sliced) — the page bound (`offset + limit`) is threaded into the column store's
>   top-K sort, so returning 20 rows from a million matches stays a bounded-K heap. No API change;
>   ordering and pagination are unchanged.
> - **`brain.graph.subgraph()` accepts a query (query→expand).** The seed selector now takes not
>   just entity id(s) but a `find()` result or a `FindParams` query — `brain.graph.subgraph({ where:
>   { team: 'platform' } }, { depth: 1 })` runs the query and expands the neighborhood of every
>   match in one call. With the native engine a metadata-only query's matched universe is handed to
>   the traversal as an opaque set with no id materialization in TypeScript (the query→expand
>   fusion); the pure-JS path materializes the matched ids and expands from them. Existing
>   id-seeded calls are unchanged.

### Headline: Database as a Value

8.0 replaces Brainy's two overlapping version-control subsystems (copy-on-write
branching and per-entity versioning, ~5,100 LOC combined) with **one
mechanism**: generational MVCC over immutable, generation-stamped records,
exposed through a Datomic-style immutable database value — the **`Db`**.

```ts
const db = brain.now()                  // pin the current state — O(1), no I/O

await brain.transact([
  { op: 'update', id: invoiceId, metadata: { status: 'paid' } }
], { meta: { author: 'billing-service', reason: 'PO-7741' } })

await db.get(invoiceId)                 // still 'pending' — pinned, forever
await brain.get(invoiceId)              // 'paid' — live
await db.release()                      // unpin when done
```

What you get:

- **`brain.now()`** — pins the current generation as an immutable `Db` view.
  True snapshot isolation: the view reads exactly its pinned state no matter
  what commits afterwards, including deletes. Readers never block writers and
  writers never block readers.
- **`brain.transact(ops, { meta, ifAtGeneration })`** — atomic multi-write
  batches (`add` / `update` / `remove` / `relate` / `unrelate`) committed as
  exactly one generation. Either every operation applies or none do.
  `ifAtGeneration` is whole-store compare-and-swap (`GenerationConflictError`
  on conflict) — the big sibling of the per-entity `ifRev` CAS from 7.31.
  `meta` is reified Datomic-style into an append-only transaction log,
  readable via `brain.transactionLog()`.
- **`brain.asOf(generation | Date | snapshotPath, { exclusive? })`** — time
  travel with the **full query surface**: `get()`, `find()` in every mode,
  semantic search, graph traversal, cursors, aggregation, all at the pinned past
  state. `exclusive: true` pins the generation immediately before the target
  (strict-before).
- **`db.with(ops)`** — speculative writes applied in memory on top of a view.
  Nothing touches disk, the generation counter, or the indexes. What-if
  analysis, then `transact()` the same ops for real.
- **`db.persist(path)`** — instant self-contained snapshots. On filesystem
  storage they are built from hard links (no entity data is copied; later
  writes to the source can never alter the snapshot because rewrites swap
  inodes). `brain.restore(path, { confirm: true })` replaces the whole store
  from one; `Brainy.load(path)` opens one read-only with the full query
  surface.
- **Range verbs over history** — answer "what happened BETWEEN two points":
  - **`db.since(Db | generation | Date)`** — the entity and relationship ids
    committed transactions touched after an **exclusive** lower bound (now
    accepts a generation or `Date`, not just a prior `Db`).
  - **`brain.diff(a, b)`** — the touched ids CLASSIFIED as `{ added, removed,
    modified }` (split by nouns/verbs) by resolving each at both endpoints; a
    touched-but-reverted id lands in none of the buckets. Endpoints are a
    generation, `Date`, or `Db`, in either order.
  - **`brain.history(id, { from?, to? })`** — every distinct version of ONE
    entity/relationship over a range, oldest first (`value: null` marks a
    removal); each version equals `asOf(version.generation).get(id)`.
  - **`brain.transactionLog({ from?, to?, limit? })`** — the commit log over an
    **inclusive** generation/`Date` window (contrast `since`'s exclusive lower
    bound); `limit` applies last.
- **Every write is versioned (Model-B).** History granularity is **per-write**:
  EVERY write — `transact()` AND a single-operation `add`/`update`/`remove`/
  `relate` — is its own immutable generation. A `now()` pin always freezes
  against later writes, and `asOf`/`since`/`diff`/`history`/`transactionLog`
  reflect single-ops exactly like transacts. `transact()` groups several
  operations into ONE atomic generation. Single-op history durability is **async
  group-commit** (the live write is acknowledged immediately; its before-image
  is batched to disk in one fsync) — a hard crash can lose only the last
  un-flushed window's *history*, never live data, and a crash mid-flush is
  recovered by drop-without-restore. A freshly-initialized brain is
  `generation() === 0` with an empty `transactionLog()` (init-time
  infrastructure is the un-versioned baseline); the first user write is gen 1.
- **`new Brainy({ retention })`** — the retention knob governs auto-compaction on
  `flush()`/`close()`: **unset → ADAPTIVE** (disk/RAM-pressure byte budget,
  zero-config; a coordinator can drive it via `brain.setRetentionBudget(bytes)`)
  · **`'all'`** → unbounded · **`{ maxGenerations?, maxAge?, maxBytes? }`** →
  explicit caps (reclaim oldest-unpinned while ANY cap is exceeded). Live pins
  are ALWAYS exempt.
- **`brain.compactHistory({ maxGenerations?, maxAge?, maxBytes? })`** — manual
  reclaim on the same caps. Compaction never breaks a pinned read. `diff`/`since`
  throw `GenerationCompactedError` below the horizon; `history` truncates to it.

The precise guarantees are documented in:

- [docs/concepts/consistency-model.md](docs/concepts/consistency-model.md) —
  the guarantees, each proven by a dedicated test in
  `tests/integration/db-mvcc.test.ts`
- [docs/guides/snapshots-and-time-travel.md](docs/guides/snapshots-and-time-travel.md)
  — the recipes: backup, restore, time-travel debugging, what-if, audit trails
- [docs/ADR-001-generational-mvcc.md](docs/ADR-001-generational-mvcc.md) — the
  design record: persisted layout, commit protocol, crash recovery, proof table

### Portable export & import (PortableGraph v1)

A portable, versioned graph format that serializes part or all of a brain to a
single JSON document and restores it — the cross-environment, cross-version
(7.x↔8.0), partial-or-whole companion to the native `persist()` snapshot.

```ts
// Export is a method on the immutable Db, so it composes with now()/asOf()/with()
const graph = await brain.export({ collection: id }, { includeVectors: true })
await otherBrain.import(graph, { onConflict: 'merge' })  // dedup-by-id

;(await brain.asOf(gen)).export(sel)        // time-travel export
brain.now().with(ops).export(sel)           // what-if export
```

- **`brain.export(selector?, options?)` / `db.export(...)`** → a versioned
  `PortableGraph` document. Selectors reuse `find()`'s grammar: `{ ids }`,
  `{ collection }` (alias `memberOf`, transitive `Contains`),
  `{ connected: { from, depth } }`, `{ vfsPath }`, predicate
  (`{ type, subtype, where, service }`), or the whole brain (omit) — and they
  compose. Options: `includeVectors`, `includeContent` (VFS file bytes),
  `includeSystem`, `edges: 'induced' | 'incident' | 'none'`.
- **`brain.import(graph, options?)`** is polymorphic: a `PortableGraph` document is
  restored as **one atomic transaction** (`onConflict: 'merge' | 'replace' | 'skip'`,
  `reembed: 'auto' | 'never'`, `remapIds` for cloning); a file/buffer routes to the
  existing CSV/PDF/Excel/JSON ingestion. No migration for ingestion callers.
- **`validatePortableGraph(data)`** — dry-run structural/version/endpoint check before import.
- **Format** (`format:'brainy-portable-graph'`, `formatVersion: 1`) is identical on
  7.x and 8.0; standard fields (`subtype`/`visibility`/`data`/…) are top-level,
  `metadata` is custom-only. Current-state (no generation history — that lives in
  `persist()`). Types exported from the package root.
- **Naming:** the type is `PortableGraph` (with `PortableGraphEntity` /
  `PortableGraphRelation`) — it is the portable interchange form of a graph, not a
  backup (that role is `persist()`/`load()`). Renamed from the short-lived
  `BackupData`/`'brainy-backup'` (introduced in 7.32.0, never adopted) with no
  compatibility shim.
- Guide: [docs/guides/export-and-import.md](docs/guides/export-and-import.md).

### Aggregation: distinctCount over any value type

`distinctCount` now counts distinct values of **any** type (strings, booleans,
numbers) — previously it silently returned `0` for non-numeric fields, missing its
primary use (distinct categories / users / tags). `percentile` (with `p`; median =
`p: 0.5`), `stddev`, and `variance` are exact and delete-safe alongside the
write-time `sum`/`count`/`avg`/`min`/`max`.

