@@ -0,0 +1,10 @@
+---
+'@object-ui/app-shell': patch
+---
+
+fix(app-shell): the Studio item header's "Saved to X's customizations" note says where the customization lives, in the publish sheet's own sentence (#30436)
+
+Clause-②: no
+Metadata-protocol: none
+
+The note on an item header (Interfaces item, navigation editor, Data object, Automations flow) now goes on with the sentence the pending-changes sheet draws under it (`preview.changes.customizationEnvironment`, from #30119): the changes are kept in this environment's database as items of the real `<base>.custom` pair, and reach another environment only through `os package export`. No new i18n key: the note reuses `customizationEnvironmentText`. Before the pair's first save the note names the `<base>.custom` id that save creates.
@@ -46,8 +46,31 @@ export function customizationEnvironmentText(t: Translate, pairId: string): stri
   });
 }
 
-/** {@link savedToCustomizationText} as an element, for the Studio item header's note line. */
-export function SavedToCustomizationNote({ baseLabel, testId }: { baseLabel: string; testId?: string }) {
+/**
+ * {@link savedToCustomizationText} as an element, for the Studio item header's
+ * note line. Given the pair's id, it goes on with the pending-changes sheet's
+ * second sentence, {@link customizationEnvironmentText}, so the header and
+ * the sheet say the same words from the same keys (objectstack#30436).
+ */
+export function SavedToCustomizationNote({
+  baseLabel,
+  pairId,
+  testId,
+}: {
+  baseLabel: string;
+  /** The base's `<base>.custom` pair; nothing more is said without one. */
+  pairId?: string | null;
+  testId?: string;
+}) {
   const { t } = useObjectTranslation();
-  return <span data-testid={testId}>{savedToCustomizationText(t, baseLabel)}</span>;
+  return (
+    <>
+      <span data-testid={testId}>{savedToCustomizationText(t, baseLabel)}</span>
+      {pairId ? (
+        <span data-testid={testId ? `${testId}-environment` : undefined} className="block">
+          {customizationEnvironmentText(t, pairId)}
+        </span>
+      ) : null}
+    </>
+  );
 }
@@ -504,13 +504,18 @@ describe('Customize a read-only base’s flow into its pair (objectstack#28570)'
 describe('the flow header says where a customized flow is saved (objectstack#29691)', () => {
   const SAVED_TO = 'Saved to HotCRM’s customizations';
   const savedTo = () => within(header()).queryByTestId('auto-flow-saved-to');
+  // objectstack#30436 — and the sheet's second sentence, naming the real pair.
+  const ENVIRONMENT =
+    'These changes are kept in this environment’s database as items of com.example.hotcrm.custom, not in your project’s source. They reach another environment only through os package export.';
+  const environment = () => within(header()).queryByTestId('auto-flow-saved-to-environment');
 
   it('Customize unlocks the flow, and the header says it is saved to the base’s customizations', async () => {
     mount();
     await openFlow();
     expect(savedTo()).toBeNull();
     await customize();
     await waitFor(() => expect(savedTo()).toHaveTextContent(SAVED_TO), { timeout: 8000 });
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
     expect(savedTo()!.closest('[data-slot="item-note"]')).not.toBeNull();
   });
 
@@ -520,6 +525,7 @@ describe('the flow header says where a customized flow is saved (objectstack#296
     mount({ listedPair: PAIR });
     await openFlow(/^Notify owner and manager$/);
     await waitFor(() => expect(savedTo()).toHaveTextContent(SAVED_TO), { timeout: 8000 });
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
   });
 
   it('CONTROL: the base’s flow before Customize says nothing of the kind', async () => {
 
