cloak-fetch

cloak-fetch — bot-protection / WAF fetch fallback

When a normal HTTP fetcher fails because the target site uses bot protection or WAF screening, route the same URL through CloakBrowser (a real Chromium with anti-bot patches at the C++ level and a genuine TLS/JA3 fingerprint) and return clean markdown via trafilatura. The agent never has to tell the user "the page is unfetchable" — it can try this skill first.

The underlying engine doesn't care which vendor is blocking the request — Cloudflare, DataDome, Akamai, PerimeterX, Imperva, Distil, Kasada, AWS WAF, or a no-name WAF rule. They all eventually let a real browser through, and CloakBrowser is a real browser.

When to trigger

Use immediately after any of these symptoms from a recent fetch tool call:

Symptom in tool output	Likely cause
`HTTP 403`, `403 Forbidden`, `HTTP 429`	Bot protection or rate-limit block
Empty body / a few hundred bytes of nothing on a content-rich URL	Silent WAF / TLS-fingerprint reject
Page rendered as a near-empty shell with a JS challenge script	SPA-only page or anti-bot challenge
`Resource was not loaded`, `net::ERR_HTTP2_PROTOCOL_ERROR`	Upstream blocked the fetch handshake
`Access denied`, `Blocked`, `You don't have permission`	Generic WAF / bot detection

Vendor-specific signatures

If the failure string roughly matches one of these, it's a CloakBrowser case — don't waste another round-trip on a plain HTTP client:

Vendor	Telltale strings / headers
Cloudflare	`Just a moment...`, `Enable JavaScript and cookies to continue`, `cf-ray:` header, `__cf_bm` cookie, `Attention Required! \| Cloudflare`, `Sorry, you have been blocked`
DataDome	`blocked by DataDome`, `<title>blocked</title>`, `dd-cookie` / `datadome` cookie, `<head>...captcha-delivery.com`, geo-block style 403 with empty body
Akamai Bot Manager	`Access Denied` with `Reference #18.` (long hex.epoch.hex) ID, `<TITLE>Access Denied</TITLE>` + Akamai `<HTML><HEAD>` boilerplate, `Pragma: akamai-x-cache`, `akamai-bot-manager` cookie
PerimeterX / HUMAN	`Please verify you are a human`, `Access to this page has been denied because we believe you are using automation tools`, `_px*` cookies (`_pxhd`, `_px3`), `<title>Human Verification</title>`
Imperva / Incapsula	`Incapsula incident ID:`, `Request unsuccessful. Incapsula incident ID`, `_Incapsula_Resource`, `visid_incap_*` cookie, `X-Iinfo` header
F5 / Distil	`Pardon Our Interruption`, `As you were browsing something about your browser made us think you were a bot`, `distil_r_captcha`, `D_RID` cookie
Kasada	`<head>` containing `ips.js`, `x-kpsdk-cd` / `x-kpsdk-cr` response headers, `429` with empty body + `kasada` reference
AWS WAF	`Request blocked` + `<aws-waf-token>`, `awswaf` cookie, body referencing `aws-waf-token`
Sucuri	`Sucuri WebSite Firewall - Access Denied`, `<title>Sucuri WebSite Firewall - CloudProxy</title>`, `X-Sucuri-ID` / `X-Sucuri-Cache` header, `sucuri-cf-id` cookie (very common on self-hosted WordPress)
reCAPTCHA / hCaptcha passive triggers	Interstitial that displays without user interaction — page replaced with `g-recaptcha`/`h-captcha` div and no real content. (See "When NOT to trigger" for interactive checkbox/slider cases.)
TLS / JA3 fingerprint reject	Connection drops, empty body, `ERR_HTTP2_PROTOCOL_ERROR`, `SSL_ERROR_ZERO_RETURN` on a site that loads fine in a normal browser

Also trigger preemptively when the user asks to fetch a page on a domain known to live behind one of these stacks — publishers (science.org, nature.com, sciencedirect.com, jstor.org), news (nytimes.com, bloomberg.com, ft.com, wsj.com), retail (nike.com, adidas.com, sephora.com), travel (kayak.com, southwest.com), financial (most broker portals). Going straight to this skill avoids a guaranteed-to-fail plain-HTTP round trip.

