diff --git a/astro.config.mjs b/astro.config.mjs
index f330868..a50ea08 100644
--- a/astro.config.mjs
+++ b/astro.config.mjs
@@ -166,5 +166,9 @@ export default defineConfig({
 		}),
 		docsMarkdownIntegration(),
 	],
-	adapter: vercel(),
+	// Deploy Astro middleware as a Vercel Edge Function so it runs at
+	// request time for ALL pages, including pre-rendered static pages.
+	// Without this, middleware only runs at build time for static pages
+	// and content negotiation (Accept: text/markdown) doesn't work.
+	adapter: vercel({ middlewareMode: 'edge' }),
 });