Borrowing it
Nothing to install: this file belongs to protostatis/unbrowser. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/protostatis/unbrowser/main/CLAUDE.mdgit clone --depth 1 https://github.com/protostatis/unbrowserWrote 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/instructions/protostatis/unbrowser/claude-md)<a href="https://agentmods.dev/instructions/protostatis/unbrowser/claude-md"><img src="https://agentmods.dev/badge/instructions/protostatis/unbrowser/claude-md/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/instructions/protostatis/unbrowser/claude-md"><img src="https://agentmods.dev/badge/instructions/protostatis/unbrowser/claude-md.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 | $0.05090 | $0.05090 |
| Opus 5.5 | $0.02036 | $0.02036 |
| Sonnet 5.5 | $0.01018 | $0.01018 |
| Haiku 4.5 | $0.00509 | $0.00509 |
Grade A, and why
unbrowser CLAUDE.md scanned grade A with 1 finding 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 2mo 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
| | curl/fetch | LLM WebFetch/Search | unbrowser | Full Chrome | How it starts
The opening of the file, as written. The whole thing — 164 lines — stays where its author put it; the contents beside it link to each section on GitHub.
unbrowser
Single statically-linked native binary that gives an LLM a headless browser with real JS execution. No rendering — designed for LLM tool-call use, not human viewing.
Distinct from ~/Projects/sky-search (QuickJS-WASM in user's browser, with iframe rendering for humans). This project ports several JS modules from sky-search but drops rendering, the WebSocket/server layers, and the iframe bridge entirely.
Why this exists
The four-way landscape:
| curl/fetch | LLM WebFetch/Search | unbrowser | Full Chrome | |
|---|---|---|---|---|
| Runs JS | No | No (provider-side, opaque) | Yes (QuickJS) | Yes (V8, JIT) |
| SPA-capable | No | Sometimes | Yes | Yes |
| Interactive (click/type/auth) | No | No | Yes | Yes |
| Session across calls | DIY | No | Yes | Yes |
| Output to LLM | Raw HTML (heavy) | Pre-summarized markdown | BlockMap (semantic, low-token) | Raw DOM or screenshot (very heavy) |
| Memory | ~0 | N/A | tens of MB | 200–500MB+ per page |
| Deploys as | one syscall | API call | one binary | a fleet |
The gap this fills: stateful, JS-required, non-visual web automation for LLM agents — log in, fill forms, navigate SPAs, scrape dashboards, follow multi-step flows — at one-binary deploy cost, with output already shaped for token efficiency.
Positioning: not "Chrome but smaller" (Chrome is the compatibility target — that framing loses). It's "WebFetch but stateful and interactive", or "curl but the page actually runs". The LLM-native output (BlockMap + element refs) is the differentiator that neither curl nor Chrome give you for free.
Honest weak spots vs Chrome: heavy JIT-bound JS (QuickJS is 20–50× slower); anti-bot that fingerprints canvas/WebGL/audio; anything visual (screenshot agents, captcha OCR); sites that lazy-load via real intersection observer + viewport metrics.
Architecture (locked)
- Native, not WASM. Rust host. Crates:
rquickjs,html5ever,wreq(Chrome-fingerprinted HTTP client — see Stealth),tokio,url,serde_json. - Runs page scripts so the DOM settles. SPA-capable.
- Interactive from day one — clicks, typing, event synthesis.
- No rendering. Replacement for human monitoring is a BlockMap: DOM walk → semantic block tree → DDM-style ASCII grid + structured JSON. Same source produces both LLM and human views.
- CSS selectors stay JS-side for v1 (reuse sky-search
dom.js). - Protocol: JSON-RPC over stdin/stdout for commands; NDJSON event stream on stderr for observability.
- Element refs (
e:142) returned by query commands are stable handles into the VDOM. - Stealth is a first-class concern, not a flag. See below.
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.
- 2mo ago First seen · 164 lines · 5,090 tokens per session scan A 8c5b91ed346f
unbrowser CLAUDE.md is an instructions file published in the GitHub repository protostatis/unbrowser (17 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 5,090 tokens to every session, about $0.0204 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
unbrowser CLAUDE.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| unbrowser CLAUDE.mdprotostatis/unbrowser | Instructions file | 17 | 2mo ago | Apache-2.0 | A | 5,090 | Claude Code |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 9,719 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | today | MIT | A | 7,461 | Codex, OpenCode |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 5,685 | GitHub Copilot |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | today | MIT | A | 4,680 | Codex, OpenCode |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 3,093 | GitHub Copilot |
| vscode model-prompts.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 2,022 | GitHub Copilot |