diff --git a/CLAUDE.md b/CLAUDE.md
index 31fd53e..eebf5ee 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -733,6 +733,43 @@ Show options with trade-offs. I will choose.
 
 ---
 
+## 11.5 Odoo 17 Model Field Compatibility
+
+When extending core Odoo models (e.g., `blog.post`), be aware of field differences:
+
+| Model | Field | Odoo 16 | Odoo 17 | Note |
+|-------|-------|---------|---------|------|
+| `blog.post` | `body_arch` | Yes | **No** | XML layout field; removed in Odoo 17 |
+| `blog.post` | `body` | Yes | **No** | HTML body field; use editor interface instead |
+| `blog.post` | `itsulu_social_id` | N/A | Custom | Add via `_inherit` for reverse relationship to custom models |
+| `mail.template` | Subject/Body | Mako syntax | Mako syntax | Renders async in send_mail(); use Mako `% for` loops, not method calls in templates |
+
+**Pattern for extending blog.post safely:**
+```python
+# addons/<module>/models/blog_post.py
+class BlogPost(models.Model):
+    _inherit = 'blog.post'
+    
+    custom_field_id = fields.One2many(
+        comodel_name='custom.model',
+        inverse_name='blog_post_id',
+        string='Custom Records',
+    )
+```
+
+**Pattern for creating blog.post test records:**
+```python
+# Use sudo() to bypass Odoo validation when creating minimal test posts
+post = self.env['blog.post'].sudo().create({
+    'name': 'Test Post',
+    'blog_id': blog.id,
+    'is_published': True,
+    # Do NOT include body, body_arch, or body_html — use website editing UI
+})
+```
+
+---
+
 ## 12. Failure Recovery Quick Reference
 
 | Symptom | Most likely cause | Fix |
@@ -751,6 +788,10 @@ Show options with trade-offs. I will choose.
 | K8s Job: `CreateContainerConfigError` | Secret key missing (e.g. `database` key not in `test-db-info`) | `kubectl describe pod <pod>` to find missing key; recreate secret with all 3 keys |
 | Docker build: `chmod: Operation not permitted` | odoo:17.0 runs as non-root; can't chmod after COPY | Do `chmod 777 /mnt/extra-addons` BEFORE COPY, then use `--chown=odoo:odoo` on COPY |
 | Docker build: `apt-get: Permission denied` | Base image runs as non-root; apt requires root | odoo:17.0 has no apt access — use `python3 -m pip` instead; no system packages possible |
+| Mail test: `mail.mail.body_html` is empty after `send_mail()` | Template rendering is async; test checks mail.mail synchronously | Use `force_send=True` in send_mail(); check mail.outgoing state or delay assertion; or manually render template with Mako before creating mail.mail |
+| Mail test: `mail.mail.subject` is `False` instead of string | Template subject field not rendered by send_mail() | Verify template fields are populated in DB; render manually if needed |
+| Odoo 17: `blog.post` doesn't accept `body` or `body_arch` fields | Fields renamed/removed in Odoo 17 | Use factory pattern with `.sudo().create()` to bypass validation; post content should be managed via editor interface, not direct assignment |
+| Odoo 17: Inverse relationship not loaded in template context | Relations lazy-load; mail.template context may not include reverse relations | Use explicit search in Mako (`for loop`) instead of relying on inverse field; or fetch record with prefetch in the render context |
 
 ---