diff --git a/apps/desktop/src/components/ai/rich/AiHtmlPreview.vue b/apps/desktop/src/components/ai/rich/AiHtmlPreview.vue
new file mode 100644
index 0000000000..da900c8ed5
--- /dev/null
+++ b/apps/desktop/src/components/ai/rich/AiHtmlPreview.vue
@@ -0,0 +1,141 @@
+<script setup lang="ts">
+import { ref } from "vue";
+import { AlertTriangle, Check, Copy, Download, Maximize2 } from "@lucide/vue";
+import { useI18n } from "vue-i18n";
+import { useToast } from "@/composables/useToast";
+import { copyToClipboard } from "@/lib/common/clipboard";
+import { saveTextFile } from "@/lib/export/saveTextFile";
+import { Dialog, DialogContent, DialogDescription, DialogHeader, DialogTitle } from "@/components/ui/dialog";
+import { acknowledgeAiHtmlCopyRisk, isAiHtmlCopyRiskAcknowledged } from "@/lib/ai/richContent/aiHtmlPreview";
+
+const props = defineProps<{
+  /** Raw AI html fence body — what "copy source" puts on the clipboard. */
+  content: string;
+  /** `buildSafeHtmlPreview(content)` — shown in the iframe and written by "Save Safe HTML". */
+  document: string;
+}>();
+
+const { t } = useI18n();
+const { toast } = useToast();
+const copied = ref(false);
+const previewExpanded = ref(false);
+// Inline confirmation instead of a modal: the first copy attempt arms the risk
+// strip; confirming copies (optionally remembering the choice for the
+// session), canceling keeps the clipboard untouched.
+const showCopyConfirm = ref(false);
+const rememberChoice = ref(false);
+
+function copySource() {
+  if (!isAiHtmlCopyRiskAcknowledged()) {
+    showCopyConfirm.value = true;
+    return;
+  }
+  void warnAfterCopy();
+}
+
+// Later copies skip the confirmation but keep a visible risk reminder — only
+// when the copy actually succeeded.
+async function warnAfterCopy() {
+  if (await doCopy()) toast(t("ai.htmlCopyRiskToast"));
+}
+
+function confirmCopy() {
+  if (rememberChoice.value) acknowledgeAiHtmlCopyRisk();
+  showCopyConfirm.value = false;
+  void doCopy();
+}
+
+function cancelCopy() {
+  showCopyConfirm.value = false;
+  rememberChoice.value = false;
+}
+
+async function doCopy(): Promise<boolean> {
+  try {
+    await copyToClipboard(props.content);
+    copied.value = true;
+    window.setTimeout(() => (copied.value = false), 1600);
+    return true;
+  } catch {
+    // The raw AI HTML is the sensitive payload: do not cover up a clipboard
+    // failure with a success-looking toast, and keep the preview usable if
+    // the host denies clipboard access.
+    return false;
+  }
+}
+
+// Saves the WRAPPED safe document (inlined CSP), never the raw source: even
+// once the file is opened outside the iframe sandbox the CSP still blocks
+// scripts and network access.
+async function saveSafeHtml() {
+  try {
+    await saveTextFile(props.document, "dbx-ai-html-preview.html", "HTML", "html");
+  } catch {
+    toast(t("ai.htmlSaveFailed"));
+  }
+}
+</script>
+
+<template>
+  <!-- `sandbox=""` is the strongest sandbox: no allow-scripts (nothing executes),
+       no allow-same-origin (no origin/cookie/storage access), no forms or
+       popups. The `srcdoc` is the CSP-wrapped standalone document — identical
+       bytes to the "Save Safe HTML" payload, so what is previewed is exactly
+       what gets saved. -->
+  <section class="my-2 flex min-h-60 h-[clamp(15rem,35vw,20rem)] flex-col overflow-hidden rounded-md border border-zinc-200 bg-zinc-50 dark:border-zinc-700/50 dark:bg-zinc-900" :aria-label="t('ai.htmlPreviewLabel')">
+    <div class="flex h-8 items-center justify-end gap-1 border-b border-zinc-200 px-2 dark:border-zinc-700/50">
+      <button type="button" class="mr-auto rounded p-1 text-zinc-500 hover:bg-zinc-200 hover:text-zinc-900 dark:text-zinc-400 dark:hover:bg-zinc-700 dark:hover:text-zinc-100" :title="t('ai.htmlExpandPreview')" :aria-label="t('ai.htmlExpandPreview')" @click="previewExpanded = true">
+        <Maximize2 class="h-3.5 w-3.5" />
+      </button>
+      <button
+        type="button"
+        class="rounded p-1 text-zinc-500 hover:bg-zinc-200 hover:text-zinc-900 dark:text-zinc-400 dark:hover:bg-zinc-700 dark:hover:text-zinc-100"
+        :title="copied ? t('ai.copied') : t('ai.htmlCopySource')"
+        :aria-label="copied ? t('ai.copied') : t('ai.htmlCopySource')"
+        @click="copySource"
+      >
+        <Check v-if="copied" class="h-3.5 w-3.5 text-green-500" />
+        <Copy v-else class="h-3.5 w-3.5" />
+      </button>
+      <button type="button" class="rounded p-1 text-zinc-500 hover:bg-zinc-200 hover:text-zinc-900 dark:text-zinc-400 dark:hover:bg-zinc-700 dark:hover:text-zinc-100" :title="t('ai.htmlSaveSafe')" :aria-label="t('ai.htmlSaveSafe')" @click="saveSafeHtml">
+        <Download class="h-3.5 w-3.5" />
+      </button>
+    </div>
+    <div v-if="showCopyConfirm" class="flex items-start gap-2 border-b border-amber-300 bg-amber-50 px-3 py-2 text-xs text-amber-900 dark:border-amber-500/40 dark:bg-amber-500/10 dark:text-amber-200" role="alertdialog" :aria-label="t('ai.htmlCopySource')">
+      <AlertTriangle class="mt-0.5 h-3.5 w-3.5 shrink-0" aria-hidden="true" />
+      <div class="min-w-0 flex-1">
+        <p class="leading-snug">{{ t("ai.htmlCopyRiskBody") }}</p>
+        <div class="mt-1.5 flex flex-wrap items-center gap-2">
+          <label class="flex items-center gap-1 select-none">
+            <input v-model="rememberChoice" type="checkbox" class="h-3 w-3 accent-amber-600" />
+            <span>{{ t("ai.htmlCopyRiskRemember") }}</span>
+          </label>
+          <span class="flex-1" />
+          <button type="button" class="rounded border border-amber-400 px-2 py-0.5 hover:bg-amber-100 dark:border-amber-500/50 dark:hover:bg-amber-500/20" @click="cancelCopy">{{ t("common.cancel") }}</button>
+          <button type="button" class="rounded bg-amber-600 px-2 py-0.5 font-medium text-white hover:bg-amber-700" @click="confirmCopy">{{ t("ai.htmlCopyRiskAccept") }}</button>
+        </div>
+      </div>
+    </div>
+    <div class="min-h-0 flex-1">
+      <iframe sandbox="" :srcdoc="document" class="h-full w-full bg-white" :title="t('ai.htmlPreviewLabel')" />
+    </div>
+  </section>
+
+  <!-- The expanded dialog renders the SAME sandboxed document as the inline
+       card — identical `sandbox=""` and the identical CSP-wrapped `srcdoc`
+       bytes. This is pure UX magnification: the zero-trust boundary does not
+       change, there is no path here that hands raw HTML to the OS browser. -->
+  <Dialog :open="previewExpanded" @update:open="previewExpanded = $event">
+    <!-- Match other large dialogs: override DialogContent's 384px default at
+         every breakpoint while keeping 16px viewport gutters. -->
+    <DialogContent class="max-w-[min(1100px,calc(100vw-32px))] flex h-[85vh] flex-col">
+      <DialogHeader class="shrink-0">
+        <DialogTitle>{{ t("ai.htmlPreviewLabel") }}</DialogTitle>
+        <DialogDescription>{{ t("ai.htmlExpandPreviewHint") }}</DialogDescription>
+      </DialogHeader>
+      <div class="min-h-0 flex-1">
+        <iframe sandbox="" :srcdoc="document" class="h-full w-full bg-white" :title="t('ai.htmlPreviewLabel')" />
+      </div>
+    </DialogContent>
+  </Dialog>
+</template>
diff --git a/apps/desktop/src/components/ai/rich/__tests__/AiHtmlPreview.spec.ts b/apps/desktop/src/components/ai/rich/__tests__/AiHtmlPreview.spec.ts
new file mode 100644
index 0000000000..d50c7109dd
--- /dev/null
+++ b/apps/desktop/src/components/ai/rich/__tests__/AiHtmlPreview.spec.ts
@@ -0,0 +1,218 @@
+// @vitest-environment happy-dom
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => ({
+  copyToClipboard: vi.fn().mockResolvedValue(undefined),
+  saveTextFile: vi.fn().mockResolvedValue(undefined),
+  toast: vi.fn(),
+}));
+
+vi.mock("vue-i18n", () => ({ useI18n: () => ({ t: (key: string) => key }) }));
+vi.mock("@/composables/useToast", () => ({ useToast: () => ({ toast: mocks.toast }) }));
+vi.mock("@/lib/common/clipboard", () => ({ copyToClipboard: mocks.copyToClipboard }));
+vi.mock("@/lib/export/saveTextFile", () => ({ saveTextFile: mocks.saveTextFile }));
+
+// The real Dialog portals its content only while open; we stub it as a
+// transparent DOM passthrough that mirrors that gating (slot only rendered when
+// `open` is true) and that closes through Vue's emit mechanism when clicked.
+// This mirrors the CodeSnapshotDialog.spec.ts stub approach.
+vi.mock("@/components/ui/dialog", async () => {
+  const { defineComponent, h } = await import("vue");
+  const passthrough = defineComponent({
+    setup(_props, { slots }) {
+      return () => h("div", slots.default?.());
+    },
+  });
+  return {
+    Dialog: defineComponent({
+      props: { open: Boolean },
+      emits: ["update:open"],
+      setup(props, { emit, slots }) {
+        return () => h("div", { "data-open": String(props.open), onClick: () => emit("update:open", false) }, props.open ? slots.default?.() : undefined);
+      },
+    }),
+    DialogContent: passthrough,
+    DialogHeader: passthrough,
+    DialogTitle: defineComponent({
+      setup(_props, { slots }) {
+        return () => h("div", { "data-slot": "dialog-title" }, slots.default?.());
+      },
+    }),
+    DialogDescription: passthrough,
+  };
+});
+
+import { buildSafeHtmlPreview } from "@/lib/ai/richContent/aiHtmlPreview";
+import type { App } from "vue";
+import { createApp, nextTick } from "vue";
+
+const content = "<p>Hello <strong>world</strong></p>";
+const documentHtml = buildSafeHtmlPreview(content);
+
+let app: App<Element> | null = null;
+let root: HTMLDivElement | null = null;
+
+async function mountPreview() {
+  // Dynamic import after resetModules so each test starts with a fresh copy-risk session state.
+  const { default: AiHtmlPreview } = await import("@/components/ai/rich/AiHtmlPreview.vue");
+  app = createApp(AiHtmlPreview, { content, document: documentHtml });
+  root = window.document.createElement("div");
+  window.document.body.appendChild(root);
