diff --git a/‎.changeset/15293-non-array-packages-refusal.md‎
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diff --git a/‎.changeset/19926-packages-null-refused.md‎
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diff --git a/‎packages/core/src/artifact-packages.test.ts‎
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diff --git a/‎packages/core/src/artifact-packages.ts‎
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diff --git a/‎packages/plugins/plugin-dev/src/dev-i18n-packages-reader.test.ts‎
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diff --git a/‎packages/plugins/plugin-dev/src/dev-i18n.ts‎
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diff --git a/‎packages/plugins/plugin-security/src/app-default-permission-set.test.ts‎
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@@ -9,5 +9,5 @@ Clause-②: no
 `packages` is declared as an array of package entries (`ObjectStackDefinitionSchema.packages: z.array(ArtifactPackageSchema).optional()`), and the rule is now written down once, beside `AssembledPackageBodySchema` in `@objectstack/spec`: an absent `packages` means a single-package artifact, and any other non-array value is malformed and refused. `resolveArtifactPackageOrder` in `@objectstack/core` already refused it, and so did the i18n detector in `@objectstack/plugin-dev` and the default-permission-set reader in `@objectstack/plugin-security`.
 
 - **What changes**: `AppPlugin` reads its collections in `start()`, and `start()` now raises the same refusal `init()` already raised through the kernel's `manifest` service. Under `os dev`, `DevPlugin`'s child-`start()` loop logs it on its `error` line, where before the app started on its top-level collections alone. `createStandaloneStack` now refuses such an artifact while it builds the stack. Before, the refusal came later, when the app registered with the `manifest` service. `loadArtifactBundle`'s runtime-module merge reports it through its existing `warn` line and skips the merge, as it already does for a malformed `packages[]` entry. `resolveProjectDatabaseUrl` no longer reads a default datasource out of such an artifact: it declines, as it already does for any artifact it cannot read, and moves on to the next rung (the unified default database). The boot that loads the artifact then refuses it.
-- **What does not change**: an absent `packages`, and `packages: null`, still return the caller's own object by identity. A well-formed `packages[]` resolves exactly as before.
+- **What does not change**: an absent `packages` still returns the caller's own object by identity. A well-formed `packages[]` resolves exactly as before. `packages: null` is not absent: it is malformed, and it is refused the same way (#19926).
 - **Fix**: remove the `packages` key for a single-package artifact, or make it an array of `{ manifest: … }` entries.
@@ -0,0 +1,24 @@
+---
+'@objectstack/core': minor
+'@objectstack/runtime': minor
+'@objectstack/plugin-dev': minor
+'@objectstack/plugin-security': minor
+---
+
+fix(core,runtime,plugin-dev,plugin-security): a release artifact whose `packages` is `null` is refused as malformed, never read as absent (#19926)
+
+Clause-②: no (narrowing)
+
+<!-- adr-0087: not-required (no-migration-prescription) Nothing authorable moves: no spec key, Zod schema, export, config field or stored metadata shape is added, removed, renamed or re-spelled. ObjectStackDefinitionSchema already refused packages null, and so did composeStacks with two or more inputs, so an authored stack that passed its schema reads exactly as before; what narrows is the runtime readers' behaviour on an artifact that bypassed that parse, and objectstack migrate meta has no document to rewrite for it. -->
+
