diff --git a/demo/golden/baselines/baselines-index.json b/demo/golden/baselines/baselines-index.json
index c6103099..95fcec0f 100644
--- a/demo/golden/baselines/baselines-index.json
+++ b/demo/golden/baselines/baselines-index.json
@@ -1,11 +1,12 @@
 {
   "schema": 1,
   "matrixVersion": 54,
-  "acceptedAt": "2026-09-04T13:10:56.492Z",
-  "sourceFingerprint": "7acb1b9d3bb384bc1a0c70fb01347386c157ae88b12b00ccd876b7658fc84a1c",
+  "acceptedAt": "2026-09-05T06:21:56.683Z",
+  "sourceFingerprint": "814851e1e157fd126309de061c720fb1203ddd6d63824cd37289542baefca406",
   "chromium": "151.0.7922.34",
+  "platform": "linux",
   "witnesses": {
-    "count": 127,
+    "count": 134,
     "floor": 10
   },
   "scenarios": {
@@ -152,7 +153,7 @@
     "support-relay-error-light-en": "e9a9ad906e106eedfa6e84c592325f1604eb64c89c51135c076ac87a6a0766b2",
     "support-tablet-preview-dark-ru": "1264e005cd764408edb9b285a5dfbe92ceb90cb925f624b8f65cd47edb96c0c9",
     "device-ripple-color-popover-mobile-ru": "d9ebf83ad0d2995b46f6174daf6e21ca5404952afa308ddd3a66ecefcee565d0",
-    "space-room-color-popover-desktop-ru": "9bbbcf9c5ea6ff5490b500be8cb3086af9d368d14ca50c304f42a697e296ece1",
+    "space-room-color-popover-desktop-ru": "04bf325ddb449001f6c0b459761dcb84eda6432dca2fbd10ce5a129484d0756c",
     "backup-full-preview-desktop-en": "0fbd23a92121668001faf5c9ed555a31107704f3074d1791709c8436517d3d1f",
     "backup-plan-only-export-desktop-en": "ce66fb57edbc87d56355b0d73a2d4203a67c275d5927d400ef1758ac0b607b34",
     "backup-space-preview-mobile-ru": "82cd93cb495ad77b92d635b4a3715601b1ae0e5e2974edcbbd461fe872c75bad",
diff --git a/demo/golden/baselines/space-room-color-popover-desktop-ru.png b/demo/golden/baselines/space-room-color-popover-desktop-ru.png
index b1711b60..df337c55 100644
Binary files a/demo/golden/baselines/space-room-color-popover-desktop-ru.png and b/demo/golden/baselines/space-room-color-popover-desktop-ru.png differ
diff --git a/demo/smoke_space_copy.mjs b/demo/smoke_space_copy.mjs
new file mode 100644
index 00000000..0b62a761
--- /dev/null
+++ b/demo/smoke_space_copy.mjs
@@ -0,0 +1,141 @@
+// #456: Copy is a real two-write workflow when the plan needs Optimize and a
+// one-write workflow when it does not. Exercise the production bundle through
+// the visible dialogs while delegating every request to the demo backend.
+import { launch, checkAll, finish } from './serve.mjs';
+
+const { page, browser } = await launch({ width: 820, height: 780 });
+const out = await page.evaluate(async () => {
+  const result = {};
+  const card = window.__card;
+  const root = () => card.shadowRoot || card.renderRoot;
+  const clone = (value) => structuredClone(value);
+  const settle = async () => {
+    await card.updateComplete;
+    await new Promise((resolve) => requestAnimationFrame(() => requestAnimationFrame(resolve)));
+  };
+  const waitFor = async (predicate, label) => {
+    for (let attempt = 0; attempt < 120; attempt++) {
+      await settle();
+      if (predicate()) return;
+      await new Promise((resolve) => setTimeout(resolve, 10));
+    }
+    throw new Error(`space-copy smoke timed out: ${label}`);
+  };
+  const currentDialog = () => root().querySelector('hp-dialog');
+  const buttonWithIcon = (dialog, icon) => [...(dialog?.querySelectorAll('button') || [])]
+    .find((button) => button.querySelector(`ha-icon[icon="${icon}"]`));
+  const openCopy = async () => {
+    card._openSpaceDialog('edit', 'f1');
+    await settle();
+    const settingsDialog = currentDialog();
+    const button = buttonWithIcon(settingsDialog, 'mdi:content-copy');
+    const outsideDanger = !!button && !button.closest('.dialog-action-danger');
+    button?.click();
+    await waitFor(() => !!card._spaceDialog?.copy, 'copy name dialog');
+    const copyDialog = currentDialog();
+    return { outsideDanger, copyDialog };
+  };
+  const nameCopy = async (dialog, title) => {
+    const input = dialog?.querySelector('#space-copy-name');
+    if (input) {
+      input.value = title;
+      input.dispatchEvent(new Event('input', { bubbles: true, composed: true }));
+    }
+    await settle();
+    return input;
+  };
+  const submitCopy = (dialog) => buttonWithIcon(dialog, 'mdi:content-copy')?.click();
+  const confirmUi = () => {
+    const component = root().querySelector('hp-confirm');
+    const dialog = component?.querySelector('hp-dialog');
+    return {
+      component,
+      dialog,
+      buttons: [...(dialog?.querySelectorAll('.danger-confirm-footer button') || [])],
+    };
+  };
+
+  const baseCall = card.hass.callWS.bind(card.hass);
+  const calls = [];
+  card.hass = {
+    ...card.hass,
+    callWS: async (message) => {
+      calls.push(clone(message));
+      return baseCall(message);
+    },
+  };
+  await settle();
+
+  // The demo's original f1 needs Optimize. Cancel must leave the name dialog
+  // intact and must not make either durable write.
