diff --git a/CLAUDE.md b/CLAUDE.md
index eebf5ee..8df28ca 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -130,6 +130,12 @@ class TestSaleOrderDiscount(TransactionCase):
 - `setUp` / inline: test-specific data (partners, orders, invoices).
 - Do **not** create shared mutable state; each test must be independent.
 
+**Critical: Never call `self.env.cr.commit()` in code being tested by TransactionCase**
+- TransactionCase uses database savepoints; each test gets rolled back automatically
+- `commit()` breaks the savepoint chain, causing `InFailedSqlTransaction` errors in subsequent tests
+- **Use `self.env.flush_all()` instead** to persist changes while keeping the test isolated
+- If you need to test explicit commits, use `TestCase` instead (slower, no auto-rollback)
+
 ### 3.2 HttpCase (use rarely — only for controllers or UI tours)
 
 ```python
@@ -792,6 +798,8 @@ post = self.env['blog.post'].sudo().create({
 | 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 |
+| Test: `IndexError: tuple index out of range` when accessing `mock.call_args[0][0]` | Mock method called with keyword-only args; `call_args[0]` is empty tuple `()` | Use `mock.call_args[1].get('key')` for kwargs; or check `mock.called` before accessing `call_args` |
+| Test: TransactionCase gets `InFailedSqlTransaction` in subsequent tests | Previous test called `self.env.cr.commit()` breaking savepoint chain | Replace `commit()` with `flush_all()` in code being tested; `commit()` is only allowed in non-test code in production |
 
 ---