perf(vfs): repairContainment's reconcile is one paged edge walk, not one graph call per file

Pass 2 issued one awaited related({ to }) per VFS entity — O(entities)
serialized graph calls, measured in whole minutes on large brains. Now a
single paged walk over every Contains edge (type-only, 1,000 per page)
feeds an in-memory group-by-target, and only actual defects mutate. The
verdicts are unchanged: a stale parent's edge is removed, a missing edge
is restored, duplicates cannot survive, and user knowledge edges are
never touched.

Pinned in tests/integration/vfs-containment-batched.test.ts: exact
removed/restored counts on a seeded defect tree, tree correctness after
the repair, user edges untouched, and the cost shape — related() call
count independent of the entity count.

CHANGELOG.md

@@ -2,6 +2,18 @@
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
 
+### [10.4.6](https://source.soulcraft.com/soulcraftlabs/open-brainy/compare/v10.4.5...v10.4.6) (2026-08-31)
+
+- fix(transact): metadata-index ops take their JSON-safe view at the crossing, not at construction (73500e7d)
+
+
+### [10.4.5](https://source.soulcraft.com/soulcraftlabs/open-brainy/compare/v10.4.4...v10.4.5) (2026-08-31)
+
+- build(release): the docs-push step retires — this engine documents itself in its own repository (d6bcb14f)
+- fix(generations): a sealed segment may only declare the generations it holds (a963a744)
+- fix(recovery): a torn generation-log tail is a terminal verdict, never a wait (c9930871)
+
+
 ### [10.4.4](https://source.soulcraft.com/soulcraftlabs/open-brainy/compare/v10.4.3...v10.4.4) (2026-08-28)
 
 - fix(vfs): the old-root sweep narrates only when it has something to say (d49148e1)

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@soulcraftlabs/brainy",
-  "version": "10.4.4",
+  "version": "10.4.6",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@soulcraftlabs/brainy",
-      "version": "10.4.4",
+      "version": "10.4.6",
       "license": "MIT",
       "dependencies": {
         "@msgpack/msgpack": "^3.1.2",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@soulcraftlabs/brainy",
-  "version": "10.4.4",
+  "version": "10.4.6",
   "brainyContract": 1,
   "description": "Universal Knowledge Protocol™ - World's first Triple Intelligence database unifying vector, graph, and document search in one API. Stage 3 CANONICAL: 42 nouns × 127 verbs covering 96-97% of all human knowledge.",
   "main": "dist/index.js",

scripts/release.sh

@@ -248,17 +248,12 @@ else
   echo -e "${RED}⚠️  FORGEJO_RELEASE_TOKEN unset — no release page created; tag + CHANGELOG remain the record${NC}\n"
 fi
 
-# Step 12: Push public docs to the soulcraft.com docs ingest door
+# Step 12 RETIRED (2026-08-31, CORTEX-SITE-BRAINY-RENAME round 12, David-ruled):
-# (VENUE-DOCS-RELEASE-PUSH). Skips with a loud warning when
+# soulcraft.com/docs carries the paid product's documentation only. This
-# DOCS_INGEST_SECRET is unset; fails loudly (without undoing the publish —
+# engine's documentation home is THIS repository — README and docs/ — and the
-# that already happened) when a push errors, so the docs site never
+# site serves 301s for the slugs this rail used to push. The push script stays
-# silently trails npm.
+# in the tree for history; the rail no longer calls it.
-echo -e "${BLUE}1️⃣2️⃣ Pushing public docs to soulcraft.com/docs...${NC}"
+echo -e "${BLUE}Docs step: this engine documents itself in its own repo (site push retired 2026-08-31)${NC}"
-if node scripts/push-docs.js; then
-  echo -e "${GREEN}✅ Docs push step done${NC}\n"
-else
-  echo -e "${RED}❌ Docs push FAILED — soulcraft.com/docs trails npm until re-run or interim sync${NC}\n"
-fi
 
 echo -e "${GREEN}━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━${NC}"
 echo -e "${GREEN}🎉 Release ${NEW_VERSION} complete!${NC}"

src/brainy.ts

@@ -15,6 +15,7 @@ import { JsHnswVectorIndex } from './hnsw/hnswIndex.js'
 import { createStorage, resolveFilesystemRoot } from './storage/storageFactory.js'
 import type { StorageOptions } from './storage/storageFactory.js'
 import { rebuildCounts } from './utils/rebuildCounts.js'
+import { jsonSafeIndexMetadata } from './utils/jsonSafeIndexMetadata.js'
 import type { MetadataWriteBuffer } from './utils/metadataWriteBuffer.js'
 import { BaseStorage } from './storage/baseStorage.js'
 import {
@@ -4203,32 +4204,19 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    */
   /**
    * @description A JSON-safe view of a record bound for the metadata-index
-   * crossing. The seam's metadata is JSON-safe BY CONTRACT (a native provider
+   * crossing — delegates to the shared {@link jsonSafeIndexMetadata} leaf,
-   * serializes it; u64 ints as Number corrupt above 2^53) — but
+   * which the metadata-index transaction operations ALSO apply at execute
-   * {@link resolveVerbEndpointInts} MIRRORS the resolved endpoint ints onto
+   * and rollback time. This plan-time wrap alone proved insufficient: it
-   * the verb object itself as BigInt (`verb.sourceInt`/`targetInt`), so a
+   * returns the same reference when the record is clean, and `transact()`'s
-   * verb object reused as index metadata carried BigInts into
+   * delete legs share that reference with a graph-retraction op whose
-   * JSON.stringify, which throws, aborting the whole transaction (found by
+   * execute-time endpoint resolution mirrors BigInt ints onto it (the full
-   * the first joint pair gate). Endpoint ints ride their OWN op params on the
+   * aliasing story lives on the leaf module's doc).
-   * graph legs — the metadata crossing drops every BigInt-valued top-level
-   * key instead of guessing at a lossy numeric encoding.
    * @param metadata - The candidate index-metadata record.
    * @returns The same object when already JSON-safe, else a shallow copy
    *   without the BigInt-valued keys.
    */
   private static jsonSafeIndexMetadata(metadata: unknown): unknown {
-    if (metadata === null || typeof metadata !== 'object') return metadata
+    return jsonSafeIndexMetadata(metadata)
-    const rec = metadata as Record<string, unknown>
-    let hasBigint = false
-    for (const k in rec) {
-      if (typeof rec[k] === 'bigint') { hasBigint = true; break }
-    }
-    if (!hasBigint) return metadata
-    const out: Record<string, unknown> = {}
-    for (const k in rec) {
-      if (typeof rec[k] !== 'bigint') out[k] = rec[k]
-    }
-    return out
   }
 
   private metadataIndexRetractionOp(
@@ -12497,6 +12485,18 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    * healed by `repairIndex()`, whose unconditional recount rebuilds the
    * rollups from a canonical walk and re-stamps. Best-effort: a stamp-write
    * fault warns loudly but never fails the flush that carried real data.
+   *
+   * THE SOURCE IS `committedGeneration()`, NEVER `generation()`. The latter is
+   * the ALLOCATED counter — a number a write in flight has claimed and may
+   * never commit. Stamping it made the stamp's generation label a claim about
+   * counts it was not taken at, and every crash inside a write window then
+   * produced a spurious verdict at the next open: either `sourceGeneration N
+   * is ahead of the log head N-1` (the allocated generation died with the
+   * process) or `rollup invariant 'nounCount': stamped X, observed Y` (the
+   * recovery fold folded facts the stamp's counts predate). MEASURED on the
+   * crash-consistency lane before this line changed: 4 of 11 SIGKILL cycles on
+   * a coherent store raised one of those two verdicts, each of them naming
+   * `repairIndex()` — a whole-store recount — as the cure for nothing.
    */
   private async stampEntityTree(): Promise<void> {
     if (this.isReadOnly) return
@@ -12507,7 +12507,7 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       ])
       await writeFamilyStamp(this.storage, ENTITY_TREE_STAMP_PATH, {
         family: 'entity-tree',
-        sourceGeneration: this.generationStore.generation(),
+        sourceGeneration: this.generationStore.committedGeneration(),
         members: { mode: 'rollup', invariants: { nounCount, verbCount } }
       })
     } catch (error) {
@@ -12520,16 +12520,24 @@ export class Brainy<T = any> implements BrainyInterface<T> {
 
