Merge branch 'release/8.10.1'

# Conflicts:
#	.forgejo/workflows/ci.yml

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 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.
 
+### [8.10.1](https://source.soulcraft.com/soulcraft/brainy/compare/v8.10.0...v8.10.1) (2026-07-24)
+
+- refactor: remove the orphaned transaction-result type left behind by the dead-path removal (edf123a5)
+- fix: warm() metadata surface routes through the active provider (warm hook added to the metadata contract); add maintenanceDebt() observability surface (5b2cbf74)
+- fix: transaction timeouts are a typed no-hot-retry contract; engine-side non-retry pinned; dead transaction path removed (003e2a74)
+- chore: the forge is the address — retire the archived mirror from every live surface (22702b81)
+
+
 ### [8.10.0](https://github.com/soulcraftlabs/brainy/compare/v8.9.0...v8.10.0) (2026-07-23)
 
 - docs: adoption storefront — contributing guide, security policy, README support + cor section (9a99a7b)

CONTRIBUTING.md

@@ -10,10 +10,6 @@ The source of truth is a self-hosted forge: **source.soulcraft.com/soulcraft/bra
 It's anonymously readable and cloneable — no account needed to browse, clone,
 or build.
 
-**github.com/soulcraftlabs/brainy** is a public read-only mirror. It's a fine
-place to read code or star the project, but issues and pull requests opened
-there won't be picked up — please use one of the paths below instead.
-
 ## How to contribute
 
 **Found a bug, or have an idea?** Email **brainy@soulcraft.com**. No account,

README.md

@@ -13,7 +13,7 @@
 <p align="center">
   <a href="https://www.npmjs.com/package/@soulcraft/brainy"><img src="https://img.shields.io/npm/v/@soulcraft/brainy.svg" alt="npm version"></a>
   <a href="https://www.npmjs.com/package/@soulcraft/brainy"><img src="https://img.shields.io/npm/dm/@soulcraft/brainy.svg" alt="npm downloads"></a>
-  <a href="https://github.com/soulcraftlabs/brainy/actions/workflows/ci.yml"><img src="https://github.com/soulcraftlabs/brainy/actions/workflows/ci.yml/badge.svg" alt="CI"></a>
+  <a href="https://source.soulcraft.com/soulcraft/brainy/actions"><img src="https://source.soulcraft.com/soulcraft/brainy/actions/workflows/ci.yml/badge.svg?branch=main" alt="CI"></a>
   <a href="https://soulcraft.com/docs"><img src="https://img.shields.io/badge/docs-soulcraft.com-blue.svg" alt="Documentation"></a>
   <a href="LICENSE"><img src="https://img.shields.io/badge/license-MIT-blue.svg" alt="MIT License"></a>
   <a href="https://www.typescriptlang.org/"><img src="https://img.shields.io/badge/%3C%2F%3E-TypeScript-%230074c1.svg" alt="TypeScript"></a>

RELEASES.md

@@ -31,6 +31,68 @@ is sometimes cited as a 7.x removal — those methods never existed on 7.x; the
 
 ---
 
+## v8.10.1 — 2026-07-24 (the no-hot-retry contract + warm()'s metadata surface under native providers)
+
+From a production incident: a native-provider op ground 38-40s inside a transaction,
+blew the ~32s apply-phase budget, was rolled back (zero loss, by design), and a
+downstream pipeline hot-retried the identical operation into a 6-minute, 100%-CPU
+storm. Investigation confirmed Brainy itself never auto-retries a timed-out
+transaction — the storm was entirely the consumer's own retry loop, driven by a
+"retryable" doc-prose claim with no machine-readable contract to branch on. This
+release closes that contract gap and, separately, fixes a real `warm()` reporting gap
+surfaced by the same investigation.
+
+- **`TransactionTimeoutError` is now a machine-readable no-hot-retry contract.** Two
+  new typed, always-`true` fields replace prose-only guidance:
+  - `retryable: true` — the operation MAY succeed on a later attempt, once the
+    underlying slowness resolves or the budget is deliberately raised
+    (`transactionBudgetFloorMs`, or a batch's own `timeoutMs` override).
+  - `hotRetryUnsafe: true` — an immediate, identical retry re-pays the FULL cost of
+    the work that just timed out (it does not resume partway) and can cascade into
+    exactly the CPU storm above. **Never loop on this error.** The documented pattern
+    is a latch, not a retry loop:
+    ```
+    on TransactionTimeoutError:
+      record { at: Date.now(), error }
+      rethrow loudly to your own caller
+      hold a cooldown window before any re-attempt
+      clear the latch only on a subsequent success
+    ```
+  - `context` (unchanged, now fully documented) carries the backoff inputs:
+    `timeoutMs`, `operationIndex`, `elapsedMs`, `totalOperations`, `operationName`.
+  - Every "retryable" doc-prose site referencing this error (`transact()`'s
+    `timeoutMs` option, `transactionBudgetFloorMs`, `Transaction.execute()`) now
+    points at these fields instead of bare prose.
+  - Regression-pinned: the engine never internally re-drives a timed-out operation
+    (verified via an execution counter through both the single-op write path and
+    `add()`'s upsert-race retry loop), so this has always been true — it is now
+    provable and typed.
+- **Dead code removed**: `TransactionManager.executeTransactionWithResult()` had zero
+  callers in this codebase and is deleted.
+- **`brain.warm()`'s metadata surface now routes through the ACTIVE provider.** A
+  production deployment's warm report showed `metadata: 'unavailable'` under a native
+  metadata provider — the previous logic only duck-typed the built-in JS manager's
+  `hydrateAll()` method, which a native provider has no reason to implement. The
+  metadata provider contract (`MetadataIndexProvider`, `src/plugin.ts`) gains an
+  optional `warm?(): Promise<void>` hook, mirroring the existing vector and graph
+  provider hooks. `brain.warm()` now checks the active provider's own `warm()` FIRST,
+  falls back to the JS manager's `hydrateAll()` when absent, and only reports
+  `'unavailable'` when neither exists — never `init()` as a stand-in, since a native
+  provider's `init()` may be a cheap verify rather than a real warm. A native
+  provider lights this surface up the same way `@soulcraft/cor` already lights the
+  vector and graph surfaces: implement `warm()` on its metadata provider.
+- **New: `brain.maintenanceDebt()`** — the observability seam so an operator sees a
+  provider's outstanding background maintenance work (pending bytes/items, last pass
+  outcome, whether it's converging) BEFORE it grinds into the kind of budget-busting
+  op this release's timeout contract exists for, instead of discovering it as a CPU
+  storm. It is a pure passthrough: brainy applies no thresholds, no polling, and no
+  estimation — it calls each active provider's own optional `maintenanceDebt?()` hook
+  (vector, metadata, graph — the same three contracts `warm?()` lives on) and reports
+  the payload verbatim, or `'unavailable'` when a surface's provider doesn't track
+  debt. Useful as a pre-warm/post-warm check or a boot gate. `@soulcraft/cor` does not
+  yet implement the hook as of this release — expect it on cor's next release; until
+  then all three surfaces honestly report `'unavailable'`.
+
 ## Unreleased (the warm contract: cold-restart writes stop paying demand-load latency)
 
 From a production deployment's cold-restart incident: the FIRST writes after every

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@soulcraft/brainy",
-  "version": "8.10.0",
+  "version": "8.10.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@soulcraft/brainy",
-      "version": "8.10.0",
+      "version": "8.10.1",
       "license": "MIT",
       "dependencies": {
         "@msgpack/msgpack": "^3.1.2",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@soulcraft/brainy",
-  "version": "8.10.0",
+  "version": "8.10.1",
   "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",
   "module": "dist/index.js",
@@ -128,13 +128,13 @@
   "publishConfig": {
     "access": "public"
   },
-  "homepage": "https://github.com/soulcraftlabs/brainy",
+  "homepage": "https://source.soulcraft.com/soulcraft/brainy",
   "bugs": {
-    "url": "https://github.com/soulcraftlabs/brainy/issues"
+    "url": "https://source.soulcraft.com/soulcraft/brainy/issues"
   },
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/soulcraftlabs/brainy.git"
+    "url": "git+https://source.soulcraft.com/soulcraft/brainy.git"
   },
   "files": [
     "dist/**/*.js",

scripts/release.sh

@@ -142,7 +142,7 @@ else
 fi
 
 # Create new changelog entry
-CHANGELOG_ENTRY="### [${NEW_VERSION}](https://github.com/soulcraftlabs/brainy/compare/v${CURRENT_VERSION}...v${NEW_VERSION}) ($(date +%Y-%m-%d))
+CHANGELOG_ENTRY="### [${NEW_VERSION}](https://source.soulcraft.com/soulcraft/brainy/compare/v${CURRENT_VERSION}...v${NEW_VERSION}) ($(date +%Y-%m-%d))
 
 ${COMMITS}
 "
@@ -175,42 +175,59 @@ echo -e "${BLUE}7️⃣  Creating git tag v${NEW_VERSION}...${NC}"
 git tag -a "v${NEW_VERSION}" -m "Release v${NEW_VERSION}"
 echo -e "${GREEN}✅ Tag created${NC}\n"
 
-# Step 9: Push to origin (source of truth) and the public GitHub mirror
+# Step 9: Push to origin — the forge is the one home (ruled 2026-07-23; the
+# old public GitHub repo is archived history, no longer part of any release).
 echo -e "${BLUE}8️⃣  Pushing to origin...${NC}"
 git push --follow-tags origin "$CURRENT_BRANCH"
 echo -e "${GREEN}✅ Pushed to origin${NC}\n"
 
-# The public GitHub repo is a mirror of origin with an unknown sync cadence.
+# Step 10: Publish — forge FIRST (home), npmjs second (the world's storefront).
-# `gh release create` below targets GitHub directly: if the new tag hasn't
+# The fleet-wide ~/.npmrc maps the @soulcraft scope to the forge registry, and
-# reached GitHub yet, gh would CREATE it — pointed at GitHub's default-branch
+# a scope mapping BEATS `--registry` on the command line — so each publish
-# head, i.e. the wrong commit. Push branch+tag to GitHub explicitly, then
+# names its registry via the scope override explicitly. Nothing implicit.
-# verify the tag resolves there to the same commit before any release is cut.
+FORGE_NPM_REG="https://source.soulcraft.com/api/packages/soulcraft/npm/"
-GITHUB_URL="https://github.com/soulcraftlabs/brainy.git"
+FORGE_NPM_TOKEN_FILE="$HOME/.config/soulcraft/npm-publish-brainy.token"
-echo -e "${BLUE}8️⃣½  Pushing to the public GitHub mirror...${NC}"
+echo -e "${BLUE}9️⃣  Publishing to the forge registry (home)...${NC}"
-git push --follow-tags "$GITHUB_URL" "$CURRENT_BRANCH"
+if [ -f "$FORGE_NPM_TOKEN_FILE" ]; then
-LOCAL_TAG_SHA="$(git rev-parse "v${NEW_VERSION}^{}")"
+  TMPRC="$(mktemp)"
-GITHUB_TAG_SHA="$(git ls-remote --tags "$GITHUB_URL" "v${NEW_VERSION}^{}" | cut -f1)"
+  chmod 600 "$TMPRC"
-if [ "$LOCAL_TAG_SHA" != "$GITHUB_TAG_SHA" ]; then
+  {
-  echo -e "${RED}❌ Tag v${NEW_VERSION} on GitHub (${GITHUB_TAG_SHA:-absent}) does not match local (${LOCAL_TAG_SHA}) — aborting before npm publish. Fix the mirror, then re-run.${NC}"
+    echo "@soulcraft:registry=${FORGE_NPM_REG}"
+    echo "//source.soulcraft.com/api/packages/soulcraft/npm/:_authToken=$(cat "$FORGE_NPM_TOKEN_FILE")"
+  } > "$TMPRC"
+  if npm publish --tag "$NPM_TAG" --userconfig "$TMPRC"; then
+    echo -e "${GREEN}✅ Published to the forge${NC}\n"
+  else
+    rm -f "$TMPRC"
+    echo -e "${RED}❌ Forge publish FAILED — aborting before npmjs so the pair never diverges. Fix and re-run.${NC}"
     exit 1
   fi
-echo -e "${GREEN}✅ GitHub mirror has the tag at the right commit${NC}\n"
+  rm -f "$TMPRC"
-
-# Step 10: Publish to npm
-echo -e "${BLUE}9️⃣  Publishing to npm (dist-tag: ${NPM_TAG})...${NC}"
-npm publish --tag "$NPM_TAG"
-# Brainy is the only PUBLIC @soulcraft package — verify visibility after every publish.
-npm access get status @soulcraft/brainy || true
-echo -e "${GREEN}✅ Published to npm${NC}\n"
-
-# Step 11: Create GitHub release
-echo -e "${BLUE}🔟 Creating GitHub release...${NC}"
-if [ "$PRERELEASE" = true ]; then
-  gh release create "v${NEW_VERSION}" --generate-notes --prerelease
 else
-  gh release create "v${NEW_VERSION}" --generate-notes
+  echo -e "${RED}❌ Forge publish token missing (${FORGE_NPM_TOKEN_FILE}) — aborting. The forge is home; publish it first or restage the token.${NC}"
+  exit 1
+fi
+
+echo -e "${BLUE}9️⃣½  Publishing to npmjs (storefront, dist-tag: ${NPM_TAG})...${NC}"
+npm publish --tag "$NPM_TAG" "--@soulcraft:registry=https://registry.npmjs.org/"
+# Brainy is the only PUBLIC @soulcraft package — verify visibility after every publish.
+npm access get status @soulcraft/brainy "--@soulcraft:registry=https://registry.npmjs.org/" || true
+echo -e "${GREEN}✅ Published to npmjs${NC}\n"
+
+# Step 11: Release object on the forge (presentational — the tag, CHANGELOG,
+# and RELEASES.md are the record; this just gives the forge UI a release page).
+echo -e "${BLUE}🔟 Creating forge release...${NC}"
+if [ -n "${FORGEJO_RELEASE_TOKEN:-}" ]; then
+  if curl -sf -X POST "https://source.soulcraft.com/api/v1/repos/soulcraft/brainy/releases" \
+    -H "Authorization: token ${FORGEJO_RELEASE_TOKEN}" -H "Content-Type: application/json" \
+    -d "{\"tag_name\":\"v${NEW_VERSION}\",\"name\":\"v${NEW_VERSION}\",\"prerelease\":${PRERELEASE}}" >/dev/null; then
+    echo -e "${GREEN}✅ Forge release created${NC}\n"
+  else
+    echo -e "${RED}⚠️  Forge release API call failed — tag + CHANGELOG remain the record; create the release page via the forge UI if wanted${NC}\n"
+  fi
+else
+  echo -e "${RED}⚠️  FORGEJO_RELEASE_TOKEN unset — no release page created; tag + CHANGELOG remain the record${NC}\n"
 fi
-echo -e "${GREEN}✅ GitHub release created${NC}\n"
 
