diff --git a/packages/email-renderer/package.json b/packages/email-renderer/package.json
index 7210be0c..38ae52f0 100644
--- a/packages/email-renderer/package.json
+++ b/packages/email-renderer/package.json
@@ -1,11 +1,12 @@
 {
   "name": "@wrnexus/email-renderer",
-  "version": "0.1.43",
+  "version": "0.1.44",
   "type": "module",
   "description": "WRNexus block email renderers with HTML, text, AMP Email, and MJML interoperability.",
   "exports": {
     ".": "./src/index.ts",
     "./blocks": "./src/blocks.ts",
+    "./browser": "./src/browser.ts",
     "./create": "./src/create.ts",
     "./style-values": "./src/style-values.ts"
   },
diff --git a/packages/email-renderer/src/browser.ts b/packages/email-renderer/src/browser.ts
new file mode 100644
index 00000000..0ab44ad8
--- /dev/null
+++ b/packages/email-renderer/src/browser.ts
@@ -0,0 +1,58 @@
+/** Browser-safe HTML/text rendering. Production AMP/MJML validation stays on the server. */
+import {
+  DEFAULT_LIMITS, defineDocumentKind, escapeHtml, object, registryForKind,
+  resolveDocumentVariables, renderTree, string, type BlockDocument,
+} from "@wrnexus/blocks";
+import { emailCoreBlocks } from "./blocks.ts";
+export const emailKind = defineDocumentKind({
+  kind: "email",
+  version: 1,
+  metadata: object({
+    subject: string({ min: 1, max: 998 }),
+    preheader: string({ max: 500, default: "" }),
+    lang: string({ max: 35, default: "en" }),
+  }) as never,
+  rootTypes: ["layout.email-document"],
+  blocks: emailCoreBlocks,
+  variables: { recipientName: "string", unsubscribeUrl: "string", organizationAddress: "string" },
+  breakpoints: { compact: 480 },
+  capabilities: ["email-html", "plain-text", "amp-email", "mjml"],
+  targets: ["emailHtml", "plainText", "ampEmail", "mjml"],
+  limits: { ...DEFAULT_LIMITS, maxOutputBytes: 2_000_000 },
+  urlSchemes: ["https", "mailto"],
+});
+
+export const emailHtmlHead = (document: BlockDocument, body: string, direction: "ltr" | "rtl") => {
+  const props = document.root.props as Record<string, unknown>;
+  const textColor = escapeHtml(props.textColor ?? "#111827");
+  const linkColor = escapeHtml(props.linkColor ?? "#2563eb");
+  const fontFamily = escapeHtml(props.fontFamily ?? "Arial, sans-serif");
+  return `<!doctype html><html lang="${escapeHtml(document.meta.lang)}" dir="${direction}"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><meta name="x-apple-disable-message-reformatting"><meta name="color-scheme" content="light dark"><title>${escapeHtml(document.meta.subject)}</title><style>a{color:${linkColor}}@media only screen and (max-width:480px){.wrn-email{width:100%!important}.wrn-columns{display:block!important}.wrn-column{display:block!important;width:100%!important}}</style></head><body style="margin:0;padding:0;color:${textColor};font-family:${fontFamily};">${document.meta.preheader ? `<div style="display:none;max-height:0;overflow:hidden;opacity:0;">${escapeHtml(document.meta.preheader)}</div>` : ""}${body}</body></html>`;
+};
+
+export async function renderEmailPreview(document: BlockDocument, options: {
+  variables?: Record<string, unknown>;
+  direction?: "ltr" | "rtl";
+  countdownImageUrl?: string;
+} = {}) {
+  const resolved = resolveDocumentVariables(document, emailKind.variables, options.variables);
+  if (!resolved.ok) return resolved;
+  const source = resolved.value;
+  const context = {
+    locale: "en", timezone: "UTC", direction: options.direction ?? "ltr",
+    brandLinkColor: String(source.root.props.linkColor ?? "#2563eb"),
+    rootBlockIds: Object.values(source.root.slots).flat().map(node => node.id),
+    countdownImageUrl: options.countdownImageUrl,
+  } as const;
+  const registry = registryForKind(emailKind).freeze();
+  const [html, text] = await Promise.all([
+    renderTree(source, emailKind, registry, { ...context, target: "emailHtml" }),
+    renderTree(source, emailKind, registry, { ...context, target: "plainText" }),
+  ]);
+  if (!html.ok) return html;
+  if (!text.ok) return text;
+  return { ok: true as const, value: {
+    html: emailHtmlHead(source, html.value.content, context.direction),
+    text: text.value.content.trimEnd() + "\n",
+  } };
+}
diff --git a/packages/email-renderer/src/email.ts b/packages/email-renderer/src/email.ts
index a08f78a8..89c093da 100644
--- a/packages/email-renderer/src/email.ts
