Agent skill

Javascript

A skill your agent uses for Synchronet's JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints, the object/class model (MsgBase, FileBase, File, User, system…

Custom licenceAuto-check passedDevelopment

Install Javascript

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a claude-code

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

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript --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/SynchronetBBS/sbbs.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/javascript .claude/skills/javascript && 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/

Paste into Claude Code

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .claude/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/SynchronetBBS/sbbs.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.claude/skills/javascript .agents/skills/javascript && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .agents/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/SynchronetBBS/sbbs.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.claude/skills/javascript .cursor/skills/javascript && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .cursor/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/SynchronetBBS/sbbs.git --path .claude/skills/javascript

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/SynchronetBBS/sbbs.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.claude/skills/javascript .gemini/skills/javascript && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .gemini/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/SynchronetBBS/sbbs.git skills-src && mkdir -p .github/skills && cp -r skills-src/.claude/skills/javascript .github/skills/javascript && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .github/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add SynchronetBBS/sbbs --skill javascript -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install SynchronetBBS/sbbs javascript --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/SynchronetBBS/sbbs.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.claude/skills/javascript .opencode/skills/javascript && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "javascript" agent skill from https://github.com/SynchronetBBS/sbbs/tree/master/.claude/skills/javascript into .opencode/skills/javascript/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "javascript", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: javascript
GitHub stars: 111
Token cost: ~17k tokens
SKILL.md length: 7,188 words
Files: 2 (incl. scripts)
Skills in repo: 8
Repo updated: Oct 6, 2026
First seen: Oct 7, 2026
Licence: Custom licence

At a glance

A skill your agent uses for Synchronet's JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints, the object/class model (MsgBase, FileBase, File, User, system…

Works in 3 steps: Host-injected globals — defined in C++… → Class-static properties — attached to… → JS-library constants — defined in…
Synchronets JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints
SKILL.md covers Before hand-rolling a utility,…, Environment variables: there…, The dialect: SpiderMonkey… and The host object model, plus 10 more sections
Runs Python scripts from its folder; calls curl and openssl; reaches archive.org

What it does

Javascript is an agent skill from SynchronetBBS/sbbs. Use for Synchronet's JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints, the object/class model (MsgBase, FileBase, File, User, system, msgarea/filearea, Socket, MQTT, etc.), how those APIs actually behave (including sharp edges like MsgBase.getallmsgheaders() lazy fields), writing tests in exec/tests/, and the stock exec/.js module ecosystem as API references. Trigger when authoring or debugging Synchronet .js/.ssjs/.xjs code, asking "how does the MsgBase/User/FileBase API work", "why…

Its SKILL.md is about 17k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including scripts (for example `scripts/jsobjs.py`).

It sits in Development, covering Debugging. It works with JavaScript and C++. The repository describes itself as: Mirror of gitlab.synchro.net/sbbs (don't submit pull requests here).

When your agent uses it

Synchronets JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints
The object/class model (MsgBase
Msgarea/filearea
How those APIs actually behave (including sharp edges like MsgBase.getallmsgheaders() lazy fields)

Example prompts

“how does the MsgBase/User/FileBase API work”
“why is h.toext undefined”
“why is JSON.parse failing on only some lines of my .jsonl”
“/javascript”

Requirements

Python 3

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

Host-injected globals — defined in C++ (js_global.cpp), added to
Class-static properties — attached to the JS class itself via
JS-library constants — defined in exec/load/*.js files. Must be

What it can do on your machine

Read from SKILL.md and the folder at commit d83fbe2. 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
Ships 1 file in scripts/ (Python), which the agent can run.
Shell commands in SKILL.md call:
- curl
- openssl
From the folder's file list and the shell code blocks in SKILL.md.
Network
Hosts in commands or code, which the agent is likely to contact:
- archive.org
Also links to:
- wiki.synchro.net
- nix.synchro.net
- developer.mozilla.org
- synchro.net
- ecma-international.org
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

Javascript loads about 17k tokens when it runs. Until then it costs about 205 tokens; SKILL.md has 7,188 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~205
When it runs · the whole SKILL.md, loaded when a task matches: ~17k

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); the scripts in this folder are not scanned.

SKILL.md

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 7,188 words (~16,904 tokens).

“This skill is about writing and reasoning about Synchronet JavaScript — the dialect, the host object model, and how the APIs behave. To actually run a script or inline probe (jsexec flags, invocation modes, capturing output, Windows debug builds), use…”