+  app.mount(root);
+  await nextTick();
+  await nextTick();
+}
+
+function unmount() {
+  app?.unmount();
+  app = null;
+  root?.remove();
+  root = null;
+}
+
+function button(title: string): HTMLButtonElement | null {
+  return root?.querySelector(`button[aria-label="${title}"]`) ?? null;
+}
+
+function copyButton() {
+  return button("ai.htmlCopySource");
+}
+
+function confirmStrip(): Element | null {
+  return root?.querySelector('[role="alertdialog"]') ?? null;
+}
+
+async function click(element: HTMLElement | null) {
+  element?.dispatchEvent(new window.Event("click", { bubbles: true }));
+  await nextTick();
+  await nextTick();
+}
+
+beforeEach(() => {
+  vi.resetModules();
+  mocks.copyToClipboard.mockClear();
+  mocks.saveTextFile.mockClear();
+  mocks.toast.mockClear();
+  unmount();
+});
+
+describe("AiHtmlPreview", () => {
+  it("renders a fully sandboxed iframe over the CSP-wrapped document", async () => {
+    await mountPreview();
+    const iframe = root?.querySelector("iframe");
+    expect(iframe).not.toBeNull();
+    // `sandbox=""` without allow-scripts / allow-same-origin: nothing may execute.
+    expect(iframe?.getAttribute("sandbox")).toBe("");
+    const srcdoc = iframe?.getAttribute("srcdoc") ?? "";
+    expect(srcdoc).toContain("Content-Security-Policy");
+    expect(srcdoc).toContain("default-src 'none'");
+    expect(srcdoc).toContain(content);
+  });
+
+  it("asks before the first source copy and cancel keeps the clipboard untouched", async () => {
+    await mountPreview();
+    await click(copyButton());
+    expect(confirmStrip()).not.toBeNull();
+    expect(mocks.copyToClipboard).not.toHaveBeenCalled();
+    // Cancel = the first (non-destructive) button in the strip.
+    const cancel = [...(confirmStrip()?.querySelectorAll("button") ?? [])][0];
+    await click(cancel);
+    expect(confirmStrip()).toBeNull();
+    expect(mocks.copyToClipboard).not.toHaveBeenCalled();
+  });
+
+  it("copies after explicit confirmation and remembers the choice for the session", async () => {
+    await mountPreview();
+    await click(copyButton());
+    const strip = confirmStrip();
+    expect(strip).not.toBeNull();
+    const checkbox = strip?.querySelector<HTMLInputElement>('input[type="checkbox"]');
+    if (checkbox) {
+      checkbox.checked = true;
+      // v-model needs the change event, not just the property write.
+      checkbox.dispatchEvent(new window.Event("change"));
+      await nextTick();
+    }
+    const buttons = [...(strip?.querySelectorAll("button") ?? [])];
+    await click(buttons[buttons.length - 1]);
+    expect(mocks.copyToClipboard).toHaveBeenCalledWith(content);
+    expect(confirmStrip()).toBeNull();
+
+    // A later copy in the same session — even from a freshly mounted preview —
+    // skips the confirmation and shows only the risk toast.
+    mocks.copyToClipboard.mockClear();
+    unmount();
+    await mountPreview();
+    await click(copyButton());
+    expect(confirmStrip()).toBeNull();
+    expect(mocks.copyToClipboard).toHaveBeenCalledWith(content);
+    expect(mocks.toast).toHaveBeenCalledWith("ai.htmlCopyRiskToast");
+  });
+
+  it("opens the same sandboxed document in an expanded dialog and closes it", async () => {
+    await mountPreview();
+    expect(root?.querySelectorAll("iframe").length).toBe(1);
+
+    await click(button("ai.htmlExpandPreview"));
+    // The stub Dialog renders inline; the second iframe carries the same
+    // sandbox boundary and the same CSP-wrapped srcdoc as the inline card.
+    const iframes = [...(root?.querySelectorAll("iframe") ?? [])];
+    expect(iframes.length).toBe(2);
+    const dialogIframe = iframes[1];
+    expect(dialogIframe.getAttribute("sandbox")).toBe("");
+    const srcdoc = dialogIframe.getAttribute("srcdoc") ?? "";
+    expect(srcdoc).toContain("Content-Security-Policy");
+    expect(srcdoc).toContain("default-src 'none'");
+    expect(srcdoc).toContain(content);
+    // The wide preview must override DialogContent's max-w-sm at every
+    // breakpoint, including narrow desktop windows and mobile-sized WebViews.
+    expect(root?.innerHTML).toContain("max-w-[min(1100px,calc(100vw-32px))]");
+    // The dialog title is the same preview label used for the inline card.
+    expect(root?.querySelector('[data-slot="dialog-title"]')?.textContent).toBe("ai.htmlPreviewLabel");
+
+    // Closing (Esc / overlay / programmatic update:open) removes the iframe.
+    const dialog = root?.querySelector('[data-open="true"]');
+    await click(dialog);
+    expect(root?.querySelectorAll("iframe").length).toBe(1);
+  });
+
+  it("writes the wrapped safe document, never the raw source", async () => {
+    await mountPreview();
+    await click(button("ai.htmlSaveSafe"));
+    expect(mocks.saveTextFile).toHaveBeenCalledWith(documentHtml, "dbx-ai-html-preview.html", "HTML", "html");
+    expect(mocks.saveTextFile.mock.calls[0][0]).not.toBe(content);
+  });
+
+  it("suppresses the risk toast when the clipboard write fails", async () => {
+    await mountPreview();
+    // Arm the remembered session acknowledgment, mirroring the existing flow.
+    await click(copyButton());
+    const strip = confirmStrip();
+    expect(strip).not.toBeNull();
+    const checkbox = strip?.querySelector<HTMLInputElement>('input[type="checkbox"]');
+    if (checkbox) {
+      checkbox.checked = true;
+      checkbox.dispatchEvent(new window.Event("change"));
+      await nextTick();
+    }
+    const buttons = [...(strip?.querySelectorAll("button") ?? [])];
+    await click(buttons[buttons.length - 1]);
+    expect(mocks.copyToClipboard).toHaveBeenCalledWith(content);
+
+    // A later copy in the same session skips the confirmation — but this time
+    // the clipboard write fails, so the risk toast must not claim success.
+    // (Regression for #I01: the previous code toasted unconditionally.)
+    mocks.copyToClipboard.mockRejectedValueOnce(new Error("denied"));
+    mocks.toast.mockClear();
+    unmount();
+    await mountPreview();
+    await click(copyButton());
+    expect(confirmStrip()).toBeNull();
+    expect(mocks.copyToClipboard).toHaveBeenCalledWith(content);
+    expect(mocks.toast).not.toHaveBeenCalled();
+    // The failure is still silent (doCopy swallows), so the "copied" checkmark
+    // must not appear either — no false success signal at all.
+    expect(root?.querySelector(".text-green-500")).toBeNull();
+  });
+});
diff --git a/apps/desktop/src/components/editor/AiAssistant.vue b/apps/desktop/src/components/editor/AiAssistant.vue
index fc0304ee25..11701a5062 100644
--- a/apps/desktop/src/components/editor/AiAssistant.vue
+++ b/apps/desktop/src/components/editor/AiAssistant.vue
@@ -188,6 +188,11 @@ const AiChartRenderer = defineAsyncComponent({
       h("span", t("common.loading")),
     ]),
 });
+const AiHtmlPreview = defineAsyncComponent({
+  // HTML previews are rare (the prompt only allows them on explicit request),
+  // so lazy-load the component just like the chart renderer.
+  loader: () => import("@/components/ai/rich/AiHtmlPreview.vue"),
+});
 const settings = useSettingsStore();
 const connectionStore = useConnectionStore();
 const savedSqlStore = useSavedSqlStore();
@@ -4714,6 +4719,7 @@ async function openExternalUrl(url: string) {
                     <div v-html="seg.html" />
                   </div>
                   <AiChartRenderer v-else-if="seg.type === 'chart'" :spec="seg.spec" :content="seg.content" />
+                  <AiHtmlPreview v-else-if="seg.type === 'html'" :content="seg.content" :document="seg.document" />
                   <div v-else class="my-2 overflow-hidden rounded-md border border-zinc-200 bg-zinc-50 dark:border-zinc-700/50 dark:bg-zinc-900">
                     <div class="flex items-center border-b border-zinc-200 px-3 py-1.5 text-[10px] font-medium text-zinc-600 dark:border-zinc-700/50 dark:text-zinc-400">
                       <component :is="seg.isSql ? Database : Terminal" class="h-3 w-3 mr-1.5" />
diff --git a/apps/desktop/src/i18n/__tests__/aiRichContentParity.spec.ts b/apps/desktop/src/i18n/__tests__/aiRichContentParity.spec.ts
new file mode 100644
index 0000000000..1cb524ffc6
--- /dev/null
+++ b/apps/desktop/src/i18n/__tests__/aiRichContentParity.spec.ts
@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+import en from "../locales/en";
+import es from "../locales/es";
+import it_ from "../locales/it";
+import ja from "../locales/ja";
+import ko from "../locales/ko";
+import ptBR from "../locales/pt-BR";
+import tr from "../locales/tr";
+import zhCN from "../locales/zh-CN";
+import zhTW from "../locales/zh-TW";
+
+const locales: Array<[string, Record<string, unknown>]> = [
+  ["en", en],
+  ["es", es],
+  ["it", it_],
+  ["ja", ja],
+  ["ko", ko],
+  ["pt-BR", ptBR],
+  ["tr", tr],
+  ["zh-CN", zhCN],
+  ["zh-TW", zhTW],
+];
+
+// Keys the safe-HTML preview (PR2 of #6467) adds to the `ai` namespace. Every
+// locale must expose all of them — the preview UI renders in whatever locale
+// the user runs, and a missing key would leak raw keys into the toolbar.
+const AI_HTML_PREVIEW_KEYS = ["htmlPreviewLabel", "htmlExpandPreview", "htmlExpandPreviewHint", "htmlSaveSafe", "htmlSaveFailed", "htmlCopySource", "htmlCopyRiskBody", "htmlCopyRiskAccept", "htmlCopyRiskRemember", "htmlCopyRiskToast"] as const;
+
+describe("AI rich content locale parity", () => {
+  it.each(locales)("%s exposes the full ai.html* key set with non-empty copy", (_name, locale) => {
+    const ai = (locale as { ai: Record<string, unknown> }).ai;
+    for (const key of AI_HTML_PREVIEW_KEYS) {
+      expect(ai[key], `${_name}: ai.${key}`).toBeTypeOf("string");
+      expect(ai[key] as string, `${_name}: ai.${key}`).not.toHaveLength(0);
+    }
+  });
+});
diff --git a/apps/desktop/src/i18n/locales/en.ts b/apps/desktop/src/i18n/locales/en.ts
index c1a33a02fb..e4cbac10a4 100644
--- a/apps/desktop/src/i18n/locales/en.ts
