Ponytail embeds a strict ruleset into your AI coding agent so it writes only the code you really need. Benchmarks on Claude models show 80–94 percent less code, 3–6× faster responses, and 42–75 percent lower cost compared to a vanilla agent. Those numbers come from five tasks—email validator, debounce, CSV sum, countdown timer, rate limiter—each run thirty times for cost and ten times for code and latency. It marks every shortcut with a “pony­tail” comment so you can see precisely where it cut boilerplate. Before writing anything, the agent climbs a six-step ladder. Step 1 asks if the code needs to exist at all. If not, it skips the task outright. Step 2 checks the standard library, then the platform’s native features, then installed dependencies. Only if none of those apply does it fall back to “one line” or the minimum custom implementation. Throughout, it preserves validation, error handling, security checks, and accessibility. The result is concise but maintainable code rather than a golfed hack. Installing Ponytail takes just two tiny Node.js hooks. From Claude Code or Codex you add the DietrichGebert/ponytail plugin; Copilot, Gemini/Antigravity, OpenClaw or Copilot CLI users follow similar steps. Once active, you get slash commands like /ponytail [lite|full|ultra|off], /ponytail-review, /ponytail-audit, and /ponytail-debt. They let you dial the shortcut level, scan diffs or entire repos for over-engineering, and collect deferred improvements in a “debt” ledger. Every session injects the rules so your AI sticks to the plan.