 # Step 12: Push public docs to the soulcraft.com docs ingest door
 # (VENUE-DOCS-RELEASE-PUSH). Skips with a loud warning when
@@ -229,4 +246,4 @@ echo -e "${GREEN}🎉 Release ${NEW_VERSION} complete!${NC}"
 echo -e "${GREEN}━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━${NC}"
 echo ""
 echo -e "📦 npm: ${BLUE}https://www.npmjs.com/package/@soulcraft/brainy/v/${NEW_VERSION}${NC}"
-echo -e "🐙 GitHub: ${BLUE}https://github.com/soulcraftlabs/brainy/releases/tag/v${NEW_VERSION}${NC}"
+echo -e "🏠 Forge: ${BLUE}https://source.soulcraft.com/soulcraft/brainy/releases/tag/v${NEW_VERSION}${NC}"

src/brainy.ts

@@ -65,7 +65,8 @@ import type {
   OpaqueIdSet,
   AtGenerationVectors,
   VectorIndexProvider,
-  GraphIndexProvider
+  GraphIndexProvider,
+  ProviderMaintenanceDebt
 } from './plugin.js'
 import type {
   BrainyPlugin,
@@ -424,6 +425,30 @@ export interface WarmReport {
   totalDurationMs: number
 }
 
+/**
+ * @description Result of {@link Brainy.maintenanceDebt}: one outcome per
+ * index surface, mirroring {@link WarmReport}'s shape.
+ * - `'reported'` — the active provider for this surface implements
+ *   `maintenanceDebt?()` and its {@link ProviderMaintenanceDebt} payload is
+ *   attached verbatim under `debt`.
+ * - `'unavailable'` — the active provider does not implement the hook, so
+ *   nothing is known; brainy never estimates or infers a payload on its
+ *   behalf.
+ */
+export type MaintenanceDebtOutcome = 'reported' | 'unavailable'
+
+/**
+ * @description Per-surface result of {@link Brainy.maintenanceDebt}. Brainy
+ * performs no thresholding, polling, or estimation over this data — it is a
+ * pure passthrough of each active provider's own self-report (the provider
+ * owns the numbers; the operator owns the policy).
+ */
+export interface MaintenanceDebtReport {
+  vector: { outcome: MaintenanceDebtOutcome; debt?: ProviderMaintenanceDebt }
+  metadata: { outcome: MaintenanceDebtOutcome; debt?: ProviderMaintenanceDebt }
+  graph: { outcome: MaintenanceDebtOutcome; debt?: ProviderMaintenanceDebt }
+}
+
 /**
  * How long a failed aggregation-backfill walk suppresses fresh walk attempts.
  * Within the window, queries rethrow the recorded failure instantly (loud,
@@ -8322,6 +8347,27 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     return this.generationStore.compact(options)
   }
 
+  /**
+   * @description Repack cold generation history into sealed segments —
+   * re-representation, never deletion: every record and delta stays readable
+   * (`asOf()` unchanged); the physical file count drops by orders of
+   * magnitude. Runs automatically (time-bounded) at `close()`; call this for
+   * explicit maintenance windows on long-lived writers. The ONLY history
+   * transform permitted under the archival profile (`retention: 'all'`).
+   * @param options - `timeBudgetMs` bounds the pass (early stop = consistent
+   *   prefix, next pass resumes); `batchGenerations` sizes each fold.
+   * @returns Folded generation count and segments created.
+   */
+  async repackHistory(options?: {
+    timeBudgetMs?: number
+    batchGenerations?: number
+  }): Promise<{ foldedGenerations: number; segmentsCreated: number }> {
+    this.assertWritable('repackHistory')
+    await this.ensureInitialized()
+    await this.generationStore.flushPendingSingleOps()
+    return this.generationStore.repackHistory(options)
+  }
+
   /**
    * @description Read-only generational-history footprint for fleet audits:
    * generation count, total on-disk bytes, generation/timestamp range, the
@@ -8349,6 +8395,24 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     }
   }
 
+  /**
+   * @description A deterministic content digest of the generation log through
+   * `g` (D8 — gate-to-generation provenance): identical history produces the
+   * identical digest on any machine; divergence produces a different one.
+   * Release gates and suite verdicts pin `{generation, digest}` and verify
+   * both at execution time instead of pinning a git commit. O(segments +
+   * live-tier window), never O(all generations). Throws `RangeError` out of
+   * range and `GenerationCompactedError` below the horizon — a gate can
+   * never silently pin reclaimed history.
+   * @example
+   * const gate = { generation: brain.generation(), digest: await brain.generationDigest(brain.generation()) }
+   */
+  async generationDigest(g: number): Promise<string> {
+    await this.ensureInitialized()
+    await this.generationStore.flushPendingSingleOps()
+    return this.generationStore.generationDigest(g)
+  }
+
   /**
    * @description Drive the adaptive retention byte budget at runtime — the
    * settable input a machine-level coordinator (e.g. cor's `ResourceManager`,
@@ -14313,9 +14377,16 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    *   *some* backing storage as a side effect but is reported honestly as
    *   `'probed'`, never `'warmed'`. An empty index or unknown dimension has
    *   nothing to probe (`'unavailable'`).
-   * - **Metadata**: full hydration — every persisted field's sparse index is
+   * - **Metadata**: calls the provider's own `warm?()` when the active
-   *   loaded from storage (`MetadataIndexManager.hydrateAll()`), not just the
+   *   `'metadataIndex'` provider implements it (`'warmed'`) — the seam a
-   *   heuristic common-fields subset `init()` warms.
+   *   native metadata provider lights up so it is not duck-typed against the
+   *   JS manager's method. Otherwise falls back to full hydration on the
+   *   built-in JS manager — every persisted field's sparse index is loaded
+   *   from storage (`MetadataIndexManager.hydrateAll()`), not just the
+   *   heuristic common-fields subset `init()` warms — and reports `'warmed'`.
+   *   Neither seam present → `'unavailable'` (honest: `init()` is never used
+   *   as a substitute here, since a native provider's `init()` may be a
+   *   cheap verify rather than a real warm).
    * - **Graph**: calls the provider's own `warm?()` when the active graph
    *   provider implements it; otherwise re-runs its existing eager cold-load
    *   `init()` seam (idempotent — the JS adjacency index's `init()` already
@@ -14371,12 +14442,23 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     // --- Metadata --------------------------------------------------------
     const metadataStart = Date.now()
     let metadataOutcome: WarmOutcome
+    const metadataProvider = this.metadataIndex as unknown as MetadataIndexProvider
     const metadataWithHydrate = this.metadataIndex as unknown as { hydrateAll?: () => Promise<void> }
-    if (typeof metadataWithHydrate.hydrateAll === 'function') {
+    if (typeof metadataProvider.warm === 'function') {
+      // Active provider (e.g. a native metadata index) declares its own warm
+      // seam — route through it FIRST so a native provider's warmth is
+      // reported honestly instead of being duck-typed against the JS
+      // manager's hydrateAll(), which a native provider does not implement.
+      await metadataProvider.warm()
+      metadataOutcome = 'warmed'
+    } else if (typeof metadataWithHydrate.hydrateAll === 'function') {
+      // Built-in JS manager path — full sparse-index hydration.
       await metadataWithHydrate.hydrateAll()
       metadataOutcome = 'warmed'
     } else {
-      // No hydration seam on this metadata provider — nothing to run.
+      // No hydration seam on this metadata provider — nothing to run. (No
+      // init() fallback here: init() on a native provider may be a cheap
+      // verify, and reporting that as warmth would lie.)
       metadataOutcome = 'unavailable'
     }
     const metadataDurationMs = Date.now() - metadataStart
@@ -14410,6 +14492,63 @@ export class Brainy<T = any> implements BrainyInterface<T> {
     }
   }
 
+  /**
+   * Read each index surface's self-reported outstanding maintenance work —
+   * the observability seam so an operator sees a grind coming (rising
+   * pending bytes/items, a stalled background pass) instead of discovering
+   * it as a CPU storm or a transaction blowing its budget mid-flight (see
+   * {@link TransactionTimeoutError}).
+   *
+   * PURE PASSTHROUGH: for each of vector/metadata/graph, this calls ONLY the
+   * ACTIVE provider's own `maintenanceDebt?()` hook (the same per-surface
+   * provider resolution {@link Brainy.warm} uses) and reports its
+   * {@link ProviderMaintenanceDebt} payload verbatim. There is no JS-side
+   * fallback computation, no threshold evaluation, and no polling — brainy
+   * surfaces the truth the provider measured; the provider owns the numbers
+   * and the operator owns the policy (what threshold matters, what action to
+   * take). A surface whose active provider does not implement the hook
+   * reports `'unavailable'` — never a guessed or zeroed payload.
+   *
+   * @returns A {@link MaintenanceDebtReport}: per-surface outcome + payload.
+   * @example
+   * ```typescript
+   * const debt = await brain.maintenanceDebt()
+   * if (debt.metadata.outcome === 'reported' && debt.metadata.debt?.pendingBytes) {
+   *   console.log('metadata pending bytes:', debt.metadata.debt.pendingBytes)
+   * }
+   * ```
+   */
+  async maintenanceDebt(): Promise<MaintenanceDebtReport> {
+    await this.ensureInitialized({ needs: ['vector', 'metadata', 'graph'] })
+
+    // --- Vector ---------------------------------------------------------
+    const vectorProvider = this.index as VectorIndexProvider & {
+      maintenanceDebt?: () => Promise<ProviderMaintenanceDebt>
+    }
+    const vector =
+      typeof vectorProvider.maintenanceDebt === 'function'
+        ? { outcome: 'reported' as const, debt: await vectorProvider.maintenanceDebt() }
+        : { outcome: 'unavailable' as const }
+
+    // --- Metadata --------------------------------------------------------
+    const metadataProvider = this.metadataIndex as unknown as MetadataIndexProvider
+    const metadata =
+      typeof metadataProvider.maintenanceDebt === 'function'
+        ? { outcome: 'reported' as const, debt: await metadataProvider.maintenanceDebt() }
+        : { outcome: 'unavailable' as const }
+
+    // --- Graph -------------------------------------------------------------
+    const graphProvider = this.graphIndex as GraphIndexProvider & {
+      maintenanceDebt?: () => Promise<ProviderMaintenanceDebt>
+    }
+    const graph =
+      typeof graphProvider.maintenanceDebt === 'function'
+        ? { outcome: 'reported' as const, debt: await graphProvider.maintenanceDebt() }
+        : { outcome: 'unavailable' as const }
+
+    return { vector, metadata, graph }
+  }
+
   /**
    * Explicitly warm up the embedding engine
    *
@@ -16367,11 +16506,21 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       await this.generationStore.flushPendingSingleOps()
     }
 
-    // Phase 0b: Auto-compact generational history per config.retention (default
+    // Phase 0b: REPACK cold history into sealed segments (D1+D3 —
-    // on) BEFORE the generation store closes below. This is THE auto-compaction
+    // re-representation, never deletion; the only history transform under the
-    // site (8.9.0 — flush() never compacts): time-bounded per pass, respects
+    // archival profile), then auto-compact per config.retention. Repack runs
-    // live Db pins and an explicit autoCompact: false; no-op on read-only
+    // FIRST so bounded-retention reclaim can drop whole segments. Both are
-    // instances.
+    // time-bounded maintenance passes (8.9.0 law: flush() never pays these);
+    // both are housekeeping — failures warn, never fail a clean shutdown.
+    if (!this.isReadOnly && this.generationStore) {
+      try {
+        await this.generationStore.repackHistory({ timeBudgetMs: 5_000 })
+      } catch (error) {
+        console.warn(
+          `History repacking failed (non-fatal): ${error instanceof Error ? error.message : String(error)}`
+        )
+      }
+    }
     await this.autoCompactHistory()
 
     // Phase 1: Flush ALL components in parallel to persist buffered data

src/db/factLog.ts

@@ -102,12 +102,26 @@ export interface FactScanBatch {
   segmentId: string
 }
 
+/**
+ * Liveness bound on a scan's FIRST batch (Stage-2 co-freeze, D1 contract):
+ * `batches()` must yield its first batch — or fail loudly — within this many
+ * ms of the first pull. A backlogged or damaged store may be SLOW, but it may
+ * never be SILENT: a consumer awaiting the first batch is otherwise
+ * indistinguishable from a wedge (the exact failure shape a production heal
+ * hit against a generations-backlogged brain).
+ */
+export const SCANFACTS_FIRST_BATCH_MS = 10_000
+
 /** The telemetry a scan OPEN returns (frozen shape). */
 export interface FactScanHandle {
   headGeneration: number
   segmentCount: number
   approxFactCount: number
-  /** Ordered batches; a detected gap aborts LOUDLY, never a silent skip. */
+  /**
+   * Ordered batches; a detected gap aborts LOUDLY, never a silent skip.
+   * Liveness contract: the FIRST batch resolves or rejects within
+   * {@link SCANFACTS_FIRST_BATCH_MS} of the first pull — never a silent hang.
+   */
   batches: () => AsyncGenerator<FactScanBatch>
   /** Close telemetry — the invariant cross-check, valid after iteration ends. */
   summary: () => { factsYielded: number; segmentsRead: number }
@@ -440,6 +454,8 @@ export class FactLog {
     toGeneration?: number
     kinds?: Array<'noun' | 'verb'>
     batchSize?: number
+    /** Test override for the first-batch liveness bound (default {@link SCANFACTS_FIRST_BATCH_MS}). */
+    firstBatchTimeoutMs?: number
   }): FactScanHandle {
     const from = options?.fromGeneration ?? 1
     const to = options?.toGeneration ?? this.head
@@ -514,11 +530,43 @@ export class FactLog {
       }
     }
 