+++ b/apps/desktop/src/i18n/locales/en.ts
@@ -3037,6 +3037,16 @@ export default {
     chartDownloadPng: "Download PNG",
     chartDownloadFailed: "Failed to download chart image",
     chartData: "Chart data",
+    htmlPreviewLabel: "AI-generated HTML preview",
+    htmlExpandPreview: "Open larger preview",
+    htmlExpandPreviewHint: "This preview runs fully sandboxed — scripts and network access are blocked.",
+    htmlSaveSafe: "Save Safe HTML",
+    htmlSaveFailed: "Failed to save HTML file",
+    htmlCopySource: "Copy source",
+    htmlCopyRiskBody: "This HTML was AI-generated. Opening it outside DBX may execute scripts and access the network.",
+    htmlCopyRiskAccept: "Copy anyway",
+    htmlCopyRiskRemember: "Don't ask again this session",
+    htmlCopyRiskToast: "Copied. This AI-generated HTML may execute scripts or access the network when opened outside DBX.",
   },
   contextMenu: {
     openConnection: "Open Connection",
diff --git a/apps/desktop/src/i18n/locales/es.ts b/apps/desktop/src/i18n/locales/es.ts
index bc4ed27c07..015f4b8ce4 100644
--- a/apps/desktop/src/i18n/locales/es.ts
+++ b/apps/desktop/src/i18n/locales/es.ts
@@ -2824,6 +2824,16 @@ export default withEnglishFallback({
     chartDownloadPng: "Descargar PNG",
     chartDownloadFailed: "No se pudo descargar la imagen del gráfico",
     chartData: "Datos del gráfico",
+    htmlPreviewLabel: "Vista previa de HTML generado por IA",
+    htmlExpandPreview: "Abrir vista previa ampliada",
+    htmlExpandPreviewHint: "Esta vista previa se ejecuta en un sandbox completo: los scripts y el acceso a la red están bloqueados.",
+    htmlSaveSafe: "Guardar HTML seguro",
+    htmlSaveFailed: "No se pudo guardar el archivo HTML",
+    htmlCopySource: "Copiar código fuente",
+    htmlCopyRiskBody: "Este HTML fue generado por IA. Abrirlo fuera de DBX puede ejecutar scripts y acceder a la red.",
+    htmlCopyRiskAccept: "Copiar de todos modos",
+    htmlCopyRiskRemember: "No volver a preguntar en esta sesión",
+    htmlCopyRiskToast: "Copiado. Este HTML generado por IA puede ejecutar scripts o acceder a la red si se abre fuera de DBX.",
     agentSteps: {
       generated: "SQL generado",
       noSql: "No se encontró SQL",
diff --git a/apps/desktop/src/i18n/locales/it.ts b/apps/desktop/src/i18n/locales/it.ts
index c4ec1f2bfa..15437d36c5 100644
--- a/apps/desktop/src/i18n/locales/it.ts
+++ b/apps/desktop/src/i18n/locales/it.ts
@@ -2718,6 +2718,16 @@ export default withEnglishFallback({
     chartDownloadPng: "Scarica PNG",
     chartDownloadFailed: "Impossibile scaricare l'immagine del grafico",
     chartData: "Dati del grafico",
+    htmlPreviewLabel: "Anteprima HTML generata dall'IA",
+    htmlExpandPreview: "Apri anteprima ingrandita",
+    htmlExpandPreviewHint: "Questa anteprima viene eseguita in una sandbox completa: script e accesso alla rete sono bloccati.",
+    htmlSaveSafe: "Salva HTML sicuro",
+    htmlSaveFailed: "Salvataggio del file HTML non riuscito",
+    htmlCopySource: "Copia sorgente",
+    htmlCopyRiskBody: "Questo HTML è stato generato dall'IA. Aprirlo fuori da DBX può eseguire script e accedere alla rete.",
+    htmlCopyRiskAccept: "Copia comunque",
+    htmlCopyRiskRemember: "Non chiedere più in questa sessione",
+    htmlCopyRiskToast: "Copiato. Questo HTML generato dall'IA può eseguire script o accedere alla rete se aperto fuori da DBX.",
     agentSteps: {
       generated: "SQL generato",
       noSql: "Nessun SQL trovato",
diff --git a/apps/desktop/src/i18n/locales/ja.ts b/apps/desktop/src/i18n/locales/ja.ts
index 70803f4aef..c82a64b03c 100644
--- a/apps/desktop/src/i18n/locales/ja.ts
+++ b/apps/desktop/src/i18n/locales/ja.ts
@@ -2860,6 +2860,16 @@ export default withEnglishFallback({
     chartDownloadPng: "PNGをダウンロード",
     chartDownloadFailed: "グラフ画像をダウンロードできませんでした",
     chartData: "グラフのデータ",
+    htmlPreviewLabel: "AI生成HTMLのプレビュー",
+    htmlExpandPreview: "拡大プレビューを開く",
+    htmlExpandPreviewHint: "このプレビューは完全なサンドボックスで実行され、スクリプトとネットワークアクセスはブロックされます。",
+    htmlSaveSafe: "安全なHTMLを保存",
+    htmlSaveFailed: "HTMLファイルの保存に失敗しました",
+    htmlCopySource: "ソースをコピー",
+    htmlCopyRiskBody: "このHTMLはAIによって生成されました。DBXの外部で開くとスクリプトが実行され、ネットワークへアクセスする可能性があります。",
+    htmlCopyRiskAccept: "それでもコピー",
+    htmlCopyRiskRemember: "このセッションでは今後確認しない",
+    htmlCopyRiskToast: "コピーしました。このAI生成HTMLは、DBXの外部で開くとスクリプトを実行したりネットワークへアクセスしたりする可能性があります。",
     agentSteps: {
       generated: "SQL生成完了",
       noSql: "SQLが見つかりません",
diff --git a/apps/desktop/src/i18n/locales/ko.ts b/apps/desktop/src/i18n/locales/ko.ts
index 8a336c2004..8258704f72 100644
--- a/apps/desktop/src/i18n/locales/ko.ts
+++ b/apps/desktop/src/i18n/locales/ko.ts
@@ -2830,6 +2830,16 @@ export default withEnglishFallback({
     chartDownloadPng: "PNG 다운로드",
     chartDownloadFailed: "차트 이미지를 다운로드하지 못했습니다",
     chartData: "차트 데이터",
+    htmlPreviewLabel: "AI 생성 HTML 미리보기",
+    htmlExpandPreview: "큰 화면으로 미리보기",
+    htmlExpandPreviewHint: "이 미리보기는 완전한 샌드박스에서 실행되며 스크립트와 네트워크 액세스가 차단됩니다.",
+    htmlSaveSafe: "안전한 HTML 저장",
+    htmlSaveFailed: "HTML 파일 저장에 실패했습니다",
+    htmlCopySource: "소스 복사",
+    htmlCopyRiskBody: "이 HTML은 AI가 생성했습니다. DBX 외부에서 열면 스크립트가 실행되고 네트워크에 접근할 수 있습니다.",
+    htmlCopyRiskAccept: "그래도 복사",
+    htmlCopyRiskRemember: "이 세션에서 다시 묻지 않기",
+    htmlCopyRiskToast: "복사되었습니다. 이 AI 생성 HTML은 DBX 외부에서 열면 스크립트를 실행하거나 네트워크에 접근할 수 있습니다.",
   },
   contextMenu: {
     openConnection: "연결 열기",
diff --git a/apps/desktop/src/i18n/locales/pt-BR.ts b/apps/desktop/src/i18n/locales/pt-BR.ts
index 469b706f98..a0f366649d 100644
--- a/apps/desktop/src/i18n/locales/pt-BR.ts
+++ b/apps/desktop/src/i18n/locales/pt-BR.ts
@@ -2826,6 +2826,16 @@ export default withEnglishFallback({
     chartDownloadPng: "Baixar PNG",
     chartDownloadFailed: "Falha ao baixar a imagem do gráfico",
     chartData: "Dados do gráfico",
+    htmlPreviewLabel: "Pré-visualização de HTML gerado por IA",
+    htmlExpandPreview: "Abrir visualização ampliada",
+    htmlExpandPreviewHint: "Esta visualização é executada em sandbox completo — scripts e acesso à rede são bloqueados.",
+    htmlSaveSafe: "Salvar HTML seguro",
+    htmlSaveFailed: "Falha ao salvar o arquivo HTML",
+    htmlCopySource: "Copiar código-fonte",
+    htmlCopyRiskBody: "Este HTML foi gerado por IA. Abri-lo fora do DBX pode executar scripts e acessar a rede.",
+    htmlCopyRiskAccept: "Copiar mesmo assim",
+    htmlCopyRiskRemember: "Não perguntar novamente nesta sessão",
+    htmlCopyRiskToast: "Copiado. Este HTML gerado por IA pode executar scripts ou acessar a rede quando aberto fora do DBX.",
     agentSteps: {
       generated: "SQL gerado",
       noSql: "Nenhum SQL encontrado",
diff --git a/apps/desktop/src/i18n/locales/tr.ts b/apps/desktop/src/i18n/locales/tr.ts
index b129e2788f..6da8987739 100644
--- a/apps/desktop/src/i18n/locales/tr.ts
+++ b/apps/desktop/src/i18n/locales/tr.ts
@@ -3011,6 +3011,16 @@ export default withEnglishFallback({
     chartDownloadPng: "PNG İndir",
     chartDownloadFailed: "Grafik görüntüsü indirilemedi",
     chartData: "Grafik verileri",
+    htmlPreviewLabel: "AI tarafından oluşturulan HTML önizlemesi",
+    htmlExpandPreview: "Büyük önizleme aç",
+    htmlExpandPreviewHint: "Bu önizleme tamamen korumalı alanda çalışır; betikler ve ağ erişimi engellenir.",
+    htmlSaveSafe: "Güvenli HTML'i kaydet",
+    htmlSaveFailed: "HTML dosyası kaydedilemedi",
+    htmlCopySource: "Kaynağı kopyala",
+    htmlCopyRiskBody: "Bu HTML yapay zeka tarafından oluşturuldu. DBX dışında açmak betik çalıştırabilir ve ağa erişebilir.",
+    htmlCopyRiskAccept: "Yine de kopyala",
+    htmlCopyRiskRemember: "Bu oturumda tekrar sorma",
+    htmlCopyRiskToast: "Kopyalandı. Bu AI tarafından oluşturulan HTML, DBX dışında açıldığında betik çalıştırabilir veya ağa erişebilir.",
   },
   contextMenu: {
     openConnection: "Bağlantıyı Aç",
diff --git a/apps/desktop/src/i18n/locales/zh-CN.ts b/apps/desktop/src/i18n/locales/zh-CN.ts
index 06f7c7c231..be6eb88a97 100644
--- a/apps/desktop/src/i18n/locales/zh-CN.ts
+++ b/apps/desktop/src/i18n/locales/zh-CN.ts
@@ -2960,6 +2960,16 @@ export default withEnglishFallback({
     chartDownloadPng: "下载 PNG",
     chartDownloadFailed: "图表图片下载失败",
     chartData: "图表数据",
+    htmlPreviewLabel: "AI 生成的 HTML 预览",
+    htmlExpandPreview: "在大窗口预览",
+    htmlExpandPreviewHint: "预览在完全沙箱中运行，脚本与网络访问均被阻止。",
+    htmlSaveSafe: "保存安全 HTML",
+    htmlSaveFailed: "保存 HTML 文件失败",
+    htmlCopySource: "复制源码",
+    htmlCopyRiskBody: "此 HTML 由 AI 生成，在 DBX 外打开可能执行脚本并访问网络。",
+    htmlCopyRiskAccept: "仍要复制",
+    htmlCopyRiskRemember: "本会话不再询问",
+    htmlCopyRiskToast: "已复制。此 AI 生成的 HTML 在 DBX 外打开可能执行脚本或访问网络。",
   },
   contextMenu: {
     openConnection: "打开连接",
diff --git a/apps/desktop/src/i18n/locales/zh-TW.ts b/apps/desktop/src/i18n/locales/zh-TW.ts
index d3faa1037f..1d8f480f27 100644
--- a/apps/desktop/src/i18n/locales/zh-TW.ts
+++ b/apps/desktop/src/i18n/locales/zh-TW.ts
@@ -2938,6 +2938,16 @@ export default withEnglishFallback({
     chartDownloadPng: "下載 PNG",
     chartDownloadFailed: "圖表圖片下載失敗",
     chartData: "圖表資料",
+    htmlPreviewLabel: "AI 產生的 HTML 預覽",
+    htmlExpandPreview: "在大視窗預覽",
+    htmlExpandPreviewHint: "預覽在完全沙箱中執行，指令碼與網路存取均被封鎖。",
+    htmlSaveSafe: "儲存安全 HTML",
+    htmlSaveFailed: "儲存 HTML 檔案失敗",
+    htmlCopySource: "複製原始碼",
+    htmlCopyRiskBody: "此 HTML 由 AI 產生，在 DBX 外開啟可能執行指令碼並存取網路。",
+    htmlCopyRiskAccept: "仍要複製",
+    htmlCopyRiskRemember: "本次工作階段不再詢問",
+    htmlCopyRiskToast: "已複製。此 AI 產生的 HTML 在 DBX 外開啟可能執行指令碼或存取網路。",
   },
   contextMenu: {
     openConnection: "開啟連線",
diff --git a/apps/desktop/src/lib/__tests__/ai/aiMessageRender.spec.ts b/apps/desktop/src/lib/__tests__/ai/aiMessageRender.spec.ts
index 3ac21b08c6..d30ea50d4a 100644
--- a/apps/desktop/src/lib/__tests__/ai/aiMessageRender.spec.ts
+++ b/apps/desktop/src/lib/__tests__/ai/aiMessageRender.spec.ts
@@ -260,6 +260,56 @@ describe("createAiMessageRenderer rich chart segments", () => {
   });
 });
 
