fix(metadata): apply ancestor templates to title defaults

packages/vinext/src/shims/metadata.tsx

@@ -343,6 +343,29 @@ function resolveStringTitle(title: Metadata["title"]): string | undefined {
   return undefined;
 }
 
+function applyTitleTemplate(template: string | undefined, title: string): string {
+  return template ? template.replace(/%s/g, title) : title;
+}
+
+function resolveTitle(title: Metadata["title"], stashedTemplate: string | undefined) {
+  if (typeof title === "string") {
+    return applyTitleTemplate(stashedTemplate, title);
+  }
+
+  if (title && typeof title === "object") {
+    let resolved =
+      title.default === undefined ? undefined : applyTitleTemplate(stashedTemplate, title.default);
+
+    if (title.absolute) {
+      resolved = title.absolute;
+    }
+
+    return resolved;
+  }
+
+  return undefined;
+}
+
 /**
  * Post-process merged metadata to cross-fill openGraph and Twitter fields.
  *
@@ -400,7 +423,7 @@ export function postProcessMetadata(merged: Metadata): Metadata {
     if (!hasTwDescription) {
       autoFill.description = result.openGraph.description || result.description || undefined;
     }
-    if (!hasTwImages) {
+    if (!hasTwImages && result.openGraph.images !== undefined) {
       autoFill.images = result.openGraph.images;
     }
 
@@ -456,25 +479,14 @@ export function mergeMetadataEntries(entries: readonly MetadataMergeEntry[]): Me
 
   const merged: Metadata = {};
 
-  // Track the most recent title template from LAYOUTS (not from page).
+  // Track the most recent ancestor title template from layouts (not from page).
   let parentTemplate: string | undefined;
 
   for (const entry of entries) {
     const meta = entry.metadata;
     const isPage = Boolean(entry.isPage);
     const contributesTitle = entry.contributesTitle !== false;
 
-    // Collect template from layouts only (page templates are ignored per Next.js spec)
-    if (
-      contributesTitle &&
-      !isPage &&
-      meta.title &&
-      typeof meta.title === "object" &&
-      meta.title.template
-    ) {
-      parentTemplate = meta.title.template;
-    }
-
     // Merge non-title keys
     for (const key of Object.keys(meta)) {
       if (key === "title") continue; // Handle title separately below
@@ -492,30 +504,19 @@ export function mergeMetadataEntries(entries: readonly MetadataMergeEntry[]): Me
 
     // Title resolution
     if (contributesTitle && meta.title !== undefined) {
-      merged.title = meta.title;
+      merged.title = resolveTitle(meta.title, parentTemplate);
     }
-  }
 
-  // Now resolve the final title, applying the parent template if applicable
-  const finalTitle = merged.title;
-  if (finalTitle) {
-    if (typeof finalTitle === "string") {
-      // Simple string title — apply parent template
-      if (parentTemplate) {
-        merged.title = parentTemplate.replace("%s", finalTitle);
-      }
-    } else if (typeof finalTitle === "object") {
-      if (finalTitle.absolute) {
-        // Absolute title — skip all templates
-        merged.title = finalTitle.absolute;
-      } else if (finalTitle.default) {
-        // Title object with default — this is used when the segment IS the
-        // defining layout (its own default doesn't get template-wrapped)
-        merged.title = finalTitle.default;
-      } else if (finalTitle.template && !finalTitle.default && !finalTitle.absolute) {
-        // Template only with no default — no title to render
-        merged.title = undefined;
-      }
+    // Collect the current layout template after resolving its own title so
+    // title.default is wrapped by the ancestor template, not by its own template.
+    if (
+      contributesTitle &&
+      !isPage &&
+      meta.title &&
+      typeof meta.title === "object" &&
+      meta.title.template
+    ) {
+      parentTemplate = meta.title.template;
     }
   }
 

tests/app-page-head.test.ts

@@ -383,7 +383,7 @@ describe("app page head resolution", () => {
         description: "Primary page",
         title: "Slot OG title",
       },
-      title: "Page",
+      title: "Page | Root",
       twitter: {
         card: "summary",
         description: "Primary page",

tests/features.test.ts

@@ -2133,6 +2133,21 @@ describe("metadata title templates", () => {
     expect(result.title).toBe("My Site");
   });
 
+  it("applies ancestor title template to child layout default title", () => {
+    // Next.js resolveTitle() applies the stashed ancestor template to title.default:
+    // https://github.com/vercel/next.js/blob/canary/packages/next/src/lib/metadata/resolvers/resolve-title.ts
+    const result = mergeMetadataEntries([
+      {
+        metadata: { title: { template: "%s | Site", default: "Site" } },
+      },
+      {
+        metadata: { title: { default: "Blog" } },
+      },
+    ]);
+
+    expect(result.title).toBe("Blog | Site");
+  });
+
   it("title.absolute skips all templates", () => {
     const result = mergeMetadata([
       { title: { template: "%s | My Site", default: "My Site" } },
@@ -2150,16 +2165,19 @@ describe("metadata title templates", () => {
     expect(result.title).toBe("Hello World - Blog");
   });
 
-  it("page template has no effect (page is terminal)", () => {
-    // If the page defines a template, it should be ignored
-    // Only layouts define templates, and page is always the last entry
+  it("applies ancestor template to page default while ignoring page template", () => {
     const result = mergeMetadata([
       { title: { template: "%s | Site", default: "Site" } },
       { title: { template: "%s - Page Template", default: "Page Default" } },
     ]);
-    // The page's template should be ignored; the page's default is used
-    // because the page has a title object (not a string), so we use its default
-    expect(result.title).toBe("Page Default");
+
+    expect(result.title).toBe("Page Default | Site");
+  });
+
+  it("does not apply a page template to the page's own default title", () => {
+    const result = mergeMetadata([{ title: { template: "%s | Page", default: "Page" } }]);
+
+    expect(result.title).toBe("Page");
   });
 
   it("preserves non-title metadata during merge", () => {
@@ -2218,7 +2236,7 @@ describe("metadata title templates", () => {
     expect(result).toEqual({
       description: "Page",
       openGraph: { title: "Slot OG title" },
-      title: "Page",
+      title: "Page | Root",
     });
   });
 });