+++ b/packages/email-renderer/src/email.ts
@@ -55,31 +55,8 @@ export interface EmailRenderBundle {
   assets: string[];
 }
 
-export const emailKind = defineDocumentKind({
-  kind: "email",
-  version: 1,
-  metadata: object({
-    subject: string({ min: 1, max: 998 }),
-    preheader: string({ max: 500, default: "" }),
-    lang: string({ max: 35, default: "en" }),
-  }) as never,
-  rootTypes: ["layout.email-document"],
-  blocks: emailCoreBlocks,
-  variables: { recipientName: "string", unsubscribeUrl: "string", organizationAddress: "string" },
-  breakpoints: { compact: 480 },
-  capabilities: ["email-html", "plain-text", "amp-email", "mjml"],
-  targets: ["emailHtml", "plainText", "ampEmail", "mjml"],
-  limits: { ...DEFAULT_LIMITS, maxOutputBytes: 2_000_000 },
-  urlSchemes: ["https", "mailto"],
-});
-
-const head = (document: BlockDocument, body: string, direction: "ltr" | "rtl") => {
-  const props = document.root.props as Record<string, unknown>;
-  const textColor = escapeHtml(props.textColor ?? "#111827");
-  const linkColor = escapeHtml(props.linkColor ?? "#2563eb");
-  const fontFamily = escapeHtml(props.fontFamily ?? "Arial, sans-serif");
-  return `<!doctype html><html lang="${escapeHtml(document.meta.lang)}" dir="${direction}"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><meta name="x-apple-disable-message-reformatting"><meta name="color-scheme" content="light dark"><title>${escapeHtml(document.meta.subject)}</title><style>a{color:${linkColor}}@media only screen and (max-width:480px){.wrn-email{width:100%!important}.wrn-columns{display:block!important}.wrn-column{display:block!important;width:100%!important}}</style></head><body style="margin:0;padding:0;color:${textColor};font-family:${fontFamily};">${document.meta.preheader ? `<div style="display:none;max-height:0;overflow:hidden;opacity:0;">${escapeHtml(document.meta.preheader)}</div>` : ""}${body}</body></html>`;
-};
+export { emailKind } from "./browser.ts";
+import { emailKind, emailHtmlHead as head } from "./browser.ts";
 const ampHead = (document: BlockDocument, body: string, direction: "ltr" | "rtl") => {
   const layoutCss = (node: BlockDocument["root"]): string => ampLayoutCss(node, String(document.root.props.linkColor ?? "#2563eb")) + Object.values(node.slots).flat().map(layoutCss).join("");
   const props = document.root.props as Record<string, unknown>;
diff --git a/packages/email-renderer/test/browser.test.ts b/packages/email-renderer/test/browser.test.ts
new file mode 100644
index 00000000..3d57163b
--- /dev/null
+++ b/packages/email-renderer/test/browser.test.ts
@@ -0,0 +1,36 @@
+import { expect, test } from "bun:test";
+import { renderEmailPreview } from "../src/browser.ts";
+import { renderEmail } from "../src/email.ts";
+import type { BlockDocument } from "@wrnexus/blocks";
+
+const document: BlockDocument = {
+  schemaVersion: 1, kind: "email", meta: { subject: "Local preview", lang: "en" }, theme: { tokens: {} },
+  root: { id: "root", type: "layout.email-document", version: 1, props: { width: "600" }, styles: {}, slots: {
+    content: [{ id: "text", type: "content.text", version: 1, props: { text: "Hello {{recipientName|friend}}" }, styles: {}, slots: {} }],
+  } },
+};
+
+test("browser preview matches production HTML/text without server validators", async () => {
+  const before = structuredClone(document);
+  for (const direction of ["ltr", "rtl"] as const) {
+    const options = { direction, variables: { recipientName: "<script>unsafe</script>" } };
+    const preview = await renderEmailPreview(document, options);
+    const production = await renderEmail(document, options);
+    expect(preview.ok).toBe(true);
+    expect(production.ok).toBe(true);
+    if (preview.ok && production.ok) {
+      expect(preview.value.html).toBe(production.value.parts.html.content);
+      expect(preview.value.text).toBe(production.value.parts.text.content);
+      expect(preview.value.html).toContain("&lt;script&gt;");
+    }
+  }
+  expect(document).toEqual(before);
+});
+
+test("browser preview rejects unknown blocks without mutating them", async () => {
+  const invalid = structuredClone(document);
+  invalid.root.slots.content[0].type = "unknown.block";
+  const before = structuredClone(invalid);
+  expect((await renderEmailPreview(invalid)).ok).toBe(false);
+  expect(invalid).toEqual(before);
+});