+**BREAKING** — an accept-set narrowing on a value the schema already refuses, shipped as `minor` under the launch-window convention (`check-changeset-no-major` refuses `major` until GA; breaking-ness is carried by this banner and the ADR-0087 disposition above, not by the level).
+
+`ObjectStackDefinitionSchema.packages` is `z.array(ArtifactPackageSchema).optional()`, and `.optional()` admits `undefined`, not `null`. The schema refused `packages: null` (`invalid_type`), and `composeStacks` refused it with two or more inputs (`STACK_SCHEMA_INVALID`, `status: 422`). The runtime readers below read it as absent instead: a single-package artifact whose own top level is the one package body. Those readers now follow the declaration. An absent `packages` is `undefined` and nothing else; `null` is one of the present, non-array values the rule beside `AssembledPackageBodySchema` calls malformed, like `{}`, `0` or `'x'`, and it is refused with the same envelope: `INVALID_ARTIFACT_PACKAGES`, `status: 422`. No error code is added.
+
+- **`@objectstack/core`**: `resolveArtifactPackageOrder` refuses `packages: null` where it returned `[artifact]`. The refusal message names the value `null`, not `object`. The resolver's callers that hand it the whole artifact raise the refusal: the kernel `manifest` service's `register()` (`ObjectQLPlugin`) and `@objectstack/verify`'s collection reader for a collection the stack's top level does not carry.
+- **`@objectstack/runtime`**: `resolveArtifactCollections` drops `null` from its absent branch, so `AppPlugin`, `createStandaloneStack`, `loadArtifactBundle`'s runtime-module merge and `resolveProjectDatabaseUrl` answer a `packages: null` artifact exactly as they already answer `packages: {}`. `carriedPackageIds`, and `resolveArtifactGrantBinding` for an artifact whose `grantedPermissions` is a record, read the package list through the core resolver and raise its refusal too.
+- **`@objectstack/plugin-dev`**: the i18n detector's private absent guard moves in lockstep with the resolver's absent branch, so `devI18nPluginOptions` reaches the resolver and raises its refusal when the `i18n` config (on the stack or its `manifest`), a non-empty `manifest.translations` and a non-empty top-level `translations` do not answer first. `DevPlugin` keeps its posture: it reports the metadata defect on its `error` line and boots on the in-memory i18n fallback.
+- **`@objectstack/plugin-security`**: `appSecurityPluginOptions` has no guard of its own and raises the resolver's refusal for `packages: null`.
+- **What does not change**: the schema; an absent `packages` (no key, or an explicit `undefined`), which still returns the caller's own object by identity; a well-formed `packages[]`; and `composeStacks` with a single input, which still returns that input by identity.
+
+No in-repo producer writes `packages: null`, and `os build` and `os validate` refuse it at the schema before any reader runs. For a single-package artifact, leave the `packages` key out.
@@ -0,0 +1,69 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * `resolveArtifactPackageOrder`'s ABSENT branch is `undefined` only (#19926,
+ * ruling A).
+ *
+ * `ObjectStackDefinitionSchema.packages` is `z.array(ArtifactPackageSchema)
+ * .optional()`, and `.optional()` admits `undefined`, not `null`. So `null` is
+ * a present, non-array `packages`: malformed, and refused with the same
+ * envelope as `{}`, `0` or `'x'`. The rule is stated once, beside
+ * `AssembledPackageBodySchema` (`@objectstack/spec`, `stack.zod.ts`).
+ *
+ * The resolver's wider behaviour (ordering, the entry gate, duplicates) is
+ * pinned where its load path is, in `@objectstack/objectql`'s
+ * `artifact-load-path.test.ts`. This file pins the one branch every reader of
+ * `packages` inherits from here.
+ */
+
+import { describe, it, expect } from 'vitest';
+import { resolveArtifactPackageOrder, type ArtifactPackageError } from './artifact-packages';
+
