agentmods.dev

arcjet-sdk-patterns

A set of implementation rules for using the Arcjet service to protect application routes from abuse and unwanted traffic.

In plain words
What is it for?
Use it when adding Arcjet protection, rate limits, bot checks, sensitive-data filters, dry-run testing, and environment-based keys.
Why use it?
It prevents common integration mistakes such as creating duplicate clients, counting requests twice, or mishandling denials and errors.

Cursor rule

1 7d ago A scan 0 tokens original Apache-2.0
View the source file arcjet/arcjet-plugin
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/arcjet/arcjet-plugin/arcjet-sdk-patterns
Clone the repo
git clone --depth 1 https://github.com/arcjet/arcjet-plugin
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 297 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 $0.00297
Opus 5 $0.00000 $0.00148
Sonnet 5 $0.00000 $0.00059
Haiku 4.5 $0.00000 $0.00030

Measured 2d ago against content hash 8c11d42f4c52, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

arcjet-sdk-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 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.

plugins/arcjet/rules/arcjet-sdk-patterns.mdc · 23 lines

What it actually says

Arcjet SDK Patterns

  • Create ONE Arcjet client instance per app, reuse via import. Never instantiate inside a request handler.
  • Call protect() inside route handlers, NOT in middleware (middleware lacks route context and fires on every request).
  • Call protect() only ONCE per request. Multiple calls cause double-counting for rate limits.
  • Use withRule() to add route-specific rules to the shared instance: aj.withRule(tokenBucket({...})).
  • Handle decision.isDenied() (JS) / decision.is_denied() (Python):
    • 429 for rate limits
    • 403 for bot/shield/filter
    • 400 for sensitive info
  • Handle decision.isErrored() / decision.is_error() — Arcjet fails open. Log the error, allow the request.
  • Start new rules in "DRY_RUN" mode. Verify via dashboard or MCP list-requests, then switch to "LIVE".
  • Never hardcode ARCJET_KEY. Use environment variables (.env.local for Next.js, .env for others).
  • Ref: https://docs.arcjet.com/llms.txt
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 · 23 lines · 0 tokens per session scan A 8c11d42f4c52

Subscribe to this mod's changes

arcjet-sdk-patterns is a cursor rule published in the GitHub repository arcjet/arcjet-plugin (1 stars, last pushed 7d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 297 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 2026-08-31.

Backend and APIsSecurityai-skillsclaude-codeclaude-code-pluginclaude-pluginclaude-skillscursor-plugin
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