### Removed surfaces and their replacements

| Removed in 8.0 | Replacement |
|---|---|
| `brain.fork(name)` | Speculation: `db.with(ops)` (in-memory). Long-lived writable copy: `brain.restore()` a persisted snapshot into a fresh data directory. |
| `brain.checkout(branch)` | Open the snapshot you want — `Brainy.load(path)` read-only, or restore into its own directory. No in-place switching: every handle always sees one unambiguous store. |
| `brain.listBranches()` / `brain.getCurrentBranch()` / `brain.deleteBranch()` | A "branch" is now a name → snapshot-path mapping owned by your application. |
| `brain.commit({ message })` | `brain.transact(ops, { meta })` — every batch is an atomic, logged, time-travelable commit; audit fields live in the database, not in commit messages. |
| `brain.getHistory()` / `brain.streamHistory()` | `brain.transactionLog({ limit })` + `db.since(olderDb)`. |
| `brain.versions.*` (`save` / `list` / `compare` / `restore` / `prune`) | A pinned `Db` or persisted snapshot captures *every* entity at that moment; `asOf()` reads any entity's past state; `restore()` for whole-store rollback. |
| `brain.data()` (DataAPI: `clear` / `import` / `export` / `getStats`) | `brain.clear()`, `brain.import()`, `db.persist(path)` (the full-fidelity export format), `brain.restore(path, { confirm: true })`, `brain.stats()`. |
| Cloud + browser storage adapters (`s3` / `gcs` / `r2` / `opfs` storage types, Azure Blob, plus the `storage.branch` option) | `filesystem` and `memory` only. Cloud backup is now an operator concern: `db.persist()` produces a plain directory — sync it with `gsutil` / `aws s3 cp` / `rclone` / `azcopy`. Passing a removed storage type throws at construction with this exact guidance. |
| Browser support | Node.js 22 LTS or Bun ≥ 1.0 (`engines` enforces `node: 22.x`); Deno works through its Node compatibility layer. |
| `brain.migrateToDiskAnn()` / `brain.migrateToHnsw()` | Gone — there is one canonical `'vector'` provider slot. A registered native vector provider selects its own operating mode; there is nothing to call. |
| Distributed-clustering subsystem — `config.distributed`, the `DistributedRole` enum, the 13 `BRAINY_*` cluster env vars (`BRAINY_DISTRIBUTED`, `BRAINY_ROLE`, `BRAINY_HTTP_PORT`, `BRAINY_WS_PORT`, `BRAINY_DNS`, `BRAINY_SERVICE`, `BRAINY_NAMESPACE`, `BRAINY_CONSENSUS`, `BRAINY_COORDINATOR`, `BRAINY_NODES`, `BRAINY_REPLICAS`, `BRAINY_SHARDS`, `BRAINY_TRANSPORT`), the storage `setDistributedComponents` hook, and the `@soulcraft/brainy/config` preset/augmentation registry | Removed. Brainy 8.0 is a single-process library — there is no coordinator, peer discovery, or consensus to operate. Scale via: the optional native provider (`@soulcraft/cor` — on-disk DiskANN to 10B+ vectors on one machine); per-tenant pools (one instance + storage dir per tenant); and horizontal read scaling (many reader processes against one shared store, single writer). The `mode: 'reader' \| 'writer'` multi-process roles are unchanged. |
| CLI `fork` / `branch` / `checkout` / `migrate` | CLI `snapshot <path>` / `restore <path>` / `history` / `generation`. |
| `BrainyZeroConfig` type | Removed. 8.0 zero-config is automatic and internal — `new Brainy()` auto-detects storage, derives HNSW quality from `config.vector.recall`, picks `persistMode` from the adapter, and sizes caches to the detected container-memory limit. There is no config-generation type to import. |
| `brain.isFullyInitialized()` / `brain.awaitBackgroundInit()` | `await brain.ready`. The built-in filesystem/memory adapters finish initialization synchronously inside `init()`, so a single readiness promise is the whole story — these methods were no-ops once cloud adapters were removed. |

**Opening a 7.x store auto-migrates it.** 8.0 stores entities at the root; 7.x
stored them branch-scoped under `branches/<branch>/`. On first open, 8.0 collapses
the **HEAD branch** (`config.storage.branch`, default `main`) to the 8.0 layout in
place and rebuilds all derived state — no action required (`autoMigrate` defaults
to `true`; set it to `false` to make 8.0 refuse a legacy layout with an explicit
error instead). Two caveats:

- **Non-HEAD branches are not imported.** 8.0 has no COW branches; only the head
  branch's data is migrated. If you care about other branches, **export each one
  while still on 7.x** (`fork → export`, or copy its store).
- **Back up first for rollback.** The migration mutates the directory in place and
  8.0 does not keep the old layout — copy the data directory before the first 8.0
  open if you need to roll back.

### Renames — find/replace pairs

Hard renames, no aliases. Every pair below is verified against the 8.0 source.

| Brainy 7.x | Brainy 8.0 |
|---|---|
| `brain.delete(id)` | `brain.remove(id)` — matches the transact op vocabulary (`add` / `update` / `remove` / `relate` / `unrelate`) |
| `brain.deleteMany(params)` | `brain.removeMany(params)` |
| `DeleteManyParams` (type) | `RemoveManyParams` |
| `brain.getRelations(paramsOrId)` | `brain.related(paramsOrId)` — the same name a pinned `Db` exposes (`db.related()`) |
| `GetRelationsParams` (type) | `RelatedParams` |
| CLI `delete <id>` | CLI `remove <id>` (JSON output `{ id, removed: true }`, matching `unrelate`) |
| `HnswProvider` (from `@soulcraft/brainy/plugin`) | `VectorIndexProvider` |
| `HNSWIndex` (exported class) | `JsHnswVectorIndex` |
| Provider keys `'hnsw'` and `'diskann'` | `'vector'` (the only key Brainy consults for the vector index) |
| `config.hnsw = { quantization, vectorStorage }` | `config.vector = { recall?, persistMode? }` (shape change — see below) |
| `config.vector.quantization` (and 7.x `config.hnsw.quantization`) | **Removed.** The JS vector path is full-precision (exact float32 distances) only — quantization at scale is the native provider's job (e.g. DiskANN PQ). |
| `hnswPersistMode: 'immediate' \| 'deferred'` (top level) | `config.vector.persistMode` (auto-selected from the storage adapter when omitted: `'immediate'` on filesystem, `'deferred'` on memory) |
| `config.storage.type: 's3' \| 'gcs' \| 'r2' \| 'opfs'` | `'filesystem'` (or `'memory'` / `'auto'`) |
| `config.storage.branch` | Removed (no COW branches) |
| `brain.stats().indexHealth.hnsw` | `brain.stats().indexHealth.vector` |
| Storage adapter contract `saveHNSWData()` / `getHNSWData()` | `saveVectorIndexData()` / `getVectorIndexData()` |
| Cache category `'hnsw'` (`CacheProvider` union) | `'vectors'` |
| `config.history = { retainGenerations, retainMs, autoCompact }` | `config.retention` — `'all'` \| `'adaptive'` \| `{ maxGenerations?, maxAge?, maxBytes?, budgetBytes?, autoCompact? }`; **unset → adaptive** (was keep-100/7-days). The fields are now **caps**, not floors. |
| `compactHistory({ retainGenerations, retainMs })` | `compactHistory({ maxGenerations, maxAge, maxBytes })` — `retainGenerations`→`maxGenerations`, `retainMs`→`maxAge` (now upper-bound CAPS), plus new `maxBytes`. |
| `CompactHistoryOptions.retainGenerations` / `.retainMs` | `.maxGenerations` / `.maxAge` (+ `.maxBytes`) |

Mechanical renames as one command (run from your repo root, review the diff):

```bash
find . -name '*.ts' -not -path '*/node_modules/*' -print0 | xargs -0 sed -i \
  -e 's/\bHnswProvider\b/VectorIndexProvider/g' \
  -e 's/\bHNSWIndex\b/JsHnswVectorIndex/g' \
  -e 's/\bsaveHNSWData\b/saveVectorIndexData/g' \
  -e 's/\bgetHNSWData\b/getVectorIndexData/g' \
  -e 's/indexHealth\.hnsw\b/indexHealth.vector/g' \
  -e "s/registerProvider('hnsw'/registerProvider('vector'/g" \
  -e "s/registerProvider('diskann'/registerProvider('vector'/g" \
  -e "s/getProvider('hnsw'/getProvider('vector'/g" \
  -e "s/getProvider('diskann'/getProvider('vector'/g" \
  -e 's/\.getRelations(/.related(/g' \
  -e 's/\bGetRelationsParams\b/RelatedParams/g' \
  -e 's/\.deleteMany(/.removeMany(/g' \
  -e 's/\bDeleteManyParams\b/RemoveManyParams/g'
```

`delete()` → `remove()` is deliberately **not** in the snippet: `.delete(` is
too common (`Map`/`Set`/storage adapters) for a blind sed. Find your
`brain.delete(...)` call sites and rename them by hand.

The config shape changes need a human (they are not 1:1 textual):

```ts
// 7.x
new Brainy({
  hnswPersistMode: 'deferred',
  hnsw: { quantization: { enabled: true, bits: 8, rerankMultiplier: 3 } }
})

// 8.0 — config.vector is { recall?, persistMode? }
new Brainy({
  vector: {
    recall: 'balanced',        // 'fast' | 'balanced' | 'accurate'
    persistMode: 'deferred'    // optional; auto-selected from storage when omitted
  }
})
```

`config.vector.recall` replaces the algorithm-internal HNSW knobs: `'balanced'`
(the default) maps to exactly the 7.x default parameters, so an upgrade without
explicit knobs changes nothing about search behaviour. `config.vector.quantization`
and `config.hnsw.vectorStorage` are removed: the JS vector path now computes exact
float32 distances throughout (no rerank/approximate branch), which is what made
its quantization a memory *increase* — it stored both the full and the quantized
vectors in RAM. Quantization at scale belongs to the native provider's own PQ.
The on-disk vector index file names are **unchanged** (e.g. `hnsw-system.json`) —
existing filesystem stores need no data migration for this rename; only the API
surface moved.

