How Ponytail Integrates with Instruction‑Tier Hosts like Cursor: Rule‑Based Setup Guide

Ponytail integrates with instruction‑tier hosts like Cursor through a single rule file located at .cursor/rules/ponytail.mdc, which the host automatically loads as an always‑on project rule without requiring additional commands or skill invocations.

The DietrichGebert/ponytail repository provides a lightweight integration mechanism for AI coding assistants that operate in instruction‑only mode. By placing a dedicated rule file in your project, you can make Ponytail’s guidelines automatically available to hosts like Cursor, Windsurf, and Cline every time they generate code.

Understanding Instruction‑Tier Hosts

Instruction‑tier hosts represent a class of AI assistants that process natural language prompts without supporting executable "skills" or command prefixes. These environments, which include Cursor, Windsurf, Cline, GitHub Copilot Chat, and Kiro, cannot invoke tools like @ponytail-review or other command‑level capabilities.

Instead, these hosts rely entirely on static rule files to shape model behavior. This contrasts with skill‑capable hosts such as Claude Code, Codex, and OpenCode, which expose commands via @ prefixes and dynamic skill invocation.

The Rule File Architecture

Core File Location

Ponytail’s integration centers on a single markdown rule file stored at /.cursor/rules/ponytail.mdc in the repository. This file contains the complete instruction set that defines Ponytail’s coding standards, safety guidelines, and style conventions.

Automatic Discovery Mechanism

When Cursor detects a project‑local .cursor/rules/ponytail.mdc file, it automatically treats the contents as a permanent project rule. According to the source code in scripts/check-rule-copies.js (line 20), the system validates this specific path: ['.cursor/rules/ponytail.mdc', stripFrontmatter]. The host reads these directives on every generation request and merges them with your natural language prompts.

Step‑by‑Step Integration Process

Step 1 — Copy the Rule File

Users must manually copy the rule file from the Ponytail repository into their own project structure. The file must reside at exactly .cursor/rules/ponytail.mdc relative to your project root.

Step 2 — Host Activation

Once the file is present, Cursor loads it as an always‑on rule set. As documented in docs/agent-portability.md, Cursor specifically looks for .cursor/rules/ponytail.mdc to establish "always‑on project rule" behavior. No additional configuration or restart is required.

Step 3 — Generation with Merged Context

During code generation, the LLM receives a merged prompt containing both your specific request and the Ponytail rules. This ensures output respects Ponytail’s guidance regarding style conventions and command patterns without requiring explicit mentions in your prompts.

Practical Setup Commands

To integrate Ponytail with Cursor, execute the following commands in your project root:

# Create the required directory structure

mkdir -p .cursor/rules

# Download the latest rule file from the Ponytail repository

curl -L https://raw.githubusercontent.com/DietrichGebert/ponytail/main/.cursor/rules/ponytail.mdc \
     -o .cursor/rules/ponytail.mdc

After copying the file, Cursor automatically applies the rules to all subsequent generation requests. To remove Ponytail’s influence, simply delete the file:

rm .cursor/rules/ponytail.mdc

Validation and Maintenance

The repository includes scripts/check-rule-copies.js to validate that rule files exist in host‑specific directories. This script references the exact path ['.cursor/rules/ponytail.mdc', stripFrontmatter] (line 20), ensuring the integration remains intact across project updates.

Instruction‑Tier vs. Skill‑Capable Hosts

The key distinction lies in command invocation capabilities:

• Instruction‑tier hosts: Rely solely on the ponytail.mdc rule file. They cannot execute @ponytail-review or similar commands. The rule file represents the only integration point.
• Skill‑capable hosts (Claude Code, Codex, OpenCode): Support dynamic skill invocation through @ prefixes and can execute Ponytail commands beyond static rules.

This design makes Ponytail portable across development assistants without requiring host‑specific code implementations.

Summary

• Ponytail integrates with instruction‑tier hosts through a single rule file at .cursor/rules/ponytail.mdc.
• Cursor, Windsurf, and Cline automatically load this file as an always‑on project rule.
• The scripts/check-rule-copies.js utility validates the presence of rule files in host‑specific paths.
• Unlike skill‑capable hosts, instruction‑tier assistants cannot invoke @ponytail-review commands and rely entirely on static rules.
• No additional configuration is required after copying the rule file into the correct directory.

Frequently Asked Questions

Which hosts support Ponytail’s rule file integration?

Cursor, Windsurf, Cline, GitHub Copilot Chat, and Kiro all support the .cursor/rules/ponytail.mdc placement. According to the docs/agent-portability.md documentation, these instruction‑tier hosts treat the file as an always‑on project rule, automatically applying it to every generation request.

Can I use Ponytail commands like @ponytail-review in Cursor?

No. Instruction‑tier hosts like Cursor lack "skill" support and cannot execute command‑level capabilities. As implemented in the DietrichGebert/ponytail source, these hosts rely exclusively on the static rule file content to shape model behavior, unlike skill‑capable hosts such as Claude Code or Codex.

Do I need to restart Cursor after copying the rule file?

No restart is required. Cursor detects the .cursor/rules/ponytail.mdc file automatically on the next generation request. The host reads the rules and merges them with your prompt immediately upon detection.

How do I verify that Ponytail rules are active in my project?

You can verify installation by running the scripts/check-rule-copies.js validation script, which checks for the presence of ['.cursor/rules/ponytail.mdc', stripFrontmatter] in your project structure. Alternatively, observe whether generated code follows Ponytail’s documented style conventions and safety guidelines.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}