+const manifest = { id: 'com.example.a', name: 'A', version: '1.0.0', type: 'app' };
+
+function refusalOf(artifact: unknown): ArtifactPackageError | undefined {
+  try {
+    resolveArtifactPackageOrder(artifact);
+    return undefined;
+  } catch (err) {
+    return err as ArtifactPackageError;
+  }
+}
+
+describe('resolveArtifactPackageOrder — `packages: null` is malformed, not absent', () => {
+  it('refuses `packages: null` with INVALID_ARTIFACT_PACKAGES / 422', () => {
+    const refused = refusalOf({ manifest, packages: null });
+    expect(refused).toBeInstanceOf(Error);
+    expect(refused?.code).toBe('INVALID_ARTIFACT_PACKAGES');
+    expect(refused?.status).toBe(422);
+  });
+
+  it.each([
+    ['{}', {}],
+    ['0', 0],
+    ["'x'", 'x'],
+  ])('refuses `packages: %s` with the same envelope — `null` is one of these, not a fourth case', (_label, packages) => {
+    const refused = refusalOf({ manifest, packages });
+    expect(refused?.code).toBe('INVALID_ARTIFACT_PACKAGES');
+    expect(refused?.status).toBe(422);
+  });
+
+  it('control: an ABSENT `packages` (no key, or an explicit `undefined`) is the single-package branch, returned by identity', () => {
+    const noKey = { manifest };
+    const explicitUndefined = { manifest, packages: undefined };
+    for (const artifact of [noKey, explicitUndefined]) {
+      expect(refusalOf(artifact)).toBeUndefined();
+      const resolved = resolveArtifactPackageOrder(artifact);
+      expect(resolved).toHaveLength(1);
+      expect(resolved[0]).toBe(artifact);
+    }
+  });
+
+  it('control: an ARRAY `packages` resolves to its bodies, by reference', () => {
+    const body = { ...manifest };
+    const resolved = resolveArtifactPackageOrder({ packages: [{ manifest: body }] });
+    expect(resolved).toHaveLength(1);
+    expect(resolved[0]).toBe(body);
+    expect(resolveArtifactPackageOrder({ packages: [] })).toEqual([]);
+  });
+});
@@ -35,7 +35,9 @@
  * - `packages` absent  → treat `manifest` (singular) as a **single-element list**.
  *
  * A `packages` that is present but is not an array takes neither branch. It is
- * refused here as `INVALID_ARTIFACT_PACKAGES`. The rule is stated once,
+ * refused here as `INVALID_ARTIFACT_PACKAGES`. `null` is one of those values:
+ * the key is declared `.optional()`, which admits `undefined` and not `null`,
+ * so ABSENT means `undefined` and nothing else. The rule is stated once,
  * beside `AssembledPackageBodySchema` (`@objectstack/spec`, `stack.zod.ts`).
  *
  * The second branch is not a convenience: it is the term ADR-0130's whole
@@ -194,7 +196,7 @@ interface ArtifactPackageNode extends OrderablePlugin {
  * @returns The manifest bodies to register, in the order to register them.
  * @throws An ADR-0112 envelope (`code` + `status: 422`):
  *   `INVALID_ARTIFACT_PACKAGES` for a `packages` that is present but is not an
- *   array, `INVALID_ARTIFACT_PACKAGE_ENTRY` for a malformed entry, and
+ *   array (`null` included), `INVALID_ARTIFACT_PACKAGE_ENTRY` for a malformed entry, and
  *   `DUPLICATE_ARTIFACT_PACKAGE` for a duplicate package id. Also
  *   `resolvePluginOrder`'s own error for a cycle.
  */
@@ -205,7 +207,12 @@ export function resolveArtifactPackageOrder(artifact: unknown): unknown[] {
   // the caller's own object IS that package's manifest body. Returned by
   // reference, unvalidated and unrewritten — this is the path every artifact
   // built to date takes, and D7 pins that it did not move.
-  if (declared === undefined || declared === null) return [artifact];
+  //
+  // ⛔ `undefined` ONLY. `null` is present, not absent: the schema's
+  // `.optional()` refuses it, so reading it as absent here would answer for an
+  // artifact the declaration calls malformed (#19926). It falls to the refusal
+  // below with every other non-array value.
+  if (declared === undefined) return [artifact];
 