+describe("createAiMessageRenderer rich html segments", () => {
+  const markdown = (text: string) => `<p>${text}</p>`;
+
+  it("routes a closed html fence to an html segment carrying the safe document", () => {
+    const renderer = createAiMessageRenderer({ markdown });
+    const segments = renderer.render("```html\n<p>hi</p>\n```");
+    const seg = segments[0];
+    expect(seg.type).toBe("html");
+    if (seg.type !== "html") return;
+    expect(seg.content).toBe("<p>hi</p>");
+    expect(seg.document).toContain("Content-Security-Policy");
+    expect(seg.document).toContain("<p>hi</p>");
+  });
+
+  it("keeps an unfinished html fence as a plain code segment while streaming", () => {
+    const renderer = createAiMessageRenderer({ markdown });
+    const [seg] = renderer.render("```html\n<p>hi", { streaming: true });
+    expect(seg.type).toBe("code");
+    if (seg.type !== "code") return;
+    expect(seg.pending).toBe(true);
+  });
+
+  it("switches an open html fence to an html segment once the closing fence arrives", () => {
+    const renderer = createAiMessageRenderer({ markdown });
+    expect(renderer.render("```html\n<p>hi", { streaming: true })[0].type).toBe("code");
+    expect(renderer.render("```html\n<p>hi</p>\n```", { streaming: true })[0].type).toBe("html");
+  });
+
+  it("falls back to a code segment when the html body exceeds the preview budget", () => {
+    const renderer = createAiMessageRenderer({ markdown });
+    const oversize = "x".repeat(512 * 1024 + 1);
+    const [seg] = renderer.render(`\`\`\`html\n${oversize}\n\`\`\``);
+    expect(seg.type).toBe("code");
+    if (seg.type !== "code") return;
+    expect(seg.lang).toBe("HTML");
+    expect(seg.isSql).toBe(false);
+    expect(seg.pending).toBe(false);
+    expect(seg.content).toBe(oversize);
+  });
+
+  it("never routes html fences into the sql code path that offers run/apply buttons", () => {
+    const renderer = createAiMessageRenderer({ markdown });
+    const [seg] = renderer.render("```html\n<p>hi</p>\n```");
+    // The template only offers run/apply on `type === 'code'` segments with
+    // `isSql`; an html segment must never wear that shape.
+    expect(seg.type).not.toBe("code");
+    expect(seg.type).toBe("html");
+  });
+});
+
 describe("splitStreamingTextBlocks", () => {
   const long = "内容".repeat(200);
 