— opening of SKILL.md by SynchronetBBS, Custom licence

name: javascript

Outline of SKILL.md

Synchronet JavaScript (the language + host API)
Before hand-rolling a utility, look for a native one
Filesystem: globbing and listing subdirectories
Downloading and unpacking: HTTPRequest + Archive
Environment variables: there is no getenv()
The dialect: SpiderMonkey 1.8.5 (ES3-ish + a few ES5 bits)
The host object model
Where Synchronet JavaScript runs (invocation contexts)
Script lifecycle: exit handlers (js.on_exit)
⚠️ Register on_exit at the script's top level — not inside a function
Prefer try/finally for clean-unwind cleanup; use on_exit only as the forced-terminate…
load() and require()
⚠️ load('file') runs in the caller's scope — capture what other scopes need
Constants: C vs JS namespaces (USER_UTF8 ≠ UTF8)
Terminal capability: runtime vs stored
MsgBase — the message-base API
get_all_msg_headers([include_votes=false] [, expand_fields=true])
⚠️ The lazy-field gotcha (read this before filtering on to_ext/from_ext/etc.)
Field types & values
Deleting messages
Modifying a header: read it UNEXPANDED or the write is refused
Reading text files: readAll()/readln() split lines at 512 bytes
Reading INI files (and the trailing-comment trap)
key : value — string literals with C escapes (never hand-roll an unescaper)
The root (unnamed) section = global defaults
Common API recipes
Sysop-configurable text strings (bbs.text) — and the multi-%s format trap
ARS access checks: bbs.compare_ars (current user) vs User.compare_ars (anyone)
Output & input: choosing the right function
Terminal control sequences are abstracted in ansiterm_lib.js — check before hardcoding…

Read the full SKILL.md on GitHub

Files

SKILL.md and 1 other file (scripts) in .claude/skills/javascript of SynchronetBBS/sbbs.

SKILL.md
scripts/jsobjs.py

Open the folder on GitHubat commit d83fbe2

Compare with similar skills

Javascript 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.

Javascript compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Javascript this skillSynchronetBBS/sbbs	111	—	~17k	Automated safety check: Pass	Custom licence	yesterday
MCP Debuggerdebugmcp/mcp-debugger	171	—	~3.8k	Automated safety check: Pass	MIT	today
SlintMoosync/Moosync	259	—	~2.4k	Automated safety check: Pass	GPL-3.0	6 days ago
Failure Oriented InstrumentationArabelaTso/Skills-4-SE	253	—	~2.1k	Automated safety check: Pass	Apache-2.0	1 mo ago
Replay Oriented InstrumentationArabelaTso/Skills-4-SE	253	—	~2.5k	Automated safety check: Pass	Apache-2.0	1 mo ago
JS Cpp Protocolnotepadqq/notepadqq	2.3k	—	~3.2k	Automated safety check: Pass	GPL-3.0	2 days ago

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Questions about Javascript

What does Javascript do?

A skill your agent uses for Synchronet's JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints, the object/class model (MsgBase, FileBase, File, User, system…. Javascript is an agent skill from SynchronetBBS/sbbs.js module ecosystem as API references.

When should I use Javascript?

Javascript fits situations like: synchronets JavaScript language and host API — the SpiderMonkey 1.8.5 dialect constraints; the object/class model (MsgBase; msgarea/filearea; how those APIs actually behave (including sharp edges like MsgBase.getallmsgheaders() lazy fields).

How do I install Javascript in Claude Code?

Run `npx skills add SynchronetBBS/sbbs --skill javascript -a claude-code`. Or copy the skill folder (.claude/skills/javascript in SynchronetBBS/sbbs) into .claude/skills/javascript in your project. Claude Code loads it when a task matches its description.

How do I install Javascript in Codex?

Run `npx skills add SynchronetBBS/sbbs --skill javascript -a codex`. Or copy the skill folder (.claude/skills/javascript in SynchronetBBS/sbbs) into .agents/skills/javascript in your project. Codex loads it when a task matches its description.

Can I use Javascript 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 SynchronetBBS/sbbs --skill javascript -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/javascript, .gemini/skills/javascript, .github/skills/javascript and .opencode/skills/javascript in your project.

What does Javascript need to run?

Going by SKILL.md and its folder, Javascript needs Python for the scripts in its folder and the command-line tools its instructions call (curl and openssl). Our summary lists: Python 3.

Does Javascript access the network?

SKILL.md names 6 domains. In commands or code: archive.org; the agent is likely to contact it when it follows the instructions. As links in the text: wiki.synchro.net, nix.synchro.net, developer.mozilla.org, synchro.net and ecma-international.org. This is read from the text; nothing was executed.

Is Javascript 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. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Javascript use?

Javascript has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does Javascript use?

About 17k tokens (SKILL.md is roughly 68k 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 Javascript?

Skills that share tags, products or a category with Javascript: MCP Debugger (debugmcp/mcp-debugger, 171 stars), Slint (Moosync/Moosync, 259 stars), Failure Oriented Instrumentation (ArabelaTso/Skills-4-SE, 253 stars) and Replay Oriented Instrumentation (ArabelaTso/Skills-4-SE, 253 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Javascript?

SynchronetBBS (a GitHub organization) maintains it in SynchronetBBS/sbbs, which has 111 GitHub stars. The repository holds 8 skills in this directory. The repository was last updated on October 6, 2026.

Source: SynchronetBBS/sbbs on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Javascript

Install Javascript

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Files

Compare with similar skills

Similar skills

MCP Debugger

Slint

Failure Oriented Instrumentation

Replay Oriented Instrumentation

JS Cpp Protocol

Extempore JIT Debugging Guide

More from SynchronetBBS/sbbs

Smbutils

Text

Control

Jsexec

Logs

Menus

Questions about Javascript

Install Javascript

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Files

Compare with similar skills

Similar skills

More from SynchronetBBS/sbbs

Related

Questions about Javascript