fix: disable GC on child collections created by includes system

packages/db/src/query/live/collection-config-builder.ts

@@ -1515,6 +1515,7 @@ function createChildCollectionEntry(
       },
     },
     startSync: true,
+    gcTime: 0,
   })
 
   const entry: ChildCollectionEntry = {

packages/db/tests/query/includes.test.ts

@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import {
   and,
   concat,
@@ -8,6 +8,7 @@ import {
   toArray,
 } from '../../src/query/index.js'
 import { createCollection } from '../../src/collection/index.js'
+import { CleanupQueue } from '../../src/collection/cleanup-queue.js'
 import { mockSyncCollectionOptions, stripVirtualProps } from '../utils.js'
 
 type Project = {
@@ -4012,4 +4013,52 @@ describe(`includes subqueries`, () => {
       })
     })
   })
+
+  describe(`child collection garbage collection`, () => {
+    beforeEach(() => {
+      vi.useFakeTimers()
+      CleanupQueue.resetInstance()
+    })
+
+    afterEach(() => {
+      vi.useRealTimers()
+      CleanupQueue.resetInstance()
+    })
+
+    it(`child collections should not be garbage collected when external subscribers unmount`, async () => {
+      const collection = buildIncludesQuery()
+      await collection.preload()
+
+      // Verify child data exists
+      const alpha = collection.get(1) as any
+      expect(childItems(alpha.issues)).toEqual([
+        { id: 10, title: `Bug in Alpha` },
+        { id: 11, title: `Feature for Alpha` },
+      ])
+
+      const beta = collection.get(2) as any
+      expect(childItems(beta.issues)).toEqual([
+        { id: 20, title: `Bug in Beta` },
+      ])
+
+      // Simulate what useLiveQuery does in React: subscribe to child collection,
+      // then unsubscribe when the component unmounts (e.g., virtual table scroll)
+      const childSub = alpha.issues.subscribeChanges(() => {})
+      childSub.unsubscribe()
+
+      // Advance well past the default gcTime (5 minutes = 300,000ms)
+      await vi.advanceTimersByTimeAsync(600_000)
+
+      // Child collection data should still be intact — the includes system
+      // owns these collections and manages their lifecycle via flushIncludesState.
+      // External GC must not destroy them.
+      expect(childItems(alpha.issues)).toEqual([
+        { id: 10, title: `Bug in Alpha` },
+        { id: 11, title: `Feature for Alpha` },
+      ])
+      expect(childItems(beta.issues)).toEqual([
+        { id: 20, title: `Bug in Beta` },
+      ])
+    })
+  })
 })