DietrichGebert/ponytail: Makes your AI agent think like the laziest senior dev in the room. The best code is the code you never wrote.

Makes your AI agent think like the laziest senior dev in the room. The best code is the code you never wrote. - DietrichGebert/ponytail

Summary

Ponytail is a prompt packaged as an "agent skill" that nudges AI coding tools toward minimal, YAGNI-style changes instead of over-built ones. The skill is essentially one instruction file (skills/ponytail/SKILL.md, with a compact AGENTS.md for rules-file agents) that the agent loads at session start. Before writing code, the agent walks a 7-rung ladder that prefers skipping the work, reusing existing code, then the standard library, then a native platform feature, then an already-installed dependency, then a one-liner, and only then the smallest working implementation.

What it is useful for

It targets a familiar failure mode: an agent that, asked for a date picker, installs flatpickr, writes a wrapper component, adds a stylesheet, and starts talking about timezones. The README's before/after example collapses that to <input type="date"> because the browser already provides one. The same pattern shows up in the cited benchmark numbers (date picker 404 lines to 23, color picker 287 to 23). The skill is also useful as a code-review tool: /ponytail-review scans a diff for over-engineering and returns a delete-list, and /ponytail-audit runs the same check across the whole repo. The /ponytail-debt command collects any ponytail: shortcuts the agent deferred, so "later" doesn't quietly become "never."

Critically, the rules don't make the agent lazy about reading. It still has to trace the code the change touches before picking a rung, and trust-boundary validation, data-loss handling, security, and accessibility are explicitly out of scope for cuts.

How engineers can use it

Install paths differ by host. For Claude Code:

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

For Codex, the README documents codex plugin marketplace add DietrichGebert/ponytail followed by codex plugin add ponytail@ponytail, then opening /hooks to trust the two lifecycle hooks before starting a new thread. For Copilot, Cursor, OpenCode, Gemini, Windsurf, Cline, Kiro, and Antigravity, the README points to INSTALL.md for per-agent steps; the universal fallback is copying AGENTS.md into the project root.

A few documented limitations. Slash commands require a skill-capable host (Claude Code, Codex, Devin CLI, OpenCode, Gemini, pi, Swival, Hermes Agent, Qoder, Grok Build); instruction-only adapters get the always-on rules but not the commands. Intensity switches via /ponytail [lite|full|ultra|off]. The README also notes that on a terse-reasoning model such as GPT-5.5, deliberating the rungs can raise thinking tokens, so cost and time may not drop the way the headline benchmark numbers suggest.