Cloak Fetch

OpenCode plugin that replaces the built-in webfetch tool with a CloakBrowser-backed fetcher.

Use it when pages need JavaScript execution, Chromium rendering, stealth browser behavior, proxy settings, locale/timezone controls, or other browser-level options that the built-in fetcher cannot provide.

Installation

Add the npm package to your OpenCode config.

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-cloak-fetch"]
}

OpenCode loads npm plugins at startup. No additional tool configuration is required. The plugin registers a tool named webfetch, which takes precedence over the built-in tool with the same name.

For a local checkout during development, use a file URL instead.

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["file:///path/to/opencode-cloak-fetch"]
}

First Startup

On startup, the plugin starts preparing the CloakBrowser browser binary in the background. The first webfetch call waits for that preparation if it is still running.

If the browser binary is not already available, CloakBrowser downloads it to its cache directory. Download and update status is shown through OpenCode toast notifications titled Cloak Fetch. CloakBrowser console output is written to the OpenCode app log instead of the tool output area.

Only one OpenCode process prepares the browser binary at a time. Other processes wait for the same preparation lock to finish.

Configuration Files

Create cloakfetch.json or cloakfetch.jsonc in any supported location. Later layers override earlier layers. Within the same directory, cloakfetch.jsonc is read after cloakfetch.json and can override it.

Read order:

1. Built-in defaults.
2. Global OpenCode config directory: cloakfetch.json, then cloakfetch.jsonc.
3. Directory from OPENCODE_CONFIG_DIR: cloakfetch.json, then cloakfetch.jsonc.
4. Nearest project .opencode directory found by walking upward from the current directory: cloakfetch.json, then cloakfetch.jsonc.

Global OpenCode config directory:

• $XDG_CONFIG_HOME/opencode, when XDG_CONFIG_HOME is set.
• ~/.config/opencode, when XDG_CONFIG_HOME is not set.

If neither cloakfetch.json nor cloakfetch.jsonc exists in the global OpenCode config directory, the plugin creates an empty cloakfetch.jsonc file on first load.

Example Configuration

{
  "$schema": "https://raw.githubusercontent.com/partment/opencode-cloak-fetch/main/configSchema.json",
  "enabled": true,
  "defaultFormat": "markdown",
  "maxChars": 120000,
  "timeout": {
    "navigationSeconds": 30,
    "launchMs": 20000,
    "closeMs": 2000,
    "extractMs": 5000,
    "challengeWaitMs": 20000,
    "postLoadDelayMs": 750
  },
  "cloakbrowser": {
    "headless": true,
    "proxy": {
      "server": "socks5://host:1080",
      "username": "user",
      "password": "pass"
    },
    "args": ["--disable-dev-shm-usage"],
    "stealthArgs": true,
    "timezone": "Asia/Taipei",
    "locale": "zh-TW",
    "geoip": false,
    "humanize": false,
    "humanPreset": "default",
    "humanConfig": {},
    "launchOptions": {}
  },
  "environment": {
    "autoUpdate": false,
    "binaryPath": null,
    "cacheDir": null,
    "downloadUrl": null,
    "skipChecksum": false
  },
  "session": {
    "enabled": false,
    "cacheDir": null
  },
  "output": {
    "includeTitle": true,
    "includeSource": true,
    "truncateMarker": "[truncated]"
  }
}

Configuration Reference

Top-Level Fields

Field	Type	Default	Description
enabled	boolean	true	Enables or disables this plugin's webfetch implementation.
defaultFormat	string	"markdown"	Output format used when the tool call does not provide format. Allowed: markdown, text, html.
maxChars	integer	120000	Maximum output size before truncation. (>=1)
timeout	object	see below	Timeout controls for browser launch, navigation, challenge waiting, extraction, and close.
cloakbrowser	object	see below	Options passed to cloakbrowser/puppeteer launch.
environment	object	see below	Environment variables used by CloakBrowser binary management.
session	object	see below	Persistent browser profile controls for retaining challenge credentials and site state.
output	object	see below	Formatting controls for text and markdown output.

