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Agent skill

Headless Fallback

by hashgraph-online in hashgraph-online/awesome-codex-plugins

A skill your agent uses when a static fetch returns nothing useful and the page needs a real browser.

Apache-2.0Auto-check passed

Install Headless Fallback

skills CLI
$ npx skills add hashgraph-online/awesome-codex-plugins --skill headless-fallback -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install hashgraph-online/awesome-codex-plugins headless-fallback --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/hashgraph-online/awesome-codex-plugins.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/kreuzberg-dev/plugins/plugins/crawlberg/skills/headless-fallback .claude/skills/headless-fallback && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
headless-fallback
GitHub stars
1.2k
Token cost
~1.2k tokens
SKILL.md length
502 words
Files
1
Skills in repo
736
Repo updated
First seen
Licence
Apache-2.0

At a glance

A skill your agent uses when a static fetch returns nothing useful and the page needs a real browser.

  • A static fetch returns nothing useful and the page needs a real browser
  • SKILL.md covers Modes, Symptoms that point to headless, External CDP endpoint and Performance cost, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Headless Fallback is an agent skill from hashgraph-online/awesome-codex-plugins. Use when a static fetch returns nothing useful and the page needs a real browser. Covers --browser-mode auto|always|never, external CDP via --browser-endpoint, symptoms of JS-only pages and WAF blocks, and the performance cost.

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with Cloudflare. The repository describes itself as: A curated list of awesome OpenAI Codex / ChatGPT plugins, skills, and resources. The 1 Codex Marketplace. See live plugins at: https://hol.org/plugins/best-codex-plugins. The licence is Apache-2.0.

When your agent uses it

  • A static fetch returns nothing useful and the page needs a real browser

Example prompts

  • “/headless-fallback”

What it can do on your machine

Read from SKILL.md and the folder at commit 16b4156. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are bash).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Headless Fallback loads about 1.2k tokens when it runs. Until then it costs about 62 tokens; SKILL.md has 502 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~62
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from hashgraph-online/awesome-codex-plugins at commit 16b4156, republished under its Apache-2.0 licence (© hashgraph-online). 502 words, ~1,221 tokens.

Download SKILL.mdSave it as .claude/skills/headless-fallback/SKILL.md (or your agent's skills folder).
name
headless-fallback
description
Use when a static fetch returns nothing useful and the page needs a real browser. Covers `--browser-mode auto|always|never`, external CDP via `--browser-endpoint`, symptoms of JS-only pages and WAF blocks, and the performance cost.
<!--
AI-RULEZ :: GENERATED FILE — DO NOT EDIT
Content-Hash: blake3:9ce8ead27ee0f0b76d36ce4a455a5d17936077d6582e737c9b9a7ba46819b686
Source-Hash: blake3:b5689383a3914da8e3cc6ad3614356ae7f98c90cf99cb1b4b47be38456ff7a7c
Schema-Version: v1
-->

Headless fallback

Some pages are unscrapable without a real browser — SPA shells, infinite scroll, Cloudflare interstitials, JS-rendered article bodies. Crawlberg ships with an optional headless-Chrome backend driven by chromiumoxide.

Modes

text
--browser-mode auto    # default — try static first, fall back to browser on JS/WAF
--browser-mode always  # skip static, go straight to browser
--browser-mode never   # static only, fail closed
auto (default)

The engine fetches statically, then inspects the response. It launches headless Chrome and re-fetches when it sees:

  • WAF responses from one of 8 detected vendor fingerprints (Cloudflare, Akamai, AWS WAF, Imperva, DataDome, PerimeterX, F5, plus a generic catch-all).
  • SPA shells: <noscript> warnings, near-empty <body> with heavy JS.
  • Heuristic JS-render-required signals.

This is the right default. The browser only spins up when needed.

always

Skip the static probe entirely. Use when:

  • The user already told you the page needs JS.
  • You are scraping a site you know is React/Vue/Svelte SPA.
  • You need <script>-emitted state that never lands in static HTML.
bash
crawlberg scrape https://spa.example.com --browser-mode always --format markdown
never

Static only — the browser path is disabled. Use when:

  • You are in a hot loop where a stray Chrome launch would blow the budget.
  • You are running in a sandbox without a Chrome binary.
  • The user explicitly wants only static fetches.

In never mode, JS-only pages return empty/stub content. Inspect markdown.content and markdown.warnings before treating the result as final.

Symptoms that point to headless

In --browser-mode never or when you suspect the auto detector missed a signal:

  • markdown.content is short, nav-only, or just a loading message.
  • status_code is 200 but metadata.headings is empty on a page that clearly has headings.
  • markdown.warnings mentions JS-render-required or WAF detection.
  • 403/406/503 with WAF response headers (server: cloudflare, cf-mitigated, x-amz-cf-id, set-cookie: __cf_bm=…).

Re-run with --browser-mode always. If that succeeds, leave it set for that host.

Show full SKILL.md (240 more words)Show less

External CDP endpoint

Point at an already-running Chrome (Browserless, Steel, your own) instead of launching locally:

bash
crawlberg scrape https://example.com \
  --browser-mode always \
  --browser-endpoint ws://browser.internal:9222/devtools/browser/<id> \
  --format markdown

The endpoint must be a WebSocket URL — ws:// or wss://. The CLI rejects anything else with a clear error.