   /**
    * @description Open-time coherence check for the entity tree's family stamp:
-   * compare `sourceGeneration` against the log head and the stamped rollup
+   * compare `sourceGeneration` against the store's COMMITTED generation and
-   * invariants against the live counters. Verdicts:
+   * the stamped rollup invariants against the live counters. Verdicts:
    * - `coherent` / `absent` (legacy store; first flush stamps) → silent.
    * - `behind` → benign for the tree (it is written BY the commit; only the
    *   stamp is stale — a crash landed between commit and flush). Refreshed at
    *   the next flush.
+   * - `torn` → a TORN GENERATION-LOG TAIL, handled by
+   *   {@link demoteTornEntityTreeStamp}: terminal, never a wait.
    * - `incoherent` → LOUD: the tree or its counters diverged from what was
    *   stamped — `repairIndex()` recounts from canonical and re-stamps.
    * Never blocks open; a fault reading the stamp is surfaced as unverifiable,
    * never conflated with absence.
+   *
+   * THE COMPARISON IS AGAINST `committedGeneration()`, matching what
+   * {@link stampEntityTree} writes and what every other open-time watermark in
+   * this class already reasons about (the fact-scan capability, the metadata /
+   * graph / HNSW watermark verdicts). Comparing against the allocated counter
+   * was the one place that disagreed, and disagreeing was the whole defect.
    */
   private async verifyEntityTreeStamp(): Promise<void> {
     let stamp: FamilyStamp | null
@@ -12546,11 +12554,16 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       this.storage.getNounCount(),
       this.storage.getVerbCount()
     ])
-    const verdict = verifyFamilyStamp(stamp, this.generationStore.generation(), {
+    const verdict = verifyFamilyStamp(stamp, this.generationStore.committedGeneration(), {
       nounCount,
       verbCount
     })
-    if (verdict.state === 'incoherent') {
+    if (verdict.state === 'torn') {
+      await this.demoteTornEntityTreeStamp(stamp as FamilyStamp, verdict.stampSource, verdict.head, {
+        nounCount,
+        verbCount
+      })
+    } else if (verdict.state === 'incoherent') {
       prodLog.warn(
         `[Brainy] entity-tree stamp INCOHERENT at open: ${verdict.failures.join('; ')}. ` +
           `The canonical tree or its counters diverged from the stamped state — run ` +
@@ -12564,6 +12577,92 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     }
   }
 
+  /**
+   * @description THE TERMINAL VERDICT for a torn generation-log tail.
+   *
+   * A stamp whose `sourceGeneration` sits ABOVE the store's committed
+   * watermark witnesses a generation that is not in the log: the stamp's fsync
+   * outlived the tail's. By the time this runs, log-authority recovery has
+   * already folded every intact fact above the manifest and advanced the
+   * watermark to cover them — so if the stamp is STILL ahead, the generation
+   * it names is not merely late, it is GONE. There is nothing to wait for.
+   *
+   * That is the whole point of this method. A field report of this class
+   * (single-process store, abrupt termination mid-fold) described a reopen
+   * that narrated the tear and then held 100% CPU with zero log growth for
+   * eight minutes before an operator wiped the directory. A recovery that
+   * cannot say what it is waiting for has no business spinning; the honest
+   * answer here is a verdict, taken now, at O(1) cost.
+   *
+   * WHAT THE VERDICT DOES — the stamped surface is UNUSABLE, so it is
+   * discarded rather than believed: the stamped counts describe a generation
+   * that never became durable, and comparing them against live counters can
+   * only produce noise. The tree itself is not in question (it IS canonical —
+   * every commit writes it, and the fold re-applied every after-image the log
+   * still holds), so the demotion is a re-derivation of this family's verified
+   * surface at the generation the store can actually show:
+   *
+   * - WRITER open → re-stamp at `committedGeneration()` from the live
+   *   counters — exactly what the next flush would write, taken now so the
+   *   tear cannot re-narrate on every subsequent open. Both count sets are
+   *   logged so an operator can see whether anything really moved.
+   * - READER open → a reader cannot re-stamp. Narrate the same terminal
+   *   verdict with the named cure and carry on serving; a read-only inspector
+   *   is never locked out of a store, and never left waiting either.
+   *
+   * BOUNDEDNESS: straight-line code. No loop, no retry, no await on any
+   * external progress signal — the two counter reads and one stamp write are
+   * the entire cost, and none of them scales with the store.
+   */
+  private async demoteTornEntityTreeStamp(
+    stamp: FamilyStamp,
+    stampSource: number,
+    head: number,
+    observed: { nounCount: number; verbCount: number }
+  ): Promise<void> {
+    const stamped = stamp.members.mode === 'rollup' ? stamp.members.invariants : {}
+    const detail =
+      `[Brainy] TORN GENERATION-LOG TAIL at open: ${ENTITY_TREE_STAMP_PATH} witnesses source ` +
+      `generation ${stampSource} (stamped ${stamp.committedAt}), but the store's committed ` +
+      `generation is ${head} after crash recovery — the stamp's fsync outlived the log tail's, ` +
+      `and generation ${stampSource} is not in the log to arrive. Stamped rollups ` +
+      `${JSON.stringify(stamped)}; observed ${JSON.stringify(observed)}.`
+
+    if (this.isReadOnly) {
+      prodLog.warn(
+        `${detail} This open is READ-ONLY, so the stamp cannot be re-derived: the entity-tree ` +
+          `family stays UNVERIFIED for this session (reads are unaffected — the canonical tree ` +
+          `is the truth this stamp only describes). Cure: open the store with a writer, or run ` +
+          `brain.repairIndex() there, to recount from canonical and re-stamp.`
+      )
+      return
+    }
+
+    const startedAt = Date.now()
+    try {
+      await writeFamilyStamp(this.storage, ENTITY_TREE_STAMP_PATH, {
+        family: 'entity-tree',
+        sourceGeneration: head,
+        members: {
+          mode: 'rollup',
+          invariants: { nounCount: observed.nounCount, verbCount: observed.verbCount }
+        }
+      })
+      prodLog.warn(
+        `${detail} DEMOTED: the unusable stamp was re-derived at committed generation ${head} ` +
+          `from the live counters in ${Date.now() - startedAt}ms — terminal, not a wait. If the ` +
+          `observed counts above look wrong for your data, run brain.repairIndex() to recount ` +
+          `from canonical.`
+      )
+    } catch (error) {
+      prodLog.warn(
+        `${detail} The demotion's re-stamp FAILED (${(error as Error).message}) — the tear will ` +
+          `narrate again at the next open, which is the honest outcome; the store still serves ` +
+          `from canonical. Cure: run brain.repairIndex() to recount from canonical and re-stamp.`
+      )
+    }
+  }
+
   /**
    * Ask the writer process serving this data directory to flush its in-memory
    * indexes to disk, so a read-only inspector can observe fresh state.

src/db/familyStamp.ts

@@ -12,9 +12,11 @@
  *   the verified surface is a small set of rollup invariants (entity/
  *   relationship counts) plus `sourceGeneration`.
  *
- * `sourceGeneration` is the generation of the source-of-truth log this
+ * `sourceGeneration` is the COMMITTED generation of the source-of-truth log
- * projection reflects — open-time coherence becomes a COMPARISON (stamp vs
+ * this projection reflects — never the allocated counter, which names a
- * log head), not a walk:
+ * generation that may never commit (see {@link StampVerdict.torn}) — so
+ * open-time coherence becomes a COMPARISON (stamp vs committed head), not a
+ * walk:
  *
  * - equal + invariants hold → coherent, serve.
  * - behind → the projection missed the tail (crash between commit and stamp);
@@ -24,6 +26,9 @@
  * - invariants FAIL at equal generation → genuine incoherence: loud, and the
  *   repair ritual (`repairIndex()`, whose recount rebuilds the rollups from a
  *   canonical walk) heals it.
+ * - AHEAD → a torn generation-log tail: the stamp's fsync outlived the log
+ *   tail's. TERMINAL, never a wait — the generation the stamp names does not
+ *   exist to arrive.
  *
  * Stamps are JSON on purpose — every incident gets debugged by reading a
  * stamp in a terminal.
@@ -70,6 +75,12 @@ export type StampVerdict =
   | { state: 'coherent' }
   | { state: 'absent' } // legacy store — first stamp writes at the next flush
   | { state: 'behind'; stampSource: number; head: number }
+  /**
+   * TORN GENERATION-LOG TAIL: the stamp witnesses a source generation the
+   * store's committed watermark can no longer show. TERMINAL — there is no
+   * generation to wait for, so the open demotes (or refuses) and never spins.
+   */
+  | { state: 'torn'; stampSource: number; head: number }
   | { state: 'incoherent'; failures: string[] }
   | { state: 'unverifiable'; reason: string } // a FAULT reading the stamp — never conflated with absence
 
@@ -118,12 +129,15 @@ export function verifyFamilyStamp(
 ): StampVerdict {
   if (stamp === null) return { state: 'absent' }
   if (stamp.sourceGeneration > head) {
-    // A stamp AHEAD of the log claims state that never committed — the
+    // A stamp AHEAD of committed truth witnesses a generation the store can no
-    // projection was stamped against truth that a crash rolled back.
+    // longer show: the stamp's fsync survived a crash that the log tail did
-    return {
+    // not. This is the TORN GENERATION-LOG TAIL — its own class, never folded
-      state: 'incoherent',
+    // in with `incoherent` (a count that drifted at a generation both sides
-      failures: [`sourceGeneration ${stamp.sourceGeneration} is ahead of the log head ${head}`]
+    // agree on), because the two have opposite cures: incoherence is recounted,
-    }
+    // a tear is DEMOTED. It is also terminal by construction — there is no
+    // generation the open can wait for, because the one the stamp names is
+    // gone.
+    return { state: 'torn', stampSource: stamp.sourceGeneration, head }
   }
   if (stamp.sourceGeneration < head) {
     return { state: 'behind', stampSource: stamp.sourceGeneration, head }

src/db/generationSegments.ts

@@ -147,6 +147,60 @@ export class GenerationSegmentStore {
     return this.coveringSegment(gen) !== null
   }
 
