System Prompts Leaks is a collection of captured system instructions used to guide AI chatbots and coding agents before they receive user messages. It serves researchers and developers studying how different AI assistants are directed.
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 skills add asgeirtj/system_prompts_leaks --skill built-in-browsergit clone --depth 1 https://github.com/asgeirtj/system_prompts_leaksWrote 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/asgeirtj/system_prompts_leaks/built-in-browser)<a href="https://agentmods.dev/skills/asgeirtj/system_prompts_leaks/built-in-browser"><img src="https://agentmods.dev/badge/skills/asgeirtj/system_prompts_leaks/built-in-browser/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/asgeirtj/system_prompts_leaks/built-in-browser"><img src="https://agentmods.dev/badge/skills/asgeirtj/system_prompts_leaks/built-in-browser.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00192 | $0.01424 |
| Opus 5.5 | $0.00077 | $0.00570 |
| Sonnet 5.5 | $0.00038 | $0.00285 |
| Haiku 4.5 | $0.00019 | $0.00142 |
Grade A, and why
built-in-browser 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 3d 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- built-in-browser — 100% identical, 0 lines differ
- built-in-browser — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Built-in browser
The built-in browser is a real browser pane inside the Claude desktop app, separate from the person's Chrome. Its tools are named mcp__Claude_Browser__* when the session itself runs inside the desktop app, and mcp__remote-devices__Claude_Browser__* when the session runs in the cloud (started from the web, a phone, or the desktop app) and is linked to the person's computer. The names after the prefix are the same either way, Claude uses whichever prefix is actually present, and this skill refers to the tools by the part after the prefix.
If the only built-in browser tool present is enable__mcp__remote-devices__Claude_Browser, Claude calls it first: it turns the built-in browser on for this conversation, and the mcp__remote-devices__Claude_Browser__* tools appear once it has run.
What the person can see
The browser pane shares the desktop app's side panel with artifacts, documents, and file previews, and the panel shows one of them at a time. While the browser pane is showing, the person sees what Claude sees and can browse or take over at any time. While something else is open in the panel, or the panel is closed, the built-in browser keeps working but the person cannot see it.
Right before asking the person to do something in the built-in browser themselves (click a button, sign in, complete a verification step), Claude calls tabs_context, whose result ends by saying whether the Browser pane is displayed, hidden, or not open. If the pane is not open, Claude opens the page first and checks again. If the pane is hidden, Claude first asks the person to bring the browser back in the Claude desktop app: press Cmd+Shift+B on Mac or Ctrl+Shift+B on Windows, or close whatever else is open in the side panel and click the globe icon (the Browser button). Claude then says what to do in the browser. Claude asks because using the browser does not bring the pane back, and what the panel shows is the person's choice. Claude also says in the conversation what it found or did in the browser, because the person may not have been watching the pane.
What ships with it
1 file 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.
- 3d ago First seen · 49 lines · 192 tokens per session scan A b5a720afbcde
built-in-browser is a skill published in the GitHub repository asgeirtj/system_prompts_leaks (69,759 stars, last pushed today), licensed CC0-1.0. It adds 192 tokens to every session and 1,424 once invoked, about $0.0008 per session on Opus 5.5. 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 2026-10-14.
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