diff --git a/craft/src/editor/LoadGate.save-guard.test.tsx b/craft/src/editor/LoadGate.save-guard.test.tsx
index 7d0d127..4c6d67a 100644
--- a/craft/src/editor/LoadGate.save-guard.test.tsx
+++ b/craft/src/editor/LoadGate.save-guard.test.tsx
@@ -30,7 +30,7 @@ import { LoadGate } from './LoadGate';
 import { TopBar } from '../panels/topbar/TopBar';
 import { SiteDesignPanel } from '../panels/right/SiteDesignPanel';
 import { EditorConfigProvider } from '../state/EditorConfigContext';
-import { SaveGuardProvider } from '../state/SaveGuardContext';
+import { SaveGuardProvider, useSaveGuard } from '../state/SaveGuardContext';
 import { PageProvider } from '../state/PageContext';
 import { SiteDesignProvider } from '../state/SiteDesignContext';
 import { WhpConfig } from '../types';
@@ -55,6 +55,9 @@ const saveBody = (i: number) => JSON.parse(saveCalls()[i][1].body);
 const q = (sel: string) => container.querySelector(sel) as HTMLElement | null;
 const flush = () => act(async () => { await Promise.resolve(); await Promise.resolve(); });
 
+let guard: ReturnType<typeof useSaveGuard>;
+const GuardProbe: React.FC = () => { guard = useSaveGuard(); return null; };
+
 function mount() {
   container = document.createElement('div');
   document.body.appendChild(container);
@@ -68,6 +71,7 @@ function mount() {
               <LoadGate />
               <TopBar device="desktop" onDeviceChange={() => {}} showGuides onToggleGuides={() => {}} />
               <SiteDesignPanel />
+              <GuardProbe />
             </PageProvider>
           </SiteDesignProvider>
         </SaveGuardProvider>
@@ -179,6 +183,8 @@ describe('load gate', () => {
     mount();
     await flush();
     expect(q('[data-testid="load-gate"]')).toBeNull();
+    // Autosave only fires for unsaved changes.
+    act(() => { guard.markDirty(); });
     await act(async () => { vi.advanceTimersByTime(30000); });
     expect(saveCalls()).toHaveLength(1);
   });
diff --git a/craft/src/editor/SaveState.test.tsx b/craft/src/editor/SaveState.test.tsx
index 2d62ee1..2707418 100644
--- a/craft/src/editor/SaveState.test.tsx
+++ b/craft/src/editor/SaveState.test.tsx
@@ -203,13 +203,39 @@ describe('dirty lifecycle and status pill', () => {
   });
 });
 
-describe('Draft badge', () => {
-  test('a no-op autosave does not flip the badge to Draft; a save after real changes does', async () => {
+describe('autosave only when dirty', () => {
+  test('an idle 30s tick makes no request; an edit makes exactly one on the next tick', async () => {
     respondWith({});
     await mount();
+    await act(async () => { vi.advanceTimersByTime(90_000); });
+    await flush();
+    expect(calls('save')).toHaveLength(0);
+
+    edit();
     await act(async () => { vi.advanceTimersByTime(30_000); });
     await flush();
     expect(calls('save')).toHaveLength(1);
+
+    // Saved and clean again: later ticks stay quiet.
+    await act(async () => { vi.advanceTimersByTime(60_000); });
+    await flush();
+    expect(calls('save')).toHaveLength(1);
+  });
+
+  test('the Save button still saves a clean editor', async () => {
+    respondWith({});
+    await mount();
+    await clickSave();
+    expect(calls('save')).toHaveLength(1);
+  });
+});
+
+describe('Draft badge', () => {
+  test('a manual save with nothing changed does not flip the badge to Draft; a save after real changes does', async () => {
+    respondWith({});
+    await mount();
+    await clickSave();
+    expect(calls('save')).toHaveLength(1);
     expect(q('.publish-badge.draft')).toBeNull();
 