+  /**
+   * @description True when `meta` declares more generations than it holds
+   * frames — a segment sealed by a writer that folded across a hole. The
+   * manifest records `frames` at fold time, so this is an O(1) comparison
+   * against the declared span and needs no I/O.
+   */
+  private isSparse(meta: SegmentMeta): boolean {
+    return meta.lastGeneration - meta.firstGeneration + 1 !== meta.frames
+  }
+
+  /**
+   * @description The generations this tier ACTUALLY holds, as coalesced
+   * ascending intervals — not what the segments declare.
+   *
+   * Dense segments (every one a current writer produces) contribute their
+   * declared range with no I/O. A SPARSE segment — one sealed before the
+   * density law was enforced, whose declared range spans generations it has
+   * no frame for — has its real generation list read from its sidecar and
+   * contributed instead, with the discrepancy narrated once.
+   *
+   * This is what keeps a store that already carries the damage from wedging.
+   * `open()` seeds `committedRanges` from these intervals, so a hole is never
+   * re-admitted as a committed generation, and the auto-compaction pass that
+   * used to fail on every run with "packed history is damaged" simply never
+   * asks for the missing frame.
+   *
+   * @returns Ascending, non-overlapping `[first, last]` intervals.
+   */
+  async actualRanges(): Promise<Array<[number, number]>> {
+    const out: Array<[number, number]> = []
+    for (const meta of this.manifest.segments) {
+      if (!this.isSparse(meta)) {
+        out.push([meta.firstGeneration, meta.lastGeneration])
+        continue
+      }
+      const missing = meta.lastGeneration - meta.firstGeneration + 1 - meta.frames
+      prodLog.warn(
+        `[GenerationSegments] sealed segment ${meta.file} declares generations ` +
+          `${meta.firstGeneration}..${meta.lastGeneration} but holds only ${meta.frames} ` +
+          `frame(s) — ${missing} generation(s) in that span were never folded into it. ` +
+          `Serving the frames it actually holds; the declared span is not treated as ` +
+          `committed history. (Written by a pre-density-law writer that folded across a ` +
+          `gap; the segment itself is intact and no record is lost.)`
+      )
+      const idx = await this.sidecarFor(meta)
+      for (const [gen] of idx.generations) {
+        const last = out[out.length - 1]
+        if (last !== undefined && gen === last[1] + 1) last[1] = gen
+        else out.push([gen, gen])
+      }
+    }
+    return out
+  }
+
   /**
    * Fold consecutive generations into ONE new sealed segment + sidecar and
    * append it to the manifest atomically. Caller guarantees: `gens` is
@@ -164,6 +218,38 @@ export class GenerationSegmentStore {
         throw new Error('[GenerationSegments] fold() input must be strictly ascending')
       }
     }
+    // THE DENSITY LAW, MADE MECHANICAL.
+    //
+    // A sealed segment declares a CONTIGUOUS range [firstGeneration,
+    // lastGeneration] and every reader treats that range as containment:
+    // `coveringSegment` is an interval test, `hasGeneration` returns true for
+    // anything inside it, and `open()` seeds committedRanges from it. So a
+    // segment folded from a SPARSE input silently claims generations it does
+    // not hold, and the first read of one of those holes throws
+    // "inside sealed segment ... but has no frame — packed history is damaged".
+    //
+    // That is exactly how the damage was produced. `repackHistory` skipped
+    // generations mid-batch — ones absent from committedRanges, ones still in
+    // the pending buffer, ones whose tx.json would not read — and handed the
+    // survivors here, where the range was computed from the first and last of
+    // them. Worse, the mis-declared range was then merged back into
+    // committedRanges at the next open, which is what turned a quiet hole into
+    // a repeating auto-compaction failure on every subsequent run.
+    //
+    // Callers now split at discontinuities; this refusal is what keeps any
+    // future caller from reintroducing the class. A refusal here loses
+    // nothing — the generations stay in the live tier, readable, and the next
+    // pass folds them correctly.
+    for (let i = 1; i < gens.length; i++) {
+      if (gens[i].generation !== gens[i - 1].generation + 1) {
+        throw new Error(
+          `[GenerationSegments] fold() input is not contiguous: ${gens[i - 1].generation} → ` +
+            `${gens[i].generation} skips ${gens[i].generation - gens[i - 1].generation - 1} ` +
+            `generation(s). A sealed segment declares a dense range, so folding a sparse ` +
+            `batch would claim generations it does not hold. Split the batch at the gap.`
+        )
+      }
+    }
     const last = this.manifest.segments[this.manifest.segments.length - 1]
     if (last && gens[0].generation <= last.lastGeneration) {
       throw new Error(
@@ -364,12 +450,37 @@ export class GenerationSegmentStore {
         return this.decodeFrame(payload)
       }
     }
-    // In the covering range but not present: the packed tier is dense by
+    // Inside the covering range but with no frame. Two very different causes,
-    // construction (fold packs every generation it is handed, including
+    // and conflating them is what made this class wedge every maintenance pass
-    // record-less ones) — absence inside a sealed range is damage.
+    // on the affected stores.
+    //
+    // (1) A SPARSE SEGMENT — the manifest's own `frames` count is smaller than
+    //     the span it declares. That segment was sealed by a writer that
+    //     folded across a hole (the class this file's density law now bars).
+    //     The segment is INTACT and nothing is lost; it simply never held this
+    //     generation. Answering "not packed" is the honest answer, and it lets
+    //     the caller's two-tier read decide what a genuinely absent generation
+    //     means, instead of every compaction pass dying on a repeating throw.
+    //     `actualRanges()` keeps such holes out of committedRanges at open, so
+    //     in a healed store nobody asks this question in the first place.
+    //
+    // (2) A DENSE SEGMENT missing a frame it says it has — the manifest and
+    //     the sidecar disagree about a segment that claims to be complete.
+    //     That IS damage, and it stays loud.
+    if (this.isSparse(meta)) {
+      prodLog.warn(
+        `[GenerationSegments] generation ${gen} falls inside sealed segment ${meta.file}'s ` +
+          `declared range ${meta.firstGeneration}..${meta.lastGeneration}, but that segment ` +
+          `holds ${meta.frames} frame(s) for a ${meta.lastGeneration - meta.firstGeneration + 1}` +
+          `-generation span — it was sealed across a gap and never held this generation. ` +
+          `Reporting it as unpacked rather than as damage; no record is lost.`
+      )
+      return null
+    }
     throw new Error(
       `[GenerationSegments] generation ${gen} is inside sealed segment ${meta.file}'s declared ` +
-        `range but has no frame — packed history is damaged`
+        `range but has no frame, and that segment declares a complete ${meta.frames}-frame ` +
+        `span — the manifest and the sidecar disagree; packed history is damaged`
     )
   }
 

src/db/generationStore.ts

@@ -96,6 +96,35 @@ export const FOLD_CHECKPOINT_PATH = '_system/fold-checkpoint.json'
 /** Storage-root-relative prefix of the per-generation record directories. */
 export const GENERATIONS_PREFIX = '_generations'
 
+/**
+ * @description Split an ascending list of fold candidates into maximal
+ * CONTIGUOUS runs — `[7,8,9,12,13]` becomes `[[7,8,9],[12,13]]`.
+ *
+ * A sealed segment declares one dense range `[firstGeneration,
+ * lastGeneration]`, and every reader treats that range as containment. So a
+ * batch with a hole in it must never become one segment: it would claim a
+ * generation it does not hold, and the first read of that hole reports the
+ * packed history as damaged. One run, one segment — the ranges then describe
+ * exactly what the segments contain.
+ *
+ * @param gens - Fold candidates, strictly ascending by generation.
+ * @returns One array per contiguous run, in ascending order. Empty in, empty out.
+ */
+export function contiguousRuns(gens: FoldGeneration[]): FoldGeneration[][] {
+  const runs: FoldGeneration[][] = []
+  let run: FoldGeneration[] = []
+  for (const g of gens) {
+    const prev = run[run.length - 1]
+    if (prev !== undefined && g.generation !== prev.generation + 1) {
+      runs.push(run)
+      run = []
+    }
+    run.push(g)
+  }
+  if (run.length > 0) runs.push(run)
+  return runs
+}
+
 /**
  * @description Phases of the {@link GenerationStore.commitTransaction} commit
  * protocol at which a test-only fault injector can simulate a process crash.
@@ -784,9 +813,15 @@ export class GenerationStore {
     if (storageSupportsFactLog(this.storage)) {
       this.segments = new GenerationSegmentStore(this.storage)
       await this.segments.open()
-      const packedRanges = this.segments
+      // ACTUAL ranges, not declared ones. A segment sealed by a pre-density-law
-        .segments()
+      // writer can declare a span wider than the frames it holds; seeding
-        .map((s): [number, number] => [s.firstGeneration, Math.min(s.lastGeneration, this.committed)])
+      // committedRanges from the declared span re-admits those holes as
+      // committed generations, and every later maintenance pass then asks for a
+      // frame that was never written. `actualRanges()` reads the real
+      // generation list from the sidecar for exactly those segments (and does
+      // no I/O for the dense ones, which is all of them on a healthy store).
+      const packedRanges = (await this.segments.actualRanges())
+        .map((r): [number, number] => [r[0], Math.min(r[1], this.committed)])
         .filter(([lo, hi]) => lo <= hi)
       if (packedRanges.length > 0) {
         // Merge packed (older) + live (newer) interval sets — both ascending;
@@ -3121,13 +3156,26 @@ export class GenerationStore {
           foldInput.push({ generation: gen, timestamp: delta.timestamp, delta, records })
         }
         if (foldInput.length === 0) continue
-        await segments.fold(foldInput)
+        // SPLIT AT DISCONTINUITIES. `eligible` is NOT contiguous — three
+        // filters above punch holes in it: a generation missing from
+        // committedRanges never appears, one still in the pending buffer is
+        // skipped, and one whose tx.json will not read is skipped. A sealed
+        // segment declares a DENSE range, so folding across such a hole makes
+        // the segment claim a generation it does not hold; the next open
+        // merges that mis-declared range into committedRanges, and every
+        // subsequent auto-compaction pass then asks for the missing frame and
+        // fails with "packed history is damaged". Fold each contiguous RUN as
+        // its own segment instead — same bytes, honest ranges.
+        for (const run of contiguousRuns(foldInput)) {
+          if (deadline !== undefined && Date.now() >= deadline) break
+          await segments.fold(run)
           segmentsCreated++
           // Segment + manifest durable → the live copies retire.
-        for (const g of foldInput) {
+          for (const g of run) {
             await this.storage.removeRawPrefix(`${GENERATIONS_PREFIX}/${g.generation}`)
           }
-        folded += foldInput.length
+          folded += run.length
+        }
       }
       if (folded > 0) {
         prodLog.info(

src/storage/adapters/baseStorageAdapter.ts

@@ -1089,6 +1089,10 @@ export abstract class BaseStorageAdapter implements StorageAdapter {
 
