deepen-plan

deepen-plan is a skill for Claude Code, Codex from marcusrbrown/systematic. It costs 76 tokens per session (4,860 once invoked), scanned A, original, MIT.

A second-pass review for an existing implementation plan that tests its decisions, order of work, system-wide effects, risks, and verification steps.

In plain words
What is it for?
Use it for complex or risky plans involving authentication, payments, migrations, external services, or other changes where confidence and sequencing matter.
Why use it?
It finds weak or unsupported parts of a plan and strengthens them with focused research before implementation begins.

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/marcusrbrown/systematic/deepen-plan
Any agent
npx skills add marcusrbrown/systematic --skill deepen-plan
Clone the repo
git clone --depth 1 https://github.com/marcusrbrown/systematic

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 deepen-plan

README.md
[![agentmods](https://agentmods.dev/badge/skills/marcusrbrown/systematic/deepen-plan.svg)](https://agentmods.dev/skills/marcusrbrown/systematic/deepen-plan)
Your own site
<a href="https://agentmods.dev/skills/marcusrbrown/systematic/deepen-plan"><img src="https://agentmods.dev/badge/skills/marcusrbrown/systematic/deepen-plan.svg" alt="Measured on agentmods" height="20"></a>
Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,860 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 $0.00076 $0.04860
Opus 5 $0.00038 $0.02430
Sonnet 5 $0.00015 $0.00972
Haiku 4.5 $0.00008 $0.00486

Measured 3d ago against content hash 81bf1e813176, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

deepen-plan 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/deepen-plan/SKILL.md · 411 lines

How it starts

The opening of the file, as written. The whole thing — 411 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Deepen Plan

Introduction

Note: The current year is 2026. Use this when searching for recent documentation and best practices.

ce:plan does the first planning pass. deepen-plan is a second-pass confidence check.

Use this skill when the plan already exists and the question is not "Is this document clear?" but rather "Is this plan grounded enough for the complexity and risk involved?"

This skill does not turn plans into implementation scripts. It identifies weak sections, runs targeted research only for those sections, and strengthens the plan in place.

document-review and deepen-plan are different:

  • Use the document-review skill when the document needs clarity, simplification, completeness, or scope control
  • Use deepen-plan when the document is structurally sound but still needs stronger rationale, sequencing, risk treatment, or system-wide thinking

Interaction Method

Use the platform's question tool when available. When asking the user a question, prefer the platform's blocking question tool if one exists (question in OpenCode, request_user_input in Codex, ask_user in Gemini; in Pi, use the blocking-question extension if available, otherwise present numbered options in chat and wait). Otherwise, present numbered options in chat and wait for the user's reply before proceeding.

Ask one question at a time. Prefer a concise single-select choice when natural options exist.

Plan File

<plan_path> #$ARGUMENTS </plan_path>

If the plan path above is empty:

  1. Check docs/plans/ for recent files
  2. Ask the user which plan to deepen using the platform's blocking question tool when available (see Interaction Method). Otherwise, present numbered options in chat and wait for the user's reply before proceeding

Do not proceed until you have a valid plan file path.

Core Principles

  1. Stress-test, do not inflate - Deepening should increase justified confidence, not make the plan longer for its own sake.
  2. Selective depth only - Focus on the weakest 2-5 sections rather than enriching everything.
  3. Prefer the simplest execution mode - Use direct agent synthesis by default. Switch to artifact-backed research only when the selected research scope is large enough that returning all findings inline would create avoidable context pressure.
  4. Preserve the planning boundary - No implementation code, no git command choreography, no exact test command recipes.
  5. Use artifact-contained evidence - Work from the written plan, its Context & Research, Sources & References, and its origin document when present.
  6. Respect product boundaries - Do not invent new product requirements. If deepening reveals a product-level gap, surface it as an open question or route back to ce:brainstorm.
  7. Prioritize risk and cross-cutting impact - The more dangerous or interconnected the work, the more valuable another planning pass becomes.

Read the full file on GitHub · 411 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. 3d ago First seen · 411 lines · 76 tokens per session scan A 81bf1e813176

Subscribe to this mod's changes

deepen-plan is a skill published in the GitHub repository marcusrbrown/systematic (24 stars, last pushed today), licensed MIT. It adds 76 tokens to every session and 4,860 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 2026-08-30.