diff --git a/src/storage/storageFactory.ts b/src/storage/storageFactory.ts
index 64b18dc1..46c67f44 100644
--- a/src/storage/storageFactory.ts
+++ b/src/storage/storageFactory.ts
@@ -154,6 +154,21 @@ export function resolveFilesystemRoot(
   ) {
     throwRemovedStorageKey('fileSystemStorage.path')
   }
+  // A nested `config` object carrying a path-shaped key is the same hazard in
+  // a shape nobody ever supported: it used to fall through SILENTLY to the
+  // shared default root — every instance writing one directory while its
+  // caller believed each had its own. (Found live: an integration test's
+  // brains shared one store across a whole single-process run and a health
+  // probe refused on the foreign edges it sampled.) Loud, with the rename.
+  const nested = (config as Record<string, unknown>).config
+  if (nested && typeof nested === 'object') {
+    const pathish = ['path', 'baseDir', 'rootDirectory', 'rootDir', 'dir', 'directory']
+    const hit = pathish.find(
+      (k) => typeof (nested as Record<string, unknown>)[k] === 'string' &&
+        ((nested as Record<string, unknown>)[k] as string).length > 0
+    )
+    if (hit) throwRemovedStorageKey(`config.${hit}`)
+  }
 
   // 3. Zero-config default. A `type: 'filesystem'` with no path lands here
   //    intentionally ("persist, default location").
diff --git a/tests/integration/batchImportWithRelations.test.ts b/tests/integration/batchImportWithRelations.test.ts
index 7fe8e511..4095b51c 100644
--- a/tests/integration/batchImportWithRelations.test.ts
+++ b/tests/integration/batchImportWithRelations.test.ts
@@ -15,13 +15,7 @@ describe('Batch Import with Immediate Relations (v5.7.3 Fix)', () => {
 
     // Initialize brain
     brain = new Brainy({ requireSubtype: false,
-      storage: {
-        type: 'filesystem',
-        config: {
-          baseDir: testDir,
-          enableCompression: false // Faster tests
-        }
-      },
+      storage: { type: 'filesystem', path: testDir },
       dimensions: 384
     })
 
diff --git a/tests/integration/readAfterWrite.test.ts b/tests/integration/readAfterWrite.test.ts
index e0ab5863..cf1dc9ec 100644
--- a/tests/integration/readAfterWrite.test.ts
+++ b/tests/integration/readAfterWrite.test.ts
@@ -34,13 +34,7 @@ describe('Read-After-Write Consistency (v5.7.2 Bug Fix)', () => {
     testDir = join(tmpdir(), `brainy-consistency-${Date.now()}-${Math.random().toString(36).substring(7)}`)
 
     brain = new Brainy({ requireSubtype: false,
-      storage: {
-        type: 'filesystem',
-        config: {
-          baseDir: testDir,
-          enableCompression: false // Faster tests
-        }
-      },
+      storage: { type: 'filesystem', path: testDir },
       dimensions: 384
     })