   // Counts changed since the last persist? Drives the write-through flush.
   protected pendingCountPersist = false
+  /** The one persist running right now, if any (single-flight law — see flushCounts). */
+  private countPersistInFlight: Promise<void> | null = null
+  /** The one trailing persist a burst has queued behind the in-flight one. */
+  private countPersistTrailing: Promise<void> | null = null
 
   /**
    * Get total noun count - O(1) operation
@@ -1341,15 +1345,46 @@ export abstract class BaseStorageAdapter implements StorageAdapter {
       return
     }
 
+    // SINGLE-FLIGHT, COALESCED. Counts are write-through on every change, so
+    // a burst of writes used to launch one persist per change, all in flight
+    // together. Two of them inside the same millisecond shared the atomic
+    // writer's temp path (`.tmp-<pid>-<ms>`): both wrote it, the first rename
+    // consumed it, the second rename found nothing — ENOENT, ~1,500 times a
+    // day on a busy production brain, with a full ledger write per change
+    // behind it. Now exactly one persist runs at a time; requests that arrive
+    // while it runs collapse into ONE trailing persist that carries the final
+    // state. A burst of N changes costs at most two writes and never races
+    // itself.
+    if (this.countPersistInFlight) {
+      // The in-flight write may have already serialised a stale snapshot —
+      // ask for one more pass after it, and let every caller in this burst
+      // await that same pass.
+      if (!this.countPersistTrailing) {
+        this.countPersistTrailing = this.countPersistInFlight
+          .catch(() => undefined)
+          .then(() => {
+            this.countPersistTrailing = null
+            return this.flushCounts()
+          })
+      }
+      return this.countPersistTrailing
+    }
+
+    this.countPersistInFlight = (async () => {
       try {
         // Persist to storage (implemented by subclass)
-      await this.persistCounts()
         this.pendingCountPersist = false
+        await this.persistCounts()
       } catch (error) {
+        // Keep the flag set so the next operation retries.
+        this.pendingCountPersist = true
         console.error('CRITICAL: Failed to flush counts to storage:', error)
-      // Keep pending flag set so we retry on next operation
         throw error
+      } finally {
+        this.countPersistInFlight = null
       }
+    })()
+    return this.countPersistInFlight
   }
 
   /**

src/storage/adapters/fileSystemStorage.ts

@@ -2400,8 +2400,15 @@ export class FileSystemStorage extends BaseStorage {
    * Atomic write via temp-file-then-rename so concurrent readers never see a
    * half-written lock JSON. Reused by writer-lock writes + heartbeat.
    */
+  /** Monotonic per-process sequence so two atomic writes never share a temp path. */
+  private static atomicWriteSeq = 0
+
   private async writeFileAtomic(filePath: string, contents: string): Promise<void> {
-    const tmp = `${filePath}.tmp-${process.pid}-${Date.now()}`
+    // pid + timestamp alone collided: two writers of the same target inside
+    // one millisecond shared this path, and the loser's rename found the
+    // winner had already moved it (ENOENT). The sequence makes every call's
+    // temp path its own.
+    const tmp = `${filePath}.tmp-${process.pid}-${Date.now()}-${++FileSystemStorage.atomicWriteSeq}`
     await fs.promises.writeFile(tmp, contents)
     await fs.promises.rename(tmp, filePath)
   }

src/transaction/operations/IndexOperations.ts

@@ -14,6 +14,7 @@ import type { MetadataIndexManager } from '../../utils/metadataIndex.js'
 import type { GraphVerb } from '../../coreTypes.js'
 import type { Operation, RollbackAction } from '../types.js'
 import { isZeroNormVector } from '../../utils/distance.js'
+import { jsonSafeIndexMetadata } from '../../utils/jsonSafeIndexMetadata.js'
 import { prodLog } from '../../utils/logger.js'
 
 /**
@@ -390,13 +391,21 @@ export class AddToMetadataIndexOperation implements Operation {
     // rollback so add + undo reference the same watermark.
     const generation = this.generationFn?.()
 
-    // Add to metadata index (skipFlush=true for transaction atomicity)
+    // The JSON-safe view is taken HERE, per crossing, never at construction:
-    await this.index.addToIndex(this.id, this.entity, true, false, generation)
+    // the entity reference this op holds can be mutated between plan and
+    // execute (a graph op's execute-time endpoint-int resolution mirrors
+    // BigInts onto a shared verb object) — see jsonSafeIndexMetadata's
+    // module doc.
+    await this.index.addToIndex(
+      this.id, jsonSafeIndexMetadata(this.entity), true, false, generation
+    )
 
     // Return rollback action
     return async () => {
       // Remove from metadata index
-      await this.index.removeFromIndex(this.id, this.entity, generation)
+      await this.index.removeFromIndex(
+        this.id, jsonSafeIndexMetadata(this.entity), generation
+      )
     }
   }
 }
@@ -432,13 +441,21 @@ export class RemoveFromMetadataIndexOperation implements Operation {
     // Resolve the removal generation once; reuse it for the rollback re-add.
     const generation = this.generationFn?.()
 
-    // Remove from metadata index
+    // Sanitized per crossing, never at construction — transact()'s delete
-    await this.index.removeFromIndex(this.id, this.entity, generation)
+    // legs hand this op the SAME verb object the graph-retraction op's
+    // execute-time endpoint resolution mutates (BigInt sourceInt/targetInt),
+    // so a plan-time view aliases the pollution. See jsonSafeIndexMetadata's
+    // module doc.
+    await this.index.removeFromIndex(
+      this.id, jsonSafeIndexMetadata(this.entity), generation
+    )
 
     // Return rollback action
     return async () => {
       // Re-add with original metadata (skipFlush=true)
-      await this.index.addToIndex(this.id, this.entity, true, false, generation)
+      await this.index.addToIndex(
+        this.id, jsonSafeIndexMetadata(this.entity), true, false, generation
+      )
     }
   }
 }

src/utils/jsonSafeIndexMetadata.ts

@@ -0,0 +1,47 @@
+/**
+ * @module utils/jsonSafeIndexMetadata
+ * @description The metadata-index crossing's JSON-safety law, as a leaf
+ * function both the coordinator and the transaction operations share.
+ *
+ * The seam's metadata is JSON-safe BY CONTRACT (a native provider serializes
+ * it; u64 ints as Number corrupt above 2^53) — but `resolveVerbEndpointInts`
+ * MIRRORS the resolved endpoint ints onto the verb object itself as BigInt
+ * (`verb.sourceInt`/`targetInt`), so a verb object reused as index metadata
+ * carries BigInts into JSON.stringify, which throws, aborting the whole
+ * transaction. Endpoint ints ride their OWN op params on the graph legs — the
+ * metadata crossing drops every BigInt-valued top-level key instead of
+ * guessing at a lossy numeric encoding.
+ *
+ * WHY THIS IS A LEAF MODULE, ENFORCED AT THE CROSSING: sanitizing only at
+ * operation-construction time is not enough. `transact()`'s delete legs pass
+ * the SAME verb object to both the graph-retraction op (whose endpoint-int
+ * thunk deliberately resolves at EXECUTE time, for same-batch forward refs)
+ * and the metadata-retraction op. At plan time the verb is still clean, so a
+ * plan-time sanitize returns the same reference — then the graph op executes
+ * first, mirrors the BigInt ints onto the shared object, and the metadata op
+ * crosses the seam with them (found by the first fleet adoption of the native
+ * pair: every transact-wrapped edge delete aborted). The crossing itself is
+ * the only place ordering cannot bypass.
+ */
+
+/**
+ * A JSON-safe view of a record bound for the metadata-index crossing.
+ *
+ * @param metadata - The candidate index-metadata record.
+ * @returns The same object when already JSON-safe, else a shallow copy
+ *   without the BigInt-valued keys.
+ */
+export function jsonSafeIndexMetadata(metadata: unknown): unknown {
+  if (metadata === null || typeof metadata !== 'object') return metadata
+  const rec = metadata as Record<string, unknown>
+  let hasBigint = false
+  for (const k in rec) {
+    if (typeof rec[k] === 'bigint') { hasBigint = true; break }
+  }
+  if (!hasBigint) return metadata
+  const out: Record<string, unknown> = {}
+  for (const k in rec) {
+    if (typeof rec[k] !== 'bigint') out[k] = rec[k]
+  }
+  return out
+}

src/vfs/VirtualFileSystem.ts

@@ -2295,6 +2295,31 @@ export class VirtualFileSystem implements IVirtualFileSystem {
       cursor = page.nextCursor
     }
 
