create-plugin

create-plugin is a skill for Claude Code from ShreyPaharia/octomux. It costs 43 tokens per session (4,309 once invoked), scanned A, original, MIT.

A guide for building an octomux plugin, which is an installable package that adds a workflow type, integration provider, or agent harness.

In plain words
What is it for?
Creating, testing, and checking a plugin that exports an apply function and may include workflow presets.
Why use it?
It explains the required package structure and registration method, reducing mistakes when extending octomux.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code; mentions Codex.

Part of the octomux plugin — 20 skills, 1 agent shipped together

Good fit Creating, testing, and checking a plugin that exports an apply function and may include workflow presets.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/shreypaharia/octomux/create-plugin
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add ShreyPaharia/octomux --skill create-plugin
Clone the repo
git clone --depth 1 https://github.com/ShreyPaharia/octomux

Made for: Claude Code.

Or install octomux, the plugin that ships this one along with the rest of its 20 skills, 1 agent.

Wrote 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.

agentmods badge for create-plugin

README.md
[![agentmods](https://agentmods.dev/badge/skills/shreypaharia/octomux/create-plugin/github.svg)](https://agentmods.dev/skills/shreypaharia/octomux/create-plugin)
Your own site
<a href="https://agentmods.dev/skills/shreypaharia/octomux/create-plugin"><img src="https://agentmods.dev/badge/skills/shreypaharia/octomux/create-plugin/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.

agentmods 80×15 button for create-plugin

Your own site · 80×15
<a href="https://agentmods.dev/skills/shreypaharia/octomux/create-plugin"><img src="https://agentmods.dev/badge/skills/shreypaharia/octomux/create-plugin.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,309 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 8 findings, 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 Prompt Injection · line 59
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 61
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 62
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 65
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 66
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 67
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 71
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Rogue Agent · line 240
    Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
    Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00043 $0.04309
Opus 5 $0.00022 $0.02155
Sonnet 5 $0.00009 $0.00862
Haiku 4.5 $0.00004 $0.00431

Measured 9d ago against content hash bec6244d2da3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

create-plugin 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 9d 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.

plugin/skills/create-plugin/SKILL.md · 340 lines

How it starts

The opening of the file, as written. The whole thing — 340 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Create an octomux plugin

Author a plugin package that registers into octomux at boot: a workflow kind, an integration provider, or a harness. A plugin is a normal npm package that exports an apply(ctx) function; octomux loads it in-process via import() — see the add-plugin skill for the trust implications of that before you ship one.

Package layout

octomux-plugin-<name>/
  package.json       # name, version, type: module, main (or exports)
  index.js           # the apply(ctx) export
  kinds/              # optional — schedule-kind presets this plugin ships
    <kind>.json

package.json needs a real main/exports field once published — during local dev (see "Testing it locally" below) a bare index.js with no package.json also resolves, because Node's module resolution falls back to index.js when no package.json is present. Don't rely on that for anything you publish.

The apply(ctx) export

export function apply(ctx) {
  ctx.logger.info({}, 'plugin applied');
  ctx.workflows.register({ kind: 'changelog', displayName: 'Changelog', surfaces: ['feed'] });
}

apply can also hang off a default export (export default { apply }) — both forms are read as "this module is the plugin."

apply(ctx) runs once at boot, in manifest order, each in its own try/catch — one plugin throwing never takes down another. It has a 10-second budget (DEFAULT_APPLY_TIMEOUT_MS in server/plugins/loader.ts); overrun it and the loader marks the plugin failed (phase apply) and revokes its context — any registrar call your apply() makes after that point throws context revoked — … refused because apply() overran its timeout budget instead of quietly landing in the live registry after the loader already reported you failed. Keep apply() synchronous-fast; don't do network calls or slow I/O in it.

An optional reconcile?(ctx) export exists on the OctomuxPlugin interface for plugins owning out-of-process state (worktrees, tmux, files written into a repo) and is documented as required for that case — but nothing in the codebase calls it yet (server/plugins/loader.ts explicitly does not; boot has no other caller). Export it if your plugin owns that kind of state so you're ready when the wiring lands, but don't depend on it running today. apply() is currently the only place your plugin's own code executes at boot.

Read the full file on GitHub · 340 lines

Changes

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.

  1. 9d ago First seen · 340 lines · 43 tokens per session scan A bec6244d2da3

Subscribe to this mod's changes

create-plugin is a skill published in the GitHub repository ShreyPaharia/octomux (22 stars, last pushed 8d ago), licensed MIT. It adds 43 tokens to every session and 4,309 once invoked, about $0.0002 per session on Opus 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.

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