openplan-core

openplan-core is a skill for Claude Code, Codex from BANANASJIM/openplan-skill. It costs 82 tokens per session (792 once invoked), scanned A, original, MIT.

A general operating guide for coding agents that keeps goals, plans, documentation, and code aligned while leaving important decisions to people.

In plain words
What is it for?
Use it to structure agent work, separate design from implementation, define coordinator and subagent responsibilities, and ground conclusions in files, reports, logs, or diffs.
Why use it?
It helps prevent agents from loading unnecessary context, changing the original goal during implementation, or treating chat history as the only record of decisions.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/bananasjim/openplan-skill/openplan-core
Any agent
npx skills add BANANASJIM/openplan-skill --skill openplan-core
Clone the repo
git clone --depth 1 https://github.com/BANANASJIM/openplan-skill

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 openplan-core

README.md
[![agentmods](https://agentmods.dev/badge/skills/bananasjim/openplan-skill/openplan-core.svg)](https://agentmods.dev/skills/bananasjim/openplan-skill/openplan-core)
Your own site
<a href="https://agentmods.dev/skills/bananasjim/openplan-skill/openplan-core"><img src="https://agentmods.dev/badge/skills/bananasjim/openplan-skill/openplan-core.svg" alt="Measured on agentmods" height="20"></a>
Per session 82 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 792 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00082 $0.00792
Opus 5 $0.00041 $0.00396
Sonnet 5 $0.00016 $0.00158
Haiku 4.5 $0.00008 $0.00079

Measured 3d ago against content hash f288c5e9f9b7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

openplan-core 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 3d 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.

skills/openplan-core/SKILL.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OpenPlan Core

Use this as the base layer for other OpenPlan-style skills. It is deliberately independent of any project-specific enforcement tooling or single agent platform.

Terminology: goal and intent are both valid. Use goal when emphasizing the desired outcome and verification. Use intent when emphasizing the human meaning, motivation, or decision behind that outcome.

Core Invariants

  1. Minimal effective context: load only what changes the next decision or review.
  2. Human-owned decisions: agents may suggest and execute, but humans own acceptance, bypass, scope, and tradeoff decisions.
  3. Externalized state: ground claims in files, diffs, reports, logs, or other durable artifacts, not chat memory.
  4. Layered authority: goal/intent and design constrain specs/plans; specs/plans constrain execution; execution does not silently rewrite the goal/intent.
  5. Dual-surface separation: when a project separates design/docs from implementation/code, preserve that separation and do not let execution redefine the source of truth.
  6. Dispatcher boundary: only the active human-facing coordinator asks the human; subagents report Human decisions required or BLOCKED instead.
  7. Role separation: alignment, research, design, implementation, testing, review, recording, gardening, and handoff are different modes even when one agent performs them.
  8. Evidence before confidence: every important claim needs observable support.
  9. Reversible automation: prefer actions that can be inspected, interrupted, replayed, or rolled back.
  10. No silent approval: "no findings" is not approval; it is a scoped review result.

Enforcement Is Optional

Hooks, isolated workspaces, CI checks, and other enforcement layers can strengthen the philosophy, but they are not the philosophy itself. In a Codex or Claude Code skill, keep the invariants as behavior, evidence, and reporting even when enforcement is unavailable.

Composition

Use this skill with:

  • $openplan-auto for orchestrating automatic/YOLO workflows.
  • $openplan-operate for session initialization, behavior constraints, and subagent delegation.
  • $openplan-align for ambiguity and requirement shaping.
  • $openplan-research for bounded evidence gathering before design or execution.
  • $openplan-docs-init for governed documentation generation setup.
  • $openplan-test for proportional test evidence and regression proof.
  • $openplan-review for YOLO/auto-mode review.
  • $openplan-handoff for cross-agent or cross-session snapshots.
  • $openplan-html-brief for temporary human-facing HTML summaries.
  • $openplan-record for maintaining memory and documentation as human goal/intent records.
  • $openplan-garden for semantic document gardening and goal/intent drift checks.

Read the full file on GitHub · 60 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 3d ago First seen · 60 lines · 82 tokens per session scan A f288c5e9f9b7

Subscribe to this mod's changes

openplan-core is a skill published in the GitHub repository BANANASJIM/openplan-skill (4 stars, last pushed 3mo ago), licensed MIT. It adds 82 tokens to every session and 792 once invoked, about $0.0004 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 2026-08-31.