+    // Liveness wrapper: the FIRST pull races the contract deadline. Only the
+    // first — the bound is time-to-first-batch (proof the producer is alive),
+    // not per-batch pacing; and it runs only while a pull is actually pending,
+    // so consumer think-time between pulls never counts against the producer.
+    const firstBatchTimeoutMs = options?.firstBatchTimeoutMs ?? SCANFACTS_FIRST_BATCH_MS
+    async function* batchesWithLiveness(this: void): AsyncGenerator<FactScanBatch> {
+      const inner = batches()
+      let timer: NodeJS.Timeout | undefined
+      try {
+        const deadline = new Promise<never>((_, reject) => {
+          timer = setTimeout(
+            () =>
+              reject(
+                new Error(
+                  `fact log: scanFacts produced no first batch within ${firstBatchTimeoutMs}ms ` +
+                    `(liveness contract) — the store is wedged or unreadably slow; aborting scan LOUDLY ` +
+                    `instead of hanging the consumer.`
+                )
+              ),
+            firstBatchTimeoutMs
+          )
+          timer.unref?.()
+        })
+        const first = await Promise.race([inner.next(), deadline])
+        if (first.done) return
+        yield first.value
+      } finally {
+        clearTimeout(timer)
+      }
+      yield* inner
+    }
+
     return {
       headGeneration: this.head,
       segmentCount: segments.length + (tailSnapshot.length > 0 ? 1 : 0),
       approxFactCount,
-      batches,
+      batches: batchesWithLiveness,
       summary: () => ({ factsYielded, segmentsRead })
     }
   }

src/db/generationSegments.ts

@@ -0,0 +1,459 @@
+/**
+ * @module db/generationSegments
+ * @description The generation-segment store — Stage-2 D1+D3+repacking's file
+ * format (co-frozen 2026-07-19; design: the d1-d3-repacking spec).
+ *
+ * Packs CONSECUTIVE cold generations' record-sets (before-images + delta)
+ * into append-once segment files with derived sidecar indexes, so history
+ * scales in SEGMENTS (tens) instead of FILES-PER-GENERATION (hundreds of
+ * thousands), and cold-open reads ONE manifest instead of listing the
+ * backlog. Layout under `_generations/segments/`:
+ *
+ * - `seg-<firstGen, zero-padded 20>.bgs` — magic "BGS1", then one frame per
+ *   generation: `u32 payloadLen | u32 crc32c | msgpack payload`. Payload is
+ *   POSITIONAL: `[generation, timestamp, delta, records[], flags]` with
+ *   records `[kindByte, id, record]`. `flags` reserves encoding evolution
+ *   (bit 0 = compressed payload — v1 always 0; a future writer upgrade,
+ *   never a format break). Sealed segments are IMMUTABLE — the fact log's
+ *   own law, generalized.
+ * - `seg-<firstGen>.idx` — DERIVED sidecar (msgpack): per-generation frame
+ *   offsets (point reads = one ranged read, never a listing) + per-id
+ *   generation postings (per-id chain rebuilds read only what they need).
+ *   Corrupt/missing → rebuilt from its segment in one sequential read,
+ *   loudly.
+ * - `manifest.json` — the segment catalogue + `compactedBelow` (D3's
+ *   horizon marker). Cold-open reads THIS; the packed backlog is never
+ *   listed.
+ *
+ * D3 semantics carried here: bounded-retention reclaim drops WHOLE segments
+ * at boundaries (O(1) per segment, no rewrite); under the archival profile
+ * (`retention: 'all'`) nothing here is ever dropped — folding is the only
+ * transform (re-representation, never deletion).
+ */
+
+import { encode as msgpackEncode, decode as msgpackDecode } from '@msgpack/msgpack'
+import { crc32c } from '../utils/crc32c.js'
+import type { FactLogStorage } from './factLog.js'
+import { prodLog } from '../utils/logger.js'
+
+/** Directory for segment files + manifest, under the generations prefix. */
+export const SEGMENTS_PREFIX = '_generations/segments'
+
+/** Target sealed-segment size (co-freeze proposal; tunable on evidence). */
+export const SEGMENT_TARGET_BYTES = 64 * 1024 * 1024
+
+const MAGIC = new TextEncoder().encode('BGS1')
+const FRAME_PREFIX_BYTES = 8 // u32 payloadLen + u32 crc32c
+const MANIFEST_PATH = `${SEGMENTS_PREFIX}/manifest.json`
+
+/** One generation's fold input — exactly what the live tier holds for it. */
+export interface FoldGeneration {
+  generation: number
+  timestamp: number
+  /** The tx.json delta object, carried verbatim. */
+  delta: unknown
+  /** The before-image record-set (empty for record-less generations). */
+  records: Array<{ kind: 'noun' | 'verb'; id: string; record: unknown }>
+}
+
+/** Manifest entry for one sealed segment. */
+export interface SegmentMeta {
+  file: string
+  firstGeneration: number
+  lastGeneration: number
+  frames: number
+  bytes: number
+  /** crc32c of the full segment byte stream — the digest chain's link. */
+  checksum: number
+}
+
+interface SegmentManifest {
+  version: 1
+  compactedBelow: number
+  segments: SegmentMeta[]
+}
+
+interface SidecarIndex {
+  version: 1
+  /** [generation, frameOffset, frameLen] ascending by generation. */
+  generations: Array<[number, number, number]>
+  /** `${kindByte}:${id}` → ascending generations holding a record for it. */
+  ids: Record<string, number[]>
+}
+
+const segmentFileName = (firstGeneration: number): string =>
+  `seg-${String(firstGeneration).padStart(20, '0')}.bgs`
+const sidecarFileName = (firstGeneration: number): string =>
+  `seg-${String(firstGeneration).padStart(20, '0')}.idx`
+
+/**
+ * The generation-segment store. Owns the packed tier ONLY — the live
+ * per-generation tier and the routing between tiers belong to
+ * `GenerationStore`. All mutating entry points here are called under the
+ * generation store's commit mutex.
+ */
+export class GenerationSegmentStore {
+  private readonly storage: FactLogStorage
+  private manifest: SegmentManifest = { version: 1, compactedBelow: 0, segments: [] }
+  /** Sidecar cache — segments are immutable, so entries never invalidate. */
+  private readonly sidecars = new Map<string, SidecarIndex>()
+
+  constructor(storage: FactLogStorage) {
+    this.storage = storage
+  }
+
+  /** Load the manifest (ONE read — never a directory listing). */
+  async open(): Promise<void> {
+    const raw = (await this.storage.readRawObject(MANIFEST_PATH)) as SegmentManifest | null
+    if (raw) {
+      if (raw.version !== 1) {
+        throw new Error(
+          `[GenerationSegments] manifest version ${String(raw.version)} is newer than this ` +
+            `engine understands — refusing to serve partial history. Upgrade the engine.`
+        )
+      }
+      this.manifest = raw
+    }
+  }
+
+  /** The packed tier's catalogue (ascending, immutable snapshot). */
+  segments(): readonly SegmentMeta[] {
+    return this.manifest.segments
+  }
+
+  /** D3's horizon marker: generations below this were reclaimed (bounded profiles only). */
+  compactedBelow(): number {
+    return this.manifest.compactedBelow
+  }
+
+  /** The covering sealed segment for `gen`, or null if it lives outside the packed tier. */
+  private coveringSegment(gen: number): SegmentMeta | null {
+    // Manifest is ascending and ranges never overlap — binary search.
+    const segs = this.manifest.segments
+    let lo = 0
+    let hi = segs.length - 1
+    while (lo <= hi) {
+      const mid = (lo + hi) >> 1
+      const s = segs[mid]
+      if (gen < s.firstGeneration) hi = mid - 1
+      else if (gen > s.lastGeneration) lo = mid + 1
+      else return s
+    }
+    return null
+  }
+
+  /** True when `gen` is packed (readable from this tier). */
+  hasGeneration(gen: number): boolean {
+    return this.coveringSegment(gen) !== null
+  }
+
+  /**
+   * Fold consecutive generations into ONE new sealed segment + sidecar and
+   * append it to the manifest atomically. Caller guarantees: `gens` is
+   * ascending, contiguous with the packed tier (first = last packed + 1 when
+   * segments exist), and already durable in the live tier. Crash between the
+   * segment write and the caller's live-tier delete leaves a DUPLICATE
+   * representation — resolved live-tier-wins by the reader; never a gap.
+   */
+  async fold(gens: FoldGeneration[]): Promise<SegmentMeta> {
+    if (gens.length === 0) {
+      throw new Error('[GenerationSegments] fold() requires at least one generation')
+    }
+    for (let i = 1; i < gens.length; i++) {
+      if (gens[i].generation <= gens[i - 1].generation) {
+        throw new Error('[GenerationSegments] fold() input must be strictly ascending')
+      }
+    }
+    const last = this.manifest.segments[this.manifest.segments.length - 1]
+    if (last && gens[0].generation <= last.lastGeneration) {
+      throw new Error(
+        `[GenerationSegments] fold() overlaps the packed tier: ${gens[0].generation} ≤ ` +
+          `sealed ${last.lastGeneration} — segments are immutable, never rewritten`
+      )
+    }
+
+    const first = gens[0].generation
+    const file = segmentFileName(first)
+    const sidecar: SidecarIndex = { version: 1, generations: [], ids: {} }
+
+    // Encode all frames, tracking offsets for the sidecar.
+    const parts: Uint8Array[] = [MAGIC]
+    let offset = MAGIC.length
+    for (const g of gens) {
+      const payload = msgpackEncode([
+        g.generation,
+        g.timestamp,
+        g.delta,
+        g.records.map((r) => [r.kind === 'noun' ? 0 : 1, r.id, r.record]),
+        0 // flags: v1 = uncompressed
+      ])
+      const frame = new Uint8Array(FRAME_PREFIX_BYTES + payload.length)
+      const view = new DataView(frame.buffer)
+      view.setUint32(0, payload.length, true)
+      view.setUint32(4, crc32c(payload), true)
+      frame.set(payload, FRAME_PREFIX_BYTES)
+      sidecar.generations.push([g.generation, offset, frame.length])
+      for (const r of g.records) {
+        const key = `${r.kind === 'noun' ? 0 : 1}:${r.id}`
+        ;(sidecar.ids[key] ??= []).push(g.generation)
+      }
+      parts.push(frame)
+      offset += frame.length
+    }
+    const total = parts.reduce((n, p) => n + p.length, 0)
+    const bytes = new Uint8Array(total)
+    let at = 0
+    for (const p of parts) {
+      bytes.set(p, at)
+      at += p.length
+    }
+
+    const meta: SegmentMeta = {
+      file,
+      firstGeneration: first,
+      lastGeneration: gens[gens.length - 1].generation,
+      frames: gens.length,
+      bytes: total,
+      checksum: crc32c(bytes)
+    }
+
+    // Durability order: segment + sidecar fsync'd BEFORE the manifest names
+    // them (a crash before the manifest = invisible orphan files, harmless);
+    // manifest last, atomically.
+    const segPath = `${SEGMENTS_PREFIX}/${file}`
+    const idxPath = `${SEGMENTS_PREFIX}/${sidecarFileName(first)}`
+    await this.storage.writeRawBytes(segPath, bytes)
+    await this.storage.writeRawBytes(idxPath, msgpackEncode(sidecar))
+    await this.storage.syncRawObjects([segPath, idxPath])
+    const next: SegmentManifest = {
+      ...this.manifest,
+      segments: [...this.manifest.segments, meta]
+    }
+    await this.storage.writeRawObject(MANIFEST_PATH, next)
+    await this.storage.syncRawObjects([MANIFEST_PATH])
+    this.manifest = next
+    this.sidecars.set(file, sidecar)
+    return meta
+  }
+
+  /** Load (or rebuild, loudly) a segment's sidecar. */
+  private async sidecarFor(meta: SegmentMeta): Promise<SidecarIndex> {
+    const cached = this.sidecars.get(meta.file)
+    if (cached) return cached
+    const idxPath = `${SEGMENTS_PREFIX}/${sidecarFileName(meta.firstGeneration)}`
+    const raw = await this.storage.readRawBytes(idxPath)
+    if (raw) {
+      try {
+        const idx = msgpackDecode(raw) as SidecarIndex
+        if (idx.version === 1) {
+          this.sidecars.set(meta.file, idx)
+          return idx
+        }
+      } catch {
+        // fall through to rebuild
+      }
+    }
+    // Sidecars are DERIVED: rebuild from the segment, loudly — never serve
+    // wrong offsets silently.
+    prodLog.warn(
+      `[GenerationSegments] sidecar for ${meta.file} missing or unreadable — rebuilding from the segment`
+    )
+    const rebuilt = await this.rebuildSidecar(meta)
+    await this.storage.writeRawBytes(idxPath, msgpackEncode(rebuilt))
+    this.sidecars.set(meta.file, rebuilt)
+    return rebuilt
+  }
+
+  /** One sequential read of the segment → a fresh sidecar. Verifies every frame CRC. */
+  private async rebuildSidecar(meta: SegmentMeta): Promise<SidecarIndex> {
+    const frames = await this.readAllFrames(meta)
+    const idx: SidecarIndex = { version: 1, generations: [], ids: {} }
+    for (const f of frames) {
+      idx.generations.push([f.generation, f.offset, f.frameLen])
+      for (const r of f.records) {
+        const key = `${r.kind === 'noun' ? 0 : 1}:${r.id}`
+        ;(idx.ids[key] ??= []).push(f.generation)
+      }
+    }
+    return idx
+  }
+
+  private decodeFrame(
+    payload: Uint8Array
+  ): { generation: number; timestamp: number; delta: unknown; records: FoldGeneration['records'] } {
+    const [generation, timestamp, delta, rawRecords] = msgpackDecode(payload) as [
+      number,
+      number,
+      unknown,
+      Array<[number, string, unknown]>,
+      number
+    ]
+    return {
+      generation,
+      timestamp,
+      delta,
+      records: rawRecords.map(([kindByte, id, record]) => ({
+        kind: kindByte === 0 ? ('noun' as const) : ('verb' as const),
+        id,
+        record
+      }))
+    }
+  }
+
+  private async readAllFrames(meta: SegmentMeta): Promise<
+    Array<ReturnType<GenerationSegmentStore['decodeFrame']> & { offset: number; frameLen: number }>
+  > {
+    const bytes = await this.storage.readRawBytes(`${SEGMENTS_PREFIX}/${meta.file}`)
+    if (!bytes) {
+      throw new Error(
+        `[GenerationSegments] sealed segment ${meta.file} is MISSING — packed history is damaged; ` +
+          `refusing to continue silently`
+      )
+    }
+    const out: Array<ReturnType<GenerationSegmentStore['decodeFrame']> & { offset: number; frameLen: number }> = []
+    let at = MAGIC.length
+    const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength)
+    while (at + FRAME_PREFIX_BYTES <= bytes.length) {
+      const payloadLen = view.getUint32(at, true)
+      const crc = view.getUint32(at + 4, true)
+      const payload = bytes.subarray(at + FRAME_PREFIX_BYTES, at + FRAME_PREFIX_BYTES + payloadLen)
+      if (payload.length !== payloadLen || crc32c(payload) !== crc) {
+        throw new Error(
+          `[GenerationSegments] frame CRC mismatch in ${meta.file} at offset ${at} — ` +
+            `packed history is damaged; refusing to serve it`
+        )
+      }
+      out.push({ ...this.decodeFrame(payload), offset: at, frameLen: FRAME_PREFIX_BYTES + payloadLen })
+      at += FRAME_PREFIX_BYTES + payloadLen
+    }
+    return out
+  }
+
+  /** Read one packed generation's frame via its sidecar offset (one ranged read). */
+  private async readFrame(
+    gen: number
+  ): Promise<ReturnType<GenerationSegmentStore['decodeFrame']> | null> {
+    const meta = this.coveringSegment(gen)
+    if (!meta) return null
+    const idx = await this.sidecarFor(meta)
+    // generations ascending → binary search.
+    const gens = idx.generations
+    let lo = 0
+    let hi = gens.length - 1
+    while (lo <= hi) {
+      const mid = (lo + hi) >> 1
+      if (gens[mid][0] < gen) lo = mid + 1
+      else if (gens[mid][0] > gen) hi = mid - 1
+      else {
+        const [, offset, frameLen] = gens[mid]
+        const bytes = await this.storage.readRawBytes(`${SEGMENTS_PREFIX}/${meta.file}`)
+        if (!bytes) {
+          throw new Error(`[GenerationSegments] sealed segment ${meta.file} is MISSING`)
+        }
+        const frame = bytes.subarray(offset, offset + frameLen)
+        const view = new DataView(frame.buffer, frame.byteOffset, frame.byteLength)
+        const payloadLen = view.getUint32(0, true)
+        const crc = view.getUint32(4, true)
+        const payload = frame.subarray(FRAME_PREFIX_BYTES, FRAME_PREFIX_BYTES + payloadLen)
+        if (payload.length !== payloadLen || crc32c(payload) !== crc) {
+          throw new Error(
+            `[GenerationSegments] frame CRC mismatch for generation ${gen} in ${meta.file} — ` +
+              `packed history is damaged; refusing to serve it`
+          )
+        }
+        return this.decodeFrame(payload)
+      }
+    }
+    // In the covering range but not present: the packed tier is dense by
+    // construction (fold packs every generation it is handed, including
+    // record-less ones) — absence inside a sealed range is damage.
+    throw new Error(
+      `[GenerationSegments] generation ${gen} is inside sealed segment ${meta.file}'s declared ` +
+        `range but has no frame — packed history is damaged`
+    )
+  }
+
+  /** The packed tier's delta for `gen` (null = not packed). */
+  async readDelta(gen: number): Promise<{ delta: unknown; timestamp: number } | null> {
+    const frame = await this.readFrame(gen)
+    return frame ? { delta: frame.delta, timestamp: frame.timestamp } : null
+  }
+
+  /** The packed tier's full record-set for `gen` (null = not packed). */
+  async readRecords(gen: number): Promise<FoldGeneration['records'] | null> {
+    const frame = await this.readFrame(gen)
+    return frame ? frame.records : null
+  }
+
+  /** One packed before-image (null = not packed OR no record for the id in that generation). */
+  async readRecord(gen: number, kind: 'noun' | 'verb', id: string): Promise<unknown | null> {
+    const frame = await this.readFrame(gen)
+    if (!frame) return null
+    const hit = frame.records.find((r) => r.kind === kind && r.id === id)
+    return hit ? hit.record : null
+  }
+
+  /**
+   * D3 reclaim: drop WHOLE segments whose lastGeneration < `belowGeneration`
+   * and bump `compactedBelow`. Partial segments are never dropped — the
+   * boundary waits. NEVER called under the archival profile (the caller
+   * enforces retention semantics; this method only executes boundary drops).
+   */
+  async dropSegmentsBelow(belowGeneration: number): Promise<{ dropped: number; compactedBelow: number }> {
+    const keep: SegmentMeta[] = []
+    const drop: SegmentMeta[] = []
+    for (const s of this.manifest.segments) {
+      ;(s.lastGeneration < belowGeneration ? drop : keep).push(s)
+    }
+    if (drop.length === 0) {
+      return { dropped: 0, compactedBelow: this.manifest.compactedBelow }
+    }
+    const compactedBelow = Math.max(
+      this.manifest.compactedBelow,
+      drop[drop.length - 1].lastGeneration + 1
+    )
+    // Manifest first (the drop is authoritative once named), then bytes —
+    // a crash between leaves orphan segment files invisible to the manifest,
+    // harmless and re-collectable.
+    const next: SegmentManifest = { ...this.manifest, compactedBelow, segments: keep }
+    await this.storage.writeRawObject(MANIFEST_PATH, next)
+    await this.storage.syncRawObjects([MANIFEST_PATH])
+    this.manifest = next
+    for (const s of drop) {
+      await this.storage.deleteRawObject(`${SEGMENTS_PREFIX}/${s.file}`)
+      await this.storage.deleteRawObject(`${SEGMENTS_PREFIX}/${sidecarFileName(s.firstGeneration)}`)
+      this.sidecars.delete(s.file)
+    }
+    return { dropped: drop.length, compactedBelow }
+  }
+
+  /**
+   * D8 rider — the packed portion of `generationDigest(g)`: a deterministic
+   * crc32c chain over sealed-segment checksums fully below `g`, plus the
+   * frame CRC of `g`'s own frame when `g` is mid-segment. O(segments), not
+   * O(generations); identical history ⇒ identical digest on any machine.
+   * The live-tier portion is composed by the caller.
+   */
+  async digestThroughPacked(g: number): Promise<number | null> {
+    let digest = 0
+    let covered = false
+    for (const s of this.manifest.segments) {
+      if (s.lastGeneration <= g) {
+        digest = crc32c(new TextEncoder().encode(`${digest}:${s.checksum}`))
+        if (s.lastGeneration === g) covered = true
+      } else if (s.firstGeneration <= g) {
+        // g is mid-segment: chain the partial prefix via g's frame CRC.
+        const frame = await this.readFrame(g)
+        if (frame === null) return null
+        const idx = await this.sidecarFor(s)
+        const upTo = idx.generations.filter(([gen]) => gen <= g)
+        for (const [gen, offset, frameLen] of upTo) {
+          digest = crc32c(new TextEncoder().encode(`${digest}:${gen}:${offset}:${frameLen}`))
+        }
+        covered = true
+        break
+      }
+    }
+    return covered || this.manifest.segments.length > 0 ? digest : null
+  }
+}

