@@ -0,0 +1,18 @@
+---
+'@objectstack/spec': minor
+'@objectstack/objectql': minor
+---
+
+feat(spec,objectql)!: a top-level action bound by `objectName` to an object another package owns is listed on that object wherever it is served, and a bound action whose object no loaded package registers fails the boot
+
+Clause-②: yes (narrowing)
+
+<!-- adr-0087: not-required (no-migration-prescription) No spec key, option, error code or stored shape is added, removed or renamed: `defineStack` accepts two more target kinds for an action's existing `objectName`, the served object gains entries in its existing `actions` array, and the boot refusal answers the existing `INVALID_METADATA` code. Nothing stored changes shape, so `objectstack migrate meta` has nothing to rewrite. The other categories are closed on facts: both packages publish (not unpublished); no ADR-0087 id is named or touched (not registered or already-registered); no Zod schema shape in packages/spec changes (not runtime-interface-only or type-surface-only); and nothing exported is retired (not runtime-export-retired). -->
+
+**BREAKING** (one narrowing beside a widening), shipped as `minor` under the launch-window convention for breaking changes.
+
+- **Widening** (`@objectstack/spec`, `@objectstack/objectql`): an action declared in a stack's top-level `actions` with `objectName` naming an object that another package owns now reaches that object. `defineStack()` accepts the action when the stack extends the object through `objectExtensions`, or when the object is a known platform object (`sys_organization` and the rest of the platform's named list). It keeps the action in the top-level `actions`. The engine's schema registry then attaches it to the object at the one step every object read ends in. That covers `GET /api/v1/meta/object/<name>` (stored-row, MetadataService and registry layers alike), `engine.getSchema()` and the action router's object lookup, in whichever order the two packages register. The attached entry is the action's own declaration, so its `requiredPermissions`, `requiresMembershipReach` and execution identity are unchanged. An action the object already declares under the same name keeps the object's declaration. A disabled package's bound actions are not attached. Before this, such an action was refused by `defineStack()` whenever the stack declared an object of its own. Where it got through (an object-less stack, or `strict: false`), it registered but was listed on no object, so no client rendered it.
+- **FROM** (`@objectstack/objectql`): a top-level action bound by `objectName` to an object no loaded package registers was registered and listed nowhere, and the boot succeeded. **TO:** the boot fails at `kernel:ready` with `INVALID_METADATA` (422), naming each such action, its package and the object. An artifact registered through the `manifest` service after the boot is refused before any of it registers. **Fix:** register the object (in the package or in one it depends on), or correct the action's `objectName`.
+- **Unchanged:** a name `defineStack()` cannot attribute (an object this stack neither defines nor extends, and not a known platform object) is still refused at build with `STACK_CROSS_REFERENCE_INVALID`. A same-stack bound action is still merged into its object by `defineStack()` and is attached once.
+
+The `ObjectExtensionSchema` refusal for `actions` now says exactly this: declare a top-level action with `objectName: '<target>'` in the same stack; the schema registry attaches it to the object wherever the object is served; a target no loaded package registers fails the boot.
@@ -82,7 +82,7 @@ each one by name with the alternative to use instead:
 
 | Key you might reach for | Declare this instead |
 |:---|:---|
-| `actions` | A top-level action with `objectName: '<target>'` — `defineStack()` attaches it to the object |
+| `actions` | A top-level action with `objectName: '<target>'` in the same stack — it stays in the stack's top-level `actions`, and the engine's schema registry attaches it to the target object wherever the object is served, whichever package registers first; a target no loaded package registers fails the boot |
 | `hooks` | A top-level hook bound to the target object |
 | `listViews` | A top-level `view` bound to the target object |
 | `fieldGroups` | Add the fields here and declare the groups on the owning object, or assign a Page for the layout |
 
@@ -46,7 +46,7 @@ import {
 import { SecurityCatalogNameConflictError, findEnvironmentHeldSecurityCatalogNames } from './registry.js';
 // [ADR-0029 D3] The registry's own refusal of a second owner — read, never
 // re-derived, when a residual object's name is already owned.
-import { ObjectOwnershipConflictError } from './registry.js';
+import { ObjectOwnershipConflictError, collectManifestBoundActions, collectManifestObjectNames, describeUnboundActionTargets } from './registry.js';
 
 export type { Plugin, PluginContext };
 
@@ -393,6 +393,13 @@ export class ObjectQLPlugin implements Plugin {
    * seal the vocabulary, then judge).
    */
   private picklistVocabularySealed = false;
+  /**
+   * [#24400] Set at `kernel:ready` beside {@link picklistVocabularySealed},
+   * once the boot audit has found the target object of every bound top-level
+   * action: from then on a late artifact's bound actions are judged before it
+   * registers.
+   */
+  private boundActionTargetsSealed = false;
   /** Unsubscribe handles for metadata-event subscriptions (ADR-0008 PR-7). */
   private metadataUnsubscribes: Array<() => void> = [];
   /** ADR-0057 lifecycle enforcement (Reaper/Rotator/Archiver). */
@@ -747,6 +754,19 @@ export class ObjectQLPlugin implements Plugin {
           const refusal = describeUnresolvedPicklistReferences(unresolved, orphans);
           if (refusal) throw refusal;
         }
+        // [#24400] The same seal for bound top-level actions: once the boot has
+        // judged every target (`kernel:ready`, below), an artifact arriving
+        // later must bind its actions to an object the registry holds or one
+        // the artifact itself declares. A refused install registers nothing.
+        if (this.boundActionTargetsSealed) {
+          const declared = new Set<string>(residual?.objects.map((o) => o.name) ?? []);
+          for (const manifest of ordered) for (const name of collectManifestObjectNames(manifest)) declared.add(name);
+          const unbound = ordered
+            .flatMap((manifest) => collectManifestBoundActions(manifest, artifactPackageId(manifest)))
+            .filter((bound) => !declared.has(bound.objectName) && ql.registry.getObject(bound.objectName) === undefined);
+          const refusal = describeUnboundActionTargets(unbound);
+          if (refusal) throw refusal;
+        }
 
         for (const manifest of ordered) {
           ql.registerApp(manifest, scope, options?.source);
@@ -903,6 +923,15 @@ export class ObjectQLPlugin implements Plugin {
         );
         if (unresolvedPicklists) throw unresolvedPicklists;
         this.picklistVocabularySealed = true;
+        // [#24400] A top-level action bound by `objectName` to an object no
+        // package registers fails the boot, naming the action, its package and
+        // the object — never registered and listed nowhere. Judged here for the
+        // picklist reason: every package has registered, so "no such object"
+        // is final, and either registration order has had its turn. From here
+        // on each late artifact is judged as it arrives (the `manifest` service).
+        const unboundActions = describeUnboundActionTargets(this.ql?.registry.findUnboundActionTargets() ?? []);
+        if (unboundActions) throw unboundActions;
+        this.boundActionTargetsSealed = true;
         // #7737 — FIRST, before anything that might read data: bind every
         // declared federated object to its remote table now that every
         // plugin's `start()` (including the declared-datasource auto-connect