diff --git a/apps/web/src/components/import-from-deco-dialog.tsx b/apps/web/src/components/import-from-deco-dialog.tsx
index 9a594a9740..cd2e11855b 100644
--- a/apps/web/src/components/import-from-deco-dialog.tsx
+++ b/apps/web/src/components/import-from-deco-dialog.tsx
@@ -12,8 +12,8 @@ import { useAutoInstallGitHub } from "@/hooks/use-auto-install-github";
 import { useNavigateToAgent } from "@/hooks/use-navigate-to-agent";
 import { resolveDecoSiteGithubRepo } from "@decocms/shared/deco-sites-github";
 import {
+  defaultPreviewServerUrl,
   pickProductionDomain,
-  productionUrlFromDomain,
 } from "@decocms/shared/deco-site-production-url";
 import { getOrgGithubConnections } from "@decocms/shared/github-repo-scope";
 import {
@@ -271,10 +271,8 @@ export function ImportFromDecoDialog({
         const projectIcon = connBody.icon ?? null;
         const slug = generateSlug(siteName);
         const siteSlug = siteName.toLowerCase();
-        // Default the preview server to the site's `{slug}.deco.site` host (legacy `productionUrl` dual-written for rollback).
-        const previewServerUrl = productionUrlFromDomain(
-          `${siteSlug}.deco.site`,
-        );
+        // Default to the `{slug}.deco.site` host (legacy `productionUrl` dual-written for rollback).
+        const previewServerUrl = defaultPreviewServerUrl(siteName);
 
         // 2. Create a space (virtual MCP) wired to both admin-mcp and GitHub.
         const result = (await client.callTool({
diff --git a/packages/shared/src/deco-site-production-url.test.ts b/packages/shared/src/deco-site-production-url.test.ts
index 7a13249a46..1a386a31db 100644
--- a/packages/shared/src/deco-site-production-url.test.ts
+++ b/packages/shared/src/deco-site-production-url.test.ts
@@ -1,5 +1,6 @@
 import { describe, expect, it } from "bun:test";
 import {
+  defaultPreviewServerUrl,
   pickProductionDomain,
   productionUrlFromDomain,
   resolvePreviewServerUrl,
@@ -82,6 +83,25 @@ describe("productionUrlFromDomain", () => {
   });
 });
 
+describe("defaultPreviewServerUrl", () => {
+  it("slugifies a bare site name into the deco.site host", () => {
+    expect(defaultPreviewServerUrl("acme")).toBe("https://acme.deco.site/");
+  });
+
+  it("slugifies a display name with spaces and symbols", () => {
+    expect(defaultPreviewServerUrl("My Cool Site!")).toBe(
+      "https://my-cool-site.deco.site/",
+    );
+  });
+
+  it("returns null for empty / whitespace-only / nullish, instead of throwing", () => {
+    expect(defaultPreviewServerUrl("")).toBeNull();
+    expect(defaultPreviewServerUrl("   ")).toBeNull();
+    expect(defaultPreviewServerUrl(null)).toBeNull();
+    expect(defaultPreviewServerUrl(undefined)).toBeNull();
+  });
+});
+
 describe("resolvePreviewServerUrl", () => {
   it("prefers previewServerUrl over the legacy productionUrl key", () => {
     expect(
diff --git a/packages/shared/src/deco-site-production-url.ts b/packages/shared/src/deco-site-production-url.ts
index 5f94aeaf56..36f76d6ad4 100644
--- a/packages/shared/src/deco-site-production-url.ts
+++ b/packages/shared/src/deco-site-production-url.ts
@@ -1,3 +1,5 @@
+import { slugify } from "./utils/slugify";
+
 /**
  * Site-URL helpers for linked deco.cx sites.
  *
@@ -6,9 +8,9 @@
  * by imports before the rename and still read as a fallback). It is usually
  * the live production site, but any deco-runtime deployment works (staging, a
  * local `https://localhost:3100`, ...), which is why the canonical name is
- * "preview server". We deliberately do NOT derive it from `siteSlug` (the
- * `{slug}.deco.site` guess) — a site's real URL can be a custom domain, so we
- * persist what deco.cx actually reports at import time.
+ * "preview server". Imports default it to the site's `{slug}.deco.site` guess
+ * (see `defaultPreviewServerUrl`) rather than a reported custom domain, so the
+ * preview always targets the deco-runtime host.
  */
 
 /** Validate/normalize a stored site URL. Returns the canonical href or `null`. */
@@ -67,3 +69,18 @@ export function productionUrlFromDomain(
   const withProtocol = /^https?:\/\//i.test(raw) ? raw : `https://${raw}`;
   return sanitizeSiteUrl(withProtocol);
 }
+
+/**
+ * Guess a site's deco.site preview host from its display name. `siteName` is
+ * a free-text title (shown as-is in the import picker), not a hostname, so it
+ * is slugified first — an unslugified name with a space or symbol makes
+ * `new URL()` throw, and `productionUrlFromDomain` swallows that into `null`,
+ * silently leaving the imported site with no preview server at all.
+ */
+export function defaultPreviewServerUrl(
+  siteName: string | null | undefined,
+): string | null {
+  const slug = slugify(siteName ?? "");
+  if (!slug) return null;
+  return productionUrlFromDomain(`${slug}.deco.site`);
+}