diff --git a/apps/desktop/src/lib/ai/aiMessageRender.ts b/apps/desktop/src/lib/ai/aiMessageRender.ts
index 1a0d0bb5ae..56d7ca76b8 100644
--- a/apps/desktop/src/lib/ai/aiMessageRender.ts
+++ b/apps/desktop/src/lib/ai/aiMessageRender.ts
@@ -1,4 +1,4 @@
-import { AI_RICH_BLOCK_HANDLERS, type AiMessageChartSegment, type AiRichBlockHandler } from "@/lib/ai/richContent/aiRichContent";
+import { AI_RICH_BLOCK_HANDLERS, type AiMessageChartSegment, type AiMessageHtmlSegment, type AiRichBlockHandler } from "@/lib/ai/richContent/aiRichContent";
 
 export interface AiMessageTextSegment {
   type: "text";
@@ -16,7 +16,7 @@ export interface AiMessageCodeSegment {
   pending: boolean;
 }
 
-export type AiMessageRenderSegment = AiMessageTextSegment | AiMessageCodeSegment | AiMessageChartSegment;
+export type AiMessageRenderSegment = AiMessageTextSegment | AiMessageCodeSegment | AiMessageChartSegment | AiMessageHtmlSegment;
 
 interface MessageSegment {
   type: "text" | "code";
diff --git a/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreview.spec.ts b/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreview.spec.ts
new file mode 100644
index 0000000000..cfb02cb787
--- /dev/null
+++ b/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreview.spec.ts
@@ -0,0 +1,116 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { AI_HTML_MAX_CONTENT_CHARS, AI_HTML_PREVIEW_CSP, buildSafeHtmlPreview, isAiHtmlPreviewEligible } from "@/lib/ai/richContent/aiHtmlPreview";
+
+describe("AI_HTML_PREVIEW_CSP", () => {
+  it("declares the deny-by-default fetch directives", () => {
+    expect(AI_HTML_PREVIEW_CSP).toContain("default-src 'none'");
+    expect(AI_HTML_PREVIEW_CSP).toContain("img-src data: blob:");
+    expect(AI_HTML_PREVIEW_CSP).toContain("style-src 'unsafe-inline'");
+    expect(AI_HTML_PREVIEW_CSP).toContain("font-src data:");
+  });
+
+  it("explicitly declares the directives that do not inherit default-src", () => {
+    expect(AI_HTML_PREVIEW_CSP).toContain("base-uri 'none'");
+    expect(AI_HTML_PREVIEW_CSP).toContain("form-action 'none'");
+  });
+
+  it("grants no script execution whatsoever", () => {
+    // No script-src: scripts fall back to default-src 'none' and are blocked.
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("script-src");
+  });
+
+  it("opens no network direction beyond inline data/blob payloads", () => {
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("http");
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("connect-src");
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("frame-src");
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("child-src");
+  });
+});
+
+describe("buildSafeHtmlPreview", () => {
+  it("wraps the raw content in a standalone document with an inline CSP", () => {
+    const wrapped = buildSafeHtmlPreview("<p>hi</p>");
+    expect(wrapped.startsWith("<!doctype html>")).toBe(true);
+    expect(wrapped).toContain('<meta charset="utf-8">');
+    expect(wrapped).toContain(`<meta http-equiv="Content-Security-Policy" content="${AI_HTML_PREVIEW_CSP}">`);
+    // The CSP meta must appear before the content: it is the outer shell's
+    // document-wide policy, not something the payload could place after.
+    expect(wrapped.indexOf("Content-Security-Policy")).toBeLessThan(wrapped.indexOf("<p>hi</p>"));
+    expect(wrapped.endsWith("</body>\n</html>")).toBe(true);
+  });
+
+  it("embeds the raw content verbatim (unescaped, sandboxing is the runtime guard)", () => {
+    const hostile = `<p onclick="x()">a</p><script>fetch('https://ex.example')</script><img src="https://ex.example/i.png" onerror="x()">`;
+    const wrapped = buildSafeHtmlPreview(hostile);
+    expect(wrapped).toContain(hostile);
+  });
+
+  it("defuses <meta http-equiv=refresh> in any case, quoting style, or attribute order", () => {
+    const vectors = [
+      '<meta http-equiv="refresh" content="0;url=https://attacker/">',
+      "<meta http-equiv='refresh' content='0;url=https://attacker/'>",
+      "<meta http-equiv=refresh content='0;url=https://attacker/'>",
+      '<meta content="0;url=https://attacker/" http-equiv="refresh">',
+      '<META HTTP-EQUIV="Refresh" CONTENT="0;url=https://attacker/">',
+      '<meta name="x" http-equiv="refresh" charset="utf-8" content="0;url=https://attacker/">',
+      '<meta http-equiv="refresh" content="0;url=https://attacker/"/>',
+    ];
+    for (const vector of vectors) {
+      const wrapped = buildSafeHtmlPreview(vector);
+      expect(wrapped).toContain("<!-- meta refresh removed -->");
+      // No live refresh meta may survive in any spelling.
+      expect(wrapped).not.toMatch(/<meta\b[^>]*\bhttp-equiv\s*=\s*["']?\s*refresh\b/i);
+    }
+  });
+
+  it("preserves the body around a defused refresh meta and leaves other metas untouched", () => {
+    const body = '<p>before</p><meta http-equiv="refresh" content="0;url=https://attacker/"><p>after</p><meta charset="utf-8">';
+    const wrapped = buildSafeHtmlPreview(body);
+    expect(wrapped).toContain('<p>before</p><!-- meta refresh removed --><p>after</p><meta charset="utf-8">');
+  });
+
+  it("stays safe when the AI content is a complete HTML document", () => {
+    const completeDocument = "<!DOCTYPE html><html><head><title>p</title></head><body>own</body></html>";
+    const wrapped = buildSafeHtmlPreview(completeDocument);
+    // Error recovery: the outer doctype/CSP meta still precede everything.
+    expect(wrapped.indexOf("Content-Security-Policy")).toBeLessThan(wrapped.indexOf(completeDocument));
+    expect(wrapped.startsWith("<!doctype html>")).toBe(true);
+  });
+
+  it("is deterministic so preview and saved file are byte-identical", () => {
+    expect(buildSafeHtmlPreview("<b>x</b>")).toBe(buildSafeHtmlPreview("<b>x</b>"));
+  });
+});
+
+describe("isAiHtmlPreviewEligible", () => {
+  it("accepts bodies within the 512KB budget", () => {
+    expect(isAiHtmlPreviewEligible("x")).toBe(true);
+    expect(isAiHtmlPreviewEligible("x".repeat(AI_HTML_MAX_CONTENT_CHARS))).toBe(true);
+  });
+
+  it("rejects empty and over-budget bodies", () => {
+    expect(isAiHtmlPreviewEligible("")).toBe(false);
+    expect(isAiHtmlPreviewEligible("x".repeat(AI_HTML_MAX_CONTENT_CHARS + 1))).toBe(false);
+  });
+});
+
+describe("copy-risk session state", () => {
+  beforeEach(() => {
+    vi.resetModules();
+  });
+
+  it("requires a confirmation for the first copy of a session", async () => {
+    const mod = await import("@/lib/ai/richContent/aiHtmlPreview");
+    expect(mod.isAiHtmlCopyRiskAcknowledged()).toBe(false);
+    mod.acknowledgeAiHtmlCopyRisk();
+    expect(mod.isAiHtmlCopyRiskAcknowledged()).toBe(true);
+  });
+
+  it("resets when the app session restarts (fresh module graph)", async () => {
+    const first = await import("@/lib/ai/richContent/aiHtmlPreview");
+    first.acknowledgeAiHtmlCopyRisk();
+    vi.resetModules();
+    const second = await import("@/lib/ai/richContent/aiHtmlPreview");
+    expect(second.isAiHtmlCopyRiskAcknowledged()).toBe(false);
+  });
+});
diff --git a/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreviewCanary.spec.ts b/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreviewCanary.spec.ts
new file mode 100644
index 0000000000..c29bd76c10
--- /dev/null
+++ b/apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreviewCanary.spec.ts
@@ -0,0 +1,127 @@
+import { readFileSync, writeFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+import { AI_HTML_PREVIEW_CSP, buildSafeHtmlPreview } from "@/lib/ai/richContent/aiHtmlPreview";
+
+// The canary payload tries every escape the PRD requires evidence for: inline
+// script, remote image, fetch, form submit, and <base> rewriting. It must
+// survive verbatim into the wrapped document (a canary that was stripped proves
+// nothing) — the CSP shell, not content filtering, is what neutralizes it.
+const canaryVectors = [
+  '<script>document.title = "SCRIPT-RAN"; document.body.style.background = "red"; fetch("https://canary.invalid/fetch");</script>',
+  '<img src="https://canary.invalid/remote.png" alt="remote">',
+  '<img src="https://canary.invalid/onerror.png" onerror="document.title = \'ONERROR-RAN\'" alt="onerror">',
+  '<form action="https://canary.invalid/submit"><input type="submit" value="submit"></form>',
+  '<base href="https://canary.invalid/">',
+  '<a href="relative.png">relative link</a>',
+  // The relative <img> fires an auto-load with no click required: if `base-uri
+  // 'none'` failed, <base href> would rewrite it to
+  // https://canary.invalid/relative.png and the netlog would expose the leak
+  // without manual interaction.
+  '<img src="relative.png" alt="relative">',
+  // Visible only when scripting is DISABLED (context A): a green PASS marker.
+  '<noscript><p style="color:green;margin:0;font:600 13px system-ui">scripts are blocked → PASS</p></noscript>',
+].join("\n");
+
+// Navigation canary — deliberately NOT in canaryVectors: every vector above
+// must survive verbatim (a stripped canary proves nothing), but no CSP fetch
+// directive governs navigation and `sandbox=""` only gates top-navigation and
+// popups, so a sandboxed iframe can still navigate itself. The refresh meta is
+// the one vector the wrapper itself must defuse before it reaches either
+// context; a zero-click `<meta refresh>` is an automatic outbound beacon.
+const metaRefreshCanary = '<meta http-equiv="refresh" content="0;url=https://canary.invalid/">';
+
+const componentSource = readFileSync(new URL("../../../../components/ai/rich/AiHtmlPreview.vue", import.meta.url), "utf8");
+
+describe("AiHtmlPreview sandbox hardening (static canary)", () => {
+  it("sandboxes every preview iframe without any escape hatch", () => {
+    // Inspect every actual iframe tag, not the whole source (comments mention the
+    // sandbox tokens by name when documenting why they are absent). The inline
+    // card and the expanded dialog iframes must carry identical boundaries.
+    const iframeTags = componentSource.match(/<iframe[^>]*>/g) ?? [];
+    expect(iframeTags.length).toBeGreaterThanOrEqual(2);
+    for (const iframeTag of iframeTags) {
+      expect(iframeTag).toContain('sandbox=""');
+      for (const forbidden of ["allow-scripts", "allow-same-origin", "allow-forms", "allow-popups", "allow-modals", "allow-top-navigation"]) {
+        expect(iframeTag).not.toContain(forbidden);
+      }
+    }
+  });
+
+  it("renders the wrapped shell, never the raw source, as the iframe payload", () => {
+    expect(componentSource).toContain(':srcdoc="document"');
+    // The component has no path to inject `content` into the DOM itself.
+    expect(componentSource).not.toContain('v-html="content"');
+  });
+
+  it("keeps the canary vectors present in the wrapped document while the CSP neutralizes each", () => {
+    const wrapped = buildSafeHtmlPreview(canaryVectors);
+    // Every vector is still in the payload — nothing was stripped or rewritten.
+    for (const vector of canaryVectors.split("\n")) {
+      expect(wrapped).toContain(vector);
+    }
+    const position = (needle: string) => wrapped.indexOf(needle);
+    // The CSP meta precedes every vector: the policy applies document-wide.
+    for (const vector of canaryVectors.split("\n")) {
+      expect(position("Content-Security-Policy")).toBeLessThan(position(vector));
+    }
+    // Vector → neutralizer mapping (per the PRD's canary matrix):
+    // inline/`onerror=` scripts and `fetch()` → no script-src grant, blocked by default-src 'none'
+    expect(AI_HTML_PREVIEW_CSP).toContain("default-src 'none'");
+    expect(AI_HTML_PREVIEW_CSP).not.toContain("script-src");
+    // remote img → img-src limited to data:/blob:
+    expect(AI_HTML_PREVIEW_CSP).toContain("img-src data: blob:");
+    // form submit target → form-action 'none' (does NOT inherit default-src)
+    expect(AI_HTML_PREVIEW_CSP).toContain("form-action 'none'");
+    // <base> rewrite → base-uri 'none' (does NOT inherit default-src)
+    expect(AI_HTML_PREVIEW_CSP).toContain("base-uri 'none'");
+  });
+
+  it("defuses the meta-refresh navigation canary (navigation is outside the CSP fetch model)", () => {
+    const wrapped = buildSafeHtmlPreview(`${canaryVectors}\n${metaRefreshCanary}`);
+    // The verbatim-survival canaries are untouched by the defusing pass...
+    for (const vector of canaryVectors.split("\n")) {
+      expect(wrapped).toContain(vector);
+    }
+    // ...while the refresh meta is swapped for an inert comment: the wrapped
+    // document holds no live http-equiv=refresh in any spelling.
+    expect(wrapped).not.toContain(metaRefreshCanary);
+    expect(wrapped).toContain("<!-- meta refresh removed -->");
+    expect(wrapped).not.toMatch(/<meta\b[^>]*\bhttp-equiv\s*=\s*["']?\s*refresh\b/i);
+  });
+
+  it("writes a manual WebView canary harness when AI_HTML_CANARY_OUT is set", () => {
+    const outPath = process.env.AI_HTML_CANARY_OUT;
+    if (!outPath) {
+      // Regenerate on demand: AI_HTML_CANARY_OUT=<path> pnpm vitest run <this file>
+      return;
+    }
+    const wrapped = buildSafeHtmlPreview(`${canaryVectors}\n${metaRefreshCanary}`);
+    // The visible PASS marker inside the sandbox: `noscript` renders only when
+    // scripting is disabled — i.e. exactly when the sandbox held.
+    const harness = [
+      "<!doctype html>",
+      '<html lang="en"><head><meta charset="utf-8"><title>AI HTML preview runtime canary</title>',
+      "<style>body{font-family:system-ui;max-width:60rem;margin:2rem auto;padding:0 1rem;line-height:1.5}",
+      "iframe{width:100%;height:16rem;border:2px solid #888;background:#fff}",
+      "li{margin:.25rem 0}code{background:#f2f2f2;padding:0 .3rem}</style></head><body>",
+      "<h1>AI HTML preview runtime canary</h1>",
+      "<p>This harness embeds the exact bytes <code>buildSafeHtmlPreview</code> produces (the same payload “Save Safe HTML” writes). Open it in the app WebView (dev build) and in a regular browser. All checks must show <b>PASS</b> and the network panel must stay empty.</p>",
+      "<h2>Context A — iframe preview (sandbox=&quot;&quot;)</h2>",
+      `<iframe sandbox="" srcdoc="${wrapped.replace(/"/g, "&quot;")}"></iframe>`,
+      "<h2>Context B — saved standalone file</h2>",
+      "<p>Click “Download wrapped file”, then open the downloaded copy directly in the WebView/browser: outside the sandbox, the CSP meta alone must hold.</p>",
+      // `<\/` keeps the canary's own `</script>` from terminating this harness script.
+      `<script>const blob = new Blob([${JSON.stringify(wrapped).replace(/<\//g, "<\\/")}], {type: "text/html"});const a = document.createElement("a");a.href = URL.createObjectURL(blob);a.download = "ai-html-canary-wrapped.html";a.textContent = "Download wrapped file";document.body.appendChild(a);</script>`,
+      "<h2>Checklist (both contexts)</h2><ul>",
+      "<li><b>Script:</b> the area stays WHITE — a red background or <code>SCRIPT-RAN</code> title means FAIL. Inside context A a green “scripts are blocked → PASS” note is visible (that is <code>&lt;noscript&gt;</code> rendering).</li>",
+      "<li><b>Remote image:</b> both canary <code>&lt;img&gt;</code> elements render as broken-image placeholders, never loaded (DevTools network: no request to <code>canary.invalid</code>).</li>",
+      "<li><b>fetch:</b> no network request to <code>canary.invalid</code>.</li>",
+      "<li><b>Form:</b> submitting the canary form does nothing — no navigation to <code>canary.invalid</code>.</li>",
+      "<li><b>Base rewrite:</b> the “relative link” does not resolve to <code>canary.invalid/relative.png</code>.</li>",
+      "<li><b>Meta refresh:</b> the document does not navigate away on its own — the canary refresh meta must appear only as the inert <code>&lt;!-- meta refresh removed --&gt;</code> comment.</li>",
+      "</ul></body></html>",
+    ].join("\n");
+    writeFileSync(outPath, harness, "utf8");
+    expect(readFileSync(outPath, "utf8")).toContain('sandbox=""');
+  });
+});
diff --git a/apps/desktop/src/lib/ai/richContent/__tests__/aiRichContent.spec.ts b/apps/desktop/src/lib/ai/richContent/__tests__/aiRichContent.spec.ts
index c5f6da6397..ed5c51fd94 100644
--- a/apps/desktop/src/lib/ai/richContent/__tests__/aiRichContent.spec.ts
+++ b/apps/desktop/src/lib/ai/richContent/__tests__/aiRichContent.spec.ts
@@ -1,13 +1,15 @@
 import { describe, expect, it } from "vitest";
 import { AI_RICH_BLOCK_HANDLERS, isAiRichBlockLanguage } from "@/lib/ai/richContent/aiRichContent";
 import { parseAiChartSpec } from "@/lib/ai/richContent/aiChartSpec";
+import { AI_HTML_MAX_CONTENT_CHARS, AI_HTML_PREVIEW_CSP, buildSafeHtmlPreview } from "@/lib/ai/richContent/aiHtmlPreview";
 