+    // Pass 2: ONE paged walk over every Contains edge, grouped by target in
+    // memory. The earlier shape issued one awaited related({ to }) per VFS
+    // entity — O(entities) serialized graph calls, measured in whole minutes
+    // on large brains. This shape is O(edges / page) calls regardless of how
+    // many entities exist; mutations alone stay per-defect.
+    const incomingByTarget = new Map<string, Relation<any>[]>()
+    {
+      const pageSize = 1000
+      let pageOffset = 0
+      for (;;) {
+        const page = await this.brain.related({
+          type: VerbType.Contains,
+          limit: pageSize,
+          offset: pageOffset
+        })
+        for (const edge of page) {
+          const bucket = incomingByTarget.get(edge.to)
+          if (bucket) bucket.push(edge)
+          else incomingByTarget.set(edge.to, [edge])
+        }
+        if (page.length < pageSize) break
+        pageOffset += pageSize
+      }
+    }
+
     let removed = 0
     let restored = 0
     for (const { id, path } of vfsEntities) {
@@ -2307,7 +2332,7 @@ export class VirtualFileSystem implements IVirtualFileSystem {
         continue
       }
 
-      const incoming = await this.brain.related({ to: id, type: VerbType.Contains })
+      const incoming = incomingByTarget.get(id) ?? []
       let expectedSeen = false
       for (const edge of incoming) {
         const isVfsEdge = edge.subtype === 'vfs-contains' || (edge.metadata as any)?.isVFS === true

tests/integration/counts-persist-single-flight.test.ts

@@ -0,0 +1,111 @@
+/**
+ * @module tests/integration/counts-persist-single-flight
+ * @description Regression for a production race in FileSystemStorage's
+ * counts ledger: `persistCounts()` was write-through on every count change
+ * with no serialization, and the atomic writer named its temp file with
+ * millisecond granularity (`.tmp-<pid>-<ms>`). Two persists inside one
+ * millisecond shared the temp path — both wrote it, the first rename
+ * consumed it, the second rename found nothing: ENOENT, ~1,500 times a day
+ * on a busy production brain, with a full ledger write per change behind it.
+ *
+ * Under pin: persists are single-flight and coalesced — one in flight, at
+ * most one trailing pass carrying the burst's final state — and every atomic
+ * write owns a unique temp path. A burst of N count changes costs at most
+ * two ledger writes, never errors, and leaves a ledger equal to memory.
+ */
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
+import * as fs from 'node:fs'
+import * as os from 'node:os'
+import * as path from 'node:path'
+import { Brainy } from '../../src/brainy.js'
+import { NounType } from '../../src/types/graphTypes.js'
+
+describe('counts persistence is single-flight, coalesced, and never races its own temp file', () => {
+  let dir: string
+  let brain: any
+
+  beforeEach(async () => {
+    process.env.BRAINY_DETERMINISTIC_EMBEDDINGS = 'true'
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'brainy-counts-race-'))
+    brain = new Brainy({
+      requireSubtype: false,
+      storage: { type: 'filesystem', path: dir },
+      dimensions: 384,
+      silent: true
+    })
+    await brain.init()
+  })
+
+  afterEach(async () => {
+    vi.restoreAllMocks()
+    await brain.close()
+    fs.rmSync(dir, { recursive: true, force: true })
+  })
+
+  it('a burst of concurrent count changes → at most two ledger writes, zero errors, ledger == memory', async () => {
+    const storage = brain.storage
+    const countsPath: string = storage.countsFilePath
+    expect(countsPath, 'the filesystem adapter persists a counts ledger').toBeTruthy()
+
+    // Let init's own persists settle so the burst is measured alone.
+    await storage.flushCounts?.()
+
+    const renameSpy = vi.spyOn(fs.promises, 'rename')
+    const errorSpy = vi.spyOn(console, 'error')
+
+    // Twenty-five concurrent count changes — the shape of a write burst; each
+    // used to launch its own persist.
+    const BURST = 25
+    await Promise.all(
+      Array.from({ length: BURST }, () => storage.scheduleCountPersist())
+    )
+
+    const ledgerRenames = renameSpy.mock.calls.filter(([, to]) => String(to) === countsPath)
+    expect(ledgerRenames.length, 'single-flight + one trailing pass').toBeLessThanOrEqual(2)
+    expect(ledgerRenames.length, 'the burst was persisted at all').toBeGreaterThanOrEqual(1)
+
+    const persistErrors = errorSpy.mock.calls.filter((args) => String(args[0]).includes('persisting counts'))
+    expect(persistErrors).toEqual([])
+
+    const ledger = JSON.parse(fs.readFileSync(countsPath, 'utf-8'))
+    expect(ledger.totalNounCount).toBe(storage.totalNounCount)
+    expect(ledger.totalVerbCount).toBe(storage.totalVerbCount)
+  })
+
+  it('real writes in parallel: the ledger lands complete and no persist error is logged', async () => {
+    const storage = brain.storage
+    const countsPath: string = storage.countsFilePath
+    const errorSpy = vi.spyOn(console, 'error')
+
+    await Promise.all(
+      Array.from({ length: 12 }, (_, i) =>
+        brain.add({ data: `burst row ${i}`, type: NounType.Thing })
+      )
+    )
+    await storage.flushCounts?.()
+
+    const persistErrors = errorSpy.mock.calls.filter((args) => String(args[0]).includes('persisting counts'))
+    expect(persistErrors).toEqual([])
+    const ledger = JSON.parse(fs.readFileSync(countsPath, 'utf-8'))
+    expect(ledger.totalNounCount).toBe(storage.totalNounCount)
+    expect(await brain.getNounCount()).toBe(ledger.totalNounCount)
+  })
+
+  it('every atomic write owns its own temp path — two writes in one millisecond never collide', async () => {
+    const storage = brain.storage
+    const tmpNames: string[] = []
+    vi.spyOn(fs.promises, 'writeFile').mockImplementation(async (p: any) => {
+      tmpNames.push(String(p))
+    })
+    vi.spyOn(fs.promises, 'rename').mockImplementation(async () => undefined)
+    const target = path.join(dir, 'probe.json')
+    await Promise.all([
+      storage.writeFileAtomic(target, '{"a":1}'),
+      storage.writeFileAtomic(target, '{"a":2}'),
+      storage.writeFileAtomic(target, '{"a":3}')
+    ])
+    const probeTmps = tmpNames.filter((n) => n.startsWith(`${target}.tmp-`))
+    expect(probeTmps.length).toBe(3)
+    expect(new Set(probeTmps).size, 'no two writes shared a temp path').toBe(3)
+  })
+})

tests/integration/entity-tree-stamp.test.ts

@@ -57,7 +57,11 @@ describe('entity-tree family stamp', () => {
     const invariants = (stamp.members as any).invariants
     expect(invariants.nounCount).toBe(await brain.storage.getNounCount())
     expect(invariants.verbCount).toBe(await brain.storage.getVerbCount())
-    expect(stamp.sourceGeneration).toBe(brain.generation())
+    // THE SOURCE IS COMMITTED TRUTH, never the allocated counter. Stamping the
+    // counter labelled the stamp with a generation a write in flight had merely
+    // claimed, so every crash inside a write window produced a spurious verdict
+    // at the next open (see the torn-tail pins below).
+    expect(stamp.sourceGeneration).toBe(brain.generationStore.committedGeneration())
     expect(stamp.generation).toBeGreaterThanOrEqual(1)
   })
 
@@ -112,6 +116,96 @@ describe('entity-tree family stamp', () => {
     expect(stillIncoherent).toEqual([])
   })
 
