Dietrich Gebert's Ponytail is a ruleset that makes AI coding agents write the least code that works — mimicking a senior engineer who's been paged at 3am one too many times. Instead of generating 50 lines of boilerplate, the agent reaches for the one-liner that does the same thing. For example, a 48-line CacheManager class is replaced by a single @lru_cache decorator.

The core philosophy follows the first rung of the ladder: stop at the first solution that holds. Does this need to exist? If it's already in the codebase, reuse it. Does the standard library do it? Use it. Native platform features, already-installed dependencies, and single-line solutions all take priority over adding new code.

Ponytail ships as a two-line install for Claude Code and supports 14+ agents including Open Code, Cursor, Windsurf, Cline, Kiro, and Zed. Commands include /ponyail lite|full|ultra for intensity control, /ponyail-review to find over-engineering in the current diff, and /pony-tail-audit to scan the whole repo for bloat.

Benchmarks show less code, fewer tokens, and the same safety across 12 feature tasks on a FastAPI + React repo. Validation, error handling, security, and accessibility are never simplified away.