fix: query-cap memory misread (MemAvailable + floor) + rootDirectory getter for native mmap fast-path

Two platform-wide production fixes for consumers on bare VMs / mmap-filesystem storage.

BUG A — auto maxQueryLimit collapsed to ~1000 on healthy VMs → 500s on legitimate
queries. getAvailableMemory() read os.freemem() (kernel MemFree, which excludes
reclaimable page cache and reads as tens of MB on a page-cache-heavy mmap box).
Now reads /proc/meminfo MemAvailable (the `free -h` figure), falling back to
os.freemem() only off-Linux; auto-detected caps (container/free branches) are floored
at 10k so a misread can't collapse them. Explicit maxQueryLimit/reservedQueryMemory
are honored as-is.

BUG B — native mmap vector fast-path never engaged (per-entity reads → 57s cold start
on a 283MB brain). FileSystemStorage now exposes a public `rootDirectory` getter; the
native vector provider feature-detects it to enable its memory-mapped graph path.
brainy stored it as the protected `rootDir`, so the gate silently failed. Self-heals
after the first post-upgrade flush writes the mmap file.

Regression tests: auto-cap floor (container/free/explicit-override) + the rootDirectory
getter. Build clean; full suite 1483 green.

RELEASES.md

@@ -10,6 +10,29 @@ Full auto-generated changelog: `CHANGELOG.md` · Releases: https://github.com/so
 
 ---
 
+## v7.31.8 — 2026-06-16
+
+**Affected products:** every consumer on a bare VM or `mmap-filesystem` storage — **upgrade recommended** (Memory, Workshop on 7.31.x; Venue on 7.28.x). Two platform-wide production fixes. Drop-in; no API or data changes.
+
+### Fix 1 — auto query-limit cap no longer collapses on a healthy VM (the 500s)
+
+`new Brainy()`'s auto-configured `maxQueryLimit` could collapse to ~1000 on a perfectly healthy box, throwing `exceeds the auto-configured query limit` on legitimate queries (e.g. `find({ limit: 2400 })`) → HTTP 500s. Root cause: detection read `os.freemem()` (kernel MemFree), which **excludes reclaimable page cache** — on a long-running box using mmap-filesystem storage the page cache grows until MemFree is a thin sliver (tens of MB) even though several GB are actually available, so `floor(freemem / 25KB)·1000` floored the cap to ~1000.
+
+- Memory detection now reads **`/proc/meminfo` `MemAvailable`** (the figure `free -h` shows — counts reclaimable cache), falling back to `os.freemem()` only off-Linux.
+- A **10,000 floor** on auto-detected caps (container / free-memory branches) so a detection miss can never silently collapse the cap. Explicit `maxQueryLimit` / `reservedQueryMemory` settings are honored as-is (never floored).
+
+No action beyond upgrading. A `MEMORY_LIMIT` override (if you set one as a workaround) is still honored.
+
+### Fix 2 — native mmap vector fast-path re-engages (cold-start 57s → instant)
+
+`FileSystemStorage` now exposes a public `rootDirectory` getter. The optional native vector provider feature-detects `storage.rootDirectory` to enable its memory-mapped graph fast path; brainy stored the path as the protected `rootDir`, so the gate silently failed and every cold start rebuilt the index via per-entity disk reads (~57s for a 283 MB brain on a measured deployment). With the getter, the mmap path engages and cold start becomes a near-instant memory-mapped load.
+
+Self-heals after the first post-upgrade flush writes the mmap file — the first restart after upgrading rebuilds once, then every subsequent boot is fast. Benefits the full deployed matrix (the gate exists in the native provider versions Memory/Workshop and Venue run).
+
+**Upgrade:** bump `@soulcraft/brainy` to `7.31.8`. No code or data migration.
+
+---
+
 ## v7.31.2 — 2026-06-09
 
 **Affected products:** none in behaviour; affects anyone reading Brainy's TypeScript

src/storage/adapters/fileSystemStorage.ts

@@ -81,6 +81,19 @@ export class FileSystemStorage extends BaseStorage {
   private readonly MAX_SHARDS = 256 // Hex range: 00-ff
   private cachedShardingDepth: number = this.SHARDING_DEPTH // Always use fixed depth
   protected rootDir: string
+
+  /**
+   * Public read-only alias for the storage root path. Native vector plugins
+   * (e.g. `@soulcraft/cortex`) feature-detect `storage.rootDirectory` to enable
+   * their memory-mapped vector fast path; brainy stores it as the protected
+   * `rootDir`, so without this getter the native mmap backend stays un-wired and
+   * the index rebuilds via slow per-entity disk reads on cold start. Exposing
+   * the alias lets the native backend memory-map its index file instead.
+   */
+  get rootDirectory(): string {
+    return this.rootDir
+  }
+
   private nounsDir!: string
   private verbsDir!: string
   private metadataDir!: string

