Ponytail: same result, a third of the code

Same prompt, same model, run 3 times each: "Add a countdown to my wedding (June 14, 2027, 4pm) on my wedding website's home page: days, hours, minutes, seconds." One run was plain Claude, the other had Ponytail's rules loaded.

1. Plain Claude: 71, 65 and 69 lines (average 68).
2. With Ponytail: 22, 31 and 24 lines (average 26).
3. Output tokens: about 1,305 vs 821 on average. The long version used roughly 60% more.
4. Both versions count down correctly to the second.
5. Fair note: the longer one also added its own styling and a "Today's the day!" message. Ponytail kept the countdown and let your site's existing style handle the look.

Tip: Fewer output tokens means you hit your usage limit later. The gap is biggest on UI widgets and helpers; on code that's already minimal, Ponytail changes almost nothing. On a tiny task (a birthday date picker) both versions were already 4 to 5 lines.

Official docs →

Ponytail is a ruleset that the plugin injects into Claude Code on every turn. Before Claude writes code, it has to climb a ladder and stop at the first rung that works: skip it, reuse what's in the codebase, use the standard library, use a native platform feature, use a dependency you already have, write one line. Only then does it write new code. Ask for a date picker and, instead of a 400-line component, you get the browser's own <input type="date">.

1. Does this need to exist? If not, skip it.
2. Is it already in this codebase? Reuse it.
3. Does the standard library do it? Use it.
4. Is it a native platform feature (like <input type="date">)? Use it.
5. Is it in a dependency you already installed? Use it.
6. Can it be one line? Write one line.
7. Only then: write the minimum that works.

Tip: It never cuts validation, error handling, security or accessibility. It's lazy about the solution, not about reading your code.

Official docs →

The plugin is for Claude Code. In the regular Claude app you can get the same habit by pasting Ponytail's core rule into a Project's instructions (or Settings → Profile → personal preferences).

1. Open a Project → Project instructions (or Settings → Profile).
2. Paste the prompt below.
3. Ask for code as usual.

Tip: This is a short version of Ponytail's AGENTS.md (MIT license, by DietrichGebert). The full file has a few more rules.

Official docs →

The plugin installs from inside Claude Code. It has to be two separate prompts, one after the other.

1. Open Claude Code in any project.
2. Send: /plugin marketplace add DietrichGebert/ponytail
3. Send, as a new prompt: /plugin install ponytail@ponytail
4. Start a new session.
5. Desktop app: you can also click + next to the prompt box → Plugins → Add plugin.

Tip: If every hook call shows "node: command not found", install Node.js. The rules still work without it, but the error goes away once Node is on your PATH.

Official docs →

Ponytail adds a few slash commands. Use the level switch to make it stricter or turn it off for a task where you want Claude to build big.

1. /ponytail lite: builds what you asked, but suggests smaller alternatives.
2. /ponytail full: the default, enforces the whole ladder.
3. /ponytail ultra: aggressive, cuts speculative features.
4. /ponytail off: turns it off.
5. /ponytail-review: reviews your current diff for over-engineering and gives you a delete-list.
6. /ponytail-audit: does the same for the whole repo.

Tip: If a command isn't found, type /ponytail and look at the suggestions. Some versions show plugin commands with a prefix, like /ponytail:ponytail.

Official docs →

The author's benchmark (12 feature tasks on a real FastAPI + React repo, Claude Haiku 4.5) measured about 54% less code, 22% fewer tokens and 20% lower cost on average. The big wins come from over-build traps: a date picker went from 404 lines to 23, a color picker from 287 to 23. An independent test by JetBrains (80 paired tasks) found smaller but real savings: about 15% less code and 10% lower cost, with no drop in quality.

1. Expect big cuts on UI widgets and helper code.
2. Expect little change on code that's already lean.
3. Install it as a plugin. JetBrains found that just copying the skill file in, without the plugin's hooks, means it basically never activates.

Tip: Treat it as a habit-shaper for Claude, not a magic token switch.

Official docs →