@@ -49,6 +49,55 @@
  * that fires on any `packages[]` at all — would satisfy the failing case alone.
  * The pair asserts what the card actually claims: that the option-B stack is
  * READ, not that it is rejected.
+ *
+ * ## ⚠️ [#18897] The refusal cases were satisfied by an IMPOSTOR — and the
+ * ## impostor is a SIBLING PASS that arrived after this file was written
+ *
+ * These three refusal cases claimed to pin `authoringRuleUnionStack` — the fold
+ * that makes the rule table's INPUT non-empty on an option-B stack. They could
+ * not. Since #18677 (`os validate`) and #18778 (`os lint`) all three doors ALSO
+ * run `runPerPackageAuthoringRules`, which judges each `packages[]` entry as its
+ * own stack. That pass sees this fixture's one package body, raises the SAME
+ * rule at the SAME path, and refuses with the same exit code. ⇒ `exit 1` +
+ * `contains(RULE)` + `contains(RULE_PATH)` is satisfied by EITHER mechanism, so
+ * the control could not tell the fold from its sibling.
+ *
+ * ⛔ Not reasoned about — measured by ablation, at `origin/main` 13d52947d8:
+ *
+ *     ablation                                          this file
+ *     `authoringRuleUnionStack` never folds             6/6 GREEN
+ *     `runPerPackageAuthoringRules` yields no findings  6/6 GREEN
+ *     BOTH of the above                                 3 RED
+ *
+ * ⭐ Either mechanism alone kept every case green; only deleting both turned the
+ * three refusal cases red. That is what a control satisfied by something other
+ * than the mechanism it names looks like from the inside — green, and green for
+ * the wrong reason.
+ *
+ * ## What discriminates them: a PEDIGREE, ⛔ not a count and ⛔ not an exit code
+ *
+ * `runPerPackageAuthoringRules` prefixes the `where` of every finding IT raises
+ * with `package '<id>' — `; it owns that prefix, and three sibling files pin the
+ * same regex. The union run renders `where` bare. Measured on THIS fixture, same
+ * command, with only the fold's presence moving:
+ *
+ *     fold intact    • object "ob_order" · field "ghost": …
+ *     fold ablated   • package 'com.example.ob' — object "ob_order" · field "ghost": …
+ *
+ * So each refusal case now asserts the refusal carries NO per-package prefix —
+ * the finding is the UNION run's, which is the mechanism this file is about.
+ *
+ * ⚠️ A real falsifier — a fixture in which the impostor structurally CANNOT
+ * raise this finding — does not exist for this rule class, and that was measured
+ * rather than assumed: the per-package pass is a SUPERSET of the union run for
+ * reference rules (`utils/artifact-packages.ts`: "the per-package run is
+ * STRICTER"), because each body is judged with the artifact's own `packages[]`
+ * handed in as resolution context. A name no package provides therefore dangles
+ * in BOTH views, under every arrangement of packages. ⇒ here the pedigree is the
+ * whole discriminant, and the negative assertion is made load-bearing by the
+ * POSITIVE control at the foot of this file — a fixture whose finding really is
+ * per-package-only. Without that pair, "the prefix is absent" would be satisfied
+ * by a prefix this suite never produces at all.
  */
 
 import { describe, expect, it } from 'vitest';
@@ -69,6 +118,15 @@ const AUTHORING_COMMANDS = ['validate', 'lint', 'build'] as const;
 const RULE = 'object-reference-unknown';
 const RULE_PATH = 'objects[0].fields.ghost.reference';
 
+/**
+ * [#18897] The `where` prefix `runPerPackageAuthoringRules` puts on every
+ * finding IT raises — the one thing that tells the union run's finding apart
+ * from the per-package pass's copy of it. ⛔ Not this file's guess at a format:
+ * the pass owns the prefix, and `validate-/lint-per-package-authoring-parity`
+ * and `build-text-face-advisory-count` pin the identical regex.
+ */
+const PER_PACKAGE_WHERE = /package '[^']+' — /;
+
 /**
  * The card's repro verbatim: no top-level `objects`, one `packages[]` entry
  * carrying an object whose `ghost` lookup points at an object that does not
@@ -100,6 +158,73 @@ const optionBStack = (reference: string): Record<string, unknown> => ({
   ],
 });
 