@@ -450,6 +450,11 @@ describe('A Chinese label names a base object\'s extension field by pinyin, suff
 describe('the object header says where a base object’s extension is saved (objectstack#29691)', () => {
   const SAVED_TO = 'Saved to HotCRM’s customizations';
   const savedTo = () => within(screen.getByTestId('data-object-header')).queryByTestId('data-object-saved-to');
+  // objectstack#30436 — and the sheet's second sentence, naming the real pair.
+  const ENVIRONMENT =
+    'These changes are kept in this environment’s database as items of com.example.hotcrm.custom, not in your project’s source. They reach another environment only through os package export.';
+  const environment = () =>
+    within(screen.getByTestId('data-object-header')).queryByTestId('data-object-saved-to-environment');
 
   it('the first add makes the extension, and the header says it is saved to the base’s customizations', async () => {
     await renderBase();
@@ -458,6 +463,7 @@ describe('the object header says where a base object’s extension is saved (obj
     await addFromFormToolbar('Region');
     await waitFor(() => expect(extensionSaves()).toHaveLength(1), { timeout: 8000 });
     await waitFor(() => expect(savedTo()).toHaveTextContent(SAVED_TO), { timeout: 8000 });
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
     expect(savedTo()!.closest('[data-slot="item-note"]')).not.toBeNull();
   });
 
@@ -467,6 +473,7 @@ describe('the object header says where a base object’s extension is saved (obj
     srv.publishedExt = { extend: OBJECT, fields: { region__c: region }, _packageId: PAIR };
     await renderBase();
     await waitFor(() => expect(savedTo()).toHaveTextContent(SAVED_TO), { timeout: 8000 });
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
   });
 
   it('CONTROL: a base object with no extension says nothing of the kind', async () => {
 
@@ -782,6 +782,10 @@ describe('Customize a read-only base’s navigation into its pair (objectstack#3
     await openPipeline();
     fireEvent.click(await within(rail()).findByTestId('if-edit-nav', undefined, { timeout: 8000 }));
     expect(await within(rail()).findByTestId('if-nav-saved-to')).toBeInTheDocument();
+    // objectstack#30436 — and the sheet's second sentence, naming the pair.
+    expect(within(rail()).getByTestId('if-nav-saved-to-environment')).toHaveTextContent(
+      'These changes are kept in this environment’s database as items of com.example.hotcrm.custom, not in your project’s source. They reach another environment only through os package export.',
+    );
     await sleep(1500);
     expect(srv.ensure).toEqual([]);
     expect(srv.saves).toEqual([]);
 
@@ -355,12 +355,18 @@ describe('the wall is read from what the server publishes (objectstack#28562)',
 describe('the item header says where the customization is saved (objectstack#29691)', () => {
   const SAVED_TO = 'Saved to HotCRM’s customizations';
   const savedTo = () => within(header()).queryByTestId('if-item-saved-to');
+  // objectstack#30436 — and the sheet's second sentence, naming the real pair.
+  const ENVIRONMENT =
+    'These changes are kept in this environment’s database as items of com.example.hotcrm.custom, not in your project’s source. They reach another environment only through os package export.';
+  const environment = () => within(header()).queryByTestId('if-item-saved-to-environment');
 
   it('after Customize the header says it, and after the first edit it still does, in the sheet’s own words', async () => {
     renderWorkbench();
     await openPipeline();
     fireEvent.click(await within(header()).findByTestId('studio-customize', undefined, { timeout: 8000 }));
     await waitFor(() => expect(savedTo()).toHaveTextContent(SAVED_TO), { timeout: 8000 });
+    // Before the first save the pair is the `<base>.custom` id that save creates.
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
     // On its own line under the title row, never in it (the fold measures the row).
     expect(savedTo()!.closest('[data-slot="item-note"]')).not.toBeNull();
     expect(within(header()).getByRole('heading', { level: 1 }).parentElement).not.toContainElement(savedTo());
@@ -369,6 +375,7 @@ describe('the item header says where the customization is saved (objectstack#296
     await waitFor(() => expect(srv.saves).toHaveLength(1), { timeout: 8000 });
     await waitFor(() => expect(panelPackage()).toBe(PAIR), { timeout: 8000 });
     expect(savedTo()).toHaveTextContent(SAVED_TO);
+    expect(environment()).toHaveTextContent(ENVIRONMENT);
     // The header line and the sheet line read the same.
     expect(screen.getByTestId('sheet-saved-to').textContent).toBe(savedTo()!.textContent);
   });
@@ -378,6 +385,7 @@ describe('the item header says where the customization is saved (objectstack#296
     await openPipeline();
     await within(header()).findByTestId('studio-customize', undefined, { timeout: 8000 });
     expect(savedTo()).toBeNull();
+    expect(environment()).toBeNull();
     expect(header().querySelector('[data-slot="item-note"]')).toBeNull();
     expect(screen.queryByTestId('sheet-saved-to')).toBeNull();
   });
 