src/db/generationStore.ts

@@ -46,6 +46,8 @@ import type {
   TxLogEntry
 } from './types.js'
 import { FactLog, storageSupportsFactLog, type CommitFact, type FactOp } from './factLog.js'
+import { GenerationSegmentStore, type FoldGeneration } from './generationSegments.js'
+import { crc32c } from '../utils/crc32c.js'
 
 /**
  * The byte-identical before-images of every id a commit touches, read UNDER
@@ -266,6 +268,21 @@ export class GenerationStore {
    */
   private historyBytesTotal: number | null = null
 
+  /**
+   * The packed tier (D1+D3): sealed segments holding folded cold
+   * generations. Null until {@link open} wires it (and on storage adapters
+   * without raw-byte primitives — the live tier then carries everything,
+   * exactly as before the packed tier existed).
+   */
+  private segments: GenerationSegmentStore | null = null
+
+  /**
+   * Live-tier window: generations newer than `committed - REPACK_LIVE_WINDOW`
+   * are never folded — the hot tail stays in the per-generation layout the
+   * write path owns. Matches the resident chain window's scale.
+   */
+  static readonly REPACK_LIVE_WINDOW = 1024
+
   /**
    * Model-B per-write group-commit — the in-memory PENDING tier.
    *
@@ -433,6 +450,33 @@ export class GenerationStore {
       this.factLog = null
     }
 
+    // PACKED TIER (D1+D3): same capability gate as the fact log. Opening
+    // reads ONE manifest — never a listing of the packed backlog — and seeds
+    // committedRanges with the sealed ranges so packed generations resolve
+    // exactly like live ones.
+    if (storageSupportsFactLog(this.storage)) {
+      this.segments = new GenerationSegmentStore(this.storage)
+      await this.segments.open()
+      const packedRanges = this.segments
+        .segments()
+        .map((s): [number, number] => [s.firstGeneration, Math.min(s.lastGeneration, this.committed)])
+        .filter(([lo, hi]) => lo <= hi)
+      if (packedRanges.length > 0) {
+        // Merge packed (older) + live (newer) interval sets — both ascending;
+        // coalesce adjacency so range arithmetic stays interval-exact.
+        const merged: Array<[number, number]> = []
+        for (const r of [...packedRanges, ...this.committedRanges].sort((a, b) => a[0] - b[0])) {
+          const last = merged[merged.length - 1]
+          if (last && r[0] <= last[1] + 1) last[1] = Math.max(last[1], r[1])
+          else merged.push([r[0], r[1]])
+        }
+        this.committedRanges = merged
+      }
+      this.horizonGen = Math.max(this.horizonGen, this.segments.compactedBelow() - 1)
+    } else {
+      this.segments = null
+    }
+
     // Hook single-op write batches so generation() is always meaningful.
     // Suppressed while a transact batch executes (the batch is ONE generation).
     if (!options?.readOnly) {
@@ -500,6 +544,51 @@ export class GenerationStore {
    * deltas (cache-bounded reads).
    * @returns Counts, bytes, generation range, and the compaction horizon.
    */
+  /**
+   * @description D8 (gate-to-generation provenance): a deterministic content
+   * digest of the generation log THROUGH `g` — identical history ⇒ identical
+   * digest on any machine; any divergence (different records, different
+   * order, reclaimed range) ⇒ different digest. Composed from the packed
+   * tier's sealed-segment checksum chain (O(segments)) plus the live tier's
+   * per-generation delta digests (O(live window at most)). Release gates pin
+   * {generation, digest} and verify both at execution time.
+   * @param g - The generation to digest through (≤ committed).
+   * @returns A hex digest string, stable across reopen and repacking states
+   *   ONLY for fully-packed prefixes — repacking changes representation, so
+   *   the composed digest is defined over CONTENT: live-tier gens hash their
+   *   delta + record ids, packed gens hash via frame CRCs. A gate should pin
+   *   after a repack pass for long-term stability, or re-pin on repack.
+   */
+  async generationDigest(g: number): Promise<string> {
+    if (!Number.isInteger(g) || g < 1 || g > this.committed) {
+      throw new RangeError(
+        `generationDigest(): generation ${g} is out of range [1, ${this.committed}]`
+      )
+    }
+    if (g <= this.horizonGen) {
+      throw new GenerationCompactedError(g, this.horizonGen)
+    }
+    let digest = 0
+    const enc = new TextEncoder()
+    if (this.segments) {
+      const packed = await this.segments.digestThroughPacked(g)
+      if (packed !== null) digest = packed
+    }
+    // Live-tier composition: every committed gen ≤ g not covered by a sealed
+    // segment hashes its delta content in ascending order.
+    for (const gen of this.committedGensAsc()) {
+      if (gen > g) break
+      if (this.segments?.hasGeneration(gen)) continue
+      const delta = await this.getDelta(gen)
+      digest = crc32c(
+        enc.encode(
+          `${digest}:${gen}:${delta.timestamp}:${[...delta.nouns].sort().join(',')}:${[...delta.verbs].sort().join(',')}`
+        )
+      )
+    }
+    return digest.toString(16).padStart(8, '0')
+  }
+
   async historyStats(): Promise<{
     generations: number
     bytes: number
@@ -538,14 +627,17 @@ export class GenerationStore {
     try {
       paths = await this.storage.listRawObjects(`${GENERATIONS_PREFIX}/${gen}/prev`)
     } catch {
-      return []
+      paths = []
     }
     const records: GenerationRecord[] = []
     for (const p of paths) {
       const record = (await this.storage.readRawObject(p)) as GenerationRecord | null
       if (record) records.push(record)
     }
-    return records
+    if (records.length > 0) return records
+    // Two-tier: folded generations serve their record-set from the segment.
+    const packed = await this.segments?.readRecords(gen)
+    return packed ? (packed.map((r) => r.record) as GenerationRecord[]) : []
   }
 
   /**
@@ -1783,9 +1875,15 @@ export class GenerationStore {
     if (pending) {
       return (kind === 'noun' ? pending.nouns : pending.verbs).get(id) ?? null
     }
-    return (await this.storage.readRawObject(
+    const live = (await this.storage.readRawObject(
       `${GENERATIONS_PREFIX}/${gen}/prev/${id}.json`
     )) as GenerationRecord | null
+    if (live) return live
+    // Two-tier: the packed tier serves folded generations (live-tier-wins).
+    if (this.segments?.hasGeneration(gen)) {
+      return (await this.segments.readRecord(gen, kind, id)) as GenerationRecord | null
+    }
+    return null
   }
 
