Ponytail (lazy-senior-dev agent guide)

A lifecycle-hook plugin (github.com/DietrichGebert/ponytail) that makes a coding agent think like 'the laziest senior dev in the room': before writing code it walks a YAGNI decision-ladder (needed? already in the codebase? stdlib? native feature? existing dep? one-liner?) and only then writes minimal code. Node.js hooks that drop into 20+ agents (Claude Code, Codex, Copilot CLI, Cursor, Windsurf); benchmarks report ~54% less code, ~20% lower cost, ~27% faster at 100% safety. A computational GUIDE (feedforward) that shapes the change before it exists.

grounded in: https://github.com/DietrichGebert/ponytail

Connected concepts

YAGNI decision-ladder for agents, Guides & sensors, Keep quality left, Prompt engineering, Harness engineering