fix(8.0): per-type counts rehydrate after cold reopen (column store, not dead sparse index)

lazyLoadCounts() read the `__sparse_index__noun` blob, but the sparse-index
WRITE path was removed in 7.20.0 — new workspaces persist the 'noun' field
ONLY to the column store. So on close()+reopen the sparse load found nothing
and left every per-type count at 0: counts.byType / byTypeEnum / topTypes /
allNounTypeCounts all read empty, while find() / getNounCount() (different
sources) stayed correct.

Rehydrate from the column store's 'noun' field instead. Its per-value
cardinality matches the warm updateTypeFieldAffinity counts exactly because
both are driven from the same addToIndex field set, in lockstep, with no
visibility gate on either — so syncTypeCountsToFixed (called right after in
init) reproduces the warm fixed-array values precisely. Legacy chunked sparse
index kept as a fallback for pre-7.20.0 workspaces.

Ground-truth verified: 12 Person + 5 Document → cold reopen now reports
person:12 / document:5 (was 0), topTypes [person, document, collection].

Tests: un-skipped the intentionally-failing phase1c "warm cache on init"
reopen test and strengthened it to exact persisted counts; added a warm==cold
element-for-element equality test. 1464 unit + count-sync/multi-process/
clear-persistence integration green.

src/utils/metadataIndex.ts

@@ -508,10 +508,41 @@ export class MetadataIndexManager implements MetadataIndexProvider {
       this.entityCountsByTypeFixed.fill(0)
       this.verbCountsByTypeFixed.fill(0)
 
-      // Load counts from sparse index (correct source)
+      // PRIMARY (8.0+): rehydrate per-type counts from the column store's 'noun'
+      // field — the authoritative on-disk source after a cold reopen.
+      //
+      // The chunked sparse-index WRITE path was removed in 7.20.0 (commit
+      // 11be039): new workspaces persist the 'noun' field ONLY to the column
+      // store, never to a `__sparse_index__noun` blob. So the legacy sparse
+      // path below finds nothing and leaves every count at 0 — which is exactly
+      // why counts.byType/byTypeEnum/topTypes/allNounTypeCounts all read empty
+      // after close()+reopen while find()/getNounCount() (different sources)
+      // stay correct. The column store's per-value cardinality matches the warm
+      // `updateTypeFieldAffinity` counts EXACTLY because both are driven from the
+      // same `addToIndex` field set, in lockstep, with no visibility gate on
+      // either — so this rehydration reproduces the warm values precisely.
+      if (this.columnStore && this.columnStore.getIndexedFields().includes('noun')) {
+        const nounValues = await this.columnStore.getFilterValues('noun')
+        for (const value of nounValues) {
+          const bitmap = await this.columnStore.filter('noun', value)
+          if (bitmap.size > 0) {
+            // Use the stored value directly as the key (the legacy sparse path
+            // did the same): it is already the normalized type string that
+            // getNounFromIndex/getEntityCountByType expect, so syncTypeCountsToFixed
+            // — called immediately after lazyLoadCounts in init() — copies it into
+            // entityCountsByTypeFixed without re-normalization drift.
+            this.totalEntitiesByType.set(value, bitmap.size)
+          }
+        }
+        prodLog.debug(`✅ Rehydrated type counts from column store: ${this.totalEntitiesByType.size} types`)
+        return
+      }
+
+      // LEGACY FALLBACK (pre-7.20.0 workspaces still on the chunked sparse index).
       const nounSparseIndex = await this.loadSparseIndex('noun')
       if (!nounSparseIndex) {
-        // No sparse index yet - counts will be populated as entities are added
+        // No column-store 'noun' field and no sparse index yet — counts will be
+        // populated as entities are added.
         return
       }
 
@@ -530,7 +561,7 @@ export class MetadataIndexManager implements MetadataIndexProvider {
     } catch (error) {
       // Silently fail - counts will be populated as entities are added
       // This maintains zero-configuration principle
-      prodLog.debug('Could not load type counts from sparse index:', error)
+      prodLog.debug('Could not load type counts:', error)
     }
   }
 
@@ -2684,10 +2715,11 @@ export class MetadataIndexManager implements MetadataIndexProvider {
   }
 
