Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/sandeepmvl/rails-skillsnpx agentmods add skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaftWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaft)<a href="https://agentmods.dev/skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaft"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaft/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaft"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/28-asset-pipeline-propshaft.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00137 | $0.02036 |
| Opus 5 | $0.00068 | $0.01018 |
| Sonnet 5 | $0.00027 | $0.00407 |
| Haiku 4.5 | $0.00014 | $0.00204 |
Grade A, and why
asset-pipeline-propshaft 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 12d 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.
How it starts
The opening of the file, as written. The whole thing — 212 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Asset Pipeline (Propshaft)
Rails 8 ships Propshaft. It does two things: maintain a load path for assets, and digest-stamp filenames for cache-busting. That's it. Sprockets did much more (preprocessing, transpilation, concatenation). Most of that moved to dedicated bundlers (esbuild, vite, sass).
The opinion
Greenfield Rails 8: Propshaft + Importmap (no Node) for simple apps. Propshaft + jsbundling-rails (esbuild) for richer apps. Propshaft + cssbundling-rails (Tailwind / Dart Sass) for Tailwind apps. Don't migrate an existing Sprockets app to Propshaft unless you audit for Sprockets-specific features (
.scss.erb, manifest directives, asset processors) — those don't translate.
What Propshaft does NOT do
- No preprocessing. No
.scss.erb. No ERB inside CSS / JS. - No transpilation. No CoffeeScript, no Babel built-in.
- No concatenation. No
//= requiredirectives. Bundle with esbuild / vite if you need. - No source maps. Bundlers handle.
What it does: serve app/assets/, stamp filenames with content digests, set Cache-Control headers.
Decision matrix — JS bundler
| App | Pick |
|---|---|
| Rails 8 monolith, server-rendered, minor JS | Importmap-rails (no Node) |
| Mixed React/Vue islands | jsbundling-rails + esbuild |
| Heavy SPA mixed in | vite_ruby (HMR, TypeScript) |
| Legacy Webpacker | Shakapacker (community fork) — migrate later |
Decision matrix — CSS
| App | Pick |
|---|---|
| Tailwind CSS | cssbundling-rails + Tailwind |
| Dart Sass | cssbundling-rails + Dart Sass |
| Vanilla CSS | Propshaft directly (no bundler) |
| Plain CSS via Sprockets (was sass-rails) | Migrate to Dart Sass via cssbundling-rails |
Core patterns
Pattern 1: Greenfield — Importmap + Propshaft
rails new myapp --asset-pipeline=propshaft --javascript=importmap
# config/importmap.rb
pin "application", preload: true
pin "@hotwired/turbo-rails", to: "turbo.min.js", preload: true
pin "@hotwired/stimulus", to: "stimulus.min.js", preload: true
pin_all_from "app/javascript/controllers", under: "controllers"
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 12d ago First seen · 212 lines · 137 tokens per session scan A 5129948f2104
asset-pipeline-propshaft is a skill published in the GitHub repository sandeepmvl/rails-skills (21 stars, last pushed 3mo ago), licensed MIT. It adds 137 tokens to every session and 2,036 once invoked, about $0.0007 per session on Opus 5. 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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