   // Present but not an array: malformed, never absent. The rule is stated
   // once, beside `AssembledPackageBodySchema`.
@@ -214,7 +221,9 @@ export function resolveArtifactPackageOrder(artifact: unknown): unknown[] {
       'INVALID_ARTIFACT_PACKAGES',
       'A release artifact\'s `packages` must be an array of package entries '
       + '(ADR-0130 D4, `ArtifactPackageEntrySchema`), but this artifact carries '
-      + `\`packages\` of type ${typeof declared}. Omit the key entirely for a `
+      // `typeof null` is `'object'`, which would name a `{}` the author never
+      // wrote; `null` is named as itself.
+      + `\`packages\` of type ${declared === null ? 'null' : typeof declared}. Omit the key entirely for a `
       + 'single-package artifact — `manifest` is retained, not replaced.',
     );
   }
 
@@ -44,7 +44,8 @@
 import { describe, it, expect, vi } from 'vitest';
 import { composeStacks, defineStack, type ObjectStackDefinition } from '@objectstack/spec';
 
-import { devI18nPluginOptions } from './dev-i18n';
+import { resolveArtifactPackageOrder } from '@objectstack/core';
+import { devI18nPluginOptions, stackDeclaresTranslations } from './dev-i18n';
 import { DevPlugin } from './dev-plugin';
 
 const absent = (name: string): Error =>
@@ -342,7 +343,9 @@ describe('#15232 — DevPlugin i18n auto-detect over a multi-package stack', ()
 
   // A `packages` that is present but is not an array is MALFORMED, not absent
   // (the rule beside `AssembledPackageBodySchema`). This reader's private guard
-  // may decide only the absent branch, so these three reach the resolver.
+  // may decide only the absent branch, so these four reach the resolver.
+  // `null` is one of them since #19926 moved the guard and the resolver's
+  // absent branch together.
   const refusalOf = (stack: unknown): (Error & { code?: string; status?: number }) | undefined => {
     try {
       devI18nPluginOptions(stack);
@@ -353,6 +356,7 @@ describe('#15232 — DevPlugin i18n auto-detect over a multi-package stack', ()
   };
 
   it.each([
+    ['null', null],
     ['{}', {}],
     ['0', 0],
     ["'x'", 'x'],
@@ -370,16 +374,49 @@ describe('#15232 — DevPlugin i18n auto-detect over a multi-package stack', ()
     expect(refusalOf(optionBProject())).toBeUndefined();
     expect(devI18nPluginOptions(optionBProject())).toEqual({ defaultLocale: undefined, fallbackLocale: 'en' });
 
-    // Absent, explicitly `undefined`, and `null`: the guard's one decision.
+    // Absent and explicitly `undefined`: the guard's one decision. `null` is
+    // not here — it is a row of the refusal table above.
     const manifest = { id: CORE_ID, name: 'x', version: '1.0.0', type: 'app' };
-    for (const absent of [{}, { packages: undefined }, { packages: null }]) {
+    for (const absent of [{}, { packages: undefined }]) {
       expect(refusalOf({ manifest, ...absent })).toBeUndefined();
       expect(devI18nPluginOptions({ manifest, ...absent })).toBeUndefined();
       expect(devI18nPluginOptions({ manifest, ...absent, translations: [{ en: {} }] }))
         .toEqual({ defaultLocale: undefined, fallbackLocale: 'en' });
     }
   });
 
+  it('LOCKSTEP — the private guard and `resolveArtifactPackageOrder` agree on `packages: null` and on an absent key', () => {
+    // The guard is bound to the resolver's absent branch: it may answer
+    // "absent" for exactly the values the resolver answers `[stack]` for, and
+    // must hand every other value to it. Asked of both directly, so a guard
+    // that drifted back to `undefined || null` goes red here even while the
+    // resolver refuses — the pair measured nothing before #19926.
+    const envelopeOf = (fn: () => unknown): { code?: unknown; status?: unknown } | undefined => {
+      try {
+        fn();
+        return undefined;
+      } catch (err) {
+        const { code, status } = err as { code?: unknown; status?: unknown };
+        return { code, status };
+      }
+    };
+    const manifest = { id: CORE_ID, name: 'x', version: '1.0.0', type: 'app' };
+
+    const nullStack = { manifest, packages: null };
+    const fromResolver = envelopeOf(() => resolveArtifactPackageOrder(nullStack));
+    const fromGuard = envelopeOf(() => stackDeclaresTranslations(nullStack));
+    expect(fromResolver).toEqual({ code: 'INVALID_ARTIFACT_PACKAGES', status: 422 });
+    expect(fromGuard).toEqual(fromResolver);
+
+    // Control: an absent key is absent to both, and neither throws.
+    for (const absent of [{ manifest }, { manifest, packages: undefined }]) {
+      expect(envelopeOf(() => resolveArtifactPackageOrder(absent))).toBeUndefined();
+      expect(resolveArtifactPackageOrder(absent)).toEqual([absent]);
+      expect(envelopeOf(() => stackDeclaresTranslations(absent))).toBeUndefined();
+      expect(stackDeclaresTranslations(absent)).toBe(false);
+    }
+  });
+
   // ── What the developer actually gets: the SERVICE ─────────────────────────
 