### Behavior changes

- **`subtype` is required by default.** 7.30's opt-in strict mode is now the
  default: every `add()` / `addMany()` / `update()` / `relate()` /
  `relateMany()` / `updateRelation()` rejects writes whose type carries no
  non-empty `subtype` (`src/brainy.ts:9759` — `requireSubtype ?? true`).
  Escape hatches: `requireSubtype: false` (last-resort opt-out for legacy
  data) or `requireSubtype: { except: [NounType.Thing, ...] }` (per-type
  allowlist). Per-type rules registered via `brain.requireSubtype(type, opts)`
  still compose. `brain.audit()` reports entries missing a subtype and the new
  `brain.fillSubtypes(rules)` migration helper backfills them — one rule per
  NounType/VerbType (literal default or per-entry function), applied only to
  entries still missing a subtype, returning
  `{ scanned, filled, skipped, errors, byType }`. Idempotent: re-running fills
  nothing, so a crashed run is resumed by running it again.
- **Verb ids are Brainy-generated UUIDs — by contract.** `relate()` now throws
  a teaching error if a caller passes an `id` field
  (`src/utils/paramValidation.ts:526`). In 7.x a supplied id was silently
  ignored (a generated UUID was used anyway); 8.0 says so out loud, because
  graph-index providers key verb-int interning on the raw UUID bytes.
- **`update({ vector })` is honored on its own.** 7.x only applied a supplied
  pre-computed vector when `data` was also passed (it was silently dropped
  otherwise). 8.0 applies an explicit `params.vector` with dimension
  validation (`src/brainy.ts:1702-1713`; proven by
  `tests/unit/brainy/update.test.ts:256`).
- **`brain.clear()` re-resolves all indexes exactly as `init()` does** —
  including plugin-provided vector/metadata/entityIdMapper factories and VFS
  root re-creation. In 7.x, clearing a plugin-accelerated brain could leave
  the metadata index rebuilt without its native id-mapper wiring.
- **`find({ connected: { …, subtype } })` with `depth > 1` now works.** 7.30
  threw `NOT_SUPPORTED` for multi-hop subtype-filtered traversal; 8.0
  implements the BFS in the JS graph index and routes to a native provider
  when one is registered.
- **Every write advances the generation clock; only `transact()` writes
  history.** Single-operation writes (`add` / `update` / `remove` / `relate`
  outside `transact()`) bump `brain.generation()` so watermarks and CAS stay
  sound, but they do not stage historical records — they remain visible
  through earlier pins and are not reported by `db.since()`. Writes you want
  to travel back through go through `transact()`. This is the documented
  contract, stated rather than papered over.
- **Reserved fields have one canonical location — enforced at every layer.**
  The Brainy-owned field names (`RESERVED_ENTITY_FIELDS`:
  `noun`/`subtype`/`createdAt`/`updatedAt`/`confidence`/`weight`/`service`/
  `data`/`createdBy`/`_rev`; verb mirror `RESERVED_RELATION_FIELDS` with
  `verb` for the type key) are now (1) a **compile error** inside any
  `metadata` param — `add`/`update`/`relate`/`updateRelation` and the
  matching `transact()` ops; (2) **normalized at write time** for untyped
  callers — user-settable fields remap to their dedicated top-level param
  (top-level wins; `update({metadata:{confidence}})` no longer silently
  no-ops, closing a 7.x trap), system-managed fields drop with a one-shot
  warning naming the right path; (3) **split at read time** through one
  canonical helper, so `entity.metadata` / `relation.metadata` contain ONLY
  custom fields on every read path — `get`, `find`, `related` (several
  paginated/by-source/by-target paths previously echoed the full stored
  record, including the `verb` type key, inside `metadata`), batch reads,
  and historical `asOf()` reads. `related()` results now also surface
  `confidence`/`updatedAt` top-level, and `updateRelation()` no longer
  erases a relationship's `service`/`createdBy`. See "Reserved fields" in
  `docs/concepts/consistency-model.md`.
- **Named errors for not-found contract failures.** `update()`, `relate()`,
  `updateRelation()`, `similar({ to: id })`, `transact()` planning, and
  speculative `db.with()` planning now throw `EntityNotFoundError` /
  `RelationNotFoundError` (both exported from the package root, both carrying
  the missing `id` as a field) instead of a generic `Error`. Message texts are
  unchanged, so existing `/not found/` matching keeps working — `instanceof`
  is now the supported way to branch.
- **Unchanged from 7.31:** per-entity `_rev`, `update({ ifRev })`
  (`RevisionConflictError`), and `add({ ifAbsent })` work exactly as before,
  and `ifRev` is also accepted on `transact()` update operations (a conflict
  rejects the whole batch).

### For provider and plugin authors

The provider contracts in `@soulcraft/brainy/plugin` (`src/plugin.ts`) changed
shape:

- **`GraphIndexProvider` speaks BigInt at the boundary.** Reads take entity
  ints and return entity/verb ints as `bigint[]`; the coordinator owns all
  UUID ↔ int conversion. `addVerb(verb, sourceInt, targetInt)` receives the
  resolved endpoint ints (also mirrored on the new optional
  `GraphVerb.sourceInt` / `GraphVerb.targetInt` fields) and returns the
  interned verb int. The batch reverse resolver
  `verbIntsToIds(verbInts: bigint[]): Promise<(string | null)[]>` is
  **required** — the provider owns durable verb-int interning; Brainy keeps
  only a bounded in-memory warm cache. Implementations may stay u32 internally
  (`Number(bigint)` narrowing is lossless under the `EntityIdSpaceExceeded`
  guard) but must speak the bigint contract.
- **`VersionedIndexProvider`** is a new optional 4-method capability —
  `generation()`, `isGenerationVisible(g)`, `pin(g)`, `release(g)`, BigInt
  generations — feature-detected on every registered index provider. Providers
  are *post-commit appliers*: the storage-record commit is the source of
  truth; on open, a provider behind the committed watermark replays the gap or
  requests a rebuild. Explicit pins override any time-based snapshot retention
  the provider has. Speculative `db.with()` overlays never reach providers. A
  provider implementing this serves historical reads with **no rebuild** —
  the open-core materializer is the correctness baseline, the provider is the
  accelerator.
- **The vector index registers under `'vector'`** and implements
  `VectorIndexProvider`. The `'hnsw'` and `'diskann'` keys are retired and
  never looked up. `CacheProvider`'s category union uses `'vectors'` in place
  of `'hnsw'`.

### Scale and cost — how the mechanisms behave

Mechanism descriptions, not benchmark numbers (none are published for 8.0 yet):

- `brain.now()` pins in O(1) and adds **zero read overhead until history
  actually moves** — while nothing has committed past the pin, every read
  delegates to the live fast paths.
- A `transact()` commit pays O(ids touched) extra writes (before-images +
  delta + manifest) — never O(store size). Single-operation writes pay an
  in-memory counter bump with coalesced persistence.
- `db.persist()` on filesystem storage is a hard-link farm: snapshot creation
  copies no entity data and the snapshot shares disk space with the source.
  Cross-device targets fall back to per-file byte copies; persisting an
  in-memory brain serializes a real, durable, loadable store.
- Historical **index-accelerated** queries (semantic search, traversal,
  cursors, aggregation) on the open-core path pay a one-time O(n at the
  pinned generation) in-memory index materialization per `Db`, cached until
  `release()`. Record-path reads (`get`, metadata `find`, filter `related`)
  at any reachable generation are served directly from the immutable record
  layer. A native `VersionedIndexProvider` serves the same reads rebuild-free.

The full cost model is in
[docs/concepts/consistency-model.md](docs/concepts/consistency-model.md).

### Upgrade checklist (from 7.x)

1. **While still on 7.x:** back up your data directory (a plain file copy is
   fine). If you used COW branches, materialize each branch you need — 8.0
   does not read branch state. If you ran a cloud storage adapter, export your
   data with 7.x tooling (`(await brain.data()).export()`) — 8.0 opens
   `filesystem` and `memory` stores only.
2. **Runtime:** Node.js 22 LTS or Bun ≥ 1.0.
3. **Config:** change removed storage types to `'filesystem'`; delete
   `storage.branch`; move `config.hnsw` / `hnswPersistMode` to
   `config.vector` per the shape example above.
4. **Renames:** run the sed snippet, then fix the manual shape changes.
5. **Removed APIs:** replace `fork` / `checkout` / branch methods / `commit` /
   `getHistory` / `streamHistory` / `versions` / `data()` per the table above.
6. **Subtypes:** if your data predates subtype discipline, start with
   `requireSubtype: false`, run `brain.audit()`, backfill with
   `brain.fillSubtypes(rules)` (one rule per type — a literal default or a
   function deriving the subtype from each entry), re-run `audit()` until
   `total === 0`, then remove the opt-out so the 8.0 default enforcement
   protects you going forward.
7. **CLI scripts:** `fork` / `branch` / `checkout` / `migrate` →
   `snapshot <path>` / `restore <path>` / `history` / `generation`.
8. **Plugin authors:** apply the contract renames and the BigInt graph
   contract; optionally implement `VersionedIndexProvider`.
9. **Verify, then take your first snapshot:** run your test suite, then
   `const db = brain.now(); await db.persist('/backups/post-8.0-upgrade');
   await db.release()`.

What did **not** change: the core query surface (`find` / `search` / `get` /
`add` / `update` / `relate` and friends), the aggregation engine, the VFS,
neural extraction, and the on-disk entity/relationship layout — 8.0 creates
its MVCC bookkeeping (`_system/generation.json`, `_system/manifest.json`,
`_system/tx-log.jsonl`, `_generations/`) alongside the existing files on
first use.

### Native-provider (Cor) compatibility

Brainy 8.0 pairs with `@soulcraft/cor` 3.0 — the renamed successor to the
`@soulcraft/cortex` 2.x native provider — shipping in lockstep. The old
`@soulcraft/cortex` 2.x cannot accelerate Brainy 8.0: 8.0 never consults the
`'hnsw'` / `'diskann'` provider keys, and the graph/column provider contracts
are BigInt at the boundary. Upgrade both packages together (`@soulcraft/brainy@8`
+ `@soulcraft/cor@3`).

---

## v7.31.2 — 2026-06-09

**Affected products:** none in behaviour; affects anyone reading Brainy's TypeScript
type definitions or coreTypes for the `hnsw.quantization.bits` option. Drop-in from 7.31.1.

### Fix: stale comment claimed SQ4 vector quantization required a paid native provider

Brainy ships a pure-JS SQ4 distance implementation (`distanceSQ4Js` in
`src/utils/vectorQuantization.ts`) that's been part of the open-core path the whole
time. Two type-definition comments incorrectly stated SQ4 required a native (paid)
provider:

```ts
// coreTypes.ts:472 + types/brainy.types.ts:1123 — before
bits?: 8 | 4   // default: 8 (SQ8). SQ4 requires cortex native.
```

The comment was simply wrong — open-core users can use SQ4 today, and the native SIMD
acceleration is a drop-in via `setSQ4DistanceImplementation`, not a hard requirement.
Corrected to:

```ts
bits?: 8 | 4   // default: 8 (SQ8). SQ4 has a pure-JS implementation;
               // cortex's distance:sq4 SIMD provider accelerates it.
```

Both locations updated. Pure documentation; no behaviour change. Caught during an
upstream open-core-boundary audit — thanks to whoever read the types carefully enough
to spot the misleading comment.

### Cortex compatibility

Zero changes required. The fix is documentation only; runtime behaviour was already
correct (`vectorQuantization.ts:412` ships `distanceSQ4Js`).

---

## v7.31.1 — 2026-06-09

**Affected products:** any consumer running `@soulcraft/brainy` against `FileSystemStorage`
that triggers concurrent flush / compaction (e.g. explicit `brain.flush()` calls overlapping
with periodic background compaction, or a backup job + a flush job racing). Production-impacting
when present: `brain.flush()` throws `ENOENT` on rename, downstream jobs that rely on flush
(GCS / S3 / Azure backups, snapshot exports) fail continuously. Drop-in from 7.31.0.

