Browser4 is an AI-native browser engine that lets autonomous agents and people control real browsers, extract information from web pages, and automate tasks at scale. It combines browser interaction through a Rust CLI and MCP with deterministic selectors, machine-learning clustering, and language-model extraction. The catalogue entries provide skills and instructions for using Browser4.
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 platonai/Browser4 --skill browser4-plugingit clone --depth 1 https://github.com/platonai/Browser4Wrote 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/platonai/browser4/browser4-plugin)<a href="https://agentmods.dev/skills/platonai/browser4/browser4-plugin"><img src="https://agentmods.dev/badge/skills/platonai/browser4/browser4-plugin/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/platonai/browser4/browser4-plugin"><img src="https://agentmods.dev/badge/skills/platonai/browser4/browser4-plugin.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00066 | $0.03307 |
| Opus 5.5 | $0.00026 | $0.01323 |
| Sonnet 5.5 | $0.00013 | $0.00661 |
| Haiku 4.5 | $0.00007 | $0.00331 |
Grade A, and why
browser4-plugin 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 15d 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.
How it starts
The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Browser4 Plugin Development
Quick Start
mvn -pl browser4-pdk install # install the PDK parent POM once
mvn archetype:generate -DarchetypeGroupId=ai.platon.pulsar \
-DarchetypeArtifactId=browser4-plugin-archetype # scaffold the plugin project
mvn -f <artifactId>/pom.xml package # build the plugin JAR
Deploy the JAR to the server's plugins/ directory (or POST it to http://localhost:18182/api/plugins/install) and restart — the plugin is auto-discovered. Prerequisites: JDK 17+, Maven 3.9+, and access to the browser4-pdk parent POM.
For the full walkthrough — requirements clarification, mount-point implementation, services/config, manifest, tests, build & deploy — see Step-by-Step Workflow.
When to Use
Use this skill when the user wants to create, build, scaffold, or extend a Browser4 plugin — CAPTCHA solving, media processing, content conversion, page-category detection, custom RPA actions, or new LLM agent tools. It is the deep guide (mount points, services, tests, deployment); for plugin code scaffolding inside this repo use the browser4-coding skill.
Do NOT create a plugin for: simple data extraction from a known site (use the browser4-cli HTML snapshot / X-SQL instead), one-off browser automation (the CLI or a quick script is faster), or modifying core Browser4 behavior (that belongs in the main source tree, not a plugin).
How It Works
A plugin is a thin JAR built against the browser4-pdk parent POM: you scaffold the project from the archetype, implement the relevant PluginMount interfaces (Browse/Load/Crawl event mounts, ToolMount, PageSnifferMount), wire Spring auto-configuration, and build. The server auto-discovers the JAR from plugins/ on restart and logs the mounted beans.
Patterns
1. Event-handling plugin (BrowseEventMount)
Scaffold with mountPoints=["BrowseEventMount"], implement the browse handler, and register it via auto-configuration. The key hook is onDocumentSteady — see Step 4a for the full code.
What ships with it
4 files 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.
- 15d ago Changed · +6 lines fb8e92323d11
- 1mo ago First seen · 144 lines · 66 tokens per session scan A ffc373a0e4bd
browser4-plugin is a skill published in the GitHub repository platonai/Browser4 (1,161 stars, last pushed yesterday), licensed Apache-2.0. It adds 66 tokens to every session and 3,307 once invoked, about $0.0003 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 2026-08-30.
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