diff --git a/.changeset/9821-registerlazy-cross-table-collision-warning.md b/.changeset/9821-registerlazy-cross-table-collision-warning.md
new file mode 100644
index 0000000000..23dee0c7bc
--- /dev/null
+++ b/.changeset/9821-registerlazy-cross-table-collision-warning.md
@@ -0,0 +1,13 @@
+---
+'@object-ui/core': patch
+---
+
+`Registry.registerLazy` now reports a bare-name collision, and `Registry.register`'s existing report is no longer blind to the other table.
+
+Clause-②: no — this adds no exported symbol, no key on a published payload, and relaxes no accept set. Which registrations the registry ACCEPTS is unchanged, and so is what `skipFallback` does; only what the registry SAYS changes.
+
+The registry has two doors onto one bare key: `register` writes `components`, `registerLazy` writes `lazyEntries`. `registerLazy` took the same `namespace && !skipFallback` fallback branch with no collision check at all, and `register`'s check read only its own table — so a contest that spans the two tables was reported by neither. Replaying this repository's own 425 declared registration claims against a real registry emitted zero collision warnings in every order, including for the one genuinely contested bare key.
+
+Both doors now consult both tables and key on the declared full type, so a contest is reported whichever order the declarations arrive in. The ordinary stub-then-real lifecycle stays silent: a stub and the registration that satisfies it name one full type, and so do the bare keys this repository stubs twice from two files with different loader closures.
+
+The two doors give different advice on purpose. `registerLazy` names `skipFallback: true`, which settles it there. `register` does not, because it clears the bare stub whether or not the fallback is taken, so that opt-out would leave the bare key resolving to nothing; it asks for the two declarations to agree on one full type instead.
diff --git a/packages/core/src/registry/Registry.ts b/packages/core/src/registry/Registry.ts
index 794aefc00f..89417a7382 100644
--- a/packages/core/src/registry/Registry.ts
+++ b/packages/core/src/registry/Registry.ts
@@ -356,6 +356,19 @@ type LazyEntry = {
   pending?: Promise<unknown>;
 };
 
+/**
+ * The full type a pending lazy stub DECLARES for a bare key.
+ *
+ * `registerLazy` computes `namespace:type` and stores the stub under both that
+ * key and the bare one; nothing on the entry itself records which bare key it
+ * claims, so the claim has to be recomputed from the entry's own meta. Spelled
+ * once here because both doors' collision guards need it and a second copy
+ * would be a second thing to keep in step with `registerLazy`'s own line.
+ */
+function lazyStubFullType(type: string, entry: LazyEntry): string {
+  return entry.meta?.namespace ? `${entry.meta.namespace}:${type}` : type;
+}
+
 /**
  * Emit the spec's `dataSource` input for a registration whose renderer wraps
  * `ElementDataSourceGate` (objectui#6678).
@@ -502,6 +515,34 @@ export class Registry<T = any> {
           `If this is intentional keep going; otherwise register "${fullType}" with ` +
           `{ skipFallback: true } so it doesn't claim the bare "${type}" key.`,
         );
+      } else if (!existing) {
+        // The CROSS-TABLE half of the same guard (objectui#9821), and the half
+        // the contest objectui#9533 measured actually went through. The check
+        // above reads `components` only, so a bare key held by a pending STUB
+        // is invisible to it: the console declared bare `dashboard` for
+        // `plugin-dashboard:dashboard` at boot, this door took the same bare key
+        // for `view:dashboard` when the chunk landed, and because `components`
+        // still held nothing under `dashboard` at that moment, NOTHING warned.
+        // Measured, not reasoned: replaying that card's three real claimants
+        // against a real registry emitted zero warnings in BOTH orders.
+        //
+        // ⚠️ The guard has to fire HERE and not only in `registerLazy`, because
+        // a contest that is only reported in one registration order is reported
+        // in the order this repository does not boot in. The `report-` and
+        // `timeline-bare-key-ownership` pins replay both orders for exactly
+        // that reason.
+        const stub = this.lazyEntries.get(type);
+        const stubType = stub ? lazyStubFullType(type, stub) : undefined;
+        if (stubType && stubType !== fullType) {
+          console.warn(
+            `Component "${type}" bare-name fallback is being overwritten by "${fullType}", ` +
+            `which a pending lazy stub already claims for "${stubType}". Which one an ` +
+            `authored "${type}" node resolves to depends on whether that chunk has loaded. ` +
+            `Make the two declarations name ONE full type — { skipFallback: true } does not ` +
+            `settle this one, because registering "${fullType}" clears the bare "${type}" ` +
+            `stub either way.`,
+          );
+        }
       }
       this.components.set(type, {
         type: fullType, // Keep reference to namespaced type
@@ -558,6 +599,48 @@ export class Registry<T = any> {
     const entry: LazyEntry = { loader, meta };
     this.lazyEntries.set(fullType, entry);
     if (meta?.namespace && !meta?.skipFallback) {
+      // Collision guard (objectui#9821). This door took the same bare-name
+      // fallback branch as `register` with no check at all, so a stub could
+      // take the bare key off another declaration in total silence — and the
+      // silence is why the class stayed invisible: two of the three claimants
+      // in the contest objectui#9533 filed came in through here.
