Phase 5 — ISR & Revalidation Webhooks

Without ISR: New WordPress content only appears after running vercel build again.

With ISR: New content appears seconds after publishing in wp-admin.

Step 1 — Create the Revalidation Endpoint

// src/app/api/revalidate/route.ts
import { revalidatePath } from "next/cache";
import { NextRequest, NextResponse } from "next/server";

export async function POST(request: NextRequest) {
  const secret = request.nextUrl.searchParams.get("secret");
  if (secret !== process.env.REVALIDATION_SECRET) {
    return NextResponse.json({ message: "Invalid secret" }, { status: 401 });
  }
  const { post_type, slug } = await request.json();

  if (post_type === "post") {
    revalidatePath(`/blog/${slug}`);
    revalidatePath("/blog");
  } else if (post_type === "projects") {
    revalidatePath(`/projects/${slug}`);
    revalidatePath("/projects");
  }
  revalidatePath("/"); // Always revalidate homepage (news banner)
  return NextResponse.json({ revalidated: true, post_type, slug });
}

Step 2 — Trigger Webhook from WordPress

// functions.php
function trigger_nextjs_revalidation($new_status, $old_status, $post) {
    if ($new_status !== 'publish') return;
    if (!in_array($post->post_type, ['post', 'projects', 'page'])) return;

    $secret = 'your-super-secret-key-here';
    $url    = 'https://yourdomain.com/api/revalidate?secret=' . $secret;

    wp_remote_post($url, array(
        'headers'  => array('Content-Type' => 'application/json'),
        'body'     => json_encode(array(
            'post_type' => $post->post_type,
            'slug'      => $post->post_name
        )),
        'timeout'  => 15,
        'blocking' => false,
    ));
}
add_action('transition_post_status', 'trigger_nextjs_revalidation', 10, 3);

Step 3 — Add Secret to Vercel

Go to your Vercel project → Settings → Environment Variables and add:

REVALIDATION_SECRET = your-super-secret-key-here

Then redeploy once for the variable to take effect.

Test the Webhook Locally

curl -X POST "http://localhost:3000/api/revalidate?secret=your-secret" \
  -H "Content-Type: application/json" \
  -d '{"post_type":"post","slug":"hello-world"}'

# Expected response:
# {"revalidated":true,"post_type":"post","slug":"hello-world"}

Recommended Revalidation Times