Prompt & Done · PONYTAIL pack

Same prompt, same Claude: 59 lines or 6.

Ponytail is a free, MIT-licensed skill that makes your coding agent "think like the laziest senior dev in the room": before writing code it checks whether the thing already exists in your codebase, the standard library or the platform.

1 Install (Claude Code)

Type these as two separate prompts in Claude Code:

/plugin marketplace add DietrichGebert/ponytail
/plugin install ponytail@ponytail

It is on every session after that. /ponytail lite|full|ultra|off changes the level. It also works with Codex, Cursor, Copilot and others: see the repo's INSTALL.md. Only install it from DietrichGebert/ponytail.

2 Our test (20 Oct 2026)

A small React + TypeScript booking-form app with its own Input component. Claude Code, Opus 5.5, the same prompt with and without Ponytail, three runs each. We counted lines added in git diff.

Task	Plain Claude	With Ponytail
Dark mode	63, 67, 63	21, 22, 20
Validation	109, 159, 157	34, 30, 32
Date picker	59, 49, 58	6, 6, 5
Photo upload	73, 124, 65	42, 15, 10
Total	1,046	243

All 24 versions passed the TypeScript check and vite build. Both date pickers block past dates in Chromium. Ponytail's runs also finished faster (323 s vs 465 s in total).

The 6-line date picker it wrote reuses the app's own Input and the browser's built-in date picker:

const [date, setDate] = useState('');
// en-CA formats as YYYY-MM-DD in the owner's local timezone (toISOString would use UTC)
const today = new Date().toLocaleDateString('en-CA');
await createBooking({ owner, pet, phone, date });
<Input label="Appointment date" type="date" min={today} value={date} onChange={(e) => setDate(e.target.value)} required />
export type Booking = { owner: string; pet: string; phone: string; date: string };

3 The four prompts

Add a date picker to the booking form so owners can choose the appointment date. Past dates shouldn't be allowed.
Add a dark mode toggle to the app.
Add form validation to the booking form with helpful error messages.
Let owners upload a photo of their pet with the booking.

4 Fair to say

Less code is not automatically better code: plain Claude wrote more tests (in 7 of 12 runs vs 4 of 12). This is one small app and one model, so your numbers will differ. Ponytail's own benchmark (39 tasks, Opus 5.5) reports 53% less code.