Collection.isItem should not classify null as an item

Context

During the 2026-05-20 Sandman run, the operator reported this failure chain while orphan-node cleanup was running:

TypeError: Cannot read properties of null (reading 'id')
    at Store.getKey (src/data/Store.mjs:554:25)
    at Store.splice (src/collection/Base.mjs:1483:45)
    at Store.splice (ai/graph/Store.mjs:161:30)
    at Store.remove (src/collection/Base.mjs:1396:14)
    at Database.removeNode (ai/graph/Database.mjs:413:18)
    at GraphService.removeNodes (ai/services/memory-core/GraphService.mjs:985-986)

The immediate follow-up question identified a small framework-core guard gap:

isItem(value) {
    // We can not use Neo.isObject() || Neo.isRecord(), since collections can store neo instances too.
    return typeof value === 'object'
}

In JavaScript, typeof null === 'object', so Neo.collection.Base#isItem(null) currently returns true.

The Problem

null is not a valid Collection item, but the helper that routes key-vs-item branches classifies it as one. That is a low-level footgun: any caller that passes null into a collection path can be routed into item-key resolution rather than the key/missing-value path, and subclasses such as Neo.data.Store can then dereference the null item inside getKey().

The Sandman failure is one observed symptom, but the fix belongs in the shared Collection helper because isItem() is the structural classifier used by collection methods and subclasses.

The Architectural Reality

• src/collection/Base.mjs:1294-1296 currently implements isItem(value) as typeof value === 'object'.
• The inline comment is correct that Neo.isObject() is too narrow because collections can store Neo instances and records.
• The missing invariant is only the JavaScript null edge case: a broad object/instance classifier still needs value !== null.
• This is framework-core behavior (Neo.collection.Base), not Memory Core specific. Sandman merely surfaced the bug path.

The Fix

Update Neo.collection.Base#isItem(value) to exclude null while preserving current support for plain objects, records, and Neo instances:

return value !== null && typeof value === 'object'

Add focused unit coverage proving isItem(null) === false while object/record/instance-like values remain item-like.

Contract Ledger Matrix

Acceptance Criteria

• Collection.isItem(null) returns false.
• Existing object / Neo-instance-compatible classification remains unchanged for non-null objects.
• A focused Playwright unit test covers the null edge case.
• No broader collection refactor or Sandman-specific workaround is introduced.

Out of Scope

• Changing Store.getKey() semantics beyond any test fixture needed for the guard.
• Broad cleanup of orphan-node pruning or Sandman graph maintenance.
• Reclassifying arrays/functions/primitives beyond the existing isItem() contract.

Related

• Sandman failure surfaced through GraphService.removeNodes() / Database.removeNode() cleanup.
• Prior key-resolution history: archived #9067 / #9069 around Store.getKey() and collection identity routing.

Origin Session ID: d13c94dd-e721-4e28-ac9e-4d0b3c0f66de

Handoff Retrieval Hints: Collection.isItem null Store.getKey Sandman removeNodes, src/collection/Base.mjs isItem typeof value object, Cannot read properties of null reading id Store.getKey.