### Fixes a same-key rename race in `saveBinaryBlob`

`FileSystemStorage.saveBinaryBlob` used a bare `${filePath}.tmp` suffix for its atomic-write
temp file. Two concurrent same-key calls computed the **same** temp path; both `writeFile`d,
the first `rename` succeeded, the second `rename` fired against a missing temp and threw
`ENOENT`. The throw propagated up through `brain.flush()` and broke any downstream job that
called it.

```
[job-queue] gcs-backup: failed — ENOENT: no such file or directory,
  rename '/data/brainy-data/.../_column_index/owner/DELETED.bin.tmp'
       -> '/data/brainy-data/.../_column_index/owner/DELETED.bin'
```

**Patch:** unique per-writer temp suffix (matches the pattern at six other atomic-write
sites in the same file) + ENOENT swallow on rename (defensive: if the temp is gone, the
work has already landed; `saveBinaryBlob` is idempotent for a given key) + temp cleanup
on any other rename failure (no orphan `.tmp.*` files).

```ts
// before (7.31.0)
const tmpPath = filePath + '.tmp'
await fs.promises.writeFile(tmpPath, data)
await fs.promises.rename(tmpPath, filePath)

// after (7.31.1)
const tmpPath = `${filePath}.tmp.${process.pid}.${Date.now()}.${Math.random().toString(36).slice(2)}`
await fs.promises.writeFile(tmpPath, data)
try {
  await fs.promises.rename(tmpPath, filePath)
} catch (err) {
  if ((err as NodeJS.ErrnoException).code === 'ENOENT') return
  await fs.promises.unlink(tmpPath).catch(() => {})
  throw err
}
```

### Scope

The fix is one site — `src/storage/adapters/fileSystemStorage.ts:992-999`. Audit results:

- **`FileSystemStorage`** — six sibling atomic-write sites already used unique suffixes;
  only `saveBinaryBlob` was the outlier. All six were rechecked. Clean.
- **`OPFSStorage`** — writes via WritableStream (no tmp+rename). Not affected.
- **`GCSStorage` / `R2Storage` / `AzureBlobStorage` / `S3CompatibleStorage`** — use
  object-store `PUT` (atomic at the API). Not affected.
- **`MemoryStorage`** — in-memory. Not affected.
- **`HistoricalStorageAdapter`** — read-only. Not affected.
- **COW / versioning / snapshot / HNSW / aggregation** — all delegate to storage adapters
  via `saveBinaryBlob` / `writeObjectToPath`. They get the fix automatically by virtue of
  using the patched primitive.

### Beneficiary surfaces (broader than the reported bug)

Column-store compaction (`_column_index/<field>/DELETED.bin`, segment files) is what the
production report named, but `saveBinaryBlob` is also used by HNSW connection persistence
(`_hnsw_conn/<nodeId>` — `src/hnsw/hnswIndex.ts:252`). If two flush paths ever raced on
HNSW persistence for the same node, they would have hit the same ENOENT. No production
reports of HNSW-side failures, but the fix removes the latent race.

### Tests

- **New `tests/integration/savebinaryblob-concurrent-rename.test.ts`** (4 tests):
  - 20 concurrent `saveBinaryBlob(sameKey, ...)` calls all resolve without throwing
  - No orphan `.tmp.*` siblings remain in the blob directory after concurrent writes
  - Production-shape: two concurrent compactor passes over 10 column-index fields
    (`owner`, `path`, `permissions`, `vfsType`, `modified`, `createdAt`, `accessed`,
    `updatedAt`, `mimeType`, `size`)
  - Single-writer path still produces correct bytes (no regression)
- The first three tests reproduce the production `ENOENT: rename '...DELETED.bin.tmp' ->
  '...DELETED.bin'` error verbatim on the pre-7.31.1 code path. Verified by stashing the
  fix and watching the tests fail with the exact production error.
- Existing suites unchanged: 1468/1468 unit. All integration suites pass.

### Cortex compatibility

Zero changes required. The bug and the fix are pure JS in the filesystem storage adapter;
the Cortex mmap-filesystem adapter wraps `FileSystemStorage` and inherits the patch
automatically.

### Forward-compat

The bare-`.tmp` pattern is gone repo-wide. 8.0's `Db.persist()` will route through the
same patched primitive; no additional work needed when the immutable Db API ships.

---

## v7.31.0 — 2026-06-09

**Affected products:** consumers that need multi-writer coordination (job
schedulers, idempotent state machines, distributed locks, optimistic UI updates)
or idempotent bootstrap of well-known singletons. Additive; drop-in from 7.30.2.

### Per-entity `_rev` + `update({ ifRev })` + `add({ ifAbsent })`

CouchDB / PouchDB / ETag-style optimistic concurrency. Every entity now carries a
monotonic `_rev: number` that Brainy auto-bumps on every successful `update()`.
Pass it back as `ifRev` to make read-modify-write race-safe without an external
lock service. `ifAbsent` adds by-ID idempotent insert for singletons / config rows
/ deterministic-ID bootstraps.

**What's new:**

- **`entity._rev: number`** — initialized to `1` on `add()`, bumped by `1` on every
  successful `update()` that reaches storage. Surfaced on `get()` (both fast metadata-
  only and full-vector paths), `find()`, `search()`, and on the `Result` flatten layer
  for backward compatibility. Pre-7.31.0 entities without `_rev` are read as `1`.
- **`update({ id, ..., ifRev: number })`** — optimistic-concurrency check. When
  provided, throws `RevisionConflictError` if the persisted `_rev` no longer matches.
  Carries `{ id, expected, actual }` for principled recovery. Omitting `ifRev` keeps
  the prior unconditional-update behavior.
- **`add({ id, ifAbsent: true })`** — by-ID idempotent insert. Returns the existing
  `id` without writing if the entity already exists. No throw, no overwrite. Ignored
  when `id` is omitted (a fresh UUID can never collide).
- **`addMany({ items, ifAbsent: true })`** — applies the flag to every item; per-item
  `ifAbsent` overrides the batch flag.

### The lock recipe (single-process or distributed)

```ts
import { Brainy, RevisionConflictError } from '@soulcraft/brainy'

const LOCK_ID = '...uuid...'

await brain.add({
  id: LOCK_ID,
  type: NounType.Document,
  data: { owner: null, expiresAt: 0 },
  ifAbsent: true
})

async function tryAcquireLock(workerId: string, ttlMs: number) {
  const lock = await brain.get(LOCK_ID)
  if (!lock) throw new Error('lock document missing')
  const state = lock.data as { owner: string | null; expiresAt: number }
  if (state.owner && state.expiresAt > Date.now()) return false

  try {
    await brain.update({
      id: LOCK_ID,
      data: { owner: workerId, expiresAt: Date.now() + ttlMs },
      ifRev: lock._rev
    })
    return true
  } catch (err) {
    if (err instanceof RevisionConflictError) return false
    throw err
  }
}
```

### Why this is scoped to `_rev` + `ifAbsent`

A public `brain.transaction(fn)` wrapper was on the table but was cut. The internal
`TransactionManager` exposes raw `Operation` classes that take a `StorageAdapter`
constructor argument; a high-level facade in 7.31.0 would have meant either
(a) delegating to `brain.add()` / `update()` / `relate()` — each of which commits
its own internal transaction before the closure returns, so multi-write rollback
wouldn't actually work (a footgun), or (b) threading `tx?` through every internal
write path — ~2 days of refactor with regression surface, and the API shape changes
again in 8.0 anyway.

The SDK-scheduler use case that drove the thread (read-then-CAS lock pattern) is
fully solved by `_rev` + `ifRev`. Multi-write atomicity is the 8.0 `brain.transact()`
use case, where the Datomic-style immutable Db makes it atomic by construction. We
chose not to ship a worse version in the interim.

### How `_rev` interacts with branches and the snapshot API

| System | What it tracks | When it advances |
|---|---|---|
| `_rev` (NEW) | Per-entity write counter | Auto, on every successful `update()` |
| `brain.versions.save()` | Named snapshots per entity | Explicit — you call `save()` |
| `brain.fork()` / branches | Whole-brain copy-on-write | Explicit — you call `fork(name)` |
| VFS file versioning | Per-VFS-file snapshots | Same as `brain.versions.save()` |

`_rev` is independent. Each branch has its own copy of every entity, so each
branch has its own `_rev` per entity (same as every other field under COW).
Snapshots taken via `brain.versions.save()` capture the entity at that moment
including its `_rev` at that time; the snapshot's own `version: number` is the
snapshot index, distinct from `_rev`.

### Docs

- **New `docs/guides/optimistic-concurrency.md`** (public, indexed at
  soulcraft.com/docs after portal deploy) — full reference: the lock pattern,
  read-modify-write retry, idempotent bootstrap, how `_rev` interacts with branches /
  snapshots / VFS, what's coming in 8.0.
- `docs/api/README.md` `add()` and `update()` entries get the new params + tips
  pointing at the guide.

### Tests

- **New `tests/integration/rev-and-ifabsent.test.ts`** (18 tests): rev initialization,
  rev bump on update, ifRev pass / fail / omit / legacy-entity-fallback, ifAbsent
  with custom id / no id / batch propagation / per-item override, plus a full
  SDK-scheduler-style two-concurrent-CAS-updaters scenario.
- Existing suites unchanged: subtype-and-facets 26/26, verb-subtype-and-enforcement
  30/30, strict-mode-self-test 13/13, find-limits 9/9. Unit 1468/1468.

### Cortex compatibility

Zero changes required. `_rev` is a metadata column already supported by
`NativeColumnStore`; the auto-bump runs in Brainy JS before any storage call.
Cortex never sees the per-entity counter — it's a single integer field updated
alongside every other metadata field on the existing write paths.

### 8.0 forward-compat

`_rev`, `ifRev`, `RevisionConflictError`, and `ifAbsent` all survive the 8.0 Db
redesign unchanged. 8.0 layers `brain.transact(tx, { ifAtGeneration })` for
whole-tx CAS on top of the same per-entity mechanism — per-entity for single-record
patterns, generation-based for "did the world move under me."

---

## v7.30.2 — 2026-06-08

**Affected products:** any consumer with `find({ limit })` call sites that pass values
≥ ~9000 — a common safety-cap pattern in production code (`limit: 10_000` against
type-filtered queries that typically return 10–500 entities). Additive; drop-in
from 7.30.1.

### Why

Brainy 7.30 introduced a memory-derived cap on `find({ limit })` to prevent OOM
from runaway queries. The cap was sound in intent but **~4× too conservative in
calibration**: the formula assumed 100 KB per result while typical entity footprint
is 7-10 KB (384-dim float32 vector ≈ 1.5 KB + standard fields + metadata). On a 900 MB
free-memory box this capped `limit` at 9000, breaking production dashboards where
cascading 500s from queries with `limit: 10_000` silently degraded the `Promise.all`
loading the canvas.

7.30.2 recalibrates the formula and changes the enforcement from synchronous-throw
to two-tier (warn-then-throw) so existing pre-7.30 code doesn't break on upgrade.

