80-94% less code · 3-6× faster · 47-77% cheaper Median of 10 runs across Haiku, Sonnet, and Opus. Reproduce it yourself.
You know him. Long ponytail. Oval glasses. Has been at the company longer than the version control. You show him fifty lines; he looks at them, says nothing, and replaces them with one.
Ponytail puts him inside your AI agent.
Before / after
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:
<!-- ponytail: browser has one --><inputtype="date">
Five everyday tasks (email validator, debounce, CSV sum, countdown timer, rate limiter), three models, three arms: no skill, the caveman skill, and ponytail. Ten runs per cell, median reported.
80-94% less code, 47-77% less cost, and 3-6× faster than a no-skill agent, on every model. Every shortcut ponytail takes is marked in the code with a ponytail: comment naming its upgrade path. Reproduce it yourself: npx promptfoo eval -c benchmarks/promptfooconfig.yaml. Method and raw numbers: benchmarks/. Production-grade tasks, where an unconstrained agent bloats far more, are written up in benchmarks/results/.
How it works
Before writing code, the agent stops at the first rung that holds:
1. Does this need to exist? → no: skip it (YAGNI)
2. Stdlib does it? → use it
3. Native platform feature? → use it
4. Installed dependency? → use it
5. One line? → one line
6. Only then: the minimum that works
Lazy, not negligent: trust-boundary validation, data-loss handling, security, and accessibility are never on the chopping block.
Open /plugins, select the Ponytail marketplace, and install Ponytail. Then
open /hooks, review and trust its two lifecycle hooks, and start a new thread.
Pi agent harness
pi install git:github.com/DietrichGebert/ponytail
OpenCode
Run OpenCode from a checkout of this repo (the plugin reuses its hooks/ and skills/), and add to opencode.json:
{"plugin":["./.opencode/plugins/ponytail.mjs"]}
Injects the ruleset every turn at the active level; adds /ponytail and /ponytail-review. OpenCode also auto-loads this repo's AGENTS.md, so the rules hold even without the plugin. The plugin adds the lite/full/ultra/off levels.
That was it. He'd be proud. He won't say it.
Active every session. /ponytail-review finds what to delete in your diff. /ponytail ultra exists for when the codebase has wronged you personally. /ponytail-help explains the rest.
In Codex, invoke the skills as @ponytail, @ponytail-review, and
@ponytail-help. Startup and mode-change text shows the current mode.