@@ -2862,6 +2862,9 @@ export function InterfacesPillar({
   const customizeBase = customizing && customization ? customization.base : null;
   const customizePair = customizing && customization ? customization.pairId : null;
   const customizeBaseLabel = customization?.baseLabel ?? packageId;
+  // objectstack#30436 — the pair the "saved to" note names: the served one, or
+  // the `<base>.custom` id the first save creates.
+  const customizeNotePair = customization ? (customization.pairId ?? pairIdOf(customization.base)) : null;
   const customizeWalled = customizing && customization?.walled === true;
   const customizeBlock: CustomizeBlock = customizeWalled
     ? 'walled'
@@ -4235,7 +4238,7 @@ export function InterfacesPillar({
       // objectstack#29693 — on a narrow row the chips and the item tools fold
       // into the ⋯ menu before the title drops below its readable width.
       foldMenu={itemMoreEl ? 'pillar' : { label: t('engine.studio.if.more', locale), testId: 'if-item-header-more' }}
-      note={ifSavedTo ? <SavedToCustomizationNote baseLabel={customizeBaseLabel} testId="if-item-saved-to" /> : undefined}
+      note={ifSavedTo ? <SavedToCustomizationNote baseLabel={customizeBaseLabel} pairId={customizeNotePair} testId="if-item-saved-to" /> : undefined}
       leading={
         <button
           type="button"
@@ -5139,7 +5142,7 @@ export function InterfacesPillar({
           {/* objectstack#30059 — where a read-only base's navigation edit is saved. */}
           {editNav && readOnly && (
             <p className="mt-1 text-[10px] text-muted-foreground">
-              <SavedToCustomizationNote baseLabel={customizeBaseLabel} testId="if-nav-saved-to" />
+              <SavedToCustomizationNote baseLabel={customizeBaseLabel} pairId={customizeNotePair} testId="if-nav-saved-to" />
             </p>
           )}
             {listOnlyCustomized && !editNav && !navMarked ? null : appStatus === 'missing' && !error ? (
@@ -7003,6 +7006,7 @@ export function DataPillar({
                 (extOpen !== null && (extOpen.published.size > 0 || extHasDraft || extDirty))) ? (
                 <SavedToCustomizationNote
                   baseLabel={customization.baseLabel}
+                  pairId={customization.pairId ?? pairIdOf(customization.base)}
                   testId="data-object-saved-to"
                 />
               ) : undefined
@@ -7807,6 +7811,8 @@ export function AutomationsPillar({
   const customizeBase = flowCustomizing && customization ? customization.base : null;
   const customizePair = flowCustomizing && customization ? customization.pairId : null;
   const customizeBaseLabel = customization?.baseLabel ?? railPackageId ?? '';
+  // objectstack#30436 — the pair the "saved to" note names.
+  const customizeNotePair = customization ? (customization.pairId ?? pairIdOf(customization.base)) : null;
   const customizeWalled = flowCustomizing && customization?.walled === true;
   const customizeBlock: CustomizeBlock = customizeWalled
     ? 'walled'
@@ -9053,7 +9059,7 @@ export function AutomationsPillar({
             // or is unlocked to customize saves to the base's pair.
             note={
               customization !== null && (!!current?.addedIn || flowInPair || flowUnlocked) ? (
-                <SavedToCustomizationNote baseLabel={customizeBaseLabel} testId="auto-flow-saved-to" />
+                <SavedToCustomizationNote baseLabel={customizeBaseLabel} pairId={customizeNotePair} testId="auto-flow-saved-to" />
               ) : undefined
             }
             leading={