Video course

Claude Code on real codebases

WordPress, PHP, and the code you inherited. You drive Claude Code through a real 240,000-line WordPress ecommerce plugin: onboard it, catch its failures, ship fixes.

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The shape of it

  • 44 lectures, about four hours.
  • One codebase throughout, roughly 240,000 lines of PHP.
  • A pinned fork, so your checkout matches the videos line for line.
  • Downloadable notes for every lecture, and a companion kit of 81 files.

The premise

240,000 lines change how the agent behaves

An agent that looks capable on a small, clean problem behaves differently once the tree is large and somebody else wrote it. Conventions live in people's heads rather than the docs, the test suite is load bearing, and the context you can hand it is a fraction of the whole.

So you get a plausible patch that breaks something three files away, or a refactor that keeps the suite green and the behaviour wrong. You find out in review, if you are lucky. This course spends all four hours in that situation rather than dipping into it.

The codebase is Easy Digital Downloads, a WordPress ecommerce plugin of roughly 240,000 lines of PHP, GPL-2.0, with a full PHPUnit suite and a live issue tracker. You clone a pinned fork, so your checkout matches the videos line for line.

After that nothing is staged: real open issues, real diffs, real test runs, and what an agent actually produces against a codebase this size.

What you will do

Twelve things you walk out able to do

  • Map a 240,000-line PHP codebase with Claude Code, and write the architecture down where the next session can use it.
  • Write project instructions that measurably change how the agent behaves, then keep pruning them as you learn the code.
  • Work out what to tell Claude to ignore, and watch the same question get a better answer.
  • Run the whole loop on a real open issue: reproduce, plan, implement, test, then read the diff like a reviewer.
  • Reject a weak plan and work from the revised one.
  • Meet the five ways coding agents fail on real code. Each one is fired on purpose and followed from prompt to diff.
  • Spot the fix that looks right and is not.
  • Run a five-minute review pass that catches all five before they reach a branch.
  • Use a test suite as the agent's feedback loop, with a known baseline that tells real failures from expected ones.
  • Set permissions, sandboxing and a security pass so the agent's reach matches how far you trust it.
  • Choose between a skill, an MCP server, a hook and a plugin, then build each one against a real convention in the repo.
  • Carry the method to your own codebase with a first-week checklist that does not depend on this plugin.

Who it is for

Who this course is for

This is for you if

  • You already pointed Claude Code at the repository you are paid to maintain, and got mediocre results.
  • You work in WordPress and PHP: plugins, themes, or ecommerce code you inherited rather than wrote.
  • You maintain a large legacy PHP codebase and want the agent to be genuinely useful inside it.
  • You can already get an agent to build something small, and now need the output to survive real tests and a real review.
  • Freelance or agency work: other people's plugin and ecommerce codebases keep landing on you.

Not for you if

  • You are new to programming. Every lecture assumes you can read code and judge a diff.
  • You own a site and want it fixed or extended without writing code. There is no no-code route here.
  • You want a feature tour of Claude Code. This is one working method on one real codebase, not a walk through the menus.

What you need

Before the first lecture

  • About two years of professional development experience. This is not a first coding course.
  • Working PHP, and a basic idea of how a WordPress plugin hooks into WordPress. You do not need to know this particular plugin.
  • Comfort with git: branches, commits, and reading a diff well enough to say whether it is right.
  • A Claude account on a paid plan, or the willingness to start one. The course assumes Claude Pro at 20 dollars a month, and Module 1 installs Claude Code from zero.
  • Docker Desktop, free for personal use. The course test suite runs inside it, and one command takes you to the baseline.
  • macOS, Windows with WSL, or Linux. The videos are recorded on macOS with a terminal and VS Code, but any editor works.

How it is made

Recorded against the real thing

The codebase is real

Easy Digital Downloads is the worked example: GPL-2.0, roughly 240,000 lines, a full PHPUnit suite, an issue tracker with real open issues. It earned the slot by being large, ordinary in its mess, and reachable in one command. The patterns travel to WooCommerce, to other ecommerce plugins, and to any hook-heavy PHP codebase.

The five ways it breaks

Five failure modes are triggered on purpose and shown whole, prompt to diff, including the ones that keep the test suite green while breaking behaviour. Nothing is edited to make the agent look better than it is. Then comes the review pass that catches all five, and the rules each failure earns in your project instructions.

Kept up to date

Tools change. When one of them changes something this course teaches, we re-record the affected lectures, upload the new version, and write down what changed in the course updates. Public, free to read, no email needed.

Made by

Sleeves Up

Fifteen years of WordPress and PHP work sits behind this course. Plugins, ecommerce, and the kind of inherited codebase where the conventions live in people's heads rather than in the docs. A decade of that was agency work, three hundred plus client projects, which is where you learn what a codebase you did not write actually costs you.

Sleeves Up makes practical AI courses and books. More about us.

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