timeout

Field	Type	Default	Description
navigationSeconds	integer	30	Page navigation timeout in seconds. The tool argument timeout overrides this per call. (1-120)
launchMs	integer	20000	Browser launch timeout in milliseconds. (>=1)
closeMs	integer	2000	Browser close timeout in milliseconds. Close errors are ignored after this timeout. (>=1)
extractMs	integer	5000	Timeout for HTML or text extraction after navigation. (>=1)
challengeWaitMs	integer	20000	Maximum time to wait for detected anti-bot challenge pages to complete before extracting content. Set to 0 to disable. (>=0)
postLoadDelayMs	integer	750	Delay after domcontentloaded before extracting content. (>=0)

cloakbrowser

Field	Type	Default	Description
headless	boolean	true	Runs Chromium in headless mode.
proxy	string or object	unset	Proxy configuration passed to CloakBrowser. Object form supports server, bypass, username, and password.
args	array	[]	Additional Chromium arguments. Array of strings.
stealthArgs	boolean	unset	Enables CloakBrowser stealth argument handling when set.
timezone	string	unset	Browser timezone, such as Asia/Taipei.
locale	string	unset	Browser locale, such as zh-TW or en-US.
geoip	boolean	unset	Enables CloakBrowser geo-IP behavior when supported by CloakBrowser.
humanize	boolean	unset	Enables CloakBrowser humanization behavior when supported by CloakBrowser.
humanPreset	string	unset	Humanization preset. Allowed: default, careful.
humanConfig	object	unset	Additional humanization settings passed to CloakBrowser.
launchOptions	object	unset	Extra Puppeteer launch options. The plugin still sets a bounded launch timeout.

proxy object form:

Field	Type	Required	Description
server	string	yes	Proxy server URL.
bypass	string	no	Proxy bypass list.
username	string	no	Proxy username.
password	string	no	Proxy password.

environment

These fields map to CloakBrowser environment variables before binary preparation.

Field	Type	Default	Environment Variable	Description
autoUpdate	boolean	false	CLOAKBROWSER_AUTO_UPDATE	Allows update checks when binaryPath and downloadUrl are not set.
binaryPath	string or null	unset	CLOAKBROWSER_BINARY_PATH	Uses an existing browser binary instead of the cached CloakBrowser binary. String value must be non-empty.
cacheDir	string or null	unset	CLOAKBROWSER_CACHE_DIR	CloakBrowser cache directory. Also stores the plugin's preparation lock. String value must be non-empty.
downloadUrl	string or null	unset	CLOAKBROWSER_DOWNLOAD_URL	Custom browser binary download URL. String value must be non-empty.
skipChecksum	boolean	false	CLOAKBROWSER_SKIP_CHECKSUM	Skips checksum verification when CloakBrowser supports it.

session

When enabled, the plugin creates a persistent Chromium profile per URL origin, such as https://example.com. This preserves cookies, localStorage, IndexedDB, and other browser profile state so the same site can reuse previously completed anti-bot challenges when the site still accepts those credentials.

Profiles are opt-in because they store site session data on disk. Delete cacheDir to clear saved state. If cloakbrowser.launchOptions.userDataDir is set, that explicit profile path is used and this automatic per-origin profile cache is skipped.

Field	Type	Default	Description
enabled	boolean	false	Enables persistent per-origin browser profiles.
cacheDir	string or null	unset	Directory for persistent session profiles. Defaults to cloakfetch-sessions under the global OpenCode config directory. String value must be non-empty.

output

Field	Type	Default	Description
includeTitle	boolean	true	Adds the page title to markdown and text output.
includeSource	boolean	true	Adds the final page URL to markdown and text output.
truncateMarker	string	"[truncated]"	Marker appended after truncated output.

Tool Arguments

The registered webfetch tool accepts:

Argument	Type	Description
url	string	Page URL to fetch. Must be a valid URL.
format	string	Optional output format. Defaults to defaultFormat. Allowed: markdown, text, html.
timeout	integer	Optional per-call navigation timeout in seconds. (1-120)

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Development

pnpm install
pnpm run typecheck
pnpm run test
pnpm run build