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 skills add davekilleen/Dex --skill dhh-rails-stylegit clone --depth 1 https://github.com/davekilleen/DexWrote 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/davekilleen/dex/dhh-rails-style)<a href="https://agentmods.dev/skills/davekilleen/dex/dhh-rails-style"><img src="https://agentmods.dev/badge/skills/davekilleen/dex/dhh-rails-style/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/davekilleen/dex/dhh-rails-style"><img src="https://agentmods.dev/badge/skills/davekilleen/dex/dhh-rails-style.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 | $0.00115 | $0.01631 |
| Opus 5.5 | $0.00046 | $0.00652 |
| Sonnet 5.5 | $0.00023 | $0.00326 |
| Haiku 4.5 | $0.00012 | $0.00163 |
Grade A, and why
dhh-rails-style 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 1mo 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.
Copies of this mod
4 near-identical copies found in the catalogue:
- dhh-rails-style — 100% identical, 0 lines differ
- dhh-rails-style — 100% identical, 0 lines differ
- dhh-rails-style — 92% identical, 25 lines differ
- dhh-rails-style — 84% identical, 6 lines differ
How it starts
The opening of the file, as written. The whole thing — 186 lines — stays where its author put it; the contents beside it link to each section on GitHub.
<essential_principles>
Core Philosophy
"The best code is the code you don't write. The second best is the code that's obviously correct."
Vanilla Rails is plenty:
- Rich domain models over service objects
- CRUD controllers over custom actions
- Concerns for horizontal code sharing
- Records as state instead of boolean columns
- Database-backed everything (no Redis)
- Build solutions before reaching for gems
What they deliberately avoid:
- devise (custom ~150-line auth instead)
- pundit/cancancan (simple role checks in models)
- sidekiq (Solid Queue uses database)
- redis (database for everything)
- view_component (partials work fine)
- GraphQL (REST with Turbo sufficient)
- factory_bot (fixtures are simpler)
- rspec (Minitest ships with Rails)
- Tailwind (native CSS with layers)
Development Philosophy:
- Ship, Validate, Refine - prototype-quality code to production to learn
- Fix root causes, not symptoms
- Write-time operations over read-time computations
- Database constraints over ActiveRecord validations </essential_principles>
- Controllers - REST mapping, concerns, Turbo responses, API patterns
- Models - Concerns, state records, callbacks, scopes, POROs
- Views & Frontend - Turbo, Stimulus, CSS, partials
- Architecture - Routing, multi-tenancy, authentication, jobs, caching
- Testing - Minitest, fixtures, integration tests
- Gems & Dependencies - What to use vs avoid
- Code Review - Review code against DHH style
- General Guidance - Philosophy and conventions
Specify a number or describe your task.
| Response | Reference to Read |
|---|---|
| 1, controller | controllers.md |
| 2, model | models.md |
| 3, view, frontend, turbo, stimulus, css | frontend.md |
| 4, architecture, routing, auth, job, cache | architecture.md |
| 5, test, testing, minitest, fixture | testing.md |
| 6, gem, dependency, library | gems.md |
| 7, review | Read all references, then review code |
| 8, general task | Read relevant references based on context |
After reading relevant references, apply patterns to the user's code.
<quick_reference>
What ships with it
6 files 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.
- 1mo ago First seen · 186 lines · 115 tokens per session scan A 1e99ea5d4f78
dhh-rails-style is a skill published in the GitHub repository davekilleen/Dex (508 stars, last pushed 3d ago), licensed MIT. It adds 115 tokens to every session and 1,631 once invoked, about $0.0005 per session on Opus 5.5. 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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