Active Storage Validations is a Ruby gem for adding validation rules to files attached through Rails Active Storage. Rails developers use it to check whether uploaded images, videos, audio files, PDFs, and other attachments meet requirements such as type, size, dimensions, duration, or quantity.
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/igorkasyanchuk/active_storage_validations/spec-matchersgit clone --depth 1 https://github.com/igorkasyanchuk/active_storage_validationsWrote 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/rules/igorkasyanchuk/active_storage_validations/spec-matchers)<a href="https://agentmods.dev/rules/igorkasyanchuk/active_storage_validations/spec-matchers"><img src="https://agentmods.dev/badge/rules/igorkasyanchuk/active_storage_validations/spec-matchers.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 | $0.00000 | $0.00344 |
| Opus 5 | $0.00000 | $0.00172 |
| Sonnet 5 | $0.00000 | $0.00069 |
| Haiku 4.5 | $0.00000 | $0.00034 |
Grade A, and why
spec-matchers 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 today.
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.
What it actually says
Matcher specs
- Follow shared conventions in
spec.mdc(namedsubject,describe/context,described_class). - Boot via
rails_helper;MatcherHelpersis auto-included forspec/matchers. - Prefer
RSpec.describe ActiveStorageValidations::Matchers::SomeValidatorMatcher. - Use shared examples:
"checks if is a valid active storage attribute","checks if is valid","has custom matcher","has valid rspec message methods","works with both instance and class","works with allow_blank","works with custom message","works with context","works with except_on","works with timeout","base comparison validator matcher only match when exact value","base comparison validator matcher equal_to rejects looser comparisons","base comparison validator matcher less_than_or_equal_to rejects less_than","base comparison validator matcher greater_than_or_equal_to rejects greater_than". - Assertions go through helpers:
is_expected_to_match_for(klass),is_expected_not_to_match_for(klass), failure/negated message helpers. - Matcher
#description/#failure_message/#failure_message_when_negatedprotect the public RSpec matcher API for gem consumers — keep those examples. - Dummy matcher models live under
test/dummy/app/models/<validator>/matcher.rb. - Ship-facing matchers remain usable from Minitest/shoulda; do not require RSpec in production matcher code paths.
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.
- today Changed 47ac958ec53a
- 5d ago First seen · 17 lines · 0 tokens per session scan A 9210c90e9933
spec-matchers is a cursor rule published in the GitHub repository igorkasyanchuk/active_storage_validations (1,191 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 344 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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