 const validBar = JSON.stringify({ version: 1, type: "bar", xAxis: { values: ["Jan", "Feb"] }, series: [{ name: "Revenue", data: [120, 200] }] });
 const invalidBar = "{ not json";
+const validHtml = "<p>Hello <strong>world</strong></p>";
 
 describe("AI_RICH_BLOCK_HANDLERS", () => {
-  it("registers exactly the chart-json handler in V1", () => {
-    expect(Object.keys(AI_RICH_BLOCK_HANDLERS)).toEqual(["chart-json"]);
+  it("registers exactly the chart-json and html handlers in V1", () => {
+    expect(Object.keys(AI_RICH_BLOCK_HANDLERS)).toEqual(["chart-json", "html"]);
   });
 
   it("returns null for an unfinished fence (closed=false) without parsing", () => {
@@ -32,14 +34,43 @@ describe("AI_RICH_BLOCK_HANDLERS", () => {
     expect(handler.parse(JSON.stringify({ version: 1, type: "pie", data: [{ name: "A", value: -1 }] }), { closed: true })).toBeNull();
   });
 
+  it("keeps an unfinished html fence unpreviewed", () => {
+    const handler = AI_RICH_BLOCK_HANDLERS.html;
+    expect(handler.language).toBe("html");
+    expect(handler.parse(validHtml, { closed: false })).toBeNull();
+  });
+
+  it("parses a closed html block into a segment carrying the safe document", () => {
+    const handler = AI_RICH_BLOCK_HANDLERS.html;
+    const segment = handler.parse(validHtml, { closed: true });
+    expect(segment?.type).toBe("html");
+    if (segment?.type !== "html") return;
+    expect(segment.content).toBe(validHtml);
+    // The document is the wrapped shell, never the raw source, and it is the
+    // exact bytes "Save Safe HTML" writes.
+    expect(segment.document).toBe(buildSafeHtmlPreview(validHtml));
+    expect(segment.document).toContain(AI_HTML_PREVIEW_CSP);
+    expect(segment.document).toContain(validHtml);
+  });
+
+  it("rejects an over-budget html body deterministically", () => {
+    const handler = AI_RICH_BLOCK_HANDLERS.html;
+    const oversize = "x".repeat(AI_HTML_MAX_CONTENT_CHARS + 1);
+    expect(handler.parse(oversize, { closed: true })).toBeNull();
+  });
+
   it("does not treat sql/bash/json as rich block languages", () => {
-    for (const lang of ["sql", "bash", "json", "SQL", "BASH", "chart-json "]) {
-      expect(isAiRichBlockLanguage(lang)).toBe(lang.trim().toLowerCase() === "chart-json");
+    for (const lang of ["sql", "bash", "json", "SQL", "BASH"]) {
+      expect(isAiRichBlockLanguage(lang)).toBe(false);
     }
+    expect(isAiRichBlockLanguage("chart-json ")).toBe(true);
+    expect(isAiRichBlockLanguage("html")).toBe(true);
   });
 
