Guide AI agents to write less code by acting like a lazy senior developer
When an agent tries to build a 335-line calendar component, Ponytail guides it to solve the problem in 10 lines by combining existing input fields and browser default features. Ponytail is a prompt file that instructs AI agents to behave like the 'laziest senior developer.' It changes the agent's decision criteria to write only the code necessary for the task, without adding exaggerated features.
Changes and results in Ponytail 5
Ponytail 5 has been completely restructured from previous versions. Benchmark results show a 53% reduction in code volume, a 41% reduction in time, a 26% reduction in cost, and a 45% reduction in token usage. Conversely, the test coverage for risky logic was 98%, higher than the 68% when Ponytail was not used. These figures are the result of running 39 tasks five times each using the Opus 5.5 model in a Claude Code environment. It was also confirmed that safety was maintained despite code reduction, as all 30 runs of six security tasks passed.
The difference between laziness and negligence
The core principle of Ponytail is 'write only what is needed,' not 'minimum tokens.' It never omits essential elements such as validation, error handling, security, and accessibility. Code becomes smaller because unnecessary parts are removed, not because code is forcibly reduced. The agent first reads the code affected by the changes and traces the actual flow before choosing a solution. It always leaves a small test for logic involving branches, loops, parsers, money, or security.
Redesign of review and audit features
The /ponytail-review command now reviews like a senior developer called in when a failure occurs, rather than simply deleting code. It reads not only the changed code but also the surrounding areas affected by that code, checking for bugs, security issues, actual load, missing tests, and speed problems. Each finding specifies the code's behavior, the error content, the fix method, and the result if left unaddressed. /ponytail-audit applies the same inspection to the entire repository, mapping entry points and data flows first before setting priorities and presenting a fix order.
Installation and compatibility
In Claude Code, install using the commands /plugin marketplace add DietrichGebert/ponytail and /plugin install ponytail@ponytail. For other agents, copy the AGENTS.md file to the project or install skills/ponytail/SKILL.md as a skill. Cursor, Windsurf, Cline, Copilot, and others operate as always-on rule files without commands. Install only from the official repository DietrichGebert/ponytail or @dietrichgebert/ponytail on npm; copies containing .exe or .dll files are not official versions.
Things to check before applying
Ponytail is distributed under the MIT license and operates at a default level even without a configuration file. You can adjust the default intensity using ~/.config/ponytail/config.json or the PONYTAIL_DEFAULT_MODE environment variable. The shortcut: comment indicates intended shortcut paths, and you can manage them collectively with the /ponytail-debt command. If other terms are specified in the project's CLAUDE.md or AGENTS.md, the comments change to those terms. Command usage is only possible on hosts that support skills (such as Claude Code, Codex, and Devin CLI); in environments that only support rule files, only level switching commands can be used.
