Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add rules/levifig/rails-instructions/importmapsgit clone --depth 1 https://github.com/levifig/rails-instructionsWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00000 | $0.00803 |
| Opus 5 | $0.00000 | $0.00402 |
| Sonnet 5 | $0.00000 | $0.00161 |
| Haiku 4.5 | $0.00000 | $0.00080 |
Grade A, and why
importmaps scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Import Maps Guide
Core Philosophy
- Eliminate JavaScript build steps while maintaining modern development practices
- Send JavaScript modules directly to the browser without bundling or transpiling
- Reference external modules using standardized module specifiers
- Embrace simplicity and developer happiness - this is the Rails Way™
Configuration Principles
- Define all JavaScript dependencies in
config/importmap.rb - Pin external libraries to specific versions for production stability
- Use semantic versioning when pinning dependencies
- Prefer CDN URLs for popular libraries to leverage browser caching
- Vendor critical dependencies that cannot tolerate CDN failures
- Always specify
preload: truefor essential modules
File Organization
- Keep all JavaScript files in the
app/javascriptdirectory - Use
controllers/subdirectory exclusively for Stimulus controllers - Create
components/for reusable UI JavaScript modules - Create
utilities/for shared helper functions - Follow Rails naming conventions consistently
Naming Conventions for AI Agents
- Name Stimulus controllers with
*_controller.jssuffix - Use descriptive nouns for component files (
modal.js,dropdown.js) - Use action-based names for utilities (
debounce.js,format_currency.js) - Maintain consistent naming patterns across the codebase
- Document module purpose at the top of each file
Module Management
- Import modules using standard ESM syntax
- Avoid polluting the global namespace
- Use named exports for better code discoverability
- Keep modules focused on a single responsibility
- Export only what needs to be public
Dependency Management
- Pin to exact versions in production for stability
- Use version ranges only in development
- Regularly audit and update dependencies
- Remove unused dependencies promptly
- Document why each dependency is needed
Performance Optimization
- Use
preload: trueonly for critical dependencies - Implement lazy loading for features not needed on initial load
- Leverage browser caching by using CDN URLs
- Evaluate module size before adding dependencies
- Consider vendoring large libraries that change infrequently
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 106 lines · 0 tokens per session scan A c3032d001251
importmaps is a cursor rule published in the GitHub repository levifig/rails-instructions (54 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 803 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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