MCP for Override Checker is a free add-on for MCP for J that lets your AI client review and fix the template overrides Joomla flags after an update, through Override Checker. Its 12 tools list the flagged overrides, read the override and the core file side by side, apply a fix, dismiss a row, restore a backup and save the review where you can read it later. Every change goes through Override Checker's own code, so a file is always backed up before it's written.
Why this exists
Override Checker's copy-paste prompt works when your AI can call your site's REST API itself, with a Joomla API token in the request header. Claude Code, Codex and Cursor can do that. Browser chats mostly can't: claude.ai's sandbox blocks the address, ChatGPT can't send the header, and a long review times out. MCP for J already handles the connection, with sign-in and per-app setup, so this add-on puts Override Checker on that connection instead of building a second one.
What Claude can do
There are 12 tools, grouped the way a review goes.
| Area | Tools | What you can do |
|---|---|---|
| Status | 1 | How many overrides Joomla has flagged per template, checked and not, how many backups and saved reviews there are, and what your account may do. |
| Flagged overrides | 5 | List the flagged rows (by template, site or admin, checked or not, or the extension that caused them), read the override and the core file it shadows, apply a fix, and dismiss one row. |
| Backups | 3 | List the backups Override Checker took before each fix, read one, and put it back. |
| Reviews | 3 | List and read saved reviews, and save a new one with its report, so the fixes and backups are filed under it. |
Installing it
You'll need Joomla 5 or 6, PHP 8.3 or later, MCP for J, and Override Checker 2.6.1 or later, which is free.
- Open Components โ MCP for J โ Browse MCP Add-Ons and click Install on this add-on. You can also download the ZIP above and install it through System โ Install โ Extensions.
- That's the whole install. The plugin switches itself on, and the tools show up in your AI client the next time it lists them.
If MCP for J isn't installed, the plugin installs switched off and tells you why, rather than leaving you with tools that go nowhere.
Using it
Start with "Review the template overrides Joomla flagged." Your AI lists the rows, reads each override next to the core file it replaces, and tells you what the update changed that your override is missing, and whether anything in it doesn't belong in a layout file. Ask it to save the review, and the report appears under Override Checker โ Sessions.
Then tell it which rows to act on: "Fix 125 and 126", "Dismiss 120". A few things are built in so a fix can't make things worse:
- Files are read whole. A fix written from part of a file would delete the rest of it, so the add-on never cuts a file short.
- A fix must match the file it was built from. If the file has changed since your AI read it, nothing is written and your AI is told to read it again.
- A PHP fix that doesn't parse is refused, because a broken layout breaks every page that uses it.
- A fix can't add risky code. Override Checker refuses a fix that adds things like
eval, shell commands, file writes or request input the file didn't already have, in case your AI has been tricked by something it read. If the change really is what you want, make it in the file yourself. - One row at a time. There's no "dismiss everything". If you say "mark them all as checked", your AI has to ask which ones.
Every fix and restore takes a backup first. "Undo the last fix" puts the old file back, and that restore is backed up too. The one thing your AI can't restore is a backup holding code like that, since it may be the backdoor a fix just removed. You can still restore it yourself from Override Checker's File backups screen.
An override with no matching core file is usually an alternative layout, one your template adds under its own name. The add-on says so instead of reporting an error, so your AI reviews it on its own.
Permissions and security
The tools use Override Checker's own permissions: View to read, and Write to fix, dismiss, restore or save a review. They're checked for the person whose MCP connection makes the request, so your AI can't do anything that person couldn't do in Override Checker. Override Checker only ever writes inside your templates' html folders. File contents are treated as site data, never as instructions, so a hacked override that tries to talk to the AI gets reported, not obeyed.
Why it's free
Override Checker is free, so this add-on is free too.
This is version 1.0.0. All 12 tools were driven on Joomla 6 against Override Checker, on a test site with real flagged overrides: reading both files, a fix, its backup and the restore, every refusal, the alternative-layout cases, and an account with only View permission. The fix and restore tools were run again against the released 2.6.1. Reviews were also read on a second live site. It was tested over MCP's own connection, not from inside each browser chat, so if yours behaves differently, I'd like to hear about it.
Open source
GPL-2.0-or-later, the same license as Joomla itself. Source lives on GitHub.
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