+  /**
+   * Rewrite the on-disk stamp so its `sourceGeneration` sits ABOVE the store's
+   * committed watermark — the durable shape a torn generation-log tail leaves
+   * behind (the stamp's fsync outlived the tail's). Fabricated rather than
+   * crash-produced so the pin is deterministic; the seeded-SIGKILL lane
+   * (`scripts/crash-consistency.mjs` in the engine repo) produces the same
+   * shape from a real abrupt termination.
+   */
+  const fabricateTear = (ahead: number): FamilyStamp => {
+    const file = path.join(dir, `${ENTITY_TREE_STAMP_PATH}.gz`)
+    const zlib = require('node:zlib')
+    const raw = JSON.parse(zlib.gunzipSync(fs.readFileSync(file)).toString('utf-8')) as FamilyStamp
+    const torn: FamilyStamp = { ...raw, sourceGeneration: raw.sourceGeneration + ahead }
+    fs.writeFileSync(file, zlib.gzipSync(JSON.stringify(torn)))
+    return torn
+  }
+
+  it('a torn generation-log tail is a TERMINAL VERDICT at open: narrated, demoted, never a wait', async () => {
+    for (let i = 0; i < 3; i++)
+      await brain.add({ data: `torn${i}`, type: 'document', metadata: { i } })
+    await brain.close()
+    const torn = fabricateTear(5)
+
+    const warn = vi.spyOn(prodLog, 'warn')
+    const startedAt = Date.now()
+    brain = await open()
+    const openMs = Date.now() - startedAt
+
+    const tearLines = warn.mock.calls.filter((c) => String(c[0]).includes('TORN GENERATION-LOG TAIL'))
+    expect(tearLines.length).toBe(1)
+    const said = String(tearLines[0][0])
+    // Narrated PRECISELY: both generations, the file, and the named cure.
+    expect(said).toContain(`source generation ${torn.sourceGeneration}`)
+    expect(said).toContain(`committed generation ${brain.generationStore.committedGeneration()}`)
+    expect(said).toContain(ENTITY_TREE_STAMP_PATH)
+    expect(said).toContain('DEMOTED')
+    expect(said).toMatch(/repairIndex\(\)/)
+    // Terminal, not a wait: the demotion is O(1) straight-line work, so a tear
+    // cannot turn an open into the 8-minute spin this class was reported as.
+    expect(openMs).toBeLessThan(30_000)
+
+    // The store SERVES — a tear in a stamp never locks an owner out of the
+    // canonical tree the stamp merely describes.
+    expect((await brain.find({ type: 'document', limit: 100 })).length).toBe(3)
+
+    // The demotion CONVERGED: the stamp now names committed truth, and the
+    // next open is quiet. A verdict that re-narrates every open is a wait
+    // wearing a different hat.
+    const restamped = (await readFamilyStamp(brain.storage, ENTITY_TREE_STAMP_PATH)) as FamilyStamp
+    expect(restamped.sourceGeneration).toBe(brain.generationStore.committedGeneration())
+    await brain.close()
+    const warn2 = vi.spyOn(prodLog, 'warn')
+    brain = await open()
+    expect(warn2.mock.calls.filter((c) => String(c[0]).includes('TORN'))).toEqual([])
+  })
+
+  it('a READ-ONLY open on a torn tail refuses to guess: terminal verdict + named cure, no re-stamp', async () => {
+    await brain.add({ data: 'ro', type: 'document', metadata: {} })
+    await brain.close()
+    const torn = fabricateTear(3)
+
+    const warn = vi.spyOn(prodLog, 'warn')
+    const reader: any = await Brainy.openReadOnly({
+      requireSubtype: false,
+      storage: { type: 'filesystem', path: dir },
+      silent: true,
+      dimensions: 384
+    })
+    const tearLines = warn.mock.calls.filter((c) => String(c[0]).includes('TORN GENERATION-LOG TAIL'))
+    expect(tearLines.length).toBe(1)
+    const said = String(tearLines[0][0])
+    expect(said).toContain('READ-ONLY')
+    expect(said).toContain('UNVERIFIED')
+    expect(said).toMatch(/repairIndex\(\)/)
+    await reader.close()
+
+    // A reader never rewrites the store: read the bytes back off disk (not
+    // through a writer open, which would demote them) — the torn stamp is
+    // exactly as it was found.
+    const onDisk = JSON.parse(
+      require('node:zlib')
+        .gunzipSync(fs.readFileSync(path.join(dir, `${ENTITY_TREE_STAMP_PATH}.gz`)))
+        .toString('utf-8')
+    ) as FamilyStamp
+    expect(onDisk.sourceGeneration).toBe(torn.sourceGeneration)
+    expect(onDisk.generation).toBe(torn.generation)
+
+    brain = await open()
+  })
+
   it('the one verifier handles both member modes', () => {
     const rollup: FamilyStamp = {
       family: 'x',
@@ -127,7 +221,13 @@ describe('entity-tree family stamp', () => {
       stampSource: 5,
       head: 9
     })
-    expect(verifyFamilyStamp(rollup, 3, { nounCount: 10 }).state).toBe('incoherent') // ahead of head
+    // AHEAD is its own class — a torn generation-log tail, never folded in
+    // with `incoherent`: the two have opposite cures (recount vs demote).
+    expect(verifyFamilyStamp(rollup, 3, { nounCount: 10 })).toEqual({
+      state: 'torn',
+      stampSource: 5,
+      head: 3
+    })
     expect(verifyFamilyStamp(null, 5, {})).toEqual({ state: 'absent' })
 
     const enumerated: FamilyStamp = {

tests/integration/history-repacking.test.ts

@@ -16,6 +16,7 @@ import { describe, it, expect, afterEach } from 'vitest'
 import * as fs from 'node:fs'
 import * as path from 'node:path'
 import * as os from 'node:os'
+import * as zlib from 'node:zlib'
 import { Brainy } from '../../src/brainy.js'
 import { NounType } from '../../src/types/graphTypes.js'
 import { GenerationStore } from '../../src/db/generationStore.js'
@@ -57,6 +58,107 @@ describe('history repacking — the two-tier lifecycle', () => {
     }
   })
 
+  /**
+   * THE HOLE, END TO END — the shape a real store carries.
+   *
+   * A forensic fixture was measured with generation directories 1..2503
+   * present except for exactly one: 1416. Its fact-log segment already showed
+   * the tell — `seg-...1410.bfl` declaring firstGeneration 1410, lastGeneration
+   * 1940 (531 generations) while recording only 530 facts.
+   *
+   * Before the fix, repacking such a store folded ACROSS that hole: the batch
+   * skipped 1416 (no readable delta) and the sealed segment declared a range
+   * spanning it anyway. The next open merged that declared range back into
+   * committedRanges, re-admitting 1416 as committed history, and every
+   * subsequent auto-compaction pass then asked the packed tier for a frame
+   * that was never written — producing, on EVERY run, the non-fatal narration
+   *
+   *   Auto-compaction of generational history failed (non-fatal): generation
+   *   N is inside sealed segment seg-....bgs's declared range but has no frame
+   *   — packed history is damaged
+   *
+   * This pin removes a generation directory to make the same hole, then
+   * requires repack + reopen + compaction to complete cleanly.
+   */
+  it('a missing generation directory does not poison the packed tier', async () => {
+    const dir = tempDir()
+    // `retention: 'all'` throughout: close() otherwise auto-compacts the
+    // history away, and this pin needs the cold generations still on disk so
+    // there is something to punch a hole in. The live window stays at its
+    // production default for the build phase, so nothing folds yet.
+    const archival = async (): Promise<Brainy> => {
+      const b = new Brainy({
+        requireSubtype: false,
+        storage: { type: 'filesystem', path: dir },
+        embeddingFunction: stub,
+        retention: 'all'
+      })
+      await b.init()
+      return b
+    }
+    const brain = await archival()
+
+    const id = await brain.add({
+      data: 'holed-entity',
+      type: NounType.Document,
+      metadata: { v: 0 }
+    })
+    // One flush per update: single-op writes coalesce inside a flush window,
+    // so a history deep enough to have a middle needs the windows separated.
+    for (let v = 1; v <= 12; v++) {
+      await brain.update({ id, metadata: { v } })
+      await brain.flush()
+    }
+    await brain.close()
+
+    // Punch the hole: delete ONE generation directory in the middle of the
+    // cold range, exactly as the real store presents it.
+    const genRoot = path.join(dir, '_generations')
+    const numeric = fs
+      .readdirSync(genRoot, { withFileTypes: true })
+      .filter((e) => e.isDirectory() && /^\d+$/.test(e.name))
+      .map((e) => Number(e.name))
+      .sort((a, b) => a - b)
+    expect(numeric.length).toBeGreaterThan(6)
+    const victim = numeric[Math.floor(numeric.length / 2)]
+    fs.rmSync(path.join(genRoot, String(victim)), { recursive: true, force: true })
+
+    // Now shrink the live window and reopen. close() repacks automatically
+    // (brainy.ts phase 0b), so this is the production sequence exactly: a
+    // store with a hole in its history gets folded by ordinary housekeeping,
+    // with nobody asking for it.
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = 3
+    const reopened = await archival()
+    const result = await reopened.repackHistory()
+    expect(result.foldedGenerations).toBeGreaterThan(0)
+
+    const segDir = path.join(dir, SEGMENTS_PREFIX)
+    const manifestPath = ['manifest.json', 'manifest.json.gz']
+      .map((f) => path.join(segDir, f))
+      .find((p) => fs.existsSync(p))!
+    const raw = manifestPath.endsWith('.gz')
+      ? zlib.gunzipSync(fs.readFileSync(manifestPath)).toString('utf8')
+      : fs.readFileSync(manifestPath, 'utf8')
+    const manifest = JSON.parse(raw) as {
+      segments: Array<{ firstGeneration: number; lastGeneration: number; frames: number }>
+    }
+
+    // THE LAW: every sealed segment declares exactly as many generations as it
+    // holds frames, and none of them spans the victim.
+    for (const s of manifest.segments) {
+      expect(s.lastGeneration - s.firstGeneration + 1).toBe(s.frames)
+      expect(victim >= s.firstGeneration && victim <= s.lastGeneration).toBe(false)
+    }
+
+    await reopened.close()
+
+    // And the pass that used to fail on every run now completes: reopen (which
+    // re-seeds committedRanges from the packed tier) then compact history.
+    const third = await openBrain(dir)
+    await expect(third.compactHistory({ maxGenerations: 2 })).resolves.toBeDefined()
+    await third.close()
+  })
+
   it('repack preserves every historical read across cold reopen; folded dirs are gone', async () => {
     ;(GenerationStore as any).REPACK_LIVE_WINDOW = 3
     const dir = tempDir()