   /**
@@ -2132,6 +2230,21 @@ export class GenerationStore {
       `${GENERATIONS_PREFIX}/${gen}/tx.json`
     )) as GenerationDelta | null
     if (delta === null) {
+      // Two-tier read (D1+D3): not in the live tier → the packed tier.
+      // Live-tier-wins ordering (a crash mid-fold leaves a duplicate, never
+      // a gap), so the segment lookup runs only after the live miss.
+      const packed = await this.segments?.readDelta(gen)
+      if (packed) {
+        const d = packed.delta as GenerationDelta
+        const entry = {
+          nouns: new Set(d.nouns),
+          verbs: new Set(d.verbs),
+          timestamp: packed.timestamp,
+          bytes: d.bytes ?? 0
+        }
+        this.setDelta(gen, entry)
+        return entry
+      }
       throw new Error(
         `Generation delta missing: ${GENERATIONS_PREFIX}/${gen}/tx.json ` +
           `(store corrupted or records removed outside compactHistory())`
@@ -2213,6 +2326,94 @@ export class GenerationStore {
    * @param options - Retention caps (see {@link CompactHistoryOptions}).
    * @returns Count of removed record-sets and the new horizon.
    */
+  /**
+   * @description The REPACKER (D1+D3+repacking): fold cold live-tier
+   * generations into sealed segments — re-representation, never deletion.
+   * Every record and delta stays readable (asOf/chains unchanged); the
+   * per-generation directories are deleted only AFTER their segment is
+   * durable (crash between = duplicate representation, resolved
+   * live-tier-wins by every reader; never a gap). This is the transform that
+   * takes a 70k-file history to tens of segment files, and the ONLY history
+   * transform permitted under the archival profile.
+   *
+   * Folds oldest-first, contiguous from the packed boundary, in batches, and
+   * stops at the live window ({@link GenerationStore.REPACK_LIVE_WINDOW})
+   * or when `timeBudgetMs` is spent — an early stop is a consistent prefix;
+   * the next pass resumes.
+   */
+  async repackHistory(options?: { timeBudgetMs?: number; batchGenerations?: number }): Promise<{
+    foldedGenerations: number
+    segmentsCreated: number
+  }> {
+    if (!this.segments) return { foldedGenerations: 0, segmentsCreated: 0 }
+    const segments = this.segments
+    return this.withMutex(async () => {
+      const deadline =
+        options?.timeBudgetMs !== undefined ? Date.now() + options.timeBudgetMs : undefined
+      const batchSize = options?.batchGenerations ?? 512
+      const coldCeiling = this.committed - GenerationStore.REPACK_LIVE_WINDOW
+      const packedThrough =
+        segments.segments().length > 0
+          ? segments.segments()[segments.segments().length - 1].lastGeneration
+          : 0
+
+      // Cold, unpacked, committed generations — ascending, contiguous scan.
+      const eligible: number[] = []
+      for (const gen of this.committedGensAsc()) {
+        if (gen > coldCeiling) break
+        if (gen <= packedThrough) continue // already packed (dup fold barred)
+        if (this.pendingBuffer.has(gen)) continue // un-flushed = live by definition
+        eligible.push(gen)
+      }
+
+      let folded = 0
+      let segmentsCreated = 0
+      for (let i = 0; i < eligible.length; i += batchSize) {
+        if (deadline !== undefined && Date.now() >= deadline) break
+        const batch = eligible.slice(i, i + batchSize)
+        const foldInput: FoldGeneration[] = []
+        for (const gen of batch) {
+          const delta = (await this.storage.readRawObject(
+            `${GENERATIONS_PREFIX}/${gen}/tx.json`
+          )) as GenerationDelta | null
+          if (delta === null) {
+            // Already folded by a prior crashed pass whose dirs were removed,
+            // or damage — getDelta's two-tier read decides which, loudly,
+            // when someone asks. Skip; never fold a generation we cannot read.
+            continue
+          }
+          const records: FoldGeneration['records'] = []
+          for (const [kind, ids] of [
+            ['noun', delta.nouns] as const,
+            ['verb', delta.verbs] as const
+          ]) {
+            for (const id of ids) {
+              const record = await this.storage.readRawObject(
+                `${GENERATIONS_PREFIX}/${gen}/prev/${id}.json`
+              )
+              if (record) records.push({ kind, id, record })
+            }
+          }
+          foldInput.push({ generation: gen, timestamp: delta.timestamp, delta, records })
+        }
+        if (foldInput.length === 0) continue
+        await segments.fold(foldInput)
+        segmentsCreated++
+        // Segment + manifest durable → the live copies retire.
+        for (const g of foldInput) {
+          await this.storage.removeRawPrefix(`${GENERATIONS_PREFIX}/${g.generation}`)
+        }
+        folded += foldInput.length
+      }
+      if (folded > 0) {
+        prodLog.info(
+          `[GenerationStore] repacked ${folded} cold generation(s) into ${segmentsCreated} segment(s) — history preserved, file count reduced`
+        )
+      }
+      return { foldedGenerations: folded, segmentsCreated }
+    })
+  }
+
   async compact(options?: CompactHistoryOptions): Promise<CompactHistoryResult> {
     return this.withMutex(async () => {
       const minPinned = this.minPinnedGeneration()
@@ -2304,6 +2505,16 @@ export class GenerationStore {
         // Reclaimed generations leave the per-id chains stale → rebuild on next read.
         this.invalidateChains()
         this.horizonGen = Math.max(this.horizonGen, highestRemoved)
+        // Packed-tier reclaim (D3): a packed generation's bytes live in a
+        // sealed segment — removeRawPrefix above was a no-op for it. Drop
+        // WHOLE segments now fully below the horizon; a partially-reclaimed
+        // segment keeps its bytes until the boundary passes it (the frozen
+        // partial-segments-wait rule; logical reclamation above still holds —
+        // the generations left committedRanges and asOf below the horizon
+        // throws regardless).
+        if (this.segments) {
+          await this.segments.dropSegmentsBelow(this.horizonGen + 1)
+        }
         const manifest: GenerationManifest = {
           version: 1,
           generation: this.committed,

src/db/types.ts

@@ -121,9 +121,13 @@ export interface TransactOptions {
    * with the batch: `max(30 000, opCount × 2 000)` — production imports on
    * network-attached disks measure ~2 s per operation, so a flat 30 s budget
    * silently capped honest bulk work at ~15 operations. A tripped budget
-   * rolls the whole batch back and throws a retryable
+   * rolls the whole batch back and throws a `TransactionTimeoutError` naming
-   * `TransactionTimeoutError` naming the operation it stopped at, the batch
+   * the operation it stopped at, the batch size, and the elapsed/budget
-   * size, and the elapsed/budget times.
+   * times. That error is retryable-with-latch, never hot-retry: its
+   * `retryable` field says a later attempt may succeed, its
+   * `hotRetryUnsafe` field says an immediate identical retry re-pays the
+   * full cost that just timed out — callers must latch and back off, never
+   * loop.
    */
   timeoutMs?: number
 }

src/index.ts

@@ -31,6 +31,11 @@ export type { DiagnosticsResult } from './brainy.js'
 // brain.warm() — eager index/storage readiness report (per-surface honest
 // outcome + timing). See the WarmReport JSDoc in brainy.ts.
 export type { WarmReport, WarmOutcome } from './brainy.js'
+// brain.maintenanceDebt() — per-surface passthrough of each active
+// provider's self-reported background maintenance debt. See the
+// MaintenanceDebtReport JSDoc in brainy.ts and ProviderMaintenanceDebt in
+// plugin.ts for the measure-only-what-you-track contract.
+export type { MaintenanceDebtReport, MaintenanceDebtOutcome } from './brainy.js'
 export type {
   GraphAuditReport,
   GraphAuditDiscrepancy
@@ -216,6 +221,7 @@ export type {
   CommitFact,
   FactOp,
   FactScanBatch,
+  SCANFACTS_FIRST_BATCH_MS,
   FactScanHandle
 } from './db/factLog.js'
 // The generalized family stamp — which source generation a projection
@@ -227,6 +233,11 @@ export type { FamilyStamp, StampMembers, StampVerdict } from './db/familyStamp.j
 export { isVersionedIndexProvider } from './plugin.js'
 export type { VersionedIndexProvider } from './plugin.js'
 export type { ProviderInvariantReport, InvariantResult, InvariantHeal } from './plugin.js'
+// Optional provider self-report of outstanding background maintenance work
+// (compaction, deferred writes, etc.) — the payload type for
+// brain.maintenanceDebt(). See the measure-only-what-you-track contract on
+// ProviderMaintenanceDebt in plugin.ts.
+export type { ProviderMaintenanceDebt } from './plugin.js'
 // Optional native graph-acceleration engine (cor 3.0) — the published provider
 // contract + its columnar wire types. Brainy feature-detects an implementation
 // and falls back to its pure-TS adjacency when absent.

src/plugin.ts

@@ -171,6 +171,37 @@ export interface ProviderInvariantReport {
   durationMs: number
 }
 
+/**
+ * @description A provider's self-report of its own outstanding background
+ * maintenance work (compaction, deferred writes, a build-new→verify→swap in
+ * flight, etc.) — the observability seam so an operator sees a grind coming
+ * (rising pending bytes/items, a stalled pass) instead of discovering it as a
+ * CPU storm or a timeout under transaction budget pressure. Every field is
+ * OPTIONAL and every field is a MEASUREMENT: a provider reports ONLY what it
+ * actually tracks, never an estimate dressed up as a fact. Absence of the
+ * {@link VectorIndexProvider.maintenanceDebt} /
+ * {@link GraphIndexProvider.maintenanceDebt} /
+ * {@link MetadataIndexProvider.maintenanceDebt} hook itself means the
+ * provider does not track debt at all — brainy reports that surface
+ * `'unavailable'` rather than inventing zeros. Brainy performs NO threshold
+ * checks, NO polling, and NO JS-side estimation over this payload — it is a
+ * pure passthrough via {@link Brainy.maintenanceDebt}; the provider owns the
+ * numbers and the operator owns the policy (what threshold matters, what to
+ * do about it).
+ */
+export interface ProviderMaintenanceDebt {
+  /** Bytes of outstanding/unmerged work, if the provider measures it (e.g. unflushed writes, unmerged segments). */
+  pendingBytes?: number
+  /** Count of outstanding items (records, segments, nodes) awaiting the provider's background pass. */
+  pendingItems?: number
+  /** Epoch millis when the provider's last maintenance pass finished, if it tracks one. */
+  lastPassCompletedAt?: number
+  /** How the last pass ended, if the provider tracks pass outcomes. */
+  lastPassOutcome?: 'completed' | 'partial' | 'failed'
+  /** `true` if the provider's own measurements show debt trending down (making progress); `false` if flat or growing; omitted if the provider can't tell. */
+  converging?: boolean
+}
+
 /**
  * The `'metadataIndex'` provider — a drop-in for `MetadataIndexManager`.
  * Brainy calls this surface via `this.metadataIndex.*` (see `brainy.ts`) and
@@ -181,6 +212,34 @@ export interface MetadataIndexProvider {
   flush(): Promise<void>
   rebuild(): Promise<void>
 
+  /**
+   * @description OPTIONAL. Eagerly load/fault-in backing storage (e.g. mmap
+   * pretouch, full sparse-index hydration) so first queries run at
+   * steady-state cost. Optional; absence means the provider demand-loads.
+   * Mirrors {@link GraphIndexProvider.warm} / the vector provider's `warm?()`
+   * (`src/plugin.ts` VectorIndexProvider). Distinct from `init()`: `init` is
+   * required and runs once automatically during brain startup; `warm` is a
+   * separate, explicit step a caller opts into via `brain.warm()` (or
+   * `warmOnOpen`) to pre-pay demand-load cost `init` left lazy. Idempotent —
+   * calling it more than once must be safe and cheap on a brain that is
+   * already warm. A provider that already loads everything eagerly in
+   * `init()` may implement `warm` as a no-op or omit it — `brain.warm()`
+   * falls back to the built-in JS manager's `hydrateAll()` duck-type when
+   * absent, and to an honest `'unavailable'` when neither exists.
+   */
+  warm?(): Promise<void>
+
+  /**
+   * @description OPTIONAL self-reported {@link ProviderMaintenanceDebt} —
+   * the observability seam so an operator sees outstanding background
+   * maintenance work (e.g. unmerged postings) BEFORE it grinds a transaction
+   * into a budget-busting op. Absence means this provider does not track
+   * debt; `brain.maintenanceDebt()` reports this surface `'unavailable'`
+   * rather than guessing. See {@link ProviderMaintenanceDebt} for the
+   * measure-only-what-you-track contract.
+   */
+  maintenanceDebt?(): Promise<ProviderMaintenanceDebt>
+
   /**
    * @description OPTIONAL honest durability signal (readiness contract,
    * mirrors `isReady?()` on the graph and vector providers). `true` ⇔ the
@@ -395,6 +454,18 @@ export interface GraphIndexProvider {
    */
   warm?(): Promise<void>
 
+  /**
+   * @description OPTIONAL self-reported {@link ProviderMaintenanceDebt} —
+   * the observability seam so an operator sees outstanding background
+   * maintenance work (e.g. a build-new→verify→swap in flight, unmerged
+   * adjacency segments) BEFORE it grinds a transaction into a
+   * budget-busting op. Absence means this provider does not track debt;
+   * `brain.maintenanceDebt()` reports this surface `'unavailable'` rather
+   * than guessing. See {@link ProviderMaintenanceDebt} for the
+   * measure-only-what-you-track contract.
+   */
+  maintenanceDebt?(): Promise<ProviderMaintenanceDebt>
+
   /**
    * @description OPTIONAL. A native provider returns true from the moment its
    * `init()` detects a large epoch-drift until its background
@@ -1057,6 +1128,18 @@ export interface VectorIndexProvider {
    */
   warm?(): Promise<void>
 
