diff --git a/test/fixtures/inventory-grandfathered.json b/test/fixtures/inventory-grandfathered.json
new file mode 100644
index 000000000..906d7bd8f
--- /dev/null
+++ b/test/fixtures/inventory-grandfathered.json
@@ -0,0 +1,76 @@
+{
+  "note": "The parts present when the R56 ledger was seeded (GST-914, PR #3837). Only these rows may say grandfathered: true; a part added later carries reason, plan, owner and measure_by (ETHOS.md: 9. Earn Its Place). Never add a key here.",
+  "keys": [
+    "autoplan",
+    "autoplan-phases",
+    "benchmark",
+    "benchmark-models",
+    "browse",
+    "canary",
+    "captain",
+    "capy-factory",
+    "capy-skill",
+    "careful",
+    "catalog",
+    "claude-code",
+    "codex",
+    "context-restore",
+    "context-save",
+    "cso",
+    "design-consultation",
+    "design-html",
+    "design-motion",
+    "design-review",
+    "design-shotgun",
+    "deslop-shared-libs",
+    "devex-review",
+    "diagram",
+    "document-generate",
+    "document-release",
+    "eval-plan",
+    "freeze",
+    "gstack",
+    "gstack-upgrade",
+    "guard",
+    "health",
+    "investigate",
+    "ios-clean",
+    "ios-design-review",
+    "ios-fix",
+    "ios-qa",
+    "ios-sync",
+    "land-and-deploy",
+    "landing-report",
+    "learn",
+    "make-pdf",
+    "modernize",
+    "office-hours",
+    "open-gstack-browser",
+    "pair-agent",
+    "plan-ceo-review",
+    "plan-design-review",
+    "plan-devex-review",
+    "plan-eng-review",
+    "plan-tune",
+    "preamble",
+    "qa",
+    "qa-only",
+    "retro",
+    "review",
+    "scrape",
+    "setup-browser-cookies",
+    "setup-deploy",
+    "setup-gbrain",
+    "ship",
+    "ship-docs-audit",
+    "ship-review-panel",
+    "skillify",
+    "spec",
+    "sync-gbrain",
+    "test-audit",
+    "ubicloud",
+    "unfreeze",
+    "verify",
+    "write-skill"
+  ]
+}
diff --git a/test/inventory.test.ts b/test/inventory.test.ts
index 6ef746820..b254831b8 100644
--- a/test/inventory.test.ts
+++ b/test/inventory.test.ts
@@ -51,8 +51,10 @@ describe('the ledger covers every key and validates', () => {
     expect(validateLedger(ledger, keys)).toEqual([]);
   });
 
-  test('the initial backlog is grandfathered and the guards are safety rows', () => {
-    for (const [key, row] of Object.entries<any>(ledger.parts)) expect([key, row.grandfathered]).toEqual([key, true]);
+  test('the initial backlog is grandfathered, nothing else is, and the guards are safety rows', () => {
+    const backlog: string[] = JSON.parse(fs.readFileSync(path.join(ROOT, 'test', 'fixtures', 'inventory-grandfathered.json'), 'utf8')).keys;
+    for (const key of backlog) expect([key, ledger.parts[key]?.grandfathered]).toEqual([key, true]);
+    for (const [key, row] of Object.entries<any>(ledger.parts)) if (row.grandfathered) expect(backlog).toContain(key);
     for (const key of ['careful', 'freeze', 'guard', 'unfreeze', 'cso']) expect(ledger.parts[key].status).toBe('safety');
     for (const key of ['capy-skill', 'capy-factory']) expect(ledger.parts[key]).toMatchObject({ status: 'untested', plan: 'none' });
   });