### Recalibrated formula — `25 KB` per result (was `100 KB`)

The auto-configured cap now uses a realistic per-result size:

| Memory source | 7.30.0–7.30.1 cap | 7.30.2 cap |
|---|---|---|
| 4 GB Cloud Run container | 10 000 | 40 000 |
| 2 GB container | 5 000 | 20 000 |
| 900 MB free system memory | 9 000 | ~36 000 |
| `reservedQueryMemory: 1 GB` | 10 000 | 40 000 |

Hard ceiling stays at 100 000. Existing `BrainyConfig.maxQueryLimit` /
`reservedQueryMemory` overrides continue to work unchanged.

### Two-tier enforcement — warn, then throw

**Below cap (`limit ≤ maxLimit`):** silent pass. No signal, no friction. Unchanged.

**Soft tier (`maxLimit < limit ≤ 2 × maxLimit`)** *NEW*: one-time warning per call
site (dedup keyed on stack location + limit value), query proceeds. Pre-7.30.2 code
that relied on the cap silently allowing safety-cap limits keeps working — the
warning teaches the recipe so consumers can fix it intentionally.

**Hard tier (`limit > 2 × maxLimit`)** *NEW*: throw with the same message format the
warning uses. Real OOM territory; the cap stops being a recommendation and becomes
a guardrail.

The 2× soft margin is chosen to absorb existing safety-cap patterns (`limit: 10_000`
against a 9 K-cap box) without disabling OOM protection. Real OOM territory on a JS
in-memory brain is hundreds of thousands of results, not 10× the safety cap.

### Improved error / warning message (mirrors the 7.30.1 enforcement-error format)

Before (7.30 → 7.30.1):
```
limit exceeds auto-configured maximum of 9000 (based on available memory)
```

After (7.30.2):
```
find({ limit: 10000 }) exceeds the auto-configured query limit of 9000 (basis:
available free memory). Choose one:
  • Increase the cap: new Brainy({ maxQueryLimit: 10000 })
  • Reserve more memory: new Brainy({ reservedQueryMemory: 256000000 })
  • Paginate: split the query with { limit, offset } pages
  at OrderService.loadDashboard (/app/src/orders/dashboard.ts:142:18)
Docs: https://soulcraft.com/docs/guides/find-limits
```

Caller location comes from the same `findCallerLocation()` helper introduced in
7.30.1 (now extracted to `src/utils/callerLocation.ts` so both subtype enforcement
and limit enforcement share it).

### New docs

New `docs/guides/subtypes-and-facets.md`-style guide at
`docs/guides/find-limits.md` (public, indexed) — explains the cap, the four memory
sources the auto-config considers, the three escape valves (`maxQueryLimit`,
`reservedQueryMemory`, pagination), and when to use which. Explicit "pagination is
the future-proof pattern" callout — the cap can get tighter in 8.0 (Datomic-style
`Db.find()` may make per-call limits stricter to keep snapshot semantics cheap),
but pagination keeps working unchanged.

`docs/api/README.md` `find()` entry gets a one-paragraph `limit` tip + pointer
to the new guide.

### Tests

- **New `tests/integration/find-limits.test.ts`** (9 tests): below-cap silent
  pass; soft-tier warns once per call site (dedup verified by exercising same vs.
  different source lines); soft-tier message format (names all three escape
  valves + docs link); soft-tier message includes caller location; hard-tier
  throws; hard-tier message format same as soft-tier; consumer `maxQueryLimit`
  override raises the cap and shifts both tiers accordingly; **the pre-7.30.2
  regression scenario** explicitly covered — `limit: 10_000` against a
  `maxQueryLimit: 9000` cap now warns and passes instead of throwing.
- Existing unit tests in `tests/unit/utils/memoryLimits.test.ts` updated to
  reflect the recalibrated formula (5 tests: hardcoded values for
  container / reserved / free-memory paths bumped 4×).
- Existing `paramValidation.test.ts` "should auto-limit based on system memory"
  test extended to cover the new three-tier semantics (below-cap pass /
  soft-tier silent / hard-tier throw).
- All prior suites still green: subtype-and-facets 26/26, verb-subtype-and-
  enforcement 30/30, strict-mode-self-test 13/13. Unit 1468/1468.

### Cortex compatibility

**No Cortex changes required for 7.30.2.** Every change is JS-side: formula
recalibration runs in `ValidationConfig.constructor()`, two-tier enforcement runs
in `validateFindParams()`, both fire before any storage/index/Cortex call. Cortex
2.x and the pending Cortex 3.0 work both stay compatible without code changes.

The new `docs/guides/find-limits.md` calls out that 8.0's Datomic-style `Db.find()`
may tighten per-call limits; that's a Brainy 8.0 / Cortex 3.0 coordination point
whose rollout staging now also covers query limits.

### What consumers should do

- **If you've been carrying a `limit: 9000` workaround for the 7.30.0–7.30.1
  cap:** drop it on bump to 7.30.2 — existing `limit: 10_000` patterns now
  warn (teaching the recipe) but no longer throw. The warning is
  one-time-per-call-site, so production logs don't spam.
- **All other consumers:** no action required if no enforcement-error was being
  hit. If you see new `[Brainy]` warnings in logs after upgrade, follow the
  recipe in the warning or read `docs/guides/find-limits.md`.
- **SDK wrappers:** wrapper-level pools that auto-construct `Brainy` instances
  should consider surfacing `maxQueryLimit` / `reservedQueryMemory` as
  consumer-facing config; Brainy now documents the knob explicitly.

---

## v7.30.1 — 2026-06-08

**Affected products:** anyone running a brain where a platform layer (SDK, framework wrapper)
has registered `brain.requireSubtype()` rules on common NounTypes, AND anyone preparing for
the upcoming Brainy 8.0 default-on strict mode. Additive; drop-in from 7.30.0. No behavior
change for consumers not using strict-mode enforcement.

### Why

Production incident 2026-06-08: a consumer using SDK 3.20.0 (which registers
`requireSubtype()` rules on `NounType.{Event, Collection, Message, Contract, Media, Document}`)
saw their booking flow start returning 500s because `brain.add({ type: NounType.Event, ... })`
calls in their codebase lacked `subtype`. An audit of Brainy's OWN source revealed 14 HIGH-risk
internal write paths that also omit subtype — VFS move/copy/symlink edges, aggregation
materializer, neural extraction, importers, integrations (Sheets/OData), MCP client, CLI.
Any consumer running `requireSubtype()` rules on those NounTypes was one step away from breaking
Brainy's own infrastructure paths, not just their own code. 7.30.1 closes both gaps before
8.0 ships and makes strict mode the default.

### New — `brain.audit()` diagnostic

Find entities and relationships missing a `subtype` value, grouped by type. The companion to
`migrateField()` (and to 8.0's `fillSubtypes()`): answers "what would break if I enabled
strict subtype enforcement?".

```typescript
const report = await brain.audit()
// {
//   entitiesWithoutSubtype: { event: 24, document: 3 },
//   relationshipsWithoutSubtype: { relatedTo: 1402 },
//   total: 1429,
//   scanned: 8400,
//   recommendation: 'Found 1429 entries without subtype. Migrate via `brain.migrateField()`
//                    (7.x) — or wait for `brain.fillSubtypes()` (8.0) which closes the same
//                    gap with caller-supplied rules.'
// }
```

VFS infrastructure entities are excluded by default (they bypass enforcement via
`metadata.isVFSEntity` markers). Pass `{ includeVFS: true }` to surface them.

### New — Improved enforcement error messages

The error fired when subtype enforcement rejects a write now includes:

1. **The caller's source location** — extracted from the JavaScript stack so you see your own
   call site, not a Brainy internal frame. Eliminates the "grep your repo for `brain.add`" step.
2. **Specific guidance** — points at the registered vocabulary when one exists; mentions
   brain-wide strict mode and the `except` escape valve when not; otherwise the
   `brain.requireSubtype()` registration recipe.
3. **A documentation link** — `https://soulcraft.com/docs/guides/subtypes-and-facets#strict-mode`
   for the canonical migration recipe.

Before:
```
add(): NounType.Event requires subtype but got undefined. Register vocabulary via brain.requireSubtype().
```

After:
```
add(): NounType.event requires subtype but got undefined.
  at OrderService.getOrCreateByToken (/app/src/orders/draft.ts:42:23)
  Pass one of: standard, recurring, milestone.
  Migration recipe: https://soulcraft.com/docs/guides/subtypes-and-facets#strict-mode
```

### Internal subtype labels — Brainy's own infrastructure paths

Every internal Brainy write path now sets a stable, queryable `subtype`. Consumers don't need
to do anything for these — they're documented here so you can query Brainy-managed data:

| Code path | NounType / VerbType | Subtype label |
|---|---|---|
| VFS root directory `/` | `Collection` | `'vfs-root'` |
| VFS subdirectories | `Collection` | `'vfs-directory'` |
| VFS files | mime-driven (e.g. `Document`/`Code`/`Image`) | `'vfs-file'` |
| VFS symlinks | `File` | `'vfs-symlink'` (NEW — distinct from `'vfs-file'`) |
| VFS Contains edges (create + move/copy/symlink/batch) | `Contains` | `'vfs-contains'` |
| Aggregation materialized output | `Measurement` | `'materialized-aggregate'` |
| Import-source provenance entity | `Document` | `'import-source'` |
| Importer-extracted entities | extractor-driven type | `'imported'` |
| Importer placeholder targets | `Thing` | `'import-placeholder'` |
| Neural extraction | extractor-driven type | `'extracted'` |
| GoogleSheets API entity writes | request-driven | `'imported-from-sheets'` |
| OData API entity writes | request-driven | `'imported-from-odata'` |
| MCP message storage | `Message` | `'mcp-message'` |
| `brainy add` CLI default | user-supplied type | `'cli-add'` |
| `brainy relate` CLI default | user-supplied verb | `'cli-relate'` |

Query examples:

```typescript
// Every VFS-managed file in your brain
await brain.find({ subtype: 'vfs-file' })

// Document breakdown — distinguishes import-source from extracted/imported/user content
brain.counts.bySubtype(NounType.Document)
// → { 'import-source': 12, 'imported': 847, 'extracted': 34, 'vfs-file': 102, ... }
```

### Caller-supplied `defaultSubtype` on importers and extraction

Importer + extraction paths now accept a caller-supplied `defaultSubtype` config so consumers
can tag a whole batch with their own provenance label instead of the Brainy default:

```typescript
// SmartImportOrchestrator / ImportCoordinator / NeuralImport all accept this
await brain.importer.import(file, {
  defaultSubtype: 'customer-upload-2026q2',  // your batch label
  // ...
})
```

Precedence: extractor-set subtype (highest) → caller's `defaultSubtype` → Brainy default
(`'imported'` for importers, `'extracted'` for extractors).

