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/langfuse/langfuse-docs/cloud-browser-previewgit clone --depth 1 https://github.com/langfuse/langfuse-docsWhat 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 | $0.00375 | $0.00375 |
| Opus 5 | $0.00187 | $0.00187 |
| Sonnet 5 | $0.00075 | $0.00075 |
| Haiku 4.5 | $0.00038 | $0.00038 |
Grade A, and why
cloud-browser-preview 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
End with an in-app browser preview
When a Cloud Agent task changes something a reviewer can see in the site, check the page on desktop and mobile viewports, then leave the in-app browser open on that page. This rule applies only to Cursor Cloud Agents.
When to preview
Open a preview if the change affects a rendered page: docs, blog, changelog, marketing, UI, layout, routing, or MDX components. Skip it for non-visual work (scripts, config, agent instructions) unless a page was still affected.
How to preview
- Use the already-running
pnpm devserver. It is started from.cursor/environment.jsonon port 3333. - Open the affected URL in the in-app browser at
http://127.0.0.1:3333/...(notlocalhost). - Wait for the first compile. After the server reports ready, the first request can take 20-40 seconds.
- Navigate to the changed page with the sidebar or a direct URL. Site search does not return results without Inkeep keys.
- Check the same page at a desktop viewport (1280×800 or wider) and a mobile viewport (375×812). Confirm layout, wrapping, overflow, navigation, and any interactive elements still work at both widths. If something breaks, fix it and re-check both viewports.
- Leave the browser on that page at the desktop viewport. Do not close the tab before ending the task.
If several pages changed, leave the most important one open. Prefer the primary user-facing route over a secondary or admin-only view.
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 · 26 lines · 375 tokens per session scan A 4daf85004dc8
cloud-browser-preview is a cursor rule published in the GitHub repository langfuse/langfuse-docs (237 stars, last pushed yesterday), licensed MIT. It adds 375 tokens to every session, about $0.0019 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 2026-08-30.
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