hotwire

A set of rules for Hotwire, a Rails approach that sends rendered HTML from the server while keeping browser-side JavaScript small.

In plain words
What is it for?
Use it when building navigation, forms, and partial page updates with Turbo Drive and Turbo Frames, including pages that should still work without JavaScript.
Why use it?
It helps Rails applications feel faster without requiring a complex JavaScript framework, while keeping more application logic on the server.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/levifig/rails-instructions/hotwire
Clone the repo
git clone --depth 1 https://github.com/levifig/rails-instructions

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 1,213 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What 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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.01213
Opus 5 $0.00000 $0.00607
Sonnet 5 $0.00000 $0.00243
Haiku 4.5 $0.00000 $0.00121

Measured 2d ago against content hash fbbbfa5f83e8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

hotwire 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 2d ago.

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.

.cursor/rules/rails/hotwire.mdc · 171 lines

How it starts

The opening of the file, as written. The whole thing — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Rails Hotwire Guide

Core Philosophy

  • Send HTML over the wire, not JSON - let the server do the rendering
  • Achieve SPA-like speed without complex JavaScript frameworks
  • Use progressive enhancement - functionality works without JavaScript
  • Keep client-side logic minimal and server-side logic rich
  • Embrace the simplicity of multi-page applications with the speed of SPAs

Turbo Drive Principles

  • Enable fast page navigation without full page reloads automatically
  • Intercept all clicks and form submissions by default
  • Maintain scroll position and focus between navigations
  • Cache pages intelligently for instant back/forward navigation
  • Preserve JavaScript state between page visits

Turbo Drive Configuration

  • Disable Turbo Drive selectively with data-turbo="false"
  • Control navigation behavior with data-turbo-action attributes
  • Use data-turbo-permanent to persist elements across navigations
  • Configure cache behavior with meta tags
  • Handle navigation events for custom behavior

Turbo Frames Principles

  • Decompose pages into independent segments that update separately
  • Scope navigation to frame boundaries automatically
  • Enable partial page updates without custom JavaScript
  • Support lazy loading for performance optimization
  • Maintain proper URL and history management

Turbo Frames Best Practices

  • Use meaningful frame IDs that describe their content
  • Keep frames focused on a single concern
  • Lazy load below-the-fold content with loading="lazy"
  • Break out of frames with data-turbo-frame="_top" when needed
  • Cache frame responses independently for better performance

Turbo Streams Principles

  • Update multiple page elements in a single response
  • Support real-time updates via WebSockets or SSE
  • Use semantic actions: append, prepend, replace, update, remove
  • Target elements by ID for surgical updates
  • Broadcast changes from models automatically

Turbo Streams Implementation

  • Return Turbo Stream responses from form submissions
  • Use turbo_stream format in controllers
  • Broadcast model changes with Action Cable
  • Target multiple elements in one response
  • Keep stream templates simple and focused

Read the full file on GitHub · 171 lines

Changes

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.

  1. 2d ago First seen · 171 lines · 0 tokens per session scan A fbbbfa5f83e8

Subscribe to this mod's changes

hotwire 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 1,213 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.