When NOT to trigger

Symptom	Why this skill won't help
`404 Not Found`	Page genuinely doesn't exist
`500 Internal Server Error`	Origin is broken, not blocking you
`401 Unauthorized` / login wall	Credentials needed — CloakBrowser does not carry them
Plain network error (DNS, connection refused, no route to host)	Network unreachable, not a bot block
Interactive captcha — slider, image-grid (reCAPTCHA "select all crosswalks"), Cloudflare Turnstile checkbox that requires a click, hCaptcha challenge	Needs a human or a paid solver service. CloakBrowser passes passive fingerprint checks but does not solve human-interaction challenges.
Geo-block where your IP's country is the actual reason (`This content is not available in your region`)	CloakBrowser uses the same IP — proxy/VPN is the fix, not a different browser
Site requires a session cookie, OAuth, or signed URL	No credential plumbing — fetch the auth artifact first via the proper channel
The normal fetcher already succeeded	No need to re-fetch

In these cases, report the actual failure to the user instead of masking it.

How to invoke

One command — the wrapper picks the right Python, runs the headless browser, extracts the main content with trafilatura, and writes clean markdown to stdout:

<SKILL_DIR>/cloak_fetch.sh "<URL>"

Where <SKILL_DIR> is wherever this skill is installed. Common locations:

Claude Code: ~/.claude/skills/cloak-fetch
OpenClaw: ~/.openclaw/skills/cloak-fetch
Codex: ~/.codex/skills/cloak-fetch
Project-local: .claude/skills/cloak-fetch or skills/cloak-fetch

A portable invocation that finds the skill across these locations:

for d in \
  "$HOME/.claude/skills/cloak-fetch" \
  "$HOME/.openclaw/skills/cloak-fetch" \
  "$HOME/.codex/skills/cloak-fetch" \
  ".claude/skills/cloak-fetch" \
  "skills/cloak-fetch"; do
  if [ -x "$d/cloak_fetch.sh" ]; then
    SKILL_DIR="$d"; break
  fi
done

"$SKILL_DIR/cloak_fetch.sh" "https://www.science.org/content/page/information-authors-research-articles"

The wrapper streams clean markdown on stdout. Save to a file with > out.md or pipe directly into further processing.

Behavior

Headless by default — no browser window opens.
Latency: ~20–40 s per call (browser launch + page render + content settle).
Output: clean markdown via trafilatura. Page chrome, navigation, ads, and cookie banners stripped. Headings, lists, links, and code blocks preserved. When trafilatura can't isolate a main content node, the wrapper falls back to emitting the rendered HTML so the agent still has something to read.
Failure modes: exits non-zero with a message on stderr if no cloakbrowser-enabled Python is found, the browser couldn't reach the URL, or CloakBrowser couldn't pass the challenge. Surface the failure honestly to the user — do not fabricate page content.

Configuration

Env var	Purpose	Default
`CLOAKBROWSER_PYTHON`	Path to the Python interpreter with `cloakbrowser` installed	`~/github/CloakBrowser/.venv/bin/python`, falling back to `python3`

For more advanced tuning (headless toggle, content-selector wait list, settle timing), edit cloak_fetch.py directly — see comments in that file.

Example end-to-end

User: "Get the authors info from https://www.science.org/content/page/information-authors-research-articles"

Agent tries WebFetch — gets HTTP 403 Forbidden.

Agent recognises the 403 → invokes this skill:

~/.claude/skills/cloak-fetch/cloak_fetch.sh \
  "https://www.science.org/content/page/information-authors-research-articles"

~25 s later, ~26 KB of clean markdown lands on stdout.
Agent answers the user from the markdown — no need to mention the underlying fetch took two attempts.

cloakFetch hook — same fallback wired up as a Claude Code PostToolUse hook (fully automatic, no agent decision required). Use the hook on Claude Code; use this skill on agents that lack a hook system (Codex, OpenCode, OpenClaw, etc.).

About this skill