tests/integration/transact-edge-delete-bigint-aliasing.test.ts

@@ -0,0 +1,184 @@
+/**
+ * @module tests/integration/transact-edge-delete-bigint-aliasing
+ * @description Regression for a fleet-adoption blocker: ANY edge delete
+ * inside `transact()` — a direct unrelate or a noun-remove's cascade —
+ * aborted with the metadata seam's BigInt JSON-guard error on a strict
+ * (native) metadata provider.
+ *
+ * The aliasing chain: `planTxUnrelate`/the remove-cascade pass the SAME verb
+ * object to the graph-retraction op and the metadata-retraction op. The
+ * metadata leg's JSON-safe wrap ran at PLAN time, when the verb was still
+ * clean — so it returned the same reference. At EXECUTE time the graph op
+ * runs first and `resolveVerbEndpointInts` mirrors BigInt
+ * `sourceInt`/`targetInt` onto the shared object (deliberately deferred for
+ * same-batch forward refs — see transact-forward-ref-graph.test.ts); the
+ * metadata op then crossed the seam with the polluted object. Direct
+ * `unrelate()` resolves ints at BUILD time, before its sanitize, which is why
+ * only the transact() shapes ever hit it.
+ *
+ * Fix under pin: the JSON-safe view is taken AT THE CROSSING — inside the
+ * metadata-index operations' execute/rollback — so no plan-vs-execute
+ * ordering can bypass it. The JS baseline index tolerates BigInts (it would
+ * mask the bug), so these pins SPY on the seam and assert what actually
+ * crossed, exactly as a strict native provider would judge it.
+ */
+import { describe, it, expect, beforeEach, afterEach } from 'vitest'
+import * as fs from 'node:fs'
+import * as os from 'node:os'
+import * as path from 'node:path'
+import { Brainy } from '../../src/brainy.js'
+import { NounType, VerbType } from '../../src/types/graphTypes.js'
+import {
+  AddToMetadataIndexOperation,
+  RemoveFromMetadataIndexOperation
+} from '../../src/transaction/operations/index.js'
+
+let seq = 0
+const freshId = (): string =>
+  `00000000-0000-4000-8000-${(++seq).toString(16).padStart(12, '0')}`
+
+/** Top-level BigInt-valued keys of a candidate seam crossing (the guard's law). */
+const bigintKeys = (metadata: unknown): string[] => {
+  if (metadata === null || typeof metadata !== 'object') return []
+  return Object.entries(metadata as Record<string, unknown>)
+    .filter(([, v]) => typeof v === 'bigint')
+    .map(([k]) => k)
+}
+
+describe('transact() edge deletes never carry BigInt across the metadata seam', () => {
+  let dir: string
+  let brain: any
+  let crossings: Array<{ door: string; id: string; keys: string[] }>
+
+  beforeEach(async () => {
+    process.env.BRAINY_DETERMINISTIC_EMBEDDINGS = 'true'
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'brainy-tx-bigint-'))
+    brain = new Brainy({
+      requireSubtype: false,
+      storage: { type: 'filesystem', path: dir },
+      dimensions: 384,
+      silent: true
+    })
+    await brain.init()
+
+    // Spy on the seam the way a strict native provider judges it: record the
+    // BigInt-valued top-level keys of every metadata argument that crosses.
+    // The JS baseline index tolerates BigInts, so without this the baseline
+    // run would green a shape the native pair aborts on.
+    crossings = []
+    const index = brain.metadataIndex
+    for (const door of ['addToIndex', 'removeFromIndex'] as const) {
+      const real = index[door].bind(index)
+      index[door] = (id: string, metadata: unknown, ...rest: unknown[]) => {
+        crossings.push({ door, id, keys: bigintKeys(metadata) })
+        return real(id, metadata, ...rest)
+      }
+    }
+  })
+
+  afterEach(async () => {
+    await brain.close()
+    fs.rmSync(dir, { recursive: true, force: true })
+  })
+
+  it('CASE 1 (the fleet repro): relate, then transact([{op: unrelate}])', async () => {
+    const a = await brain.add({ id: freshId(), data: 'a', type: NounType.Thing })
+    const b = await brain.add({ id: freshId(), data: 'b', type: NounType.Thing })
+    const verbId = await brain.relate({ from: a, to: b, type: VerbType.RelatedTo })
+
+    crossings.length = 0
+    await brain.transact([{ op: 'unrelate', id: verbId }])
+
+    const polluted = crossings.filter((c) => c.keys.length > 0)
+    expect(polluted).toEqual([])
+    expect(await brain.storage.getVerb(verbId)).toBeFalsy()
+  })
+
+  it('CASE 2 (the cascade shape): transact([{op: remove}]) cascading edge deletes', async () => {
+    const a = await brain.add({ id: freshId(), data: 'a', type: NounType.Thing })
+    const b = await brain.add({ id: freshId(), data: 'b', type: NounType.Thing })
+    const c = await brain.add({ id: freshId(), data: 'c', type: NounType.Thing })
+    const ab = await brain.relate({ from: a, to: b, type: VerbType.RelatedTo })
+    const ca = await brain.relate({ from: c, to: a, type: VerbType.RelatedTo })
+
+    crossings.length = 0
+    await brain.transact([{ op: 'remove', id: a }])
+
+    const polluted = crossings.filter((c2) => c2.keys.length > 0)
+    expect(polluted).toEqual([])
+    expect(await brain.get(a)).toBeFalsy()
+    expect(await brain.storage.getVerb(ab)).toBeFalsy()
+    expect(await brain.storage.getVerb(ca)).toBeFalsy()
+  })
+
+  it('CASE 3 (one batch, both legs): adds + relate + unrelate of a pre-existing edge', async () => {
+    const a = await brain.add({ id: freshId(), data: 'a', type: NounType.Thing })
+    const b = await brain.add({ id: freshId(), data: 'b', type: NounType.Thing })
+    const old = await brain.relate({ from: a, to: b, type: VerbType.RelatedTo })
+
+    const x = freshId()
+    crossings.length = 0
+    await brain.transact([
+      { op: 'add', id: x, data: 'x', type: NounType.Thing },
+      { op: 'relate', from: a, to: x, type: VerbType.RelatedTo },
+      { op: 'unrelate', id: old }
+    ])
+
+    const polluted = crossings.filter((c) => c.keys.length > 0)
+    expect(polluted).toEqual([])
+    expect(await brain.storage.getVerb(old)).toBeFalsy()
+    const edges = await brain.related({ from: a })
+    expect(edges.length).toBe(1)
+    expect(edges[0].id).not.toBe(old)
+  })
+})
+
+describe('the metadata-index operations sanitize at the crossing, not at construction', () => {
+  /** A strict seam: refuses BigInts exactly as the native provider does. */
+  const strictIndex = () => {
+    const seen: Array<{ door: string; keys: string[] }> = []
+    const judge = (door: string, metadata: unknown) => {
+      const keys = bigintKeys(metadata)
+      seen.push({ door, keys })
+      if (keys.length > 0) {
+        throw new Error(
+          `${door}: the metadata object violates the provider seam's JSON ` +
+            `contract — BigInt at ${keys.join(', ')}.`
+        )
+      }
+    }
+    return {
+      seen,
+      addToIndex: async (_id: string, metadata: unknown) => judge('addToIndex', metadata),
+      removeFromIndex: async (_id: string, metadata: unknown) => judge('removeFromIndex', metadata)
+    }
+  }
+
+  it('RemoveFromMetadataIndexOperation: entity mutated AFTER construction still crosses clean', async () => {
+    const index = strictIndex()
+    const verb: Record<string, unknown> = { id: 'v1', sourceId: 'a', targetId: 'b' }
+    const op = new RemoveFromMetadataIndexOperation(index as any, 'v1', verb, () => 7n)
+
+    // The graph leg's execute-time endpoint resolution, simulated: the shared
+    // object is polluted between plan and execute.
+    verb.sourceInt = 800_000n
+    verb.targetInt = 800_001n
+
+    const rollback = await op.execute()
+    await rollback()
+    expect(index.seen.map((s) => s.keys)).toEqual([[], []])
+  })
+
+  it('AddToMetadataIndexOperation: same law on the add leg and its rollback', async () => {
+    const index = strictIndex()
+    const verb: Record<string, unknown> = { id: 'v2', sourceId: 'a', targetId: 'b' }
+    const op = new AddToMetadataIndexOperation(index as any, 'v2', verb, () => 7n)
+
+    verb.sourceInt = 800_000n
+    verb.targetInt = 800_001n
+
+    const rollback = await op.execute()
+    await rollback()
+    expect(index.seen.map((s) => s.keys)).toEqual([[], []])
+  })
+})

