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.
npx skills add ching-kuo/claude-codex --skill plan-codexgit clone --depth 1 https://github.com/ching-kuo/claude-codexWrote 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.
[](https://agentmods.dev/skills/ching-kuo/claude-codex/plan-codex)<a href="https://agentmods.dev/skills/ching-kuo/claude-codex/plan-codex"><img src="https://agentmods.dev/badge/skills/ching-kuo/claude-codex/plan-codex/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.
<a href="https://agentmods.dev/skills/ching-kuo/claude-codex/plan-codex"><img src="https://agentmods.dev/badge/skills/ching-kuo/claude-codex/plan-codex.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00071 | $0.01145 |
| Opus 5.5 | $0.00028 | $0.00458 |
| Sonnet 5.5 | $0.00014 | $0.00229 |
| Haiku 4.5 | $0.00007 | $0.00114 |
Grade A, and why
plan-codex 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.
How it starts
The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Plan-Codex — Claude Plans, Codex Audits
Input
The user's message after the trigger is either:
- A file path to an existing plan or requirements doc — read it and extract task description, goals, constraints
- A direct task description — use as-is
Confirm with user before proceeding if key context is missing.
Model Recommendation
Works best with claude-opus-4-6. Override with /model opus before invoking for complex architectural tasks.
Tool Requirements
Advisory checklist — ensure these tools are available:
AskUserQuestion— ask clarifying questionsmcp__codex__codexandmcp__codex__codex-reply— Codex audit loopTask— launch planner subagentRead,Glob,Grep— codebase researchWrite,Bash— save plan file
Core Protocols
- Code Sovereignty: Codex has zero filesystem write access during planning — all file operations by Claude only
- Stop-Loss: Do not proceed to next phase until current phase output is validated
- Language: Use English when calling tools/models; communicate with user in their language
- Planning Only: Never modify production code during this skill
Execution Workflow
Phase 1: Plan Creation
Launch a Task agent (subagent_type: "Plan") with the task description. The Plan agent will research the codebase and return a structured implementation plan.
If requirements are ambiguous before launching the planner, ask clarifying questions first.
Save the returned plan to .claude/plan/<feature-name>.md.
Phase 2: Codex Audit Loop (max 3 iterations)
MANDATORY Codex availability check: mcp__codex__codex MUST be listed in the available tools (either in the tool list or in <available-deferred-tools>). Do NOT skip or bypass this phase. If the tool is genuinely absent from both locations, stop and tell the user: "Codex MCP is not available. This skill requires Codex for plan audit. Please add the Codex MCP server." Do not proceed without Codex — the audit loop is this skill's core value.
What ships with it
2 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.
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.
- 1mo ago First seen · 102 lines · 71 tokens per session scan A eb1b8f61900b
plan-codex is a skill published in the GitHub repository ching-kuo/claude-codex (24 stars, last pushed 6mo ago), licensed MIT. It adds 71 tokens to every session and 1,145 once invoked, about $0.0003 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 2026-08-30.
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