   const bootWith = async (stack: Record<string, unknown> | undefined) => {
 
@@ -109,11 +109,13 @@ const declaresTranslationArray = (body: unknown): boolean => {
  * reader to exactly the old path, and it goes red without the guard.
  *
  * ⛔ So the guard is allowed to decide ONE thing: the ABSENT branch, spelled
- * exactly as the resolver's own absent branch (`undefined` / `null`). Every
- * other value goes to the resolver, so a present non-array `packages` (`{}`,
- * `0`, `'x'`) is REFUSED as `INVALID_ARTIFACT_PACKAGES`. ⛔ Never widen it to
- * `Array.isArray`: that is the silent fall-through the rule above forbids. If
- * the resolver's absent branch ever changes, this line changes with it.
+ * exactly as the resolver's own absent branch (`undefined`, and nothing else).
+ * Every other value goes to the resolver, so a present non-array `packages`
+ * (`null`, `{}`, `0`, `'x'`) is REFUSED as `INVALID_ARTIFACT_PACKAGES`. ⛔ Never
+ * widen it to `Array.isArray`: that is the silent fall-through the rule above
+ * forbids. If the resolver's absent branch ever changes, this line changes with
+ * it — it did once, when `null` stopped being absent (#19926), and the two moved
+ * in one change.
  *
  * ## A malformed `packages[]` is refused, not skipped
  *
@@ -163,7 +165,7 @@ const declaresTranslationArray = (body: unknown): boolean => {
  *   array.
  * @throws An ADR-0112 envelope (`Error & { code, status: 422 }`) from
  *   `resolveArtifactPackageOrder` when `packages` is present but not loadable:
- *   `INVALID_ARTIFACT_PACKAGES` (not an array), `INVALID_ARTIFACT_PACKAGE_ENTRY`
+ *   `INVALID_ARTIFACT_PACKAGES` (not an array, `null` included), `INVALID_ARTIFACT_PACKAGE_ENTRY`
  *   (an entry that is not `{ manifest: … }`, a body carrying authoring-time
  *   globs where definitions belong, or a manifest with no usable id) or
  *   `DUPLICATE_ARTIFACT_PACKAGE`.
@@ -179,7 +181,7 @@ export function stackDeclaresTranslations(stack: unknown): boolean {
   if (declaresTranslationArray(stack)) return true;
 
   const packages = asBag(stack)?.packages;
-  if (packages === undefined || packages === null) return false;
+  if (packages === undefined) return false;
 
   for (const body of resolveArtifactPackageOrder(stack)) {
     if (declaresTranslationArray(body)) return true;
 
@@ -341,8 +341,10 @@ describe('appSecurityPluginOptions over `packages[]` (ADR-0130 D4, #15007)', ()
 
     // A `packages` that is present but is not an array is MALFORMED, not absent
     // (the rule beside `AssembledPackageBodySchema`). This reader keeps no
-    // `packages` guard of its own, so the refusal is the resolver's.
+    // `packages` guard of its own, so the refusal is the resolver's — `null`
+    // included, since #19926 took `null` out of the resolver's absent branch.
     it.each([
+      ['null', null],
       ['{}', {}],
       ['0', 0],
       ["'x'", 'x'],
@@ -359,9 +361,10 @@ describe('appSecurityPluginOptions over `packages[]` (ADR-0130 D4, #15007)', ()
       expect(refusalOf({ packages: [wellFormed] })).toEqual({});
       expect(appSecurityPluginOptions({ packages: [wellFormed] })).toEqual({ fallbackPermissionSet: CORE_PROFILE });
 
-      // Absent, explicitly `undefined`, and `null`: all three read the top level
-      // exactly as before the private guard was dropped.
-      for (const absent of [{}, { packages: undefined }, { packages: null }]) {
+      // Absent and explicitly `undefined`: both read the top level exactly as
+      // before the private guard was dropped. `null` is a row of the refusal
+      // table above, not an absent key.
+      for (const absent of [{}, { packages: undefined }]) {
         expect(refusalOf({ ...absent, permissions: [permissionSet('top')] })).toEqual({});
         expect(appSecurityPluginOptions({ ...absent, permissions: [permissionSet('top')] }))
           .toEqual({ fallbackPermissionSet: 'top' });