tests/integration/vfs-containment-batched.test.ts

@@ -0,0 +1,115 @@
+/**
+ * @module tests/integration/vfs-containment-batched
+ * @description repairContainment costs O(edges/page) graph calls, not O(entities) (10.4.9 train).
+ *
+ * Pass 2 used to issue one awaited `related({ to })` per VFS entity — minutes
+ * of serialized graph calls on large brains. Now one paged walk over every
+ * Contains edge feeds an in-memory group-by-target, and only actual defects
+ * mutate. These pins hold the verdicts (duplicate removed, stale parent
+ * removed, missing edge restored, user knowledge edges untouched) AND the
+ * cost shape (related() call count independent of the entity count).
+ */
+import { describe, it, expect, beforeAll, afterAll, vi } from 'vitest'
+import { Brainy } from '../../src/brainy'
+import { NounType, VerbType } from '../../src/types/graphTypes'
+
+const FILES = 60
+
+describe('repairContainment: batched pass 2', () => {
+  let brain: Brainy<any>
+  let result: { removed: number; restored: number }
+  let relatedCalls = 0
+
+  beforeAll(async () => {
+    brain = new Brainy({ requireSubtype: false, storage: { type: 'memory' } })
+    await brain.init()
+    const vfs = (brain as any).vfs ?? (brain as any)._vfs
+    expect(vfs).toBeTruthy()
+    await vfs.init()
+
+    // A directory and FILES entries under it, wired as real VFS rows.
+    const mkNode = async (id: string, path: string, vfsType: string): Promise<void> => {
+      await brain.add({
+        id,
+        data: `vfs node ${path}`,
+        type: NounType.File,
+        visibility: 'system',
+        metadata: { vfsType, path }
+      })
+    }
+    await mkNode('dir', '/docs', 'directory')
+    const rootId = vfs.rootEntityId ?? (await vfs.initializeRoot?.())
+    if (rootId) {
+      await brain.relate({
+        from: rootId,
+        to: 'dir',
+        type: VerbType.Contains,
+        subtype: 'vfs-contains',
+        metadata: { isVFS: true }
+      })
+    }
+    for (let i = 0; i < FILES; i++) {
+      await mkNode(`f-${i}`, `/docs/f-${i}.md`, 'file')
+      if (i === 0) continue // f-0: MISSING edge — must be restored
+      await brain.relate({
+        from: 'dir',
+        to: `f-${i}`,
+        type: VerbType.Contains,
+        subtype: 'vfs-contains',
+        metadata: { isVFS: true }
+      })
+    }
+    // NOTE: relate() is idempotent for an identical from/to/type, so a true
+    // duplicate (a concurrent-writer artifact) cannot be seeded through the
+    // public API — the duplicate branch is covered by the tree-correctness
+    // pin below, which proves at most one vfs edge survives per file.
+    // f-2: STALE parent edge (from a sibling file) — must be removed.
+    await brain.relate({
+      from: 'f-3',
+      to: 'f-2',
+      type: VerbType.Contains,
+      subtype: 'vfs-contains',
+      metadata: { isVFS: true }
+    })
+    // A USER knowledge Contains edge (not vfs-flagged) — must be untouched.
+    await brain.relate({ from: 'f-4', to: 'f-5', type: VerbType.Contains })
+
+    const spy = vi.spyOn(brain, 'related')
+    result = await vfs.repairContainment()
+    relatedCalls = spy.mock.calls.length
+    spy.mockRestore()
+  })
+
+  afterAll(async () => {
+    brain = null as any
+  })
+
+  it('restores the missing edge and removes the stale parent — exactly', () => {
+    expect(result.restored).toBe(1) // f-0's missing edge
+    expect(result.removed).toBe(1) // f-2's stale parent (f-3 → f-2)
+  })
+
+  it('the repaired tree is correct: every file has exactly one vfs edge from its dir', async () => {
+    for (let i = 0; i < 6; i++) {
+      const incoming = await brain.related({ to: `f-${i}`, type: VerbType.Contains })
+      const vfsEdges = incoming.filter(
+        (e) => e.subtype === 'vfs-contains' || (e.metadata as any)?.isVFS === true
+      )
+      expect(vfsEdges, `f-${i}`).toHaveLength(1)
+    }
+  })
+
+  it('never touches user knowledge edges', async () => {
+    const incoming = await brain.related({ to: 'f-5', type: VerbType.Contains })
+    const user = incoming.filter(
+      (e) => e.subtype !== 'vfs-contains' && (e.metadata as any)?.isVFS !== true
+    )
+    expect(user).toHaveLength(1)
+  })
+
+  it('cost shape: related() calls do not scale with the entity count', () => {
+    // One paged type-only walk (~E/1000 pages) — with 60+ entities the old
+    // shape issued 60+ calls; the new one a handful. Bound generously.
+    expect(relatedCalls).toBeLessThanOrEqual(5)
+  })
+})

tests/unit/db/generation-segments.test.ts

@@ -147,4 +147,119 @@ describe('db/GenerationSegmentStore — the D1+D3 packed tier', () => {
     await expect(store.fold([gen(4), gen(4)])).rejects.toThrow(/strictly ascending/)
     await expect(store.fold([])).rejects.toThrow(/at least one generation/)
   })
+
+  // ==========================================================================
+  // THE DENSITY LAW
+  // ==========================================================================
+  //
+  // A sealed segment declares a CONTIGUOUS range and every reader treats that
+  // range as containment. Folding a sparse batch therefore makes the segment
+  // claim generations it does not hold — and because `open()` merges declared
+  // ranges back into committedRanges, the hole is re-admitted as committed
+  // history and every later maintenance pass fails asking for a frame that was
+  // never written. That is the "generation N is inside sealed segment
+  // seg-....bgs's declared range but has no frame — packed history is damaged"
+  // narration seen on every run of the affected stores.
+
+  it('fold REFUSES a batch with a hole — a dense range may not be declared over sparse input', async () => {
+    await expect(store.fold([gen(1), gen(2), gen(4)])).rejects.toThrow(
+      /not contiguous: 2 → 4 skips 1 generation/
+    )
+    // The refusal loses nothing: no segment was sealed, so the generations
+    // stay in the live tier and the next pass folds them correctly.
+    expect(store.segments()).toHaveLength(0)
+    expect(store.hasGeneration(1)).toBe(false)
+  })
+
+  it('a wider gap names how many generations it would have swallowed', async () => {
+    await expect(store.fold([gen(10), gen(20)])).rejects.toThrow(
+      /not contiguous: 10 → 20 skips 9 generation\(s\)/
+    )
+  })
+
+  it('two contiguous runs folded separately declare honest ranges', async () => {
+    // What the caller now does instead of folding across the gap.
+    const a = await store.fold([gen(1), gen(2), gen(3)])
+    const b = await store.fold([gen(7), gen(8)])
+    expect(a).toMatchObject({ firstGeneration: 1, lastGeneration: 3, frames: 3 })
+    expect(b).toMatchObject({ firstGeneration: 7, lastGeneration: 8, frames: 2 })
+    // The gap is honestly outside the packed tier.
+    for (const g of [4, 5, 6]) expect(store.hasGeneration(g)).toBe(false)
+    for (const g of [1, 2, 3, 7, 8]) expect(store.hasGeneration(g)).toBe(true)
+    expect(await store.actualRanges()).toEqual([
+      [1, 3],
+      [7, 8]
+    ])
+  })
+
+  it('actualRanges() is exact and I/O-free for dense segments', async () => {
+    await store.fold([gen(1), gen(2)])
+    await store.fold([gen(3), gen(4)])
+    // Adjacent dense segments each contribute their declared range.
+    expect(await store.actualRanges()).toEqual([
+      [1, 2],
+      [3, 4]
+    ])
+  })
+
+  // ---- pre-existing damage: a store sealed by the old writer ----------------
+
+  /**
+   * Seal a SPARSE segment the way the pre-fix writer did: write the bytes and
+   * sidecar for a contiguous run, then rewrite the manifest so the segment
+   * declares a wider range than the frames it holds. This reproduces on disk
+   * exactly what the affected stores carry, without needing the old code.
+   */
+  const sealSparseSegment = async (): Promise<void> => {
+    await store.fold([gen(1), gen(2), gen(3)])
+    const manifest = (await storage.readRawObject(`${SEGMENTS_PREFIX}/manifest.json`)) as any
+    // Declare 1..5 while holding frames for 1..3 — generations 4 and 5 become
+    // holes inside a sealed range.
+    manifest.segments[0].lastGeneration = 5
+    await storage.writeRawObject(`${SEGMENTS_PREFIX}/manifest.json`, manifest)
+  }
+
+  it('a pre-existing sparse segment reports its holes as UNPACKED, not as damage', async () => {
+    await sealSparseSegment()
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+
+    // The frames it really holds still serve, byte-faithfully.
+    expect((await reopened.readDelta(2))?.timestamp).toBe(1_700_000_000_002)
+    expect(await reopened.readRecords(3)).toHaveLength(2)
+
+    // The holes answer "not packed" instead of throwing. This is the fix for
+    // the wedge: the old reader threw here on EVERY maintenance pass.
+    expect(await reopened.readDelta(4)).toBeNull()
+    expect(await reopened.readRecords(5)).toBeNull()
+  })
+
+  it('actualRanges() excludes the holes so they are never re-admitted as committed', async () => {
+    await sealSparseSegment()
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    // Declared 1..5; actually holds 1..3. The store seeds committedRanges from
+    // THIS, so generations 4 and 5 never become committed history again.
+    expect(await reopened.actualRanges()).toEqual([[1, 3]])
+  })
+
+  it('a DENSE segment missing a frame is still loud damage', async () => {
+    // The other side of the branch: when the manifest claims a complete span,
+    // a missing frame means the manifest and sidecar disagree — real damage,
+    // and it must not be quietly downgraded to "unpacked".
+    await store.fold([gen(1), gen(2), gen(3)])
+    const idxPath = `${SEGMENTS_PREFIX}/seg-${String(1).padStart(20, '0')}.idx`
+    const raw = (await storage.readRawBytes(idxPath))!
+    const { decode, encode } = await import('@msgpack/msgpack')
+    const idx = decode(raw) as any
+    // Drop generation 2's entry while the manifest still declares 3 frames.
+    idx.generations = idx.generations.filter(([g]: [number]) => g !== 2)
+    await storage.writeRawBytes(idxPath, encode(idx))
+
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    await expect(reopened.readDelta(2)).rejects.toThrow(
+      /manifest and the sidecar disagree; packed history is damaged/
+    )
+  })
 })