Use external CDP when:

  • You are running in containers or CI without a local Chrome.
  • You want a shared, warm browser pool across many crawl jobs.
  • You need browser-side residential proxies or stealth configuration the local Chrome cannot provide.

Performance cost

Headless Chrome is expensive relative to a static fetch:

  • Cold start: 1-3 seconds the first time it launches.
  • Per-page overhead: 500 ms-2 s for NetworkIdle wait, plus the page's own JS load time.
  • Memory: each tab takes 100-300 MB; long crawls should bound --concurrent.

Mitigations:

  • Stay in --browser-mode auto — the engine only pays the cost when it needs to.
  • Use --browser-endpoint to share one warm browser across jobs.
  • Drop --concurrent when you know the crawl will route through Chrome.

Wait strategies

Pass via --config JSON when you need control:

bash
crawlberg scrape https://example.com --browser-mode always \
  --config '{"browser":{"wait":"selector","wait_selector":".article-body"}}'

Supported strategies (the browser.wait field is a string enum; pair "selector" with a sibling wait_selector):

  • network_idle (default) — wait until the network goes quiet.
  • selector — wait until the CSS selector in wait_selector resolves.
  • fixed — wait a fixed duration.

extra_wait adds milliseconds on top of the wait strategy if the page keeps loading content after the primary signal.

Persistent profiles

bash
crawlberg scrape https://app.example.com --browser-mode always \
  --config '{"browser_profile":"prod","save_browser_profile":true}'

Profile names are path-traversal-validated. Use them to keep cookies, localStorage, and login state across runs without re-authenticating.

© hashgraph-online, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/kreuzberg-dev/plugins/plugins/crawlberg/skills/headless-fallback of hashgraph-online/awesome-codex-plugins.

Open the folder on GitHubat commit 16b4156

Compare with similar skills

Headless Fallback next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Headless Fallback compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Headless Fallback this skillhashgraph-online/awesome-codex-plugins1.2k—~1.2kAutomated safety check: PassApache-2.0
Cloudflare Browser Renderingcloudflare/moltworker9.9k—~742Automated safety check: PassApache-2.0
Turnstile Spincloudflare/skills3k4 repos~7.2kAutomated safety check: NotesApache-2.0
Star Office UI Setupringhyacinth/Star-Office-UI7.5k—~1.3kAutomated safety check: PassMIT
Cloudflarehodgef/apiker1277 repos~2.2kAutomated safety check: PassMIT
Webhome Extension Builderwebhtv/webhtv1.7k—~2.8kAutomated safety check: PassGPL-3.0

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  • Cloudflare Browser Rendering

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    Drives headless Chrome through Cloudflare Browser Rendering over a CDP WebSocket to take screenshots, navigate and scrape pages, and record multi-page videos.

    9.9k GitHub stars~742 tokensUpdated 5 mo ago
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  • Turnstile Spin

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    Set up, repair, or migrate to Cloudflare Turnstile bot verification in an existing frontend and backend, including server-side Siteverify.

    3k GitHub starsUsed in 4 repos~7.2k tokens
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Works with

Questions about Headless Fallback

What does Headless Fallback do?

A skill your agent uses when a static fetch returns nothing useful and the page needs a real browser. Headless Fallback is an agent skill from hashgraph-online/awesome-codex-plugins. Use when a static fetch returns nothing useful and the page needs a real browser.

When should I use Headless Fallback?

Headless Fallback fits situations like: A static fetch returns nothing useful and the page needs a real browser.

How do I install Headless Fallback in Claude Code?

Run `npx skills add hashgraph-online/awesome-codex-plugins --skill headless-fallback -a claude-code`. Or copy the skill folder (plugins/kreuzberg-dev/plugins/plugins/crawlberg/skills/headless-fallback in hashgraph-online/awesome-codex-plugins) into .claude/skills/headless-fallback in your project. Claude Code loads it when a task matches its description.

How do I install Headless Fallback in Codex?

Run `npx skills add hashgraph-online/awesome-codex-plugins --skill headless-fallback -a codex`. Or copy the skill folder (plugins/kreuzberg-dev/plugins/plugins/crawlberg/skills/headless-fallback in hashgraph-online/awesome-codex-plugins) into .agents/skills/headless-fallback in your project. Codex loads it when a task matches its description.

Can I use Headless Fallback in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add hashgraph-online/awesome-codex-plugins --skill headless-fallback -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/headless-fallback, .gemini/skills/headless-fallback, .github/skills/headless-fallback and .opencode/skills/headless-fallback in your project.

What does Headless Fallback need to run?

SKILL.md names no scripts, command-line tools or credentials: Headless Fallback is instructions for the agent only.

Does Headless Fallback access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Headless Fallback safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Headless Fallback use?

Headless Fallback is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Headless Fallback use?

About 1.2k tokens (SKILL.md is roughly 4.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Headless Fallback?

Skills that share tags, products or a category with Headless Fallback: Cloudflare Browser Rendering (cloudflare/moltworker, 9.9k stars), Turnstile Spin (cloudflare/skills, 3k stars), Star Office UI Setup (ringhyacinth/Star-Office-UI, 7.5k stars) and Cloudflare (hodgef/apiker, 127 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Headless Fallback?

hashgraph-online (a GitHub organization) maintains it in hashgraph-online/awesome-codex-plugins, which has 1,232 GitHub stars. The repository holds 736 skills in this directory. The repository was last updated on October 6, 2026.

Source: hashgraph-online/awesome-codex-plugins on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.