+      //
+      // ⭐ The predicate keys on the FULL TYPE and reads BOTH tables, and both
+      // halves of that were decided by the census rather than chosen:
+      //
+      //   - BOTH tables, because the contention is cross-table. Copying the
+      //     guard above verbatim would compare `lazyEntries` against itself,
+      //     and the one contested bare key on this tree is a stub in this table
+      //     against a loaded registration in the other one. A same-table check
+      //     would not have caught the card that produced this one.
+      //   - FULL TYPE and not loader identity, because the ordinary correct
+      //     shape here is a stub re-declared with a DIFFERENT loader closure
+      //     for the SAME full type: two console files drive the same plugin
+      //     set, and nine of this tree's bare keys are registered twice that
+      //     way. Keying on the loader would warn on all nine, every boot.
+      //
+      // Census taken on the declared population of this repository (the same
+      // one `check-registry-bare-name-collisions.mjs` reads): of 31 bare keys
+      // a stub claims, 30 name exactly one full type across both tables — the
+      // stub-then-real lifecycle this must stay silent about — and one is a
+      // genuine contest.
+      const loaded = this.components.get(type);
+      const priorStub = loaded ? undefined : this.lazyEntries.get(type);
+      const claimedBy = loaded
+        ? loaded.type
+        : priorStub
+          ? lazyStubFullType(type, priorStub)
+          : undefined;
+      if (claimedBy && claimedBy !== fullType) {
+        console.warn(
+          `Lazy component "${type}" bare-name fallback is being overwritten by "${fullType}", ` +
+          `which ${loaded ? 'a loaded registration' : 'another pending stub'} already claims ` +
+          `for "${claimedBy}". If this is intentional keep going; otherwise register ` +
+          `"${fullType}" with { skipFallback: true } so it doesn't claim the bare "${type}" ` +
+          `key — on this door that opt-out does settle it, because the stub then claims only ` +
+          `"${fullType}".`,
+        );
+      }
       this.lazyEntries.set(type, entry);
     }
     // Bump the version but do NOT notify: the set of KNOWN types grew, so
diff --git a/packages/core/src/registry/__tests__/Registry.test.ts b/packages/core/src/registry/__tests__/Registry.test.ts
index 10df100bec..4867f2c154 100644
--- a/packages/core/src/registry/__tests__/Registry.test.ts
+++ b/packages/core/src/registry/__tests__/Registry.test.ts
@@ -462,4 +462,132 @@ describe('Registry', () => {
       expect(registry.get('textarea')).toBe(field); // bare clobbered (the regression)
     });
   });
+
+  /**
+   * CROSS-TABLE bare-name collisions (objectui#9821).
+   *
+   * The registry has two doors onto one bare key: `register` writes
+   * `components`, `registerLazy` writes `lazyEntries`. Before this card only
+   * `register` checked for a collision, and it read only its own table — so
+   * the contest objectui#9533 filed, where a console stub claims bare
+   * `dashboard` for `plugin-dashboard:dashboard` and the package then claims
+   * the same bare key for `view:dashboard`, produced ZERO warnings. That zero
+   * was measured against a real registry, in BOTH orders, before this fix.
+   *
+   * ⭐ Both orders are asserted deliberately, the discipline
+   * `report-bare-key-ownership` / `timeline-bare-key-ownership` established: a
+   * contest reported in only one registration order is a detector whose answer
+   * depends on when it was asked, which is the defect, not the fix.
+   */
+  describe('cross-table bare-name collisions (objectui#9821)', () => {
+    const loader = () => Promise.resolve();
+    const collisionWarnings = () =>
+      consoleWarnSpy.mock.calls
+        .map((args: unknown[]) => (typeof args[0] === 'string' ? args[0] : ''))
+        .filter((text: string) => text.includes('bare-name fallback is being overwritten'));
+
+    it('warns when a LOADED registration takes a bare key a pending stub claims (the objectui#9533 order)', () => {
+      // What the console actually does: stubs at boot, chunk later.
