diff --git a/README.md b/README.md
index 197e5d3..97d08aa 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ For each Ghost blog you configure:
 
 - Creates a `site.standard.publication` record on your PDS (you pick the handle / app password / publication metadata)
 - Listens for Ghost webhooks (auto-installed during setup)
-- On `post.published` / `post.published.edited`: fetches the post, uploads its cover image as a blob, writes a `site.standard.document` record, and updates the post's per-post `codeinjection_head` so its `<head>` carries the link tag — all without touching Ghost's editor UI
+- On `post.published` / `post.published.edited`: fetches the post, uploads its cover image as a blob, writes a `site.standard.document` record (the post body travels as [`at.markpub.markdown`](https://github.com/AramZS/markpub.at) content, converted from Ghost's HTML), and updates the post's per-post `codeinjection_head` so its `<head>` carries the link tag — all without touching Ghost's editor UI
 - On `post.unpublished` / `post.deleted`: deletes the document record from the PDS
 - Tracks every post's `ghost_post_id` ↔ AT-URI mapping in a local SQLite (so deletes always know which record to remove)
 
diff --git a/src/lib/transform.test.ts b/src/lib/transform.test.ts
new file mode 100644
index 0000000..5929611
--- /dev/null
+++ b/src/lib/transform.test.ts
@@ -0,0 +1,30 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+
+import { ghostPostToRecord, type GhostPostLike } from './transform.js';
+import { MARKPUB_MARKDOWN_TYPE } from './content-shape.js';
+
+const PUBLICATION_URI = 'at://did:plc:example/site.standard.publication/self';
+
+const basePost: GhostPostLike = {
+  id:           '64f0000000000000000000ab',
+  title:        'Hello',
+  slug:         'hello',
+  status:       'published',
+  published_at: '2026-07-06T10:00:00.000Z',
+  html:         '<h2>Hi</h2><p>Body text.</p>',
+};
+
+test('record carries the markpub content member when the post has HTML', () => {
+  const record  = ghostPostToRecord(basePost, PUBLICATION_URI, null);
+  const content = record.content as { $type: string; text: { markdown: string } };
+  assert.equal(content.$type, MARKPUB_MARKDOWN_TYPE);
+  assert.match(content.text.markdown, /## Hi/);
+  // textContent is untouched by this feature — both representations coexist.
+  assert.match(String(record.textContent), /Body text\./);
+});
+
+test('record omits content when the post has no HTML', () => {
+  const record = ghostPostToRecord({ ...basePost, html: null }, PUBLICATION_URI, null);
+  assert.ok(!('content' in record));
+});
diff --git a/src/lib/transform.ts b/src/lib/transform.ts
index 1ac8110..9136148 100644
--- a/src/lib/transform.ts
+++ b/src/lib/transform.ts
@@ -1,11 +1,10 @@
 // Pure transform: Ghost post object → site.standard.document payload.
 // No I/O, no client state — caller passes the publication AT-URI and (optionally)
 // an already-uploaded cover-image blob ref.
-//
-// Real implementation TBD — porting from the parent bridge.
 
 import { convert as htmlToText } from 'html-to-text';
 import type { BlobRef } from '@atproto/api';
+import { buildMarkpubContent } from './content-shape.js';
 
 export const DOCUMENT_COLLECTION = 'site.standard.document';
 
@@ -61,5 +60,11 @@ export function ghostPostToRecord(
   }
   if (coverImageBlob)           record.coverImage  = coverImageBlob;
 
+  // Post body as at.markpub.markdown — the document content union is open
+  // (`closed: false`), so no lexicon registration is needed; the shared $type
+  // is what markpub-aware readers key on.
+  const content = buildMarkpubContent(post.html ?? '');
+  if (content)                  record.content     = content;
+
   return record;
 }