   /**
-   * Get all entity types and their counts - O(1) operation
-   * Fixed - totalEntitiesByType is correctly populated by updateTypeFieldAffinity
-   * during add operations. lazyLoadCounts was reading wrong data but that doesn't
-   * affect freshly-added entities within the same session.
+   * Get all entity types and their counts - O(1) operation.
+   * `totalEntitiesByType` is populated by `updateTypeFieldAffinity` during add
+   * operations (warm path) and rehydrated from the column store's 'noun' field
+   * by `lazyLoadCounts` on init (cold reopen), so this is accurate both within a
+   * session and after close()+reopen.
    */
   getAllEntityCounts(): Map<string, number> {
     return new Map(this.totalEntitiesByType)

tests/integration/brainy-phase1c-integration.test.ts

@@ -377,23 +377,69 @@ describe('Brainy - Phase 1c: Type-Aware Integration', () => {
         silent: true
       })
 
-      await brainy2.init() // init() is expected to rehydrate type counts from the persisted noun index
+      await brainy2.init() // init() rehydrates type counts from the persisted column store
 
       try {
         // After reopening a persisted brain, counts.topTypes() must reflect the
-        // stored data. NOTE (8.0): this currently FAILS — the metadataIndex-backed
-        // counts.* surface (topTypes/byTypeEnum/entities/allNounTypeCounts) returns
-        // empty after reopen even though the data is fully present (find() and
-        // getNounCount() both return the right values). This is a genuine library
-        // bug in count rehydration, intentionally left failing rather than papered
-        // over. See the agent's realBugs report for the precise repro.
+        // stored data. Regression guard for the 8.0 cold-reopen count bug:
+        // lazyLoadCounts read the dead `__sparse_index__noun` blob (sparse WRITE
+        // path removed in 7.20.0) and left every per-type count at 0, so
+        // counts.topTypes/byTypeEnum/allNounTypeCounts returned empty after reopen
+        // even though find()/getNounCount() were correct. Fixed by rehydrating
+        // from the column store's 'noun' field.
         const topTypes = brainy2.counts.topTypes(3)
         expect(topTypes[0]).toBe('person') // Most common type
         expect(topTypes[1]).toBe('document')
+
+        // Counts must rehydrate to the EXACT persisted values, not just be ordered.
+        expect(brainy2.counts.byTypeEnum('person')).toBe(100)
+        expect(brainy2.counts.byTypeEnum('document')).toBe(50)
+        expect(await brainy2.counts.byType('person')).toBe(100)
+
+        const allNoun = brainy2.counts.allNounTypeCounts()
+        expect(allNoun.get('person' as any)).toBe(100)
+        expect(allNoun.get('document' as any)).toBe(50)
       } finally {
         await brainy2.close()
       }
     })
+
+    it('rehydrated per-type counts after cold reopen equal the warm counts exactly', async () => {
+      // Audit mandate: add N of a type → byTypeEnum(t) === N, both WARM and after
+      // a close()+reopen, with warm and cold reporting identical maps.
+      for (let i = 0; i < 7; i++) {
+        await brainy.add({ data: `Person ${i}`, type: NounType.Person, metadata: { name: `P${i}` } })
+      }
+      for (let i = 0; i < 3; i++) {
+        await brainy.add({ data: `Task ${i}`, type: NounType.Task, metadata: { title: `T${i}` } })
+      }
+      await brainy.flush()
+
+      // Capture the warm (in-session) counts before closing.
+      const warmPerson = brainy.counts.byTypeEnum('person')
+      const warmTask = brainy.counts.byTypeEnum('task')
+      const warmAll = Object.fromEntries(brainy.counts.allNounTypeCounts() as Map<string, number>)
+      expect(warmPerson).toBe(7)
+      expect(warmTask).toBe(3)
+
+      const reopened = new Brainy({
+        requireSubtype: false,
+        storage: { type: 'filesystem', rootDirectory: testDir },
+        dimensions: 384,
+        silent: true
+      })
+      await reopened.init()
+      try {
+        // Cold counts equal the exact persisted values...
+        expect(reopened.counts.byTypeEnum('person')).toBe(7)
+        expect(reopened.counts.byTypeEnum('task')).toBe(3)
+        // ...and equal the warm counts map element-for-element.
+        const coldAll = Object.fromEntries(reopened.counts.allNounTypeCounts() as Map<string, number>)
+        expect(coldAll).toEqual(warmAll)
+      } finally {
+        await reopened.close()
+      }
+    })
   })
 
   describe('Performance Characteristics', () => {