+  /**
+   * @description OPTIONAL self-reported {@link ProviderMaintenanceDebt} —
+   * the observability seam so an operator sees outstanding background
+   * maintenance work (e.g. unflushed writes, a pending rebuild) BEFORE it
+   * grinds a transaction into a budget-busting op. Absence means this
+   * provider does not track debt; `brain.maintenanceDebt()` reports this
+   * surface `'unavailable'` rather than guessing. See
+   * {@link ProviderMaintenanceDebt} for the measure-only-what-you-track
+   * contract.
+   */
+  maintenanceDebt?(): Promise<ProviderMaintenanceDebt>
+
   /**
    * @description OPTIONAL honest durability signal (readiness contract,
    * mirrors {@link GraphIndexProvider.isReady}). `true` ⇔ the persisted

src/storage/adapters/memoryStorage.ts

@@ -133,6 +133,11 @@ export class MemoryStorage extends BaseStorage {
    */
   protected async deleteObjectFromPath(path: string): Promise<void> {
     this.objectStore.delete(path)
+    // Filesystem parity: on disk, objects and raw BYTE files are both just
+    // files — unlink removes whichever exists. Without this, deleteRawObject
+    // on a raw-bytes path (fact-log/generation segments) silently no-ops on
+    // memory storage: the delete "succeeds" and the bytes remain.
+    this.rawBytesStore.delete(path)
   }
 
   /**

src/transaction/Transaction.ts

@@ -62,9 +62,10 @@ const DEFAULT_BUDGET_FLOOR_MS = 30_000
  * NEXT operation may start (see {@link Transaction.execute}), never whether
  * already-completed work is rolled back after the fact. A trip mid-batch
  * still rolls back every operation applied so far, atomically, and throws a
- * retryable, fully-labeled TransactionTimeoutError — that zero-loss guarantee
+ * fully-labeled `TransactionTimeoutError` — retryable-with-latch, never
- * doesn't change; only the point at which the clock stops mattering does (at
+ * hot-retry (see its `retryable` and `hotRetryUnsafe` fields) — that
- * the last operation, not one check later).
+ * zero-loss guarantee doesn't change; only the point at which the clock
+ * stops mattering does (at the last operation, not one check later).
  *
  * @param opCount - Number of operations in the batch.
  * @param override - A full override for this call; wins over everything else.

src/transaction/TransactionManager.ts

@@ -19,7 +19,6 @@
 import { Transaction } from './Transaction.js'
 import {
   TransactionFunction,
-  TransactionResult,
   TransactionOptions
 } from './types.js'
 import { TransactionError } from './errors.js'
@@ -105,34 +104,6 @@ export class TransactionManager {
     }
   }
 
-  /**
-   * Execute a transaction and return detailed result
-   */
-  async executeTransactionWithResult<T>(
-    fn: TransactionFunction<T>,
-    options?: TransactionOptions
-  ): Promise<TransactionResult<T>> {
-    const startTime = Date.now()
-    const transaction = new Transaction(options)
-
-    try {
-      const value = await fn(transaction)
-      await transaction.execute()
-
-      const executionTimeMs = Date.now() - startTime
-
-      return {
-        value,
-        operationCount: transaction.getOperationCount(),
-        executionTimeMs
-      }
-
-    } catch (error) {
-      // Transaction failed
-      throw error
-    }
-  }
-
   /**
    * Get transaction statistics
    */

src/transaction/errors.ts

@@ -73,14 +73,47 @@ export class InvalidTransactionStateError extends TransactionError {
 
 /**
  * Error for transaction timeout
+ *
+ * Machine-readable no-hot-retry contract: {@link retryable} and
+ * {@link hotRetryUnsafe} are both always `true` on this class — they exist
+ * so a caller can branch on the *shape* of the error instead of parsing
+ * message text. Read them together: the operation may eventually succeed,
+ * but never by looping on it immediately.
+ *
+ * `context` (inherited from {@link TransactionError}) carries the caller's
+ * backoff inputs — see the field docs below.
  */
 export class TransactionTimeoutError extends TransactionError {
+  /**
+   * The failed operation MAY succeed on a later attempt — once the
+   * underlying slowness resolves (e.g. a cold page cache warms up) or the
+   * budget is deliberately raised (`transactionBudgetFloorMs`, or a larger
+   * `timeoutMs` override on the batch). This is a statement about eventual
+   * retryability, not a license to retry now — see {@link hotRetryUnsafe}.
+   */
+  public readonly retryable = true
+
+  /**
+   * An immediate, identical retry re-pays the FULL cost of the work that
+   * just timed out — it does not resume partway. Looping on this error
+   * (hot-retrying) repeats that full cost every attempt and can cascade
+   * into a CPU/resource storm on the caller's side. Callers MUST latch: on
+   * this error, record `{ at: Date.now(), error }`, surface one loud
+   * failure to their own caller, and hold a cooldown window before any
+   * re-attempt (clearing the latch only on success). Never retry this error
+   * in a tight loop.
+   */
+  public readonly hotRetryUnsafe = true
+
   constructor(
     timeoutMs: number,
     operationIndex: number,
     telemetry?: {
+      /** Milliseconds elapsed in the transaction when the budget tripped. */
       elapsedMs?: number
+      /** Total number of operations in the batch that timed out. */
       totalOperations?: number
+      /** Name of the operation the batch was about to start when it tripped, if named. */
       operationName?: string
     }
   ) {
@@ -93,8 +126,16 @@ export class TransactionTimeoutError extends TransactionError {
       telemetry?.elapsedMs !== undefined ? `${telemetry.elapsedMs}ms elapsed, ` : ''
     super(
       `Transaction timed out at operation ${progress}${name} — ${elapsed}budget ${timeoutMs}ms. ` +
-        `The batch rolled back atomically; retry with a higher timeoutMs or a smaller batch.`,
+        `The batch rolled back atomically; retryable after the underlying slowness resolves or ` +
-      { timeoutMs, operationIndex, ...telemetry }
+        `the budget is raised, but hot-retry-unsafe — latch and back off, never loop.`,
+      {
+        // Caller backoff inputs — all present on every instance:
+        /** Configured budget (ms) that was exceeded. */
+        timeoutMs,
+        /** Index of the operation the batch was about to start when it tripped. */
+        operationIndex,
+        ...telemetry
+      }
     )
     this.name = 'TransactionTimeoutError'
   }

src/transaction/types.ts

@@ -66,26 +66,6 @@ export interface TransactionContext {
  */
 export type TransactionFunction<T> = (ctx: TransactionContext) => Promise<T>
 
-/**
- * Transaction execution result
- */
-export interface TransactionResult<T> {
-  /**
-   * Result value from user function
-   */
-  value: T
-
-  /**
-   * Number of operations executed
-   */
-  operationCount: number
-
-  /**
-   * Execution time in milliseconds
-   */
-  executionTimeMs: number
-}
-
 /**
  * Transaction execution options
  */

src/types/brainy.types.ts

@@ -1658,8 +1658,10 @@ export interface BrainyConfig {
    * **start** — never whether already-completed work gets rolled back after
    * the fact (a single-op write can never time out post-hoc: it either runs
    * or it commits). A trip mid-batch still rolls back every applied operation
-   * atomically and throws a retryable `TransactionTimeoutError`; only the
+   * atomically and throws a `TransactionTimeoutError` that is
-   * floor of the formula is configurable here.
+   * retryable-with-latch, never hot-retry (see its `retryable` and
+   * `hotRetryUnsafe` fields); only the floor of the formula is configurable
+   * here.
    *
    * Raise this when a cold store's first writes after a restart legitimately
    * take longer than 30s per operation (e.g. page-cache-cold canonical writes

tests/integration/history-repacking.test.ts

@@ -0,0 +1,186 @@
+/**
+ * @module tests/integration/history-repacking
+ * @description The D1+D3 two-tier history lifecycle end-to-end on a real
+ * brain. Laws: (1) repacking is RE-REPRESENTATION — after folding, every
+ * asOf() read below the fold boundary answers exactly as before, across a
+ * cold reopen; (2) folded per-generation directories are physically gone
+ * (the file-count cure is real, not cosmetic); (3) repack + reclaim compose:
+ * bounded retention after repacking drops whole segments and asOf below the
+ * horizon throws GenerationCompactedError; (4) repackHistory is explicit
+ * API and time-bounded (spent budget = consistent no-op).
+ *
+ * Uses a tiny REPACK_LIVE_WINDOW override so a small history has a cold
+ * tier at all (the production window is 1024).
+ */
+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 { Brainy } from '../../src/brainy.js'
+import { NounType } from '../../src/types/graphTypes.js'
+import { GenerationStore } from '../../src/db/generationStore.js'
+import { GenerationCompactedError } from '../../src/db/errors.js'
+import { SEGMENTS_PREFIX } from '../../src/db/generationSegments.js'
+
+const stub = async (text: string): Promise<number[]> => {
+  const h = text.split('').reduce((a, c) => a + c.charCodeAt(0), 0)
+  return new Array(384).fill(0).map((_, i) => Math.sin(h + i))
+}
+
+const openBrain = async (dir: string): Promise<Brainy> => {
+  const brain = new Brainy({
+    requireSubtype: false,
+    storage: { type: 'filesystem', path: dir },
+    embeddingFunction: stub
+  })
+  await brain.init()
+  return brain
+}
+
+describe('history repacking — the two-tier lifecycle', () => {
+  const dirs: string[] = []
+  const tempDir = (): string => {
+    const d = fs.mkdtempSync(path.join(os.tmpdir(), 'brainy-repack-'))
+    dirs.push(d)
+    return d
+  }
+  const originalWindow = GenerationStore.REPACK_LIVE_WINDOW
+
+  afterEach(() => {
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = originalWindow
+    for (const d of dirs.splice(0)) {
+      try {
+        fs.rmSync(d, { recursive: true, force: true })
+      } catch {
+        /* best effort */
+      }
+    }
+  })
+
+  it('repack preserves every historical read across cold reopen; folded dirs are gone', async () => {
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = 3
+    const dir = tempDir()
+    const brain = await openBrain(dir)
+
+    const id = await brain.add({
+      data: 'versioned-entity',
+      type: NounType.Document,
+      metadata: { v: 0 }
+    })
+    for (let v = 1; v <= 10; v++) await brain.update({ id, metadata: { v } })
+    await brain.flush()
+
+    // Ground truth BEFORE repacking: capture asOf views for early generations.
+    const before: Record<number, number> = {}
+    for (const g of [2, 4, 6]) {
+      const db = await brain.asOf(g)
+      before[g] = (await db.get(id))?.metadata?.v as number
+      await db.release()
+    }
+
+    const result = await brain.repackHistory()
+    expect(result.foldedGenerations).toBeGreaterThan(0)
+    expect(result.segmentsCreated).toBeGreaterThan(0)
+
+    // The folded per-generation directories are PHYSICALLY gone…
+    const genDirs = fs
+      .readdirSync(path.join(dir, '_generations'), { withFileTypes: true })
+      .filter((e) => e.isDirectory() && /^\d+$/.test(e.name)).length
+    expect(genDirs).toBeLessThanOrEqual(4) // live window (3) + at most the newest
+    // …and the segment tier exists (the filesystem adapter stores objects
+    // gzipped, so the manifest may live at either spelling).
+    const segDir = path.join(dir, SEGMENTS_PREFIX)
+    expect(
+      fs.existsSync(path.join(segDir, 'manifest.json')) ||
+        fs.existsSync(path.join(segDir, 'manifest.json.gz'))
+    ).toBe(true)
+    expect(fs.readdirSync(segDir).some((f) => f.endsWith('.bgs'))).toBe(true)
+
+    // Same asOf answers from the packed tier, same process…
+    for (const g of [2, 4, 6]) {
+      const db = await brain.asOf(g)
+      expect((await db.get(id))?.metadata?.v).toBe(before[g])
+      await db.release()
+    }
+    await brain.close()
+
+    // …and across a COLD REOPEN (manifest discovery, no live dirs to list).
+    const reopened = await openBrain(dir)
+    for (const g of [2, 4, 6]) {
+      const db = await reopened.asOf(g)
+      expect((await db.get(id))?.metadata?.v).toBe(before[g])
+      await db.release()
+    }
+    expect((await reopened.get(id))?.metadata?.v).toBe(10) // live state untouched
+    await reopened.close()
+  })
+
+  it('repack + bounded reclaim compose: whole segments drop, horizon is loud', async () => {
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = 2
+    const dir = tempDir()
+    const brain = await openBrain(dir)
+    const id = await brain.add({ data: 'reclaim-probe', type: NounType.Document, metadata: { v: 0 } })
+    for (let v = 1; v <= 8; v++) await brain.update({ id, metadata: { v } })
+    await brain.flush()
+    await brain.repackHistory()
+
+    // Reclaim down to the 3 newest generations — packed segments below the
+    // horizon drop whole; asOf below throws loudly.
+    const res = await brain.compactHistory({ maxGenerations: 3 })
+    expect(res.removedGenerations).toBeGreaterThan(0)
+    await expect(brain.asOf(1)).rejects.toBeInstanceOf(GenerationCompactedError)
+    expect((await brain.get(id))?.metadata?.v).toBe(8)
+    await brain.close()
+  })
+
+  it('generationDigest: reopen-stable, divergence-sensitive, loud below the horizon', async () => {
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = 2
+    const dir = tempDir()
+    const brain = await openBrain(dir)
+    const id = await brain.add({ data: 'digest-probe', type: NounType.Document, metadata: { v: 0 } })
+    for (let v = 1; v <= 6; v++) await brain.update({ id, metadata: { v } })
+    await brain.flush()
+    await brain.repackHistory()
+
+    const gen = brain.generation()
+    const atHead = await brain.generationDigest(gen)
+    const atMid = await brain.generationDigest(3)
+    expect(atHead).toMatch(/^[0-9a-f]{8}$/)
+    expect(atMid).not.toBe(atHead) // more history ⇒ different digest
+    await brain.close()
+
+    // Reopen-stable: same history, same digests (packed prefix stability).
+    const reopened = await openBrain(dir)
+    expect(await reopened.generationDigest(gen)).toBe(atHead)
+    expect(await reopened.generationDigest(3)).toBe(atMid)
+
+    // New history diverges the head digest.
+    await reopened.update({ id, metadata: { v: 7 } })
+    await reopened.flush()
+    expect(await reopened.generationDigest(reopened.generation())).not.toBe(atHead)
+
+    // Below the horizon: LOUD, never a silent pin of reclaimed history.
+    await reopened.compactHistory({ maxGenerations: 2 })
+    await expect(reopened.generationDigest(1)).rejects.toBeInstanceOf(GenerationCompactedError)
+    await reopened.close()
+  })
+
+  it('a spent time budget is a consistent no-op; the next pass resumes', async () => {
+    ;(GenerationStore as any).REPACK_LIVE_WINDOW = 2
+    const dir = tempDir()
+    const brain = await openBrain(dir)
+    const id = await brain.add({ data: 'budget-probe', type: NounType.Document, metadata: { v: 0 } })
+    for (let v = 1; v <= 6; v++) await brain.update({ id, metadata: { v } })
+    await brain.flush()
+
+    const bounded = await brain.repackHistory({ timeBudgetMs: 0 })
+    expect(bounded).toEqual({ foldedGenerations: 0, segmentsCreated: 0 })
+
+    const resumed = await brain.repackHistory()
+    expect(resumed.foldedGenerations).toBeGreaterThan(0)
+    const db = await brain.asOf(3)
+    expect((await db.get(id))?.metadata?.v).toBeDefined()
+    await db.release()
+    await brain.close()
+  })
+})

tests/transaction/TransactionManager.unit.test.ts

@@ -5,7 +5,6 @@
  * - High-level transaction API
  * - Statistics tracking
  * - Error handling
- * - Result wrapping
  */
 
 import { describe, it, expect, beforeEach } from 'vitest'
@@ -84,42 +83,6 @@ describe('TransactionManager', () => {
     })
   })
 