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+      consoleWarnSpy.mockClear();
+      registry.register('dashboard', () => 'view', { namespace: 'view' });
+
+      const warned = collisionWarnings();
+      expect(warned).toHaveLength(1);
+      expect(warned[0]).toContain('view:dashboard');
+      expect(warned[0]).toContain('plugin-dashboard:dashboard');
+      expect(warned[0]).toContain('pending lazy stub');
+    });
+
+    it('warns when a stub takes a bare key a LOADED registration claims (the reverse order)', () => {
+      registry.register('dashboard', () => 'view', { namespace: 'view' });
+      consoleWarnSpy.mockClear();
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+
+      const warned = collisionWarnings();
+      expect(warned).toHaveLength(1);
+      expect(warned[0]).toContain('Lazy component "dashboard"');
+      expect(warned[0]).toContain('plugin-dashboard:dashboard');
+      expect(warned[0]).toContain('view:dashboard');
+    });
+
+    it('warns when one stub takes a bare key another stub claims for a different full type', () => {
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+      consoleWarnSpy.mockClear();
+      registry.registerLazy('dashboard', () => Promise.resolve(), { namespace: 'view' });
+
+      const warned = collisionWarnings();
+      expect(warned).toHaveLength(1);
+      expect(warned[0]).toContain('another pending stub');
+    });
+
+    it('stays SILENT on the ordinary stub-then-real lifecycle, in both orders', () => {
+      // 30 of this tree's 31 stub-claimed bare keys are exactly this shape: the
+      // console declares `plugin-charts:chart` and the package registers the
+      // same full type. A guard that fired here would fire at every boot.
+      registry.registerLazy('chart', loader, { namespace: 'plugin-charts' });
+      registry.register('chart', () => 'chart', { namespace: 'plugin-charts' });
+      expect(collisionWarnings()).toHaveLength(0);
+
+      const reverse = new Registry();
+      reverse.register('chart', () => 'chart', { namespace: 'plugin-charts' });
+      reverse.registerLazy('chart', loader, { namespace: 'plugin-charts' });
+      expect(collisionWarnings()).toHaveLength(0);
+    });
+
+    it('stays SILENT when two files stub one full type with DIFFERENT loader closures', () => {
+      // `preview-gallery.tsx` and `register-plugins.ts` drive the same plugin
+      // set, so nine bare keys on this tree are stubbed twice with two distinct
+      // arrow functions. This is why the predicate keys on the full type and
+      // NOT on loader identity — the latter would warn on all nine, every boot.
+      registry.registerLazy('metric', () => Promise.resolve(), { namespace: 'plugin-dashboard' });
+      registry.registerLazy('metric', () => Promise.resolve(), { namespace: 'plugin-dashboard' });
+
+      expect(collisionWarnings()).toHaveLength(0);
+    });
+
+    it('stays SILENT when the stub declines the bare key with skipFallback', () => {
+      registry.register('dashboard', () => 'view', { namespace: 'view' });
+      consoleWarnSpy.mockClear();
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard', skipFallback: true });
+
+      expect(collisionWarnings()).toHaveLength(0);
+      expect(registry.hasLazy('dashboard', 'plugin-dashboard')).toBe(true);
+      expect(registry.hasLazy('dashboard')).toBe(false); // bare key left alone
+    });
+
+    /**
+     * ⭐ Why the two doors give DIFFERENT advice, pinned as behaviour and not
+     * only as prose. `register` clears the bare stub unconditionally — outside
+     * the fallback branch — so telling that door's author to pass
+     * `skipFallback: true` would leave the bare key resolving to nothing at
+     * all. On the lazy door the same opt-out really does settle it.
+     */
+    it('skipFallback on the EAGER door does not preserve the stub\'s bare claim', () => {
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+      expect(registry.hasLazy('dashboard')).toBe(true);
+
+      registry.register('dashboard', () => 'view', { namespace: 'view', skipFallback: true });
+
+      // The bare key is now claimed by nobody: the stub was deleted anyway and
+      // the registration declined to take it.
+      expect(registry.hasLazy('dashboard')).toBe(false);
+      expect(registry.get('dashboard')).toBeUndefined();
+    });
+
+    it('each door prescribes the remedy that is true for it', () => {
+      registry.register('dashboard', () => 'view', { namespace: 'view' });
+      consoleWarnSpy.mockClear();
+      registry.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+      expect(collisionWarnings()[0]).toMatch(/skipFallback: true/);
+
+      const other = new Registry();
+      consoleWarnSpy.mockClear();
+      other.registerLazy('dashboard', loader, { namespace: 'plugin-dashboard' });
+      other.register('dashboard', () => 'view', { namespace: 'view' });
+      // ⛔ Not a wording preference: the eager door must not prescribe an
+      // opt-out that the test above shows does not settle the contest.
+      expect(collisionWarnings()[0]).toMatch(/does not\s+settle this one/);
+    });
+  });
 });