### CLI `--subtype` flag

`brainy add` and `brainy relate` gain a `--subtype <value>` (`-s`) flag for use with
strict-mode brains:

```bash
brainy add "Avery Brooks — runs the AI lab" --type person --subtype employee
brainy relate alice manages bob --subtype direct
```

When the flag isn't supplied, the CLI uses `'cli-add'` / `'cli-relate'` as defaults so
ad-hoc CLI usage still works against strict-mode brains.

### Cortex compatibility

**No Cortex changes required for 7.30.1.** Every change is JS-side: internal subtype labels are
arbitrary strings stored transparently by Cortex; `brain.audit()` runs purely on JS via existing
`storage.getNouns()` / `getVerbs()` pagination; the CLI is JS-only; error messages fire in
Brainy before any native call.

**For Cortex 3.0 (forward-looking, not blocking):**

- **Native `audit()` proxy.** For billion-scale brains, `audit()` walks every entity (O(N)).
  A native implementation reading from a "null-subtype" bitmap in the column store would be
  O(buckets).
- **Strict-mode parity test.** Cortex should mirror Brainy's new
  `tests/integration/strict-mode-self-test.test.ts` against their native paths to catch any
  latent bug where native writes bypass JS validation.
- **Reserved-label awareness (optional).** Brainy's internal labels (`'vfs-*'`,
  `'materialized-aggregate'`, `'imported'`, `'extracted'`, `'mcp-message'`, `'cli-*'`) become
  a documented part of the 8.0 contract; useful for telemetry that surfaces "X% of entities are
  Brainy-managed infrastructure".

### Docs

Updated `docs/guides/subtypes-and-facets.md` with a new "Strict mode in practice" section
covering the SDK_CORE_VOCABULARY pattern, a 4-step migration recipe, the Brainy-internal label
reference table, and an 8.0 forward-look. `docs/api/README.md` documents `brain.audit()` and
adds a strict-mode tip to the `add()` / `relate()` reference entries.

### Tests

- **New `tests/integration/strict-mode-self-test.test.ts`** (13 tests): creates a brain under
  a realistic consumer vocabulary shape + brain-wide strict mode, then exercises every
  internal Brainy path (VFS root/mkdir/writeFile/cp/mv/ln, aggregation engine, audit
  diagnostic, error-message UX). Zero rejections expected.
- Existing 7.30.0 + 7.29.0 integration suites unchanged: 26/26 + 30/30.
- Unit suite unchanged: 1468/1468.

---

## v7.30.0 — 2026-06-05

**Affected products:** consumers modeling typed relationships with sub-classification
(direct vs dotted-line management; spouse / sibling / colleague; collaborator vs competitor;
etc.), and anyone wanting to enforce the pairing of `type` + `subtype` on every write.
Additive; drop-in from 7.29.x. No deprecations.

### Symmetric — `subtype` on relationships (parity with 7.29.0 nouns)

`subtype?: string` is now a first-class standard field on every relationship, mirroring the
noun-side work shipped in 7.29.0. Verbs and nouns are now first-class peers — every API
available on the noun side has a verb-side mirror.

```typescript
const ceoId = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'Avery' })
const vpId = await brain.add({ type: NounType.Person, subtype: 'employee', data: 'Jordan' })

await brain.relate({
  from: ceoId,
  to: vpId,
  type: VerbType.ReportsTo,
  subtype: 'direct'                    // sub-classification on the edge
})
```

**Read & filter:**

```typescript
// Fast-path filter — column-store hit, not metadata fallback
const direct = await brain.getRelations({
  from: ceoId,
  type: VerbType.ReportsTo,
  subtype: 'direct'
})

// Set membership
const all = await brain.getRelations({
  from: ceoId,
  type: VerbType.ReportsTo,
  subtype: ['direct', 'dotted-line']
})

// Traversal filter (depth-1 in JS; multi-hop lands on Cortex native)
const reports = await brain.find({
  connected: { from: ceoId, via: VerbType.ReportsTo, subtype: 'direct', depth: 1 }
})
```

### New — `updateRelation()` closes a long-standing gap

Verbs previously had no update method — the only way to change a relationship was
delete-then-recreate, which lost the relation id. 7.30 ships `brain.updateRelation()`:

```typescript
await brain.updateRelation({ id: relId, subtype: 'dotted-line' })
await brain.updateRelation({ id: relId, weight: 0.5, confidence: 0.9 })

// Change verb type — re-indexes in graph adjacency, id preserved
await brain.updateRelation({ id: relId, type: VerbType.WorksWith })
```

### New — O(1) verb subtype counts via the persisted rollup

`_system/verb-subtype-statistics.json` mirrors the noun-side rollup shipped in 7.29.0.
Per-VerbType-per-subtype counts are maintained incrementally and persisted; reads are O(1):

```typescript
brain.counts.byRelationshipSubtype(VerbType.ReportsTo)
// → { direct: 12, 'dotted-line': 3 }

brain.counts.byRelationshipSubtype(VerbType.ReportsTo, 'direct')   // O(1) point
// → 12

brain.counts.topRelationshipSubtypes(VerbType.ReportsTo, 3)
// → [['direct', 12], ['dotted-line', 3]]

brain.relationshipSubtypesOf(VerbType.ReportsTo)
// → ['direct', 'dotted-line']
```

### New — `brain.requireSubtype(type, options)` per-type enforcement

Unified API for noun OR verb types — register specific types as requiring a subtype,
optionally with a fixed vocabulary:

```typescript
brain.requireSubtype(NounType.Person, {
  values: ['employee', 'customer', 'vendor'],
  required: true
})

brain.requireSubtype(VerbType.ReportsTo, {
  values: ['direct', 'dotted-line'],
  required: true
})

// Now this throws — Person requires subtype:
await brain.add({ type: NounType.Person, data: 'no subtype' })

// And this throws — 'matrix' isn't in the registered vocabulary:
await brain.relate({ from: a, to: b, type: VerbType.ReportsTo, subtype: 'matrix' })
```

### New — Brain-wide strict mode

`new Brainy({ requireSubtype: true })` enforces subtype on every public write across the
whole brain. Composes with per-type rules; per-type rules win when both apply.

```typescript
// Every write must include subtype
const brain = new Brainy({ requireSubtype: true })

// Exempt specific types (e.g. catch-all Thing)
const brain2 = new Brainy({
  requireSubtype: { except: [NounType.Thing, NounType.Custom] }
})
```

When strict mode is on:
- Every `add()` / `addMany()` / `update()` / `relate()` / `relateMany()` / `updateRelation()`
  rejects writes missing a subtype on a non-exempt type.
- `addMany()` and `relateMany()` validate every item BEFORE any storage write —
  atomic-fail semantics, no partial writes.
- Brainy's own infrastructure writes (VFS root, directories, files) bypass via the
  `metadata.isVFSEntity: true` marker so existing consumers' VFS usage continues to work.

The brain-wide flag becomes the default in 8.0.0; the type-level `subtype` field becomes
required at the type system level. The full 8.0 contract upgrade is coordinated through the
internal platform handoff (`CTX-SUBTYPE-8.0-CONTRACT`).

### `migrateField()` extended to verbs

The migration helper shipped in 7.29.0 now walks verbs too via the new `entityKind` option:

```typescript
// Migrate verb-side metadata.kind → top-level subtype
await brain.migrateField({
  from: 'metadata.kind',
  to: 'subtype',
  entityKind: 'verb'
})

// Or walk nouns and verbs in one pass
await brain.migrateField({
  from: 'metadata.kind',
  to: 'subtype',
  entityKind: 'both'
})
```

Default is `entityKind: 'noun'` (backward-compatible).

### Symmetry — noun + verb capability matrix

7.30 closes every gap between nouns and verbs. Every capability available on the noun side
has a verb-side mirror:

| Capability | Nouns | Verbs |
|---|---|---|
| `subtype` top-level field | ✓ (7.29) | ✓ (7.30 new) |
| Standard-field set | `STANDARD_ENTITY_FIELDS` | `STANDARD_VERB_FIELDS` (new) |
| Field resolver helper | `resolveEntityField` | `resolveVerbField` (new) |
| Statistics rollup | `_system/subtype-statistics.json` | `_system/verb-subtype-statistics.json` (new) |
| Counts breakdown | `counts.bySubtype` / `topSubtypes` / `subtypesOf` | `counts.byRelationshipSubtype` / `topRelationshipSubtypes` / `relationshipSubtypesOf` (new) |
| Fast-path filter | `find({type, subtype})` | `getRelations({type, subtype})` + `find({connected, subtype})` (new) |
| Update method | `update()` | `updateRelation()` (new — closed pre-7.30 gap) |
| Migration helper | `migrateField()` | `migrateField({entityKind: 'verb'\|'both'})` (new) |
| Enforcement | `requireSubtype(NounType, ...)` | `requireSubtype(VerbType, ...)` — one unified API |
| Brain-wide strict mode | `new Brainy({ requireSubtype })` covers both | same |

### Cortex compatibility

Verb subtype works under Cortex out of the box via auto-field-indexing. Cortex parity items
for the verb side (native query planner recognition, `verbSubtypeCountsByType` native rollup,
per-edge subtype on native graph adjacency for multi-hop traversal filtering) ship in the
next Cortex release. Not a Brainy blocker.

### Docs

Full guide: `docs/guides/subtypes-and-facets.md` (extended with Layer V + Enforcement
sections). The verb subtype + enforcement APIs are documented in `docs/api/README.md`.

---

## v7.29.0 — 2026-06-04

**Affected products:** anyone modeling entities with per-product sub-classification — every
consumer that's been reaching for `metadata.kind`, a custom `metadata.subtype` field, a
`data.kind` shape inside the payload, or similar ad-hoc conventions. Additive; drop-in from
7.28.x. No deprecations.

### New — `subtype` promoted to a top-level standard field

`subtype?: string` is now a first-class standard field on every entity, alongside `type` /
`confidence` / `weight`. Use it as the platform-standard primitive for sub-classifying entities
within a NounType (`Person` → `'employee'` / `'customer'`; `Document` → `'invoice'` / `'contract'`;
`Event` → `'milestone'` / `'meeting'`):

```typescript
await brain.add({
  data: 'Avery Brooks — runs the AI lab',
  type: NounType.Person,
  subtype: 'employee',                  // top-level write param
  metadata: { department: 'ai-lab' }
})

// Fast-path filter — column-store hit, not metadata fallback:
const employees = await brain.find({ type: NounType.Person, subtype: 'employee' })

// Set membership:
const internal = await brain.find({
  type: NounType.Person,
  subtype: ['employee', 'contractor']
})
```

Flat string, no hierarchy — your vocabulary, your choice. Brainy stores and counts, never validates.

