megaplan

megaplan is a skill for Claude Code, Codex from peteromallet/Arnold. It costs 20 tokens per session (12,688 once invoked), scanned A, original, Apache-2.0.

A system for coordinating Claude and GPT agents to make and carry out detailed plans. An agent is a software process that performs tasks or makes decisions on a user's behalf.

In plain words
What is it for?
It helps break down large tasks, coordinate multiple AI models, and execute an organised implementation plan.
Why use it?
It is intended to make complex plans more robust before execution and coordinate the work needed to complete them.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions subagents; mentions Claude Code; mentions Codex.

Good fit It helps break down large tasks, coordinate multiple AI models, and execute an organised implementation plan.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/peteromallet/arnold/claude
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 peteromallet/Arnold --skill claude
Clone the repo
git clone --depth 1 https://github.com/peteromallet/Arnold

Made for: Claude Code, Codex.

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 megaplan

README.md
[![agentmods](https://agentmods.dev/badge/skills/peteromallet/arnold/claude/github.svg)](https://agentmods.dev/skills/peteromallet/arnold/claude)
Your own site
<a href="https://agentmods.dev/skills/peteromallet/arnold/claude"><img src="https://agentmods.dev/badge/skills/peteromallet/arnold/claude/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 megaplan

Your own site · 80×15
<a href="https://agentmods.dev/skills/peteromallet/arnold/claude"><img src="https://agentmods.dev/badge/skills/peteromallet/arnold/claude.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 12,688 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.
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 $0.00020 $0.12688
Opus 5.5 $0.00008 $0.05075
Sonnet 5.5 $0.00004 $0.02538
Haiku 4.5 $0.00002 $0.01269

Measured 1mo ago against content hash ee7bab66825d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

megaplan 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 1mo 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • megaplan — 92% identical, 328 lines differ
arnold_pipelines/megaplan/data/_composed/claude_skill.md · 649 lines

How it starts

The opening of the file, as written. The whole thing — 649 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Authority status (M11): Zero-authority history. All repair, audit, and deployment authority has been migrated to canonical delegation. This document is retained for reference only — it must not be used to materialize commands, grant authority, or drive automated actions.

Megaplan

Before you invoke megaplan, run the megaplan-prep skill. It's the front door for every run: it sizes the work (one plan vs. an epic), shapes the brief, and picks the profile (intelligence tier), robustness level, and thinking depth. Do not run <launcher> init without it.

Scope: This skill covers tooling — how to invoke and drive megaplan. For the decisions that come before invocation (scoping, brief, profile, robustness, depth), consult the megaplan-prep skill. If anything here contradicts megaplan-prep on decision-making content, megaplan-prep wins.

Route every step through the Arnold CLI's Megaplan subcommands. Never call agents directly. Before the first CLI call, resolve a working launcher and reuse it for the whole run. Do not assume the removed megaplan entrypoint is on PATH; command presence alone is not enough. Prove the launcher works by successfully running a harmless CLI call with it first. In the instructions below, treat <launcher> as that verified command. Launcher resolution order:

  1. Try python -m arnold_pipelines.megaplan config show.
  2. If that fails, try ./.venv/bin/python -m arnold_pipelines.megaplan config show.
  3. If that fails, try uv run python -m arnold_pipelines.megaplan config show.
  4. If those fail, stop and report that the Arnold Megaplan module launcher is unavailable.
  5. Do not use the removed megaplan module or console entrypoint; the repo-root megaplan.py file is a clean-break guard.

Triage

Decision-making (scoping, profile, robustness, depth, brief structure) lives in the megaplan-prep skill — consult it before running <launcher> init. Always run megaplan, even for tiny work — bare robustness is the floor, never skip the harness. The few seconds of overhead pay back in the captured brief, plan, and outcome record.

Read the full file on GitHub · 649 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. 1mo ago First seen · 649 lines · 20 tokens per session scan A ee7bab66825d

Subscribe to this mod's changes

megaplan is a skill published in the GitHub repository peteromallet/Arnold (98 stars, last pushed yesterday), licensed Apache-2.0. It adds 20 tokens to every session and 12,688 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-04.

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