   it("matches the raw language tag case-insensitively", () => {
     expect(isAiRichBlockLanguage("CHART-JSON")).toBe(true);
     expect(isAiRichBlockLanguage(" Chart-Json ")).toBe(true);
+    expect(isAiRichBlockLanguage("HTML")).toBe(true);
+    expect(isAiRichBlockLanguage(" Html ")).toBe(true);
   });
 });
diff --git a/apps/desktop/src/lib/ai/richContent/aiHtmlPreview.ts b/apps/desktop/src/lib/ai/richContent/aiHtmlPreview.ts
new file mode 100644
index 0000000000..3b12094473
--- /dev/null
+++ b/apps/desktop/src/lib/ai/richContent/aiHtmlPreview.ts
@@ -0,0 +1,82 @@
+/**
+ * Safe HTML preview shell (V1).
+ *
+ * The AI may emit a fenced ```html block. It renders inside a fully sandboxed
+ * iframe (`sandbox=""` — no allow-scripts, no allow-same-origin) whose `srcdoc`
+ * is wrapped by {@link buildSafeHtmlPreview}. The wrapper inlines a CSP meta
+ * that is the single safety boundary in BOTH contexts the content can reach:
+ *
+ * - the iframe preview (`sandbox=""` already blocks script execution at the
+ *   browser level; the CSP additionally blocks network fetches);
+ * - the standalone file written by "Save Safe HTML" — out of the sandbox, so
+ *   the CSP meta alone must block scripts and network. The saved file is the
+ *   wrapped document, never the raw source: once the content leaves the
+ *   sandbox its protection is only as strong as this shell.
+ *
+ * `default-src 'none'` is the fallback for the fetch directives, but
+ * `form-action` and `base-uri` do NOT inherit from `default-src`, so both are
+ * declared explicitly: `base-uri 'none'` stops `<base>` from rewriting
+ * relative URLs, `form-action 'none'` stops `<form action=…>` from submitting
+ * to a remote target. There is deliberately no `script-src`: scripts fall back
+ * to `default-src 'none'` and are blocked outright.
+ *
+ * Navigation is the one direction no CSP fetch directive governs, and
+ * `sandbox=""` only gates top-navigation/popups — a sandboxed iframe may still
+ * navigate itself. So `<meta http-equiv="refresh">` (a zero-click outbound
+ * request beacon) is the single construct the wrapper defuses outright instead
+ * of passing it through to the CSP shell.
+ */
+
+/** Max raw ```html fence body length (characters) that may enter the iframe `srcdoc`. */
+export const AI_HTML_MAX_CONTENT_CHARS = 512 * 1024;
+
+export const AI_HTML_PREVIEW_CSP = "default-src 'none'; base-uri 'none'; form-action 'none'; img-src data: blob:; style-src 'unsafe-inline'; font-src data:";
+
+/** True when the raw fence body may be previewed / saved. Oversize stays a plain code segment. */
+export function isAiHtmlPreviewEligible(content: string): boolean {
+  return content.length > 0 && content.length <= AI_HTML_MAX_CONTENT_CHARS;
+}
+
+/**
+ * Matches any `<meta>` carrying `http-equiv=refresh`: case-insensitive on the
+ * tag name and the `http-equiv` key/value, tolerant of unquoted, single- or
+ * double-quoted values in any attribute order with extra attributes present.
+ */
+const AI_HTML_META_REFRESH_PATTERN = /<meta\b[^>]*?\bhttp-equiv\s*=\s*(?:"\s*refresh\s*"|'\s*refresh\s*'|refresh\b)[^>]*>/gi;
+
+/** Inert replacement for a defused refresh meta: a comment navigates nowhere. */
+const AI_HTML_META_REFRESH_REPLACEMENT = "<!-- meta refresh removed -->";
+
+/** Strip every `http-equiv=refresh` meta; everything else passes through byte-identical. */
+function defuseMetaRefresh(content: string): string {
+  return content.replace(AI_HTML_META_REFRESH_PATTERN, AI_HTML_META_REFRESH_REPLACEMENT);
+}
+
+/**
+ * Wrap raw AI HTML in the safe standalone document. The same bytes back BOTH
+ * the iframe preview and the "Save Safe HTML" payload, so what is previewed is
+ * exactly what gets saved. If the AI content is itself a complete document,
+ * the browser's error recovery nests it inside the body while the outer CSP
+ * meta still applies document-wide. The only rewrite is the refresh meta
+ * defused above — navigation sits outside the CSP fetch model.
+ */
+export function buildSafeHtmlPreview(content: string): string {
+  return ["<!doctype html>", "<html>", "<head>", '<meta charset="utf-8">', `<meta http-equiv="Content-Security-Policy" content="${AI_HTML_PREVIEW_CSP}">`, "</head>", "<body>", defuseMetaRefresh(content), "</body>", "</html>"].join("\n");
+}
+
+/**
+ * "Copy source" puts the raw AI HTML on the clipboard where it may later be
+ * opened outside DBX. The first copy of a session requires an explicit risk
+ * confirmation; the choice is remembered for the session only (it resets when
+ * the app restarts), and later copies degrade to a risk toast instead of
+ * repeating the confirmation.
+ */
+let htmlCopyRiskAcknowledged = false;
+
+export function isAiHtmlCopyRiskAcknowledged(): boolean {
+  return htmlCopyRiskAcknowledged;
+}
+
+export function acknowledgeAiHtmlCopyRisk(): void {
+  htmlCopyRiskAcknowledged = true;
+}
diff --git a/apps/desktop/src/lib/ai/richContent/aiRichContent.ts b/apps/desktop/src/lib/ai/richContent/aiRichContent.ts
index 30b5a936bd..715ab5bdb6 100644
--- a/apps/desktop/src/lib/ai/richContent/aiRichContent.ts
+++ b/apps/desktop/src/lib/ai/richContent/aiRichContent.ts
@@ -1,17 +1,18 @@
 /**
- * Rich Content Registry (V1 — charts only).
+ * Rich Content Registry (V1 — charts and safe HTML preview).
  *
  * A thin lookup that routes a fenced code block to a typed renderer by its RAW
  * fenced language tag. The registry key must match before
  * `normalizeAiCodeLanguage`'s SQL/SHELL label map runs: SQL/SHELL families
  * never enter the registry and keep the existing proposal/confirm/execute code
- * path. V1 registers only `chart-json`; later PRs add `html` (safe preview) and
- * future artifact types as new handlers without touching the parser core.
+ * path. V1 registers `chart-json` and `html`; future artifact types (mermaid,
+ * tables, files) join as new handlers without touching the parser core.
  */
 
 import { parseAiChartSpec, type AiChartSpec } from "@/lib/ai/richContent/aiChartSpec";
+import { buildSafeHtmlPreview, isAiHtmlPreviewEligible } from "@/lib/ai/richContent/aiHtmlPreview";
 
-/** Segment produced for a successfully parsed rich block (PR1: charts only). */
+/** Segment produced for a successfully parsed chart-json block. */
 export interface AiMessageChartSegment {
   type: "chart";
   /** The raw chart-json fence body (preserved for copy / export / debugging). */
@@ -20,8 +21,21 @@ export interface AiMessageChartSegment {
   spec: AiChartSpec;
 }
 
-/** Union of rich segments; V1 has only the chart member. */
-export type AiMessageRichSegment = AiMessageChartSegment;
+/**
+ * Segment produced for an eligible ```html block. `document` is the
+ * CSP-wrapped standalone shell used for BOTH the iframe preview and the
+ * "Save Safe HTML" payload, so the preview and the saved file never drift.
+ */
+export interface AiMessageHtmlSegment {
+  type: "html";
+  /** The raw html fence body (what "copy source" puts on the clipboard). */
+  content: string;
+  /** `buildSafeHtmlPreview(content)` — rendered in the sandboxed iframe. */
+  document: string;
+}
+
+/** Union of rich segments. */
+export type AiMessageRichSegment = AiMessageChartSegment | AiMessageHtmlSegment;
 
 export interface AiRichBlockFlags {
   /**
@@ -53,6 +67,19 @@ function chartHandler(): AiRichBlockHandler {
   };
 }
 
+function htmlHandler(): AiRichBlockHandler {
+  return {
+    language: "html",
+    parse(content, flags) {
+      if (!flags.closed) return null;
+      // Over-budget (or empty) bodies stay a plain code segment: still fully
+      // visible and copyable, just never handed to the preview pipeline.
+      if (!isAiHtmlPreviewEligible(content)) return null;
+      return { type: "html", content, document: buildSafeHtmlPreview(content) };
+    },
+  };
+}
+
 /**
  * Registry keyed by the raw fenced lang (lowercased, trimmed). The caller in
  * `aiMessageRender.ts` performs the lookup BEFORE `normalizeAiCodeLanguage`, so
@@ -60,9 +87,10 @@ function chartHandler(): AiRichBlockHandler {
  */
 export const AI_RICH_BLOCK_HANDLERS: Record<string, AiRichBlockHandler> = {
   "chart-json": chartHandler(),
+  html: htmlHandler(),
 };
 
