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 skills/ag0os/rails-dev-plugin/rails-mailer-patternsnpx skills add ag0os/rails-dev-plugin --skill rails-mailer-patternsgit clone --depth 1 https://github.com/ag0os/rails-dev-pluginWrote 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/ag0os/rails-dev-plugin/rails-mailer-patterns)<a href="https://agentmods.dev/skills/ag0os/rails-dev-plugin/rails-mailer-patterns"><img src="https://agentmods.dev/badge/skills/ag0os/rails-dev-plugin/rails-mailer-patterns.svg" alt="Measured on agentmods" 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 | $0.00097 | $0.01292 |
| Opus 5 | $0.00048 | $0.00646 |
| Sonnet 5 | $0.00019 | $0.00258 |
| Haiku 4.5 | $0.00010 | $0.00129 |
Grade A, and why
rails-mailer-patterns 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 4d 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 — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Mailer Patterns
Analyze and recommend Action Mailer patterns for reliable, well-structured email delivery in Rails applications.
Follow standard Rails conventions for basic mailer structure, mail() calls, delivery configuration, multipart templates, attachments, and I18n subjects. Focus on the opinionated patterns below.
Supporting Documentation
- patterns.md - detailed code examples
- delivery-trigger.native.md / delivery-trigger.extracted.md - what triggers delivery, per Axis A
Resolve the axis first
What triggers email delivery forks on Axis A — logic placement (rails-stack-profiles). Resolve it (or reuse the session value), then read the matching delivery-trigger guide above. native if it cannot be resolved.
Quick Reference
| Pattern | Use When |
|---|---|
Parameterized mailer with before_action |
Shared context across multiple mailer methods |
| Mailer preview per method | Every mailer method needs a preview — catches layout issues CI cannot |
| Staging interceptor | Prevent real emails in non-production environments |
_later/_now convention |
Model triggers delivery; mailer is just the template layer |
Core Principles
- Always
deliver_later: Email delivery is I/O — background job by default - Mailers are views, not logic: Assemble data and call
mail(). No business logic - One email per method: No conditionals choosing between templates
- Preview every email: Mailer previews catch layout issues CI cannot
_later/_nowon the model: The model defines when to send; the mailer defines what to send
Parameterized Mailers
Share context across methods without repeating arguments:
class UserMailer < ApplicationMailer
before_action { @user = params[:user] }
before_action { @account = params[:user].account }
default to: -> { @user.email }
def welcome
mail(subject: "Welcome to #{@account.name}")
end
def weekly_digest
@events = @user.events.from_last_week
mail(subject: "Your weekly digest")
end
end
# Usage
UserMailer.with(user: user).welcome.deliver_later
What ships with it
3 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.
- 4d ago First seen · 150 lines · 97 tokens per session scan A b3c4bbbc7aa8
rails-mailer-patterns is a skill published in the GitHub repository ag0os/rails-dev-plugin (5 stars, last pushed 3mo ago), licensed MIT. It adds 97 tokens to every session and 1,292 once invoked, about $0.0005 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 2026-08-31.
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