diff --git a/app/utils/resolve-og-image.ts b/app/utils/resolve-og-image.ts
new file mode 100644
index 0000000..d2e7e17
--- /dev/null
+++ b/app/utils/resolve-og-image.ts
@@ -0,0 +1,14 @@
+/**
+ * Resolves an article's og:image to an absolute URL.
+ * Strategy (D-05): frontmatter `image` if present, else branded fallback `/og-blog-default.jpg`.
+ * Consumed by: app/pages/blog/[slug].vue (useSeoMeta.ogImage + defineArticle.image)
+ *              app/pages/blog/index.vue (useSeoMeta.ogImage fallback only).
+ */
+const SITE_URL = 'https://killiandalcin.fr'
+const FALLBACK = '/og-blog-default.jpg'
+
+export function resolveOgImage(article?: { image?: string } | null): string {
+  const raw = article?.image?.trim() || FALLBACK
+  if (raw.startsWith('http://') || raw.startsWith('https://')) return raw
+  return `${SITE_URL}${raw.startsWith('/') ? raw : `/${raw}`}`
+}
diff --git a/public/og-blog-default.jpg b/public/og-blog-default.jpg
new file mode 100644
index 0000000..fd256f9
--- /dev/null
+++ b/public/og-blog-default.jpg
@@ -0,0 +1 @@
+PLACEHOLDER: Replace with actual 1200x630 og:image for killiandalcin.fr