diff --git a/packages/data-schemas/src/models/plugins/tenantIsolation.coverage.spec.ts b/packages/data-schemas/src/models/plugins/tenantIsolation.coverage.spec.ts
new file mode 100644
index 0000000000..13b7af41c2
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+++ b/packages/data-schemas/src/models/plugins/tenantIsolation.coverage.spec.ts
@@ -0,0 +1,52 @@
+import mongoose from 'mongoose';
+import { createModels } from '../index';
+
+/**
+ * Global symbol set by applyTenantIsolation() on every schema it processes.
+ * Recreated here via Symbol.for (the global registry) so the guard can detect
+ * plugin application without the plugin exporting anything.
+ */
+const TENANT_ISOLATION_APPLIED = Symbol.for('librechat:tenantIsolation');
+
+/**
+ * Models that carry a `tenantId` field but intentionally do NOT use the
+ * tenant-isolation plugin. SystemGrant scopes tenancy manually inside its
+ * methods (see models/systemGrant). Adding an entry here must be a deliberate,
+ * reviewed decision — that is the whole point of this guard.
+ */
+const MANUAL_TENANT_SCOPING = new Set<string>(['SystemGrant']);
+
+function isPluginApplied(schema: mongoose.Schema): boolean {
+  return (schema as unknown as { [key: symbol]: boolean })[TENANT_ISOLATION_APPLIED] === true;
+}
+
+describe('tenant-isolation plugin coverage', () => {
+  beforeAll(() => {
+    createModels(mongoose);
+  });
+
+  it('applies the tenant-isolation plugin to every model that has a tenantId field', () => {
+    const missing: string[] = [];
+
+    for (const [name, model] of Object.entries(mongoose.models)) {
+      const hasTenantId = Boolean(model.schema.path('tenantId'));
+      if (!hasTenantId || MANUAL_TENANT_SCOPING.has(name)) {
+        continue;
+      }
+      if (!isPluginApplied(model.schema)) {
+        missing.push(name);
+      }
+    }
+
+    expect(missing).toEqual([]);
+  });
+
+  it('keeps the manual-scoping allowlist accurate (tenantId field, no plugin)', () => {
+    for (const name of MANUAL_TENANT_SCOPING) {
+      const model = mongoose.models[name];
+      expect(model).toBeDefined();
+      expect(Boolean(model.schema.path('tenantId'))).toBe(true);
+      expect(isPluginApplied(model.schema)).toBe(false);
+    }
+  });
+});