+/**
+ * [#18897] The POSITIVE half of the pedigree pair: a project whose ONLY
+ * author-time finding is one the union run genuinely cannot see.
+ *
+ * `core` owns `ob_account`; `orders` owns the view that displays
+ * `ob_account.industry`. Folded into one union the field HAS a consumer and
+ * nothing is raised; judged per package, `core` declares a field nothing in
+ * `core` reads — so the survivor is the per-package pass's alone and carries its
+ * `where` prefix. It is the falsifier shape PR #18878 landed in
+ * `lint-per-package-authoring-parity.test.ts`, and it is here for one job: to
+ * prove that {@link PER_PACKAGE_WHERE} is a prefix this suite CAN observe, so
+ * the refusal cases' `toBe(false)` is a measurement and not the silence of a
+ * regex that never matches anything. ⛔ Do not remove the view to "simplify" it.
+ */
+const perPackageOnlyStack = (): Record<string, unknown> => {
+  const coreManifest = {
+    id: 'com.example.obflip.core', name: 'obflip core', namespace: 'ob',
+    version: '1.0.0', type: 'app', engines: { protocol: '^17' },
+  };
+  const coreObjects = [{
+    name: 'ob_account', label: 'Account', pluralLabel: 'Accounts', sharingModel: 'private',
+    fields: {
+      name: { name: 'name', type: 'text', label: 'Account Name', required: true },
+      industry: { name: 'industry', type: 'text', label: 'Industry' },
+    },
+  }];
+  const coreApps = [{
+    name: 'ob_crm', label: 'OB CRM',
+    navigation: [{
+      id: 'sales_group', type: 'group', label: 'Sales',
+      children: [{ id: 'nav_accounts', type: 'object', objectName: 'ob_account', label: 'Accounts' }],
+    }],
+  }];
+  const ordersManifest = {
+    id: 'com.example.obflip.orders', name: 'obflip orders', namespace: 'ob',
+    version: '1.0.0', type: 'module', engines: { protocol: '^17' },
+    dependencies: { 'com.example.obflip.core': '^1.0.0' },
+  };
+  const ordersObjects = [{
+    name: 'ob_order', label: 'Order', pluralLabel: 'Orders', sharingModel: 'private',
+    fields: {
+      name: { name: 'name', type: 'text', label: 'Order Number', required: true },
+      account: { name: 'account', type: 'lookup', label: 'Account', reference: 'ob_account' },
+    },
+  }];
+  const ordersViews = [
+    {
+      name: 'ob_account_list', label: 'Account List', object: 'ob_account',
+      list: { label: 'Account List', columns: ['name', 'industry'] },
+    },
+    {
+      name: 'ob_order_list', label: 'Order List', object: 'ob_order',
+      list: { label: 'Order List', columns: ['name', 'account'] },
+    },
+  ];
+  return {
+    manifest: coreManifest,
+    objects: [...ordersObjects, ...coreObjects],
+    apps: [...coreApps],
+    views: [...ordersViews],
+    packages: [
+      { manifest: { ...ordersManifest, objects: ordersObjects, views: ordersViews } },
+      { manifest: { ...coreManifest, objects: coreObjects, apps: coreApps } },
+    ],
+  };
+};
+
 interface Run {
   code: number;
   output: string;
@@ -152,6 +277,23 @@ describe('#17069 — os validate and os lint judge the option-B stack, not an em
         `os ${command} named ${RULE} at a different path than the other doors — the three commands ` +
           `must report one finding one way`,
       ).toContain(RULE_PATH);
+      // ⭐ [#18897] PEDIGREE. Everything above this line is satisfied by the
+      // per-package authoring pass, which raises the same rule at the same path
+      // on this one-package body and refuses with the same code — measured: with
+      // `authoringRuleUnionStack` ablated all six cases here stayed GREEN, and
+      // only ablating the per-package pass TOO turned these three red. The union
+      // run renders `where` bare; the per-package pass prefixes it. So the
+      // absence of that prefix is what makes this case a reading of the FOLD.
+      expect(
+        PER_PACKAGE_WHERE.test(run.output),
+        `os ${command} refused this stack through the PER-PACKAGE authoring pass, not through the ` +
+          `union fold this file pins: the finding carries ${String(PER_PACKAGE_WHERE)}, the prefix ` +
+          `runPerPackageAuthoringRules puts on its own findings. The fold is what makes the rule ` +
+          `table's INPUT non-empty on an option-B stack, and with it gone this command is refusing ` +
+          `for a reason #17069 did not buy. ⛔ Do not answer this by deleting the assertion — the ` +
+          `pedigree is the only thing here that can tell the two mechanisms apart.` +
+          `\n--- output ---\n${run.output}`,
+      ).toBe(false);
     },
     180_000,
   );
@@ -171,4 +313,34 @@ describe('#17069 — os validate and os lint judge the option-B stack, not an em
     },
     180_000,
   );
+
+  it.each(AUTHORING_COMMANDS)(
+    '⭐ PEDIGREE CONTROL — os %s DOES render the per-package prefix when the finding is the pass\'s own',
+    (command) => {
+      // The other half of the pair above. A `toBe(false)` on a regex is only a
+      // measurement if the same suite can make it true; without this case an
+      // absent prefix and a prefix nothing ever emits read identically — which
+      // is the whole class of defect #18897 is about, one level up.
+      const run = runCommand(command, perPackageOnlyStack());
+      expect(
+        run.code,
+        `os ${command} exited ${run.code} on the per-package-only fixture. Its single finding is an ` +
+          `ADVISORY (field-no-consumers), so every door reports it and none of them fails on it.` +
+          `\n--- output ---\n${run.output}`,
+      ).toBe(0);
+      expect(
+        PER_PACKAGE_WHERE.test(run.output),
+        `os ${command} raised no per-package-prefixed finding on a fixture whose only finding the ` +
+          `union run cannot see (core declares ob_account.industry; orders owns the view that ` +
+          `displays it). Either the pass stopped running on this door, or the prefix was re-spelled ` +
+          `— and in both cases the refusal cases above are asserting the absence of something this ` +
+          `suite no longer produces.\n--- output ---\n${run.output}`,
+      ).toBe(true);
+      // …and it is that field, not some other advisory that happens to be
+      // prefixed: the pedigree names the member, never just the shape.
+      expect(run.output, `os ${command} prefixed a finding, but not the one this fixture is built on`)
+        .toContain('industry');
+    },
+    180_000,
+  );
 });