src/utils/paramValidation.ts

@@ -32,6 +32,24 @@ const getSystemMemory = (): number => {
 }
 
 const getAvailableMemory = (): number => {
+  // Prefer /proc/meminfo `MemAvailable` — it counts reclaimable page cache as
+  // available, which `os.freemem()` (kernel MemFree) does NOT. On a long-running
+  // box using mmap-filesystem storage, the page cache grows until MemFree is a
+  // thin sliver (tens of MB) even though several GB are actually available; the
+  // freemem reading then collapses the auto query-limit cap to ~1000 and 500s
+  // legitimate queries. MemAvailable reflects the real figure `free -h` shows.
+  if (fs) {
+    try {
+      const meminfo = fs.readFileSync('/proc/meminfo', 'utf8') as string
+      const match = meminfo.match(/^MemAvailable:\s+(\d+)\s*kB/m)
+      if (match) {
+        const bytes = parseInt(match[1], 10) * 1024
+        if (bytes > 0) return bytes
+      }
+    } catch {
+      // Not Linux / no procfs — fall through to freemem.
+    }
+  }
   if (os) {
     return os.freemem()
   }
@@ -137,6 +155,11 @@ const getContainerMemoryLimit = (): number | null => {
  *   the throw tier still fires before OOM territory (72 K+).
  */
 const MAX_LIMIT_KB_PER_RESULT = 25
+// Floor for AUTO-DETECTED caps (container/free-memory branches). A memory
+// misread must never silently collapse the cap below a practical safety value
+// and 500 legitimate queries; explicit operator settings (maxQueryLimit /
+// reservedQueryMemory) are honored as-is and bypass this floor.
+const MIN_AUTO_QUERY_LIMIT = 10000
 
 /**
  * One-time-per-call-site warning dedup. Keyed on the caller location returned
@@ -230,9 +253,12 @@ export class ValidationConfig {
       // Reserve 25% for query operations
       const queryMemory = this.detectedContainerLimit * 0.25
 
-      this.maxLimit = Math.min(
-        100000,
-        Math.floor(queryMemory / (1024 * 1024 * MAX_LIMIT_KB_PER_RESULT)) * 1000
+      this.maxLimit = Math.max(
+        MIN_AUTO_QUERY_LIMIT,
+        Math.min(
+          100000,
+          Math.floor(queryMemory / (1024 * 1024 * MAX_LIMIT_KB_PER_RESULT)) * 1000
+        )
       )
       this.limitBasis = 'containerMemory'
 
@@ -246,9 +272,12 @@ export class ValidationConfig {
     // Priority 4: Free memory (fallback, current behavior)
     const availableMemory = getAvailableMemory()
 
-    this.maxLimit = Math.min(
-      100000,
-      Math.floor(availableMemory / (1024 * 1024 * MAX_LIMIT_KB_PER_RESULT)) * 1000
+    this.maxLimit = Math.max(
+      MIN_AUTO_QUERY_LIMIT,
+      Math.min(
+        100000,
+        Math.floor(availableMemory / (1024 * 1024 * MAX_LIMIT_KB_PER_RESULT)) * 1000
+      )
     )
     this.limitBasis = 'freeMemory'
 

tests/unit/storage/fileSystemStorage-rootDirectory.test.ts

@@ -0,0 +1,28 @@
+/**
+ * Regression: FileSystemStorage must expose a public `rootDirectory` getter.
+ *
+ * Native vector plugins (e.g. @soulcraft/cortex's NativeHNSWWrapper) feature-detect
+ * `storage.rootDirectory` to enable their memory-mapped vector fast path. Brainy
+ * stores the path as the protected `rootDir`; without this public alias the native
+ * mmap backend stayed un-wired and the index rebuilt via slow per-entity disk reads
+ * on cold start (BRAINY-MMAP-VECTOR-HOOK). The getter is the load-bearing line, so
+ * guard it explicitly.
+ */
+import { describe, it, expect } from 'vitest'
+import { mkdtempSync, rmSync } from 'fs'
+import { tmpdir } from 'os'
+import { join } from 'path'
+import { FileSystemStorage } from '../../../src/storage/adapters/fileSystemStorage.js'
+
+describe('FileSystemStorage.rootDirectory (native mmap-backend hook)', () => {
+  it('exposes the constructor root path via a public rootDirectory getter', () => {
+    const dir = mkdtempSync(join(tmpdir(), 'brainy-rootdir-'))
+    try {
+      const storage = new FileSystemStorage(dir)
+      // The exact property a native vector backend reads to engage its mmap path.
+      expect((storage as unknown as { rootDirectory: string }).rootDirectory).toBe(dir)
+    } finally {
+      rmSync(dir, { recursive: true, force: true })
+    }
+  })
+})

tests/unit/utils/memoryLimits.test.ts

@@ -399,4 +399,32 @@ describe('Memory Limits - Container Detection & Smart Calculation', () => {
       await brain.close()
     })
   })
+
+  // Regression: a memory MISREAD (tiny detected limit, or os.freemem reading a
+  // sliver on a page-cache-heavy mmap box) must NOT collapse the auto cap to
+  // ~1000 and 500 legitimate queries. Auto-detected caps are floored at 10k;
+  // explicit operator settings still pass through unfloored.
+  describe('Auto-cap floor (BUG: querycap collapse on healthy VM)', () => {
+    it('floors the container-derived cap so a tiny/misread limit cannot collapse it', () => {
+      // 50 MB → queryMemory 12.5 MB → floor(12.5/25)·1000 = 0 pre-fix.
+      process.env.MEMORY_LIMIT = String(50 * 1024 * 1024)
+      const config = ValidationConfig.getInstance()
+      expect(config.limitBasis).toBe('containerMemory')
+      expect(config.maxLimit).toBe(10000) // floored, not 0/1000
+    })
+
+    it('floors the free-memory-derived cap as well', () => {
+      // No container env → freeMemory branch. On any real box this is well
+      // above the floor; the guarantee is it can never drop below it.
+      const config = ValidationConfig.getInstance()
+      expect(config.limitBasis).toBe('freeMemory')
+      expect(config.maxLimit).toBeGreaterThanOrEqual(10000)
+    })
+
+    it('does NOT floor an explicit (small) operator override', () => {
+      const config = ValidationConfig.getInstance({ maxQueryLimit: 500 })
+      expect(config.limitBasis).toBe('override')
+      expect(config.maxLimit).toBe(500) // explicit intent respected, not floored
+    })
+  })
 })