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/kernel/skills/kernel-best-practicesgit clone --depth 1 https://github.com/kernel/skillsWhat 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 | $0.00010 | $0.00225 |
| Opus 5 | $0.00005 | $0.00112 |
| Sonnet 5 | $0.00002 | $0.00045 |
| Haiku 4.5 | $0.00001 | $0.00022 |
Grade A, and why
kernel-best-practices 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 yesterday.
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
- always delete browsers when done. use try/finally to guarantee cleanup.
- set
timeout_secondson every browser as a safety net. default is 60s — increase for longer tasks, max is 72h. - use
stealth: truewhen accessing any site with bot detection. stealth mode adds a recaptcha solver and residential proxy automatically. - use browser profiles for sites requiring authentication. set
save_profile_changes: trueto persist session changes. - prefer the playwright execution API (
execute_playwright_code) for simple one-off scripts. use the SDK + CDP connection for complex multi-step automations. - use
headless: truefor faster execution when you don't need to watch the browser via live view. - proxy quality for anti-detection, best to worst: mobile > residential > ISP > datacenter.
- no charges for idle time — only for active browser usage.
- never hardcode credentials in automation code. use kernel's managed auth or browser profiles instead.
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.
- yesterday First seen · 15 lines · 10 tokens per session scan A 8afbec9bea23
kernel-best-practices is a cursor rule published in the GitHub repository kernel/skills (10 stars, last pushed 5d ago), licensed MIT. It adds 10 tokens to every session and 225 once invoked, about $0.0001 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.
Other cursor rules, from other repositories
webkit-browser
Cursor rule "webkit-browser" from duckduckgo/apple-browsers, covering webkit & browser development guidelines, webview configuration, basic webview setup, user scripts management and tab management.
cypress-e2e-testing-cursorrules-prompt-file
Cursor rules for Cypress development with E2E testing.
vasu-playwright-utils
../../templates/cursor-rules/vasu-playwright-utils.mdc.
dev-browser
Fallback browser automation with persistent Chrome state. Use only when Browser Use is unavailable or blocked.
node-dependencies
Enforce Node.js versioning and package management best practices.
security-standards
Cursor rule "security-standards" from wjgogogo/cursor-rules, covering 安全规范, 核心原则 [p0], 输入验证, xss 防护 and csrf 防护.