### New — O(1) subtype counts via the persisted rollup

A new `_system/subtype-statistics.json` rollup is maintained incrementally as entities are added,
updated, and deleted — mirroring the existing `nounCountsByType` machinery with the same self-heal
behavior on poison detection. Counts are O(1) at billion scale:

```typescript
brain.counts.bySubtype(NounType.Person)
// → { employee: 12, customer: 847, vendor: 34 }

brain.counts.bySubtype(NounType.Person, 'employee')   // O(1) point count
// → 12

brain.counts.topSubtypes(NounType.Person, 3)
// → [['customer', 847], ['employee', 12], ['vendor', 34]]

brain.subtypesOf(NounType.Person)
// → ['customer', 'employee', 'vendor']
```

### New — `brain.trackField()` for other metadata facets

For facets that aren't the *primary* sub-classification (`status`, `source`, `role`, `paradigm`),
`trackField` registers a field for cardinality + per-NounType breakdown stats without promoting
each one to a top-level slot. Piggybacks on the existing aggregation engine, so backfill-on-define
applies — registering on a populated brain scans existing entities on the first query:

```typescript
brain.trackField('status', { perType: true })

await brain.counts.byField('status')
// → { todo: 12, doing: 3, done: 47 }

await brain.counts.byField('status', { type: NounType.Task })
// → { todo: 8, doing: 2, done: 30 }

// Opt-in vocabulary validation:
brain.trackField('priority', { values: ['low', 'medium', 'high'] })
// brain.add({ ..., metadata: { priority: 'urgent' } }) → throws
```

### New — generic `brain.migrateField()` for one-shot rewrites

Streams every entity and copies a value from one field path to another. Supports top-level
standard fields, `metadata.*`, and `data.*` paths; idempotent; with optional `readBoth: true`
deprecation window that preserves the source field alongside the new one:

```typescript
// Phase 1: dual-populate (legacy readers still work)
await brain.migrateField({
  from: 'metadata.kind',
  to: 'subtype',
  readBoth: true
})

// ...readers migrate to subtype at their own pace...

// Phase 2: clear the source field
await brain.migrateField({ from: 'metadata.kind', to: 'subtype' })
// → { scanned: 1500, migrated: 1500, skipped: 0, errors: [] }
```

Supports `batchSize` and `onProgress` for large brains.

### Aggregation composition

`subtype` is a standard-field group-by dimension out of the box — no `where:` wrapper, no
metadata-fallback overhead:

```typescript
await brain.find({
  aggregate: {
    groupBy: ['type', 'subtype'],
    metrics: { count: { op: 'COUNT' } }
  }
})
// [
//   { groupKey: { type: 'person',   subtype: 'customer' }, count: 847 },
//   { groupKey: { type: 'person',   subtype: 'employee' }, count: 12 },
//   { groupKey: { type: 'document', subtype: 'invoice'  }, count: 2103 },
//   ...
// ]
```

### Cortex compatibility

Subtype works under Cortex out of the box via auto-field-indexing. Cortex will land its own
native-side query-planner recognition + `subtypeCountsByType` native rollup in the next Cortex
release for full parity with `type`'s fast path. Not a Brainy blocker — subtype reads/writes
function correctly with current Cortex.

### Docs

Full guide: `docs/guides/subtypes-and-facets.md`. Subtype is documented as a core primitive
throughout `README.md`, `docs/DATA_MODEL.md`, `docs/architecture/finite-type-system.md`,
`docs/api/README.md`, and `docs/QUERY_OPERATORS.md`.

---

## v7.24.0 — 2026-05-26

**Affected products:** aggregation/reporting users + anyone calling `extractEntities` on
multi-entity text. Additive; drop-in from 7.23.x.

### New — array-unnest `groupBy` (tag frequency / faceted counts)

A `groupBy` dimension can now be `{ field, unnest: true }`: the field holds an array and the
entity contributes once per **distinct** element. Enables tag-frequency / label-count style
aggregates:

```typescript
brain.defineAggregate({
  name: 'tag_frequency',
  source: { type: NounType.Document },
  groupBy: [{ field: 'tags', unnest: true }],
  metrics: { count: { op: 'count' } }
})
// queryAggregate('tag_frequency', { orderBy: 'count', order: 'desc' })
```

Duplicate elements on one entity count once; an entity with an empty/missing array joins no group.

### Perf — entity extraction batch-embeds candidates

`extractEntities` / `extractConcepts` now embed all unique candidate spans in a single
`embedBatch` call instead of one `embed()` per candidate (N sequential model calls before). No
behavior change — and with vectors reliably available, the embedding signal more consistently
reinforces correct types (e.g. clearer Organization confidence). Falls back to per-candidate
embedding if a batch call fails.

---

## v7.23.0 — 2026-05-26

**Affected products:** anyone using aggregation (stats/dashboards), graph traversal, or entity
extraction. Adds two report APIs and fixes three correctness gaps surfaced by BR-ADV-FEATURES-BUN.
Drop-in upgrade from 7.22.x.

### New — `brain.queryAggregate(name, params)`

A first-class report API returning the clean `AggregateResult[]` shape
(`{ groupKey, metrics, count }[]`) directly, instead of the search-`Result` wrapper that
`find({ aggregate })` returns. Accepts `where` / `having` / `orderBy` / `order` / `limit` / `offset`.

### New — HAVING (filter groups by metric value)

`find({ aggregate, having: { revenue: { greaterThan: 1000 } } })` (and the same on
`queryAggregate`) filters groups by their computed metrics — the analytics equivalent of SQL
`HAVING`, complementing `where` (which filters group keys). Evaluated per group: **O(groups),
independent of entity count.**

### Fix — aggregates now backfill when defined over existing data (R1)

Defining an aggregate on a store that already holds matching entities returned `[]` because
write-time hooks only saw *future* writes. It now backfills from existing entities on first query
(one-time scan via `getNouns`, then incremental) — storage-agnostic, so it works under durable
backends (Cortex) where a brain reopens pre-populated. Also: `groupBy:['noun']` now resolves to
the entity type instead of a single null group. `find({ aggregate })` rows now expose
`groupKey`/`metrics`/`count` at the top level (previously only under `.metadata`).

### Fix — multi-hop `find({ connected: { depth, via } })` (traversal)

`depth` and `via` are now honored at **every hop** (previously only the immediate neighbour was
returned, and verb filtering applied to hop 1 only). The BFS is bounded by `limit`.

### Fix — entity extraction type accuracy (R3)

`extractEntities` no longer lets a type indicator in one candidate's surrounding text bleed onto
neighbours (e.g. "Corp" in "Sarah Chen founded Acme Corp" no longer types "Sarah Chen" as
Organization). Each candidate is typed by its own span; context may only reinforce the same type.

---

## v7.22.1 — 2026-05-26

**Affected products:** Anyone using `extractEntities()` / `extractConcepts()`, native
aggregation (`find({ aggregate })`), or multi-hop graph traversal
(`find({ connected: { depth } })`). Three advanced-API correctness fixes — all reproduce on
Node, so they were **not** Bun-specific despite the original report (BR-ADV-FEATURES-BUN).

### Entity/concept extraction no longer returns `[]`

`extractEntities()` / `extractConcepts()` returned empty for entity-rich text. The SmartExtractor
ensemble scored agreeing signals with a weighted **sum** against an absolute 0.60 gate, so a
confident low-weight signal (e.g. a name pattern at 0.82) lost selection to a mediocre
high-weight signal that then failed the gate — dropping the whole result. It now selects and
gates on a normalized weighted **average**. Also: the `confidence` option now actually controls
the threshold (was a dead hardcoded 0.60), and the embedding-signal timeout was raised
100ms → 2000ms so the neural signal isn't silently dropped on slower runtimes.

*Known limitation:* type accuracy on dense multi-entity sentences is still imperfect — a strong
indicator in one entity's surrounding text can bleed onto neighbours. Tracked separately.

### `find({ aggregate })` exposes `groupKey` / `metrics` / `count`

Aggregation always computed correct values, but rows nested them under `.metadata`, so callers
expecting the documented `AggregateResult` shape saw empty-looking rows. Those three fields are
now also present at the top level of each result row.

### Multi-hop `find({ connected: { depth } })` honours depth

Previously returned only the immediate (1-hop) neighbour at any depth because the graph-search
path ignored `depth` / `via`. It now performs the full depth-aware traversal.

---

## v7.22.0 — 2026-05-15

**Affected products:** All. Fixes a silent-data-loss class affecting `find()` and
`brain.stats()`, plus Cortex-compatibility regression from 7.21.0. Recommended
upgrade for everyone on 7.20.x or 7.21.x.

### Two correctness fixes

#### 1. `find({ where })` no longer silently returns `[]` (BR-FIND-WHERE-ZERO)

The 7.20.0 column-store refactor deleted the legacy sparse-index write path
but left `getStats()` and `getIds()` reading from sparse indices. New
workspaces had no sparse-index files, so:
- `brain.stats().entityCount` was `0` regardless of actual entity count
- `find({ where: { ... } })` returned `[]` regardless of actual matches
- `rebuildIndexesIfNeeded()` saw `0` entries → fired the `[Brainy] CRITICAL ...
  Second rebuild result: 0 entries` log → application saw no indexed data

7.22.0 makes the ColumnStore the single source of truth post-7.20.0:
- `MetadataIndex.getStats()` reads from `ColumnStore.getIndexedFields()` and
  `idMapper.size`. Entity count is now accurate across writer → close →
  reader-open cycles.
- `MetadataIndex.getIdsFromChunks()` throws `BrainyError(FIELD_NOT_INDEXED)`
  when neither column store nor legacy sparse index has the field.
- `MetadataIndex.getIdsForFilter()` catches per-clause, logs
  `[brainy] find() where-clause referenced unindexed field(s): ...`, returns
  `[]`. Production `find()` is now consistent with `brain.explain()`'s
  `path: 'none'` diagnostic.

Separately, `BaseStorage.getNounType()` was hardcoded to return `'thing'`
since a type-cache removal in commit `42ae5be`. Every noun save attributed
the entity to `'thing'` regardless of its actual type, poisoning
`_system/type-statistics.json` and `brain.stats().entitiesByType`. 7.22.0
restores type-correct attribution:
- New `nounTypeByIdCache: Map<string, NounType>` on `BaseStorage`, populated
  in `saveNounMetadata_internal` and consumed in `saveNoun_internal`.
- New `flushCounts()` override that persists `nounCountsByType` /
  `verbCountsByType` alongside the per-entity counter. Readers opening the
  same directory after a writer flush now see correct per-type counts.