+  const cancelStart = calls.length;
+  const cancel = await openCopy();
+  const proposedName = cancel.copyDialog?.querySelector('#space-copy-name')?.value || '';
+  await nameCopy(cancel.copyDialog, 'Cancelled copy');
+  submitCopy(cancel.copyDialog);
+  await waitFor(() => confirmUi().buttons.length === 2, 'Optimize warning for Cancel');
+  const cancelWarning = confirmUi();
+  const warningText = cancelWarning.dialog?.textContent || '';
+  cancelWarning.buttons[0].click();
+  await waitFor(() => !confirmUi().component && card._spaceDialog?.copy?.busy === false,
+    'Cancel returns to name');
+  const cancelWrites = calls.slice(cancelStart)
+    .filter((call) => call.type === 'houseplan/plan/optimize'
+      || call.type === 'houseplan/config/set');
+  result.copyButtonIsNeutralAndDefaultNameIsNumbered = cancel.outsideDanger
+    && proposedName.endsWith(' (2)');
+  result.optimizeWarningNamesTheWholePlan = warningText.includes('entire plan')
+    && warningText.includes('including other spaces');
+  result.optimizeCancelMakesZeroWritesAndKeepsName = cancelWrites.length === 0
+    && card._spaceDialog?.copy?.title === 'Cancelled copy';
+  card._spaceDialog = null;
+  await settle();
+
+  // Accept uses the real demo backend in the promised order and enters the
+  // roomless copy after both writes succeed.
+  const acceptStart = calls.length;
+  const accepted = await openCopy();
+  await nameCopy(accepted.copyDialog, 'Optimized copy');
+  submitCopy(accepted.copyDialog);
+  await waitFor(() => confirmUi().buttons.length === 2, 'Optimize warning for Accept');
+  confirmUi().buttons[1].click();
+  await waitFor(() => card._spaceDialog === null && card._space !== 'f1',
+    'accepted copy transition');
+  const acceptedCalls = calls.slice(acceptStart)
+    .filter((call) => call.type === 'houseplan/plan/optimize'
+      || call.type === 'houseplan/config/set');
+  const optimizedCopy = card._serverCfg.spaces.find((space) => space.title === 'Optimized copy');
+  result.optimizeAcceptWritesInOrder = acceptedCalls.length === 2
+    && acceptedCalls[0].type === 'houseplan/plan/optimize'
+    && acceptedCalls[1].type === 'houseplan/config/set';
+  result.acceptCreatesAndEntersRoomlessCopy = !!optimizedCopy
+    && optimizedCopy.id === card._space
+    && optimizedCopy.rooms?.length === 0
+    && optimizedCopy.wall_segments?.length === 0
+    && optimizedCopy.partitions?.length > 0
+    && card._mode === 'plan' && card._tool === 'draw';
+
+  // The accepted config is now optimized. Submitting a second name is itself
+  // the only confirmation and produces exactly one config write.
+  card._commitSpace('f1', true);
+  await settle();
+  const cleanStart = calls.length;
+  const clean = await openCopy();
+  await nameCopy(clean.copyDialog, 'Clean copy');
+  submitCopy(clean.copyDialog);
+  await waitFor(() => card._spaceDialog === null && card._space !== 'f1',
+    'clean copy transition');
+  const cleanCalls = calls.slice(cleanStart)
+    .filter((call) => call.type === 'houseplan/plan/optimize'
+      || call.type === 'houseplan/config/set');
+  const cleanCopy = card._serverCfg.spaces.find((space) => space.title === 'Clean copy');
+  result.cleanCopyNeedsNoExtraConfirmation = !confirmUi().component
+    && cleanCalls.length === 1 && cleanCalls[0].type === 'houseplan/config/set';
+  result.cleanCopyIsInsertedAfterSourceAndSelected = !!cleanCopy
+    && card._serverCfg.spaces[1]?.id === cleanCopy.id
+    && card._space === cleanCopy.id;
+  return result;
+});
+
+checkAll(out);
+await finish(browser, out);