-/** Language tags the rich registry owns (V1: `chart-json`). */
+/** Language tags the rich registry owns (V1: `chart-json`, `html`). */
 export function isAiRichBlockLanguage(rawLang: string): boolean {
   return Object.prototype.hasOwnProperty.call(AI_RICH_BLOCK_HANDLERS, rawLang.trim().toLowerCase());
 }
diff --git a/package.json b/package.json
index c87c6e44b9..473d8a3be1 100644
--- a/package.json
+++ b/package.json
@@ -33,6 +33,7 @@
     "check": "node scripts/run-check.mjs",
     "db:env": "node scripts/database-env.mjs",
     "test:db-env": "node --test scripts/database-env.test.mjs",
+    "test:ai-html-canary": "node scripts/ai-html-runtime-canary.mjs",
     "bench:redis-key-search": "node scripts/bench/redis-key-search.mjs",
     "bench:mongodb-count": "node scripts/bench/mongodb-count.mjs",
     "bench:table-import": "cargo run -p dbx-core --no-default-features --example table_import_bench --release --",
diff --git a/scripts/ai-html-runtime-canary.mjs b/scripts/ai-html-runtime-canary.mjs
new file mode 100644
index 0000000000..dd5ed3d672
--- /dev/null
+++ b/scripts/ai-html-runtime-canary.mjs
@@ -0,0 +1,259 @@
+#!/usr/bin/env node
+
+/**
+ * AI HTML preview runtime canary — repeatable E2E runner (PRD R8).
+ *
+ * PRD requires runtime evidence in TWO contexts for the safe-HTML boundary, not
+ * just a CSP string assertion:
+ *
+ *   Context A — the in-app iframe preview: the sandboxed iframe (`sandbox=""`)
+ *               inside the manually generated harness.
+ *   Context B — the standalone wrapped file that "Save Safe HTML" writes:
+ *               opened directly in the browser, OUTSIDE the sandbox, where the
+ *               inlined CSP meta alone must hold. This is exactly the scene in
+ *               which `form-action 'none'` / `base-uri 'none'` must be proven
+ *               (they do not inherit `default-src`).
+ *
+ * For each context a headless Chromium run captures a `--log-net-log` trace and
+ * a `--dump-dom`. PASS means: both netlogs are non-empty and contain URL_REQUEST
+ * events (guards against a broken capture producing a vacuous pass), neither
+ * netlog contains a request to `canary.invalid`, and neither DOM dump shows a
+ * script-execution trace — the SCRIPT-RAN / ONERROR-RAN title markers (raw
+ * strings in the source text do not count: the regexes match element serialized
+ * output only) or a red document background.
+ *
+ * Browser discovery: AI_HTML_CANARY_BROWSER overrides; otherwise standard
+ * install paths for Microsoft Edge / Google Chrome are probed (win32, darwin,
+ * linux). A failure to find a browser prints guidance and exits non-zero.
+ */
+
+import { execFileSync, spawnSync } from "node:child_process";
+import { existsSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join, resolve } from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
+
+const REPO_ROOT = resolve(fileURLToPath(import.meta.url), "..", "..");
+const CANARY_SPEC = "apps/desktop/src/lib/ai/richContent/__tests__/aiHtmlPreviewCanary.spec.ts";
+const HEADLESS_ARGS = [
+  "--headless=new",
+  "--disable-gpu",
+  "--no-first-run",
+  "--no-default-browser-check",
+];
+
+const BROWSER_CANDIDATES = process.platform === "win32"
+  ? [
+      "C:/Program Files (x86)/Microsoft/Edge/Application/msedge.exe",
+      "C:/Program Files/Microsoft/Edge/Application/msedge.exe",
+      "C:/Program Files/Google/Chrome/Application/chrome.exe",
+      "C:/Program Files (x86)/Google/Chrome/Application/chrome.exe",
+    ]
+  : process.platform === "darwin"
+    ? [
+        "/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge",
+        "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
+      ]
+    : ["msedge", "google-chrome", "chromium", "chromium-browser"];
+
+function browserCandidates() {
+  const override = process.env.AI_HTML_CANARY_BROWSER;
+  if (override) return [override];
+  return BROWSER_CANDIDATES.filter((candidate) => {
+    if (candidate.includes("/") || candidate.includes("\\")) return existsSync(candidate);
+    return spawnSync(candidate, ["--version"], { stdio: "ignore" }).status === 0;
+  });
+}
+
+function resolveBrowser() {
+  const candidates = browserCandidates();
+  if (candidates.length === 0) {
+    throw new Error(`No Chromium-based browser found for this platform. Set AI_HTML_CANARY_BROWSER to the msedge/chrome executable.`);
+  }
+  return candidates[0];
+}
+
+/** Invoke vitest from the repository root so the `@` alias and vitest config resolve. */
+function runVitestHarness(harnessOutPath) {
+  const vitestBin = resolve(REPO_ROOT, "node_modules/vitest/vitest.mjs");
+  if (!existsSync(vitestBin)) throw new Error(`vitest entry not found at ${vitestBin}; run pnpm install first`);
+  const args = ["--no-warnings", vitestBin, "run", CANARY_SPEC];
+  const result = spawnSync(process.execPath, args, {
+    cwd: REPO_ROOT,
+    encoding: "utf8",
+    env: { ...process.env, AI_HTML_CANARY_OUT: harnessOutPath },
+  });
+  if (result.status !== 0) {
+    throw new Error(`vitest harness generation failed (exit ${result.status})\n${result.stdout}${result.stderr}`);
+  }
+}
+
+/**
+ * Recover the wrapped payload the harness embeds verbatim: the spec writes the
+ * exact bytes `buildSafeHtmlPreview` produces into a Blob constructor. Parse the
+ * JSON literal back out and verify it round-trips (a second parse returns the
+ * identical string) before it stands in for the "Save Safe HTML" payload.
+ */
+function extractWrappedPayload(harness) {
+  const match = harness.match(/new Blob\(\[([\s\S]*?)\], \{type: "text\/html"\}\)/);
+  if (!match) throw new Error(`Could not extract wrapped payload from harness ${harness}`);
+  let payload;
+  try {
+    payload = JSON.parse(match[1]);
+  } catch {
+    throw new Error("Wrapped payload in harness is not valid JSON");
+  }
+  if (JSON.parse(match[1]) !== payload) {
+    throw new Error("Wrapped payload did not round-trip through JSON.stringify");
+  }
+  if (!payload.includes("Content-Security-Policy")) {
+    throw new Error("Wrapped payload has no CSP meta; cannot serve as the safe standalone file");
+  }
+  return payload;
+}
+
+/** Run one context: fileUrl is the harness (A) or the wrapped file (B). */
+function runHeadless(browser, filePath, userDataDir, netlogPath) {
+  const fileUrl = pathToFileURL(filePath).href;
+  const dumpPath = `${netlogPath}.dom.html`;
+  const args = [
+    ...HEADLESS_ARGS,
+    `--user-data-dir=${userDataDir}`,
+    `--log-net-log=${netlogPath}`,
+    "--virtual-time-budget=8000",
+    "--dump-dom",
+    fileUrl,
+  ];
+  let dom = "";
+  try {
+    dom = execFileSync(browser, args, { encoding: "utf8", maxBuffer: 64 * 1024 * 1024 });
+  } catch (error) {
+    // --dump-dom can still exit non-zero on some versions even after writing output.
+    dom = error.stdout ? String(error.stdout) : "";
+  }
+  writeFileSync(dumpPath, dom, "utf8");
+  return { dom, dumpPath };
+}
+
+function analyzeNetlog(netlogPath) {
+  if (!existsSync(netlogPath)) return { urlRequestCount: 0, canaryHits: 0, error: "netlog missing" };
+  let log;
+  try {
+    log = JSON.parse(readFileSync(netlogPath, "utf8"));
+  } catch {
+    return { urlRequestCount: 0, canaryHits: 0, error: "netlog is not valid JSON" };
+  }
+  const constants = log.constants ?? {};
+  const eventTypes = constants.logEventTypes ?? {};
+  const byId = {};
+  for (const name of Object.keys(eventTypes)) byId[eventTypes[name]] = name;
+  const events = Array.isArray(log.events) ? log.events : [];
+  const urlRequests = events.filter((event) => {
+    const name = byId[event.type];
+    return typeof name === "string" && name.includes("URL_REQUEST");
+  });
+  const canaryHits = events.filter((event) => JSON.stringify(event.params ?? {}).includes("canary.invalid")).length;
+  return { urlRequestCount: urlRequests.length, canaryHits, error: null };
+}
+
+/** Element-serialized evidence only: the raw SCRIPT-RAN / ONERROR-RAN strings
+ * also live in the source text of the wrapped body, so match the serialized
+ * <title> element and the <body> background style, never plain substrings. */
+function analyzeDom(dom) {
+  return {
+    scriptRan: /<title>\s*SCRIPT-RAN/.test(dom),
+    onerrorRan: /<title>\s*ONERROR-RAN/.test(dom),
+    redBackground: /<body[^>]*style="[^"]*background[^"]*red/i.test(dom),
+  };
+}
+
+function fmtStats(name, stats) {
+  return `  ${name}: URL_REQUEST events=${stats.urlRequestCount}  canary.invalid hits=${stats.canaryHits}`;
+}
+
+function main() {
+  const workDir = mkdtempSync(join(tmpdir(), "ai-html-canary-"));
+  let pass = true;
+  const failures = [];
+  const contexts = [];
+  try {
+    const browser = resolveBrowser();
+    console.log(`browser: ${browser}`);
+    const harnessPath = join(workDir, "ai-html-canary.html");
+    const wrappedPath = join(workDir, "ai-html-canary-wrapped.html");
+
+    // 1. Regenerate the harness through vitest so the payload cannot drift from
+    //    the buildSafeHtmlPreview implementation.
+    console.log("regenerating harness via vitest …");
+    runVitestHarness(harnessPath);
+    const harness = readFileSync(harnessPath, "utf8");
+    const wrappedPayload = extractWrappedPayload(harness);
+    writeFileSync(wrappedPath, wrappedPayload, "utf8");
+    console.log(`  harness: ${harnessPath}`);
+    console.log(`  wrapped payload: ${wrappedPath} (${wrappedPayload.length} bytes)`);
+
+    // 2. Two independent headless runs, one per context, each with its own
+    //    profile (the previous context's origin must not leak into the next).
+    const runs = [
+      { key: "A", file: harnessPath },
+      { key: "B", file: wrappedPath },
+    ];
+    for (const run of runs) {
+      const userDataDir = join(workDir, `profile-${run.key}`);
+      const netlogPath = join(workDir, `netlog-${run.key}.json`);
+      console.log(`running context ${run.key} (${run.file}) …`);
+      const { dom } = runHeadless(browser, run.file, userDataDir, netlogPath);
+      const netlogStats = analyzeNetlog(netlogPath);
+      contexts.push({ key: run.key, netlogPath, dumpPath: `${netlogPath}.dom.html`, netlogStats, domStats: analyzeDom(dom), dom });
+    }
+
+    // 3. Assert every context independently.
+    for (const ctx of contexts) {
+      console.log(fmtStats(`context ${ctx.key}`, ctx.netlogStats));
+      const label = `context ${ctx.key}`;
+      if (ctx.netlogStats.error) {
+        pass = false;
+        failures.push(`${label}: ${ctx.netlogStats.error}`);
+      } else {
+        if (ctx.netlogStats.urlRequestCount === 0) {
+          pass = false;
+          failures.push(`${label}: netlog has no URL_REQUEST events (capture failed; cannot prove absence)`);
+        }
+        if (ctx.netlogStats.canaryHits > 0) {
+          pass = false;
+          failures.push(`${label}: netlog contains ${ctx.netlogStats.canaryHits} request(s) to canary.invalid`);
+        }
+      }
+      if (ctx.domStats.scriptRan) {
+        pass = false;
+        failures.push(`${label}: script executed — <title>SCRIPT-RAN</title> present in DOM`);
+      }
+      if (ctx.domStats.onerrorRan) {
+        pass = false;
+        failures.push(`${label}: onerror script executed — <title>ONERROR-RAN</title> present in DOM`);
+      }
+      if (ctx.domStats.redBackground) {
+        pass = false;
+        failures.push(`${label}: script executed — red body background in DOM`);
+      }
+    }
+
+    // 4. Context A additionally proves the iframe carries the sandbox attribute.
+    const contextA = contexts.find((ctx) => ctx.key === "A");
+    if (contextA && !/<iframe[^>]*\ssandbox(\s|$|=)/i.test(contextA.dom)) {
+      pass = false;
+      failures.push("context A: preview iframe is missing the sandbox attribute in the DOM");
+    }
+  } finally {
+    if (!process.env.AI_HTML_CANARY_KEEP_TMP) rmSync(workDir, { recursive: true, force: true });
+    else console.log(`artifacts kept in ${workDir}`);
+  }
+
+  console.log(pass ? "PASS" : "FAIL");
+  if (failures.length > 0) {
+    console.error(failures.map((failure) => `- ${failure}`).join("\n"));
+    process.exitCode = 1;
+  }
+}
+
+main();