**Self-heal at init.** If `loadTypeStatistics()` detects the poisoned-state
signature (all nouns attributed to `'thing'` with multiple non-`thing`
entities on disk), it auto-runs `rebuildTypeCounts()` once and rewrites the
file. A `[BaseStorage] Detected poisoned type-statistics.json signature ...`
warning is logged. Operators don't need to take any action — the first 7.22
open of a directory poisoned by 7.20.0/7.21.0 fixes it.

**`brainy inspect repair`** can also be used to manually trigger
`rebuildTypeCounts()`. It's now public on `BaseStorage`.

#### 2. Cortex 2.2.x no longer crashes 7.21.0 boot (BR-DEFENSIVE-INTERFACE)

7.21.0 added new storage-adapter methods (`supportsMultiProcessLocking`,
`acquireWriterLock`, etc.) and called them unconditionally. Cortex 2.2.0's
mmap storage adapter bundles a pre-7.21 `BaseStorage` and doesn't define
them, so a consumer's 7.21.0 upgrade attempt threw
`TypeError: this.storage.supportsMultiProcessLocking is not a function`
at boot.

7.22.0 introduces `hasStorageMethod(name)` on Brainy and guards every new-
method call site. Older adapters degrade with a one-line warning at init:
```
[brainy] Storage adapter `CortexMmapStorage` predates the 7.21
multi-process methods. Writer locking and the flush-request RPC are
disabled for this directory. Upgrade the plugin (e.g.
`@soulcraft/cortex` ≥2.3.0) for full enforcement.
```

### Dead-code cleanup

Removed `MetadataIndexManager.dirtyChunks`, `dirtySparseIndices`, and the
`flushDirtyMetadata()` no-op machinery. These accumulators stopped being
populated when the sparse-index write path was deleted in 7.20.0; the
remaining 6 callers wasted async hops on an empty Map iteration.

### Upgrade notes

- **Behaviour change:** `find({ where: { unindexedField: ... } })` previously
  returned `[]` silently. It now logs a one-line warning and still returns
  `[]`. The diagnostic message names the field — use
  `brain.explain({ where: { ... } })` for full diagnosis. No code change
  needed for callers that already handle empty results.
- **Behaviour change (good):** `brain.stats()` and `brain.health()` now
  report accurate per-type counts. If you previously relied on the buggy
  `entitiesByType.thing` over-count, update consumers.
- **No API breaks.** Pure additive on the public surface.

### Cortex consumers

Cortex 2.2.x continues to work against 7.22.0 thanks to the defensive
guards, but for full multi-process protection on Cortex-backed stores and
to make sure Cortex's native MetadataIndex picks up the find-where-zero
fix, Cortex 2.3.0 is recommended. Tracked as `CX-MULTIPROC-METHOD` in the
internal platform handoff.

---

## v7.21.0 — 2026-05-15

**Affected products:** All consumers using filesystem storage (production deploys,
local development).

### Multi-process safety + first-class read-only inspector

Filesystem storage now enforces **single-writer, many-reader**. Previously, opening
a second writer process against a live data directory silently produced wrong query
results — no error, no warning, just empty or stale data. This release replaces
that footgun with a hard refusal at init time and a dedicated read-only inspection
mode.

#### New: `Brainy.openReadOnly()`
```ts
const reader = await Brainy.openReadOnly({
  storage: { type: 'filesystem', rootDirectory: '/data/brain' }
})
const bookings = await reader.find({ where: { entityType: 'booking' } })
```
- Does NOT acquire the writer lock — coexists with a live writer.
- Every mutation method throws `Cannot mutate a read-only Brainy instance`.
- `flush()` and `close()` are safe (no-op + clean shutdown).

#### New: writer lock at init
- `new Brainy({ ... })` (default `mode: 'writer'`) acquires
  `<rootDir>/locks/_writer.lock` containing `{ pid, hostname, startedAt, lastHeartbeat, version }`.
- A second writer on the same directory **throws** with the PID, hostname,
  heartbeat, and a pointer to `openReadOnly()`.
- Stale-lock detection: same hostname + dead PID OR heartbeat > 60s ago → overwritten with a warning.
- Heartbeat: writer rewrites `lastHeartbeat` every 10s (unref'd timer).
- Override: pass `{ force: true }` to bypass when you've verified the existing lock is stale.

#### New: `brain.requestFlush({ timeoutMs })`
Cross-process RPC for inspectors to force a fresh snapshot:
- In-process: just calls `flush()`.
- Out-of-process: writes a request file, polls for ack. Times out gracefully.
- Watcher runs in every writer instance (filesystem only).

#### New: `brain.stats()`
Operator-facing summary: `entityCount`, `entitiesByType`, `relationCount`,
`relationsByType`, `fieldRegistry`, `indexHealth`, `storage.backend`, `writerLock`, `version`.
Designed for `/api/health` endpoints and incident triage.

#### New: `brain.explain(findParams)`
Shows which index path serves each `where` clause: `column-store` | `sparse-chunked` | `none`.
**This is the answer to "why is `find()` returning empty?"** — `path: "none"` means
the field has no index entries and the query will silently return `[]`. Includes
notes on likely causes (writer hasn't flushed; typo; field genuinely absent).

#### New: `brain.health()`
Invariant-check battery: HNSW vs metadata count parity, field registry sanity,
`_seeded` entity sweep, writer heartbeat freshness. Returns `{ overall: 'pass' | 'warn' | 'fail', checks: [...] }`.

#### New: `brainy inspect` CLI (13 subcommands)
All read-only by default (internally uses `openReadOnly()`):
```
brainy inspect stats   <path>
brainy inspect find    <path> --type Event --where '{"status":"paid"}' --limit 20
brainy inspect get     <path> <id>
brainy inspect relations <path> <id> --direction both
brainy inspect explain <path> --where '{"entityType":"booking"}'
brainy inspect health  <path>
brainy inspect sample  <path> --type Event --n 20
brainy inspect fields  <path>
brainy inspect dump    <path> --type Event > backup.jsonl
brainy inspect watch   <path> --type Event
brainy inspect backup  <path> /backups/brain.tar
brainy inspect repair  <path>           # writer mode — stop live writer first
brainy inspect diff    <pathA> <pathB>
```
Default behaviour: ask the writer to flush via the RPC first (skip with `--no-fresh`).

### Brainy + Cortex

Cortex segments (`*.cidx`) are immutable mmap files; `MANIFEST.json` uses atomic
rename. The single writer lock at `<rootDir>/locks/_writer.lock` covers both Brainy
and Cortex. Read-only inspectors mmap Cortex segments with zero coordination.

### What's NOT enforced yet

- **Cloud storage backends** (S3, GCS, R2, Azure) — no multi-process locking.
  A best-effort warning logs in writer mode against non-filesystem backends.
- **The `find({ where })`-returns-0 root-cause bug** — tracked separately. The
  new `brain.explain()` and `brain.health()` surface it loudly
  (`path: 'none'`, `index-parity warn`) instead of letting it be silent.

### Upgrade notes

- **Default behaviour change:** opening a Brainy directory in writer mode while
  another writer is live now THROWS where it previously silently produced wrong
  results. If you have scripts that intentionally co-opened a writer directory,
  switch them to `Brainy.openReadOnly()` or pass `{ force: true }`.
- **Cloud backends unchanged** — no lock acquisition for S3/GCS/R2/Azure.
- All existing APIs unchanged. Pure addition.

### Docs

- README "Single-Writer Model" section.
- `docs/concepts/multi-process.md` — full model + Cortex compatibility.
- `docs/guides/inspection.md` — operator recipes.
- JSDoc on every new API.

---

## v7.19.10 — 2026-02-24

**Affected products:** All Bun/ESM consumers

### ESM crypto fix in SSTable

Replaced `require('crypto')` with `import { createHash } from 'node:crypto'` in the
SSTable implementation. Fixes a crash in Bun and strict ESM environments where
CommonJS `require` is unavailable.

No API changes — upgrade and redeploy.

---

## v7.19.2 — 2026-02-18

**Affected products:** All

### Metadata index cleanup on delete

Fixed: metadata indexes were not cleaned up after `delete()` / `deleteMany()`. Stale
index entries could cause phantom results in metadata-filtered queries after deletion.

No API changes. If you were seeing ghost results in filtered queries, this fixes it.

---

## v7.18.0 — 2026-02-16

**Affected products:** Analytics, reporting, and session-summary consumers

### Aggregation engine

New `brain.aggregate()` API — incremental SUM, COUNT, AVG, MIN, MAX with GROUP BY
and time window support. Computes over entity collections without loading all records
into memory.

```typescript
const result = await brain.aggregate({
  collection: 'bookings',
  metrics: [
    { field: 'revenue', fn: 'SUM' },
    { field: 'id', fn: 'COUNT' },
  ],
  groupBy: 'staffId',
  timeWindow: { field: 'createdAt', from: startOfMonth, to: now },
})
```

SDK exposure: `sdk.brainy.aggregate()` — available once SDK is updated to pass through.

---

## v7.17.0 — 2026-02-09

**Affected products:** All (schema evolution, data migrations)

### Migration system

New `brain.migrate()` API with error handling, validation, and enterprise hardening.
Run schema migrations reliably across Brainy data directories.

```typescript
await brain.migrate({
  version: 3,
  up: async (brain) => {
    // transform entities, rename fields, etc.
  },
})
```

---

## v7.16.0 — 2026-02-09

**Affected products:** All

### Data/metadata separation enforced + numeric range queries

- Entity `data` and `metadata` fields are now strictly separated at the storage layer
- Numeric range queries now supported in metadata filters: `{ age: { $gte: 18, $lt: 65 } }`
- Fixes edge cases where mixed data/metadata storage caused inconsistent query results

**Breaking for anyone storing numeric values in metadata and relying on range queries:**
verify your filter syntax matches the new `$gte/$lte/$gt/$lt` operators.

---

## v7.15.5 — 2026-02-02

**Affected products:** Anyone using `@soulcraft/cortex` plugin

### Plugin opt-in clarified

Cortex and other plugins are opt-in. Pass explicitly:
```typescript
new Brainy({ plugins: ['@soulcraft/cortex'] })
```
Without `plugins`, no external plugins are loaded regardless of what's installed.

---

## v7.15.2 — 2026-02-01

**Affected products:** All (data safety)

### Graph LSM flush on close

Fixed: graph LSM-trees were not flushed on `brain.close()`, risking data loss across
restarts. Graph edges written in the final seconds before shutdown are now guaranteed
to be persisted.

No API changes — upgrade immediately if running Brainy in a long-lived server process.