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
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/platonai/Browser4npx agentmods add skills/platonai/browser4/browser4-experienceWrote 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-experience)<a href="https://agentmods.dev/skills/platonai/browser4/browser4-experience"><img src="https://agentmods.dev/badge/skills/platonai/browser4/browser4-experience/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-experience"><img src="https://agentmods.dev/badge/skills/platonai/browser4/browser4-experience.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Excessive Agency · line 109 Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
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 | $0.00042 | $0.02942 |
| Opus 5.5 | $0.00017 | $0.01177 |
| Sonnet 5.5 | $0.00008 | $0.00588 |
| Haiku 4.5 | $0.00004 | $0.00294 |
Grade A, and why
browser4-experience 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 — 238 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Progressive Experience Memory (PEM)
The PEM system makes Browser4 progressively smarter: each successfully completed task deposits reusable knowledge so that future tasks — identical, similar, or on similar sites — complete faster with fewer steps.
1. Core Loop
Before task ──▶ experience_query ──▶ Get stored selectors, steps, blockers
│ │
▼ ▼
Execute task P1: Replay directly
│ P2: Verify then replay
▼ P3: Hint mode (verify all)
After task ──▶ experience_save ──▶ P4: Advisory only
P5: Cold start (no knowledge)
Copy-Paste Template
The experience tools are MCP tools called by the agent during browser4-cli agent run. The agent should call them as part of its tool set:
# Before starting a task — the agent calls experience_query to check prior knowledge
# After completing a task — the agent calls experience_save to persist what it learned
browser4-cli agent run "Go to https://amazon.com/dp/test and extract product details"
# To inspect stored knowledge, the agent calls experience_list
browser4-cli agent run "List experience knowledge entries for amazon"
2. Key Concepts
- Knowledge store — a local directory tree of memory artifacts (tasks, traces, index); the store layout is described in section 8.
- experience_save — persist a completed task's trace (selectors, steps, blockers) into the store.
- experience_query — retrieve relevant past traces before starting a new task; returns a replay tier P1-P5.
- experience_list — inspect what is stored, filtered by domain or intent.
- Replay tiers — P1 (replay directly) → P5 (cold start), the confidence ladder used by the Decision Tree in section 4.
3. Command Map
experience_save
Persists a task execution trace to the knowledge store.
| Argument | Required | Description |
|---|---|---|
url |
Yes | The URL the task operated on |
trace |
Yes | JSON-encoded ExecutionTrace (steps, selectors, extraction results) |
outcome |
No | "success" (default) or "failure" |
task_type |
No | Canonical task type (e.g., extract_product_list, publish_post) |
intent |
No | Free-text description of what the task was trying to do |
facts |
No | Retrospective knowledge patch (inline JSON, or @file.json through the CLI): selectors / interaction_hints / known_blockers / anti_patterns (camelCase and snake_case keys both accepted), merged into the (domain, intent) facts entry — the writer path for lessons learned. Refused when the entry is VERIFIED (immutable); the response then reports facts_rejected |
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 · +2 lines 757b71349aec
- 1mo ago Changed · +72 lines 3f954cb03242
- 1mo ago First seen · 164 lines · 42 tokens per session scan A fe50c286bc9f
browser4-experience is a skill published in the GitHub repository platonai/Browser4 (1,161 stars, last pushed yesterday), licensed Apache-2.0. It adds 42 tokens to every session and 2,942 once invoked, about $0.0002 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.
Other skills, from other repositories
eric-task-master
Run durable local Chrome automation with the installed Task Master CLI. Use when an Agent needs to create and execute a one-off browser task, follow its progress, or manage its Chrome Profile.
browse
Use the browse CLI for Browserbase browser automation, Browserbase cloud APIs, Browserbase Functions, templates, web fetch/search, diagnostics, and Browse.sh skill discovery/installation. Use when the user asks to navigate pages, inspect browser state, run local or remote browser sessions, manage Browserbase…
e2e-testing-patterns
Master end-to-end testing with Playwright and Cypress to build reliable test suites that catch bugs, improve confidence, and enable fast deployment. Use when implementing E2E tests, debugging flaky tests, or establishing testing standards.
computer-use
Read and drive native desktop apps through the accessibility layer — list apps, snapshot a window as a numbered element tree, then click/type/scroll/drag by element index or screen coordinates. Use for a desktop app, not a web page. macOS + Windows; off unless enabled in Settings.
feature-demo-recording
Record a demo video of a web feature from a real browser. Two modes -- a NARRATED film where measured voiceover drives the timeline (designed slides, subtitles, punch-in camera, rendered from an HTML timeline), and a SILENT evidence clip for a PR or a QA pass. Use when the user asks to record a video, demo, or screen…
browser-auth
Browse sites that need a logged-in session with playwright-cli, using attach mode, saved storage state, or individual cookies. Use when a page is behind a login wall and a plain open lands on a sign-in screen.