     edit();
diff --git a/craft/src/hooks/useWhpApi.export-cache.test.ts b/craft/src/hooks/useWhpApi.export-cache.test.ts
new file mode 100644
index 0000000..4c2db7d
--- /dev/null
+++ b/craft/src/hooks/useWhpApi.export-cache.test.ts
@@ -0,0 +1,83 @@
+import { describe, test, expect, vi, beforeEach } from 'vitest';
+
+vi.mock('../utils/html-export', () => ({
+  exportBodyHtml: vi.fn((state: string) => {
+    if (state.startsWith('BAD')) throw new Error('export boom');
+    return { html: `<p>${state}</p>`, css: `/*${state}*/` };
+  }),
+}));
+
+import { exportBodyHtml } from '../utils/html-export';
+import { buildSavePayload, clearExportCache } from './useWhpApi';
+import { PageData } from '../types';
+import { DEFAULT_SITE_DESIGN } from '../state/SiteDesignContext';
+
+const spy = vi.mocked(exportBodyHtml);
+const page = (id: string, craftState: string | null): PageData => ({ id, name: id, slug: id, craftState });
+const header = page('__header__', 'H1');
+const footer = page('__footer__', 'F1');
+
+function build(pages: PageData[], live: string, activePageId = pages[0].id, h = header, f = footer) {
+  return buildSavePayload({
+    siteId: 1, siteName: 's', liveCraftState: live, pages, headerPage: h, footerPage: f,
+    activePageId, isEditingHeader: false, isEditingFooter: false,
+    headCode: DEFAULT_SITE_DESIGN.headCode, design: DEFAULT_SITE_DESIGN,
+  });
+}
+const exported = () => spy.mock.calls.map(([s]) => s);
+
+beforeEach(() => {
+  clearExportCache();
+  spy.mockClear();
+  vi.spyOn(console, 'error').mockImplementation(() => {});
+});
+
+describe('buildSavePayload export memoisation', () => {
+  test('an identical second build only re-exports the live canvas page', () => {
+    const pages = [page('home', 'HOME'), page('a', 'A'), page('b', 'B')];
+    build(pages, 'LIVE1');
+    expect(exported().sort()).toEqual(['A', 'B', 'F1', 'H1', 'LIVE1']);
+    spy.mockClear();
+    const p = build(pages, 'LIVE2');
+    expect(exported()).toEqual(['LIVE2']);
+    expect(p.pages.map((x) => x.html)).toEqual(['<p>LIVE2</p>', '<p>A</p>', '<p>B</p>']);
+  });
+
+  test('only the page whose state changed is re-exported', () => {
+    const pages = [page('home', 'HOME'), page('a', 'A'), page('b', 'B')];
+    build(pages, 'LIVE');
+    spy.mockClear();
+    const p = build([pages[0], page('a', 'A2'), pages[2]], 'LIVE');
+    expect(exported().sort()).toEqual(['A2', 'LIVE']);
+    expect(p.pages[1].html).toBe('<p>A2</p>');
+    expect(p.pages[2].html).toBe('<p>B</p>');
+  });
+
+  test('header and footer are memoised the same way', () => {
+    const pages = [page('home', 'HOME')];
+    build(pages, 'LIVE');
+    spy.mockClear();
+    const p = build(pages, 'LIVE', 'home', page('__header__', 'H2'));
+    expect(exported().sort()).toEqual(['H2', 'LIVE']);
+    expect(p.header_html).toBe('<p>H2</p>');
+    expect(p.footer_html).toBe('<p>F1</p>');
+  });
+
+  test('a failed export is not cached and is retried on the next build', () => {
+    const pages = [page('home', 'HOME'), page('x', 'BAD1')];
+    const first = build(pages, 'LIVE');
+    expect(first.pages[1].html).toBe('');
+    spy.mockClear();
+    build(pages, 'LIVE');
+    expect(exported()).toContain('BAD1');
+  });
+
+  test('a deleted page is evicted, so re-adding its state exports again', () => {
+    const pages = [page('home', 'HOME'), page('a', 'A')];
+    build(pages, 'LIVE');
+    build([pages[0]], 'LIVE');
+    spy.mockClear();
+    build(pages, 'LIVE');
+    expect(exported()).toContain('A');
+  });
+});
diff --git a/craft/src/hooks/useWhpApi.ts b/craft/src/hooks/useWhpApi.ts
index b830408..873c65d 100644
--- a/craft/src/hooks/useWhpApi.ts
+++ b/craft/src/hooks/useWhpApi.ts
@@ -8,6 +8,20 @@ import { repairOrphanNodes } from '../utils/orphan-repair';
 import { PageData } from '../types';
 import { useSaveGuard } from '../state/SaveGuardContext';
 
+/**
+ * Per-state export memo. A craft-state string fully determines its exported
+ * HTML/CSS, so unchanged pages skip the export on every autosave. Only
+ * stored (non-live) states are cached, failures never are, and each build
+ * evicts every entry it did not use, so deleted/edited pages cannot pile up.
+ */
+type ExportResult = ReturnType<typeof exportBodyHtml>;
+const exportCache = new Map<string, ExportResult>();
+
+/** Test hook: forget every memoised export. */
+export function clearExportCache() {
+  exportCache.clear();
+}
+
 export interface BuildSavePayloadInput {
   siteId: number;
   siteName: string;
@@ -58,6 +72,18 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
 
   const isPageActive = !isEditingHeader && !isEditingFooter;
 
+  // Stored states touched by this build; the cache is pruned to this set.
+  const usedStates = new Set<string>();
+  /** Export a stored (not live) state, reusing the memo. Throws like exportBodyHtml. */
+  const exportStored = (state: string): ExportResult => {
+    usedStates.add(state);
+    const hit = exportCache.get(state);
+    if (hit) return hit;
+    const result = exportBodyHtml(state);
+    exportCache.set(state, result);
+    return result;
+  };
+
   // I-1 (data-loss): `activePageId` can go dangling -- e.g. the original
   // Home page (id 'home') is deleted, its replacement gets a fresh id
   // (`page_<ts>`), and a reload re-initializes `activePageId` back to the
@@ -79,7 +105,7 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
   let headerHtml = '';
   try {
     if (headerCraftState) {
-      headerHtml = exportBodyHtml(headerCraftState).html;
+      headerHtml = (isEditingHeader ? exportBodyHtml(headerCraftState) : exportStored(headerCraftState)).html;
     }
   } catch (e) {
     console.error('Header HTML export failed:', e);
@@ -88,7 +114,7 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
   let footerHtml = '';
   try {
     if (footerCraftState) {
-      footerHtml = exportBodyHtml(footerCraftState).html;
+      footerHtml = (isEditingFooter ? exportBodyHtml(footerCraftState) : exportStored(footerCraftState)).html;
     }
   } catch (e) {
     console.error('Footer HTML export failed:', e);
@@ -117,7 +143,7 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
     currentCraftState = landingPage?.craftState ?? null;
     try {
       if (currentCraftState) {
-        const result = exportBodyHtml(currentCraftState);
+        const result = exportStored(currentCraftState);
         currentHtml = result.html;
         css = result.css;
       }
@@ -141,7 +167,7 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
       pageHtml = currentHtml;
     } else if (page.craftState) {
       try {
-        pageHtml = exportBodyHtml(page.craftState).html;
+        pageHtml = exportStored(page.craftState).html;
       } catch (e) {
         console.error(`HTML export failed for page ${page.name}:`, e);
       }
@@ -179,6 +205,10 @@ export function buildSavePayload(input: BuildSavePayloadInput) {
     seo: page.seo,
   }));
 
+  for (const key of exportCache.keys()) {
+    if (!usedStates.has(key)) exportCache.delete(key);
+  }
+
   return {
     site_id: siteId,
     name: siteName,
diff --git a/craft/src/panels/topbar/TopBar.tsx b/craft/src/panels/topbar/TopBar.tsx
index 377e270..404021b 100644
--- a/craft/src/panels/topbar/TopBar.tsx
+++ b/craft/src/panels/topbar/TopBar.tsx
@@ -106,9 +106,11 @@ export const TopBar: React.FC<TopBarProps> = ({ device, onDeviceChange, showGuid
     // Paused until the site has loaded, and while the empty-save banner is up.
     if (!isWHP || !canSave || emptyRefusal) return;
     // A running publish does its own save; a second one would race it.
-    const interval = setInterval(() => { if (!publishingRef.current) void runSave(); }, 30000);
+    // Read through refs/isDirty() at tick time, never a stale closure.
+    const autosaveDue = () => isDirty() && !publishingRef.current;
+    const interval = setInterval(() => { if (autosaveDue()) void runSave(); }, 30000);
     return () => clearInterval(interval);
-  }, [isWHP, canSave, emptyRefusal, runSave]);
+  }, [isWHP, canSave, emptyRefusal, runSave, isDirty]);
 
   const handleSave = runSave;