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Skills & Subagents

Long Horizon comes with a set of skills and subagents that give your AI coding agent specialized knowledge for browser testing. They include curated prompts, testing procedures, and rules that help your agent write better tests and debug failures more effectively.

What gets installed

During project setup, Long Horizon adds files to your repository that your coding agent reads as context:

  • Skills — Prompts and procedures for common testing tasks (login flows, form validation, navigation testing)
  • Subagents — Specialized agent configurations for planning and executing tests
  • Rule templates — Placeholder files for your team's testing conventions

These files are added to a Long Horizon directory in your project. Review the changes after setup to understand what was added.

Customizing rules

Long Horizon creates two rule files you can customize:

PLANNING_RULES.md

Guidelines for how your agent should approach test planning. Add your team's conventions for test scope, data setup requirements, and scenario prioritization.

TESTING_RULES.md

Conventions for test execution. Document forbidden patterns, required assertions, cleanup procedures, and environment-specific considerations.

Your agent reads these files as context when planning and running tests. The more specific your rules, the better your agent will follow your team's practices.

Version management

Long Horizon tracks which version of skills and subagents are installed in your project. The project.json file includes:

  • subagent_content_version — Version of the installed bundle
  • subagent_agents — Which agents the bundle was configured for

When Long Horizon releases updated skills and subagents, they will automatically be updated in your project. Syncing updates the bundle files while preserving your custom rules.

Using multiple agents

You can install skills and subagents for multiple coding agents in the same project.

Troubleshooting

  • Agent ignores rules: Make sure the rule files are in the expected location and your agent has access to read them
  • Skills not appearing: Re-run the bootstrap process from Long Horizon's project settings