-  describe('executeTransactionWithResult', () => {
-    it('should return detailed result', async () => {
-      const result = await manager.executeTransactionWithResult(async (tx) => {
-        tx.addOperation({
-          execute: async () => {
-            await new Promise(resolve => setTimeout(resolve, 1))
-            return async () => {}
-          }
-        })
-        tx.addOperation({ execute: async () => undefined })
-        return 'success'
-      })
-
-      expect(result.value).toBe('success')
-      expect(result.operationCount).toBe(2)
-      expect(result.executionTimeMs).toBeGreaterThanOrEqual(0)
-    })
-
-    it('should measure execution time', async () => {
-      const result = await manager.executeTransactionWithResult(async (tx) => {
-        tx.addOperation({
-          execute: async () => {
-            await new Promise(resolve => setTimeout(resolve, 25))
-            return async () => {}
-          }
-        })
-        return 'done'
-      })
-
-      // Timer coalescing can fire a setTimeout up to a few ms EARLY under
-      // load, so assert well below the sleep — this tests that time is
-      // MEASURED, not the OS timer's precision.
-      expect(result.executionTimeMs).toBeGreaterThanOrEqual(20)
-    })
-  })
-
   describe('Statistics Tracking', () => {
     it('should track total transactions', async () => {
       await manager.executeTransaction(async (tx) => {

tests/unit/brainy/maintenance-debt.test.ts

@@ -0,0 +1,122 @@
+/**
+ * @module tests/unit/brainy/maintenance-debt
+ * @description Coverage for `brain.maintenanceDebt()` (8.10.1) — the
+ * observability seam so an operator sees a provider's outstanding background
+ * maintenance work (compaction, deferred writes, a build-new→verify→swap in
+ * flight, ...) BEFORE it grinds a transaction into a budget-busting op, the
+ * same failure class documented on `TransactionTimeoutError`
+ * (src/transaction/errors.ts). Sibling to tests/unit/brainy/warm.test.ts,
+ * which establishes this file's technique: shape the probe points brain.ts
+ * reads (`typeof provider.maintenanceDebt === 'function'`) directly on the
+ * REAL, live provider instances rather than hand-rolling full fakes for the
+ * larger `MetadataIndexProvider` / `GraphIndexProvider` interfaces.
+ *
+ * `brain.maintenanceDebt()` is a PURE PASSTHROUGH: no thresholds, no
+ * polling, no JS-side estimation — these tests pin exactly that by asserting
+ * the returned payload is the provider's object, verbatim.
+ */
+import { describe, it, expect } from 'vitest'
+import { Brainy } from '../../../src/brainy.js'
+import { NounType } from '../../../src/types/graphTypes.js'
+import type { ProviderMaintenanceDebt } from '../../../src/plugin.js'
+
+// Brainy's ValidationConfig fixes vectors at exactly 384 dimensions
+// (src/utils/paramValidation.ts) — match it so add() doesn't reject test data.
+const DIM = 384
+const V = (seed = 1): number[] => Array.from({ length: DIM }, (_, i) => Math.sin(seed + i))
+
+async function freshBrain(): Promise<Brainy<any>> {
+  const brain = new Brainy({
+    requireSubtype: false,
+    storage: { type: 'memory' },
+    silent: true
+  })
+  await brain.init()
+  await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })
+  return brain
+}
+
+describe('brain.maintenanceDebt()', () => {
+  it('reports "unavailable" for every surface when no active provider implements maintenanceDebt() (the built-in JS stack today)', async () => {
+    const brain = await freshBrain()
+
+    const report = await brain.maintenanceDebt()
+
+    expect(report.vector.outcome).toBe('unavailable')
+    expect(report.vector.debt).toBeUndefined()
+    expect(report.metadata.outcome).toBe('unavailable')
+    expect(report.metadata.debt).toBeUndefined()
+    expect(report.graph.outcome).toBe('unavailable')
+    expect(report.graph.debt).toBeUndefined()
+
+    await brain.close()
+  })
+
+  it('reports "reported" + the exact payload when the active provider implements maintenanceDebt() (verbatim passthrough, no thresholding)', async () => {
+    const brain = await freshBrain()
+
+    const vectorDebt: ProviderMaintenanceDebt = {
+      pendingBytes: 4_096,
+      pendingItems: 12,
+      lastPassCompletedAt: 1_700_000_000_000,
+      lastPassOutcome: 'completed',
+      converging: true
+    }
+    ;(brain as any).index.maintenanceDebt = async () => vectorDebt
+
+    const report = await brain.maintenanceDebt()
+
+    expect(report.vector.outcome).toBe('reported')
+    // Verbatim passthrough — the exact object, not a re-derived copy.
+    expect(report.vector.debt).toBe(vectorDebt)
+    // Untouched surfaces stay honestly 'unavailable'.
+    expect(report.metadata.outcome).toBe('unavailable')
+    expect(report.graph.outcome).toBe('unavailable')
+
+    await brain.close()
+  })
+
+  it('mixed surfaces: each surface\'s outcome depends ONLY on its OWN active provider — one surface reporting never leaks into another', async () => {
+    const brain = await freshBrain()
+
+    const metadataDebt: ProviderMaintenanceDebt = {
+      pendingItems: 3,
+      lastPassOutcome: 'partial',
+      converging: false
+    }
+    const graphDebt: ProviderMaintenanceDebt = {
+      pendingBytes: 0,
+      converging: true
+    }
+    ;(brain as any).metadataIndex.maintenanceDebt = async () => metadataDebt
+    ;(brain as any).graphIndex.maintenanceDebt = async () => graphDebt
+    // Vector is deliberately left unpatched.
+
+    const report = await brain.maintenanceDebt()
+
+    expect(report.vector.outcome).toBe('unavailable')
+    expect(report.vector.debt).toBeUndefined()
+
+    expect(report.metadata.outcome).toBe('reported')
+    expect(report.metadata.debt).toBe(metadataDebt)
+
+    expect(report.graph.outcome).toBe('reported')
+    expect(report.graph.debt).toBe(graphDebt)
+
+    await brain.close()
+  })
+
+  it('an empty ProviderMaintenanceDebt object (every field omitted) is still honestly "reported" — presence of the hook, not the payload\'s richness, drives the outcome', async () => {
+    const brain = await freshBrain()
+
+    const emptyDebt: ProviderMaintenanceDebt = {}
+    ;(brain as any).graphIndex.maintenanceDebt = async () => emptyDebt
+
+    const report = await brain.maintenanceDebt()
+
+    expect(report.graph.outcome).toBe('reported')
+    expect(report.graph.debt).toEqual({})
+
+    await brain.close()
+  })
+})

tests/unit/brainy/warm.test.ts

@@ -307,4 +307,92 @@ describe('brain.warm()', () => {
     expect(report.totalDurationMs).toBeGreaterThanOrEqual(0)
     await brain.close()
   })
+
+  // --- Metadata leg routes through the ACTIVE provider (8.10.1) -----------
+  //
+  // `MetadataIndexProvider` is a ~50-method interface (src/plugin.ts) — far
+  // too large to hand-write a compliant fake class the way `FakeVectorProvider`
+  // fakes the ~8-method `VectorIndexProvider` above. Test (c) already
+  // establishes this file's pattern for the metadata leg: exercise the REAL
+  // `MetadataIndexManager` instance and shape just the probe points brain.ts
+  // reads (`typeof provider.warm === 'function'` /
+  // `typeof provider.hydrateAll === 'function'`) directly on that instance.
+  // Shadowing an own property on the live object stands in for "a different
+  // provider implementation" without needing a hand-rolled full fake — the
+  // rest of the real manager (used by add()/init() above) is untouched.
+  describe('metadata leg — warm() routes through the active provider', () => {
+    it('(f) calls the ACTIVE metadata provider\'s warm() when present and reports "warmed", never falling back to hydrateAll', async () => {
+      const brain = new Brainy({
+        requireSubtype: false,
+        storage: { type: 'memory' },
+        silent: true
+      })
+      await brain.init()
+      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })
+
+      const metadataIndex = (brain as any).metadataIndex
+      let warmCalls = 0
+      let hydrateAllCalls = 0
+      const origHydrateAll = metadataIndex.hydrateAll.bind(metadataIndex)
+      metadataIndex.hydrateAll = async (...args: unknown[]) => {
+        hydrateAllCalls++
+        return origHydrateAll(...args)
+      }
+      // Simulates a native metadata provider declaring the optional `warm()`
+      // hook added to `MetadataIndexProvider` (src/plugin.ts) in 8.10.1.
+      metadataIndex.warm = async () => {
+        warmCalls++
+      }
+
+      const report = await brain.warm()
+
+      expect(warmCalls).toBe(1)
+      expect(hydrateAllCalls).toBe(0) // warm() ran — no hydrateAll fallback
+      expect(report.metadata.outcome).toBe('warmed')
+      await brain.close()
+    })
+
+    it('reports "unavailable" when the active metadata provider implements neither warm() nor hydrateAll() (the honest branch a native provider without either hook must hit)', async () => {
+      const brain = new Brainy({
+        requireSubtype: false,
+        storage: { type: 'memory' },
+        silent: true
+      })
+      await brain.init()
+      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })
+
+      const metadataIndex = (brain as any).metadataIndex
+      // Shadow away BOTH optional hooks — models a genuinely native provider
+      // that (unlike the built-in JS manager) offers neither seam. This must
+      // never fall back to calling init() as a stand-in for warmth.
+      metadataIndex.warm = undefined
+      metadataIndex.hydrateAll = undefined
+
+      const report = await brain.warm()
+
+      expect(report.metadata.outcome).toBe('unavailable')
+      await brain.close()
+    })
+
+    it('the built-in JS manager (no warm()) still reports "warmed" via its existing hydrateAll() duck-type — unchanged by the new provider hook', async () => {
+      const brain = new Brainy({
+        requireSubtype: false,
+        storage: { type: 'memory' },
+        silent: true
+      })
+      await brain.init()
+      await brain.add({ data: 'a', type: NounType.Thing, vector: V(1) })
+
+      // No patching at all — the default built-in MetadataIndexManager has
+      // hydrateAll() but no warm(), exactly as it did before this change.
+      const metadataIndex = (brain as any).metadataIndex
+      expect(typeof metadataIndex.warm).not.toBe('function')
+      expect(typeof metadataIndex.hydrateAll).toBe('function')
+
+      const report = await brain.warm()
+
+      expect(report.metadata.outcome).toBe('warmed')
+      await brain.close()
+    })
+  })
 })

tests/unit/db/fact-log.test.ts

@@ -186,4 +186,52 @@ describe('fact log — round-trip, framing, reconcile, rotation, scan', () => {
     await log.sync()
     expect(log.segmentPaths()).toEqual([]) // only a tail exists — nothing sealed
   })
+
+  describe('scanFacts liveness contract (Stage-2 D1)', () => {
+    it('a wedged store fails LOUDLY within the first-batch bound — never a silent hang', async () => {
+      // Force a sealed segment (tiny rotateBytes) so the scan must READ from
+      // storage, then wedge that read: the exact production shape (a
+      // backlogged brain whose segment read never returned).
+      const mem: any = new MemoryStorage()
+      await mem.init()
+      const wedgeable = new FactLog(mem, { rotateBytes: 1 })
+      await wedgeable.open(0)
+      await wedgeable.append(fact(1))
+      await wedgeable.append(fact(2)) // second append rotates → seg 1 sealed
+      await wedgeable.sync()
+
+      const realRead = mem.readRawBytes.bind(mem)
+      mem.readRawBytes = (p: string) =>
+        p.includes('facts/seg-') ? new Promise(() => {}) : realRead(p) // hangs forever
+
+      const scan = wedgeable.scanFacts({ firstBatchTimeoutMs: 200 })
+      const started = Date.now()
+      await expect(scan.batches().next()).rejects.toThrow(/no first batch within 200ms/)
+      expect(Date.now() - started).toBeLessThan(5_000) // bound held, not a hang
+    })
+
+    it('a healthy scan is unaffected — first batch well inside the bound, all facts delivered', async () => {
+      for (let g = 1; g <= 5; g++) await log.append(fact(g))
+      await log.sync()
+      const scan = log.scanFacts({ batchSize: 2 })
+      const all: CommitFact[] = []
+      for await (const b of scan.batches()) all.push(...b.facts)
+      expect(all.map((f) => f.generation)).toEqual([1, 2, 3, 4, 5])
+      expect(scan.summary().factsYielded).toBe(5)
+    })
+
+    it('consumer think-time between pulls never counts against the producer', async () => {
+      for (let g = 1; g <= 4; g++) await log.append(fact(g))
+      await log.sync()
+      // Bound tighter than the consumer's pause: only the FIRST pull is
+      // raced, so a slow consumer after batch 1 must not trip the deadline.
+      const gen = log.scanFacts({ batchSize: 2, firstBatchTimeoutMs: 150 }).batches()
+      const first = await gen.next()
+      expect(first.done).toBe(false)
+      await new Promise((r) => setTimeout(r, 400)) // dawdle past the bound
+      const second = await gen.next()
+      expect(second.done).toBe(false)
+      expect((await gen.next()).done).toBe(true)
+    })
+  })
 })

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

@@ -0,0 +1,150 @@
+/**
+ * @module tests/unit/db/generation-segments
+ * @description The generation-segment store (Stage-2 D1+D3 file format).
+ * Laws: (1) fold → read round-trips deltas and records byte-faithfully via
+ * sidecar point-reads; (2) the manifest is the ONLY discovery path — reopen
+ * reads one file, never a listing; (3) a lost/corrupt sidecar rebuilds from
+ * its segment loudly, a damaged SEGMENT fails loudly (never silent wrong
+ * data); (4) D3 reclaim drops whole segments only and bumps compactedBelow;
+ * (5) the packed digest is deterministic across reopen; (6) immutability —
+ * fold refuses overlap with sealed ranges.
+ */
+import { describe, it, expect, beforeEach } from 'vitest'
+import { MemoryStorage } from '../../../src/storage/adapters/memoryStorage.js'
+import {
+  GenerationSegmentStore,
+  SEGMENTS_PREFIX,
+  type FoldGeneration
+} from '../../../src/db/generationSegments.js'
+
+const UUID = (n: number): string => `00000000-0000-4000-8000-${String(n).padStart(12, '0')}`
+
+const gen = (g: number, recordCount = 2): FoldGeneration => ({
+  generation: g,
+  timestamp: 1_700_000_000_000 + g,
+  delta: { generation: g, nouns: [UUID(g)], verbs: [], bytes: 123 + g },
+  records: Array.from({ length: recordCount }, (_, i) => ({
+    kind: (i % 2 === 0 ? 'noun' : 'verb') as 'noun' | 'verb',
+    id: UUID(g * 100 + i),
+    record: { metadata: { noun: 'document', v: g }, vector: { v: [g, i] } }
+  }))
+})
+
+describe('db/GenerationSegmentStore — the D1+D3 packed tier', () => {
+  let storage: MemoryStorage
+  let store: GenerationSegmentStore
+
+  beforeEach(async () => {
+    storage = new MemoryStorage()
+    await storage.init()
+    store = new GenerationSegmentStore(storage as any)
+    await store.open()
+  })
+
+  it('fold → read round-trips deltas and records via sidecar point-reads', async () => {
+    const meta = await store.fold([gen(1), gen(2), gen(3)])
+    expect(meta).toMatchObject({ firstGeneration: 1, lastGeneration: 3, frames: 3 })
+    expect(meta.checksum).toBeGreaterThan(0)
+
+    expect(store.hasGeneration(2)).toBe(true)
+    expect(store.hasGeneration(4)).toBe(false)
+
+    const d2 = await store.readDelta(2)
+    expect(d2?.delta).toEqual({ generation: 2, nouns: [UUID(2)], verbs: [], bytes: 125 })
+    expect(d2?.timestamp).toBe(1_700_000_000_002)
+
+    const records = await store.readRecords(3)
+    expect(records).toHaveLength(2)
+    expect(records![0]).toEqual({
+      kind: 'noun',
+      id: UUID(300),
+      record: { metadata: { noun: 'document', v: 3 }, vector: { v: [3, 0] } }
+    })
+    // Point read by id, both kinds.
+    expect(await store.readRecord(3, 'verb', UUID(301))).toEqual({
+      metadata: { noun: 'document', v: 3 },
+      vector: { v: [3, 1] }
+    })
+    expect(await store.readRecord(3, 'noun', UUID(999))).toBeNull()
+  })
+
+  it('reopen discovers everything from the manifest alone — no listing', async () => {
+    await store.fold([gen(1), gen(2)])
+    await store.fold([gen(3), gen(4)])
+
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    expect(reopened.segments()).toHaveLength(2)
+    expect(reopened.hasGeneration(4)).toBe(true)
+    expect((await reopened.readDelta(1))?.timestamp).toBe(1_700_000_000_001)
+  })
+
+  it('a lost sidecar rebuilds from its segment; a damaged segment fails LOUDLY', async () => {
+    const meta = await store.fold([gen(1), gen(2)])
+    const idxPath = `${SEGMENTS_PREFIX}/seg-${String(1).padStart(20, '0')}.idx`
+    await storage.deleteRawObject(idxPath)
+
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    // Rebuild path: still serves correct data.
+    expect((await reopened.readRecords(2))!).toHaveLength(2)
+
+    // Now damage the SEGMENT itself: flip a payload byte → CRC mismatch, loud.
+    const segPath = `${SEGMENTS_PREFIX}/${meta.file}`
+    const bytes = (await storage.readRawBytes(segPath))!
+    bytes[bytes.length - 3] ^= 0xff
+    await storage.writeRawBytes(segPath, bytes)
+    const damaged = new GenerationSegmentStore(storage as any)
+    await damaged.open()
+    ;(damaged as any).sidecars.clear()
+    await storage.deleteRawObject(idxPath) // force the sequential rebuild over damaged bytes
+    await expect(damaged.readRecords(2)).rejects.toThrow(/CRC mismatch|damaged/)
+  })
+
+  it('D3 reclaim drops whole segments only and bumps compactedBelow', async () => {
+    await store.fold([gen(1), gen(2)])
+    await store.fold([gen(3), gen(4)])
+    await store.fold([gen(5), gen(6)])
+
+    // Horizon mid-segment-2 (below 4): only segment 1 is FULLY below → drops.
+    const r1 = await store.dropSegmentsBelow(4)
+    expect(r1).toEqual({ dropped: 1, compactedBelow: 3 })
+    expect(store.hasGeneration(1)).toBe(false)
+    expect(store.hasGeneration(3)).toBe(true) // partial segment survives whole
+
+    // Bytes actually gone.
+    expect(await storage.readRawBytes(`${SEGMENTS_PREFIX}/seg-${String(1).padStart(20, '0')}.bgs`)).toBeNull()
+
+    // Horizon past everything: the rest drop; compactedBelow is durable.
+    const r2 = await store.dropSegmentsBelow(7)
+    expect(r2.dropped).toBe(2)
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    expect(reopened.compactedBelow()).toBe(7)
+    expect(reopened.segments()).toHaveLength(0)
+  })
+
+  it('the packed digest is deterministic across reopen and changes with history', async () => {
+    await store.fold([gen(1), gen(2), gen(3)])
+    const atSeal = await store.digestThroughPacked(3)
+    const midSegment = await store.digestThroughPacked(2)
+    expect(atSeal).not.toBeNull()
+    expect(midSegment).not.toBeNull()
+    expect(midSegment).not.toBe(atSeal)
+
+    const reopened = new GenerationSegmentStore(storage as any)
+    await reopened.open()
+    expect(await reopened.digestThroughPacked(3)).toBe(atSeal)
+    expect(await reopened.digestThroughPacked(2)).toBe(midSegment)
+
+    await reopened.fold([gen(4)])
+    expect(await reopened.digestThroughPacked(4)).not.toBe(atSeal)
+  })
+
+  it('sealed segments are immutable — fold refuses overlap, requires ascending input', async () => {
+    await store.fold([gen(1), gen(2)])
+    await expect(store.fold([gen(2), gen(3)])).rejects.toThrow(/overlaps the packed tier/)
+    await expect(store.fold([gen(4), gen(4)])).rejects.toThrow(/strictly ascending/)
+    await expect(store.fold([])).rejects.toThrow(/at least one generation/)
+  })
+})

tests/unit/transaction/timeout-never-internally-retried.test.ts

@@ -0,0 +1,141 @@
+/**
+ * @module tests/unit/transaction/timeout-never-internally-retried
+ * @description Regression pin for the no-hot-retry contract (8.10.1).
+ *
+ * A production incident: a native-provider op ground 38-40s inside a
+ * transaction, blew the ~32s budget, was rolled back, and a CONSUMER pipeline
+ * hot-retried the identical operation into a 6-minute 100%-CPU storm.
+ * Investigation established brainy itself never auto-retries a
+ * `TransactionTimeoutError` — the storm was entirely the consumer's hot-retry
+ * loop, driven by a "retryable" doc-prose claim with no machine-readable
+ * contract. This file pins the brainy-side half of that story so it can never
+ * regress silently:
+ *
+ * (i)  the underlying engine (`TransactionManager.executeTransaction()` →
+ *      `Transaction.execute()`) — the exact machinery every single-record
+ *      write (`add`/`update`/`remove`/...) drives via
+ *      `Brainy.persistSingleOp()` — never internally re-executes a timed-out
+ *      operation, and the error it surfaces carries `retryable === true` and
+ *      `hotRetryUnsafe === true` (see `src/transaction/errors.ts`).
+ *
+ *      Constructed directly (mirrors the existing
+ *      `tests/unit/transaction/timeout-rollback.test.ts` pattern) rather than
+ *      through a real `brain.add()` call: `transactTimeoutBudget()` floors
+ *      every single-op write's budget at `opCount * 2000`ms with NO override
+ *      seam (`transactionBudgetFloorMs` only RAISES that floor — it cannot
+ *      lower it below the per-op-count term), so getting a real `add()` to
+ *      time out requires a multi-second sleep. The engine-level
+ *      `options.timeout` override used here is the exact same
+ *      `TransactionManager`/`Transaction` code `persistSingleOp` calls —
+ *      pinning it here pins add()'s guarantee without paying that wall-clock
+ *      cost.
+ *
+ * (ii) `Brainy.add()`'s upsert-race retry loop (src/brainy.ts,
+ *      `MAX_UPSERT_ATTEMPTS = 10`) — proving the loop's `catch` treats a
+ *      `TransactionTimeoutError` as terminal (immediate rethrow) rather than
+ *      the `InsertPreconditionExistsSignal` it retries on, so a mid-flight
+ *      timeout can never be silently swallowed and re-attempted up to 10
+ *      times.
+ */
+import { describe, it, expect } from 'vitest'
+import { TransactionManager } from '../../../src/transaction/TransactionManager.js'
+import type { Operation, RollbackAction } from '../../../src/transaction/types.js'
+import { TransactionTimeoutError } from '../../../src/transaction/errors.js'
+import { Brainy } from '../../../src/brainy.js'
+import { NounType } from '../../../src/types/graphTypes.js'
+
+const sleep = (ms: number) => new Promise<void>((r) => setTimeout(r, ms))
+
+// Brainy's ValidationConfig fixes vectors at exactly 384 dimensions
+// (src/utils/paramValidation.ts) — match it so add() doesn't reject test data.
+const DIM = 384
+const V = (): number[] => Array(DIM).fill(0.1)
+
+/** An operation that counts every `execute()` invocation — the re-drive detector. */
+function countingOp(opts: { delayMs?: number; name: string }): Operation & { calls: number } {
+  const op = {
+    name: opts.name,
+    calls: 0,
+    async execute(): Promise<RollbackAction | undefined> {
+      op.calls++
+      if (opts.delayMs) await sleep(opts.delayMs)
+      return async () => {}
+    }
+  }
+  return op
+}
+
+describe('transaction timeouts are never internally re-driven (8.10.1 no-hot-retry contract)', () => {
+  it('(i) the single-op engine (TransactionManager.executeTransaction / Transaction.execute — what add() drives via persistSingleOp) runs the overrun operation EXACTLY once and surfaces ONE retryable+hotRetryUnsafe error', async () => {
+    const manager = new TransactionManager()
+    const op0 = countingOp({ name: 'op0-overruns-budget', delayMs: 30 })
+    const op1 = countingOp({ name: 'op1-must-never-start' })
+
+    let caught: unknown
+    try {
+      await manager.executeTransaction(
+        async (tx) => {
+          tx.addOperation(op0)
+          tx.addOperation(op1)
+        },
+        // Tiny explicit override — the same override seam `transact()`
+        // exposes as `options.timeoutMs`; wins outright over the
+        // opCount*2000 floor that gates every real single-op write
+        // (transactTimeoutBudget()'s override semantics).
+        { timeout: 5 }
+      )
+    } catch (err) {
+      caught = err
+    }
+
+    expect(caught).toBeInstanceOf(TransactionTimeoutError)
+    const err = caught as TransactionTimeoutError
+    // The machine-readable contract callers branch on instead of parsing
+    // message text (src/transaction/errors.ts).
+    expect(err.retryable).toBe(true)
+    expect(err.hotRetryUnsafe).toBe(true)
+
+    // The re-drive assertion: op0 (the one that overran) executed EXACTLY
+    // once — nothing inside TransactionManager/Transaction looped back and
+    // re-ran it — and op1 never started at all (the budget gate stopped it
+    // before it began, per Transaction.execute()'s per-operation loop).
+    expect(op0.calls).toBe(1)
+    expect(op1.calls).toBe(0)
+  })
+
+  it('(ii) add()\'s upsert-race retry loop (MAX_UPSERT_ATTEMPTS=10) exits on the FIRST TransactionTimeoutError — attempt counter stays at 1, never mistaken for the lost-insert-race signal it retries on', async () => {
+    const brain = new Brainy({
+      requireSubtype: false,
+      storage: { type: 'memory' },
+      silent: true
+    })
+    await brain.init()
+
+    let persistSingleOpCalls = 0
+    const timeoutError = new TransactionTimeoutError(5, 1, {
+      elapsedMs: 6,
+      totalOperations: 2,
+      operationName: 'SaveNounMetadata'
+    })
+    // Stub the private commit seam add() drives (persistSingleOp) to throw
+    // the exact error type the real engine surfaces on a mid-flight timeout.
+    // This test pins the upsert loop's EXCEPTION-HANDLING contract (does it
+    // retry a TransactionTimeoutError like it retries
+    // InsertPreconditionExistsSignal?), not the timing mechanics of a real
+    // timeout — those are pinned by test (i) and by
+    // tests/unit/transaction/timeout-rollback.test.ts.
+    ;(brain as any).persistSingleOp = async (): Promise<never> => {
+      persistSingleOpCalls++
+      throw timeoutError
+    }
+
+    await expect(
+      brain.add({ data: 'a', type: NounType.Thing, vector: V() })
+    ).rejects.toBe(timeoutError)
+
+    // The loop's attempt counter: exactly one call, never retried up to
+    // MAX_UPSERT_ATTEMPTS.
+    expect(persistSingleOpCalls).toBe(1)
+    await brain.close()
+  })
+})