He says nothing.
He writes one line. It works.
~54% less code · ~20% cheaper · ~27% faster · 100% safe
Overview
The best code is the code you never wrote.
Ponytail puts the laziest senior dev inside your AI agent. Before writing code, your agent stops and asks: does this need to exist? Does the stdlib do it? Can one line cover it? Only then does it write the minimum that works.
A real feedback loop, not just automation
The agent proposes a change, evaluates whether it's necessary, and writes only what the task needs — no flatpickr for a date picker, no wrapper components, no timezone debates.
Safety is never on the chopping block
Lazy, not negligent. Trust-boundary validation, data-loss handling, security, and accessibility are never sacrificed. The code ends up small because it is necessary, not golfed.
Works with 14+ agent platforms
Claude Code, Codex, OpenCode, Gemini CLI, Cursor, Windsurf, Cline, GitHub Copilot, Aider, Kiro, Zed, CodeWhale, OpenClaw, and pi. One ruleset, every agent.
Measured on real repos, not synthetic prompts
Benchmarked against a headless Claude Code session editing a real FastAPI + React repo — 12 feature tickets, n=4, Haiku 4.5. The numbers are from real agentic work.
How It Works
The lazy-decision ladder
Before writing code, the agent stops at the first rung that holds. Each step is a gate that prevents over-engineering.
Does this need to exist?
No → skip it (YAGNI). Most code doesn't need to be written at all.
Stdlib does it?
Use the standard library. It's already there, already maintained, already tested.
Native platform feature?
The browser's <input type="date"> beats any date picker library.
Installed dependency?
Before adding a new one, check if an existing dependency covers it.
Can one line cover it?
If it fits in one line, write one line.
Only then: the minimum that works
Write only what the task needs, and nothing more.
Before / After
Before ponytail
You ask for a date picker. Your agent installs flatpickr, writes a wrapper component, adds a stylesheet, and starts a discussion about timezones.
With ponytail
<input type="date">
Numbers
Measured improvement vs no-skill baseline
Real agent, real repo (FastAPI + React), 12 feature tickets, n=4, Haiku 4.5. Ponytail is the only arm that cuts every metric while staying 100% safe.
// vs "YAGNI + one-liners" prompt: 95% safe
The cut is biggest where there is a real over-build trap (date picker: 404 to 23 lines, color picker: 287 to 23) and near zero on code that is already minimal.
FAQ
The fastest answers to the questions people ask first
Start here if you want to understand ponytail, how it works, and how to install it without reading the full repo.
Does it need a config file?
No. An optional ~/.config/ponytail/config.json or PONYTAIL_DEFAULT_MODE env var can set the default level (lite/full/ultra/off), but nothing is required.
What if I really need the 120-line cache class?
You don't. Insist anyway and he'll build it. Slowly. Correctly. While looking at you.
Does it scale?
The code you never wrote scales infinitely. Zero bugs, zero CVEs, 100% uptime since forever.
What agents does it support?
Claude Code, Codex, OpenCode, Gemini CLI, Cursor, Windsurf, Cline, GitHub Copilot, Aider, Kiro, Zed, CodeWhale, OpenClaw, pi. Copy the matching rules file from the repo.
Why "ponytail"?
You know exactly why.
What license is it under?
MIT. The shortest license that works.