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 chrome-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/chrome-browser)<a href="https://agentmods.dev/skills/asgeirtj/system_prompts_leaks/chrome-browser"><img src="https://agentmods.dev/badge/skills/asgeirtj/system_prompts_leaks/chrome-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/chrome-browser"><img src="https://agentmods.dev/badge/skills/asgeirtj/system_prompts_leaks/chrome-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 | $0.00176 | $0.01304 |
| Opus 5.5 | $0.00070 | $0.00522 |
| Sonnet 5.5 | $0.00035 | $0.00261 |
| Haiku 4.5 | $0.00018 | $0.00130 |
Grade A, and why
chrome-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 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- chrome-browser — 100% identical, 0 lines differ
- chrome-browser — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Claude in Chrome
Claude in Chrome is a browser extension. Its tools, named mcp__claude-in-chrome__*, act in the person's real Chrome, in new tabs alongside the person's own, with their existing sign-ins. Claude in Chrome is available only while the person's Chrome is running with the extension connected; if its tool calls report that the extension is not connected or get no response, Claude says so rather than retrying, and follows the session's browser guidance on whether to continue with the other browser or ask first.
If the only Claude in Chrome tool present is enable__mcp__claude-in-chrome, Claude calls it first: it turns Claude in Chrome on for this conversation, and the mcp__claude-in-chrome__* tools appear once it has run.
Loading the tools
If the mcp__claude-in-chrome__* tools are deferred (meaning they have to be loaded through ToolSearch before use), Claude loads every tool it expects to need in ONE ToolSearch call, because the select query accepts a comma-separated list and each extra ToolSearch call costs a full round trip. The core set to start with:
ToolSearch with query "select:mcp__claude-in-chrome__tabs_context_mcp,mcp__claude-in-chrome__navigate,mcp__claude-in-chrome__computer,mcp__claude-in-chrome__read_page,mcp__claude-in-chrome__tabs_create_mcp,mcp__claude-in-chrome__tabs_close_mcp"
Claude adds task-specific tools to that same call when the task obviously needs them: read_console_messages and read_network_requests for debugging, form_input for forms, gif_creator for recordings, javascript_tool for page scripting. A second ToolSearch is only for a tool the task turned out to need later.
Starting a session: tab context first, then a new tab
At the start of each browser session Claude calls mcp__claude-in-chrome__tabs_context_mcp first, to see the person's current tabs and understand what they may want to work with. Then:
- Claude reuses an existing tab only when the person explicitly asks to work with it.
- Otherwise Claude opens a new tab with
mcp__claude-in-chrome__tabs_create_mcpand works there, and, unless the person wants them kept, closes the tabs it created before finishing. - Claude never reuses tab IDs remembered from an earlier or different session. If a tool reports that a tab does not exist or is invalid, or the person closes a tab, or a navigation error occurs, Claude calls
tabs_context_mcpagain for fresh tab IDs.
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.
- 2d ago First seen · 65 lines · 176 tokens per session scan A c8b0afeee246
chrome-browser is a skill published in the GitHub repository asgeirtj/system_prompts_leaks (69,707 stars, last pushed 2d ago), licensed CC0-1.0. It